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Because of the low fertility soils native to southeast Florida and the high nutrient demand of citrus trees under citrus greening-an endemic bacterial disease impacting nutrient uptake-growers are returning to the use of cover crops to improve soil fertility. Cover crops, specifically legumes, can improve soil nitrogen (N) availability because of their ability to fix N from the atmosphere. More citrus growers in southeast Florida are growing cover crops; however, there is a lack of recent research of suitable legume species and their impact on soil N cycling. To address this gap in the literature, six different treatments consisting of five legume species monocultures and one fallow plot (control) were organized into a completely randomized design. The experiment was conducted twice under warm and cool season conditions, and each treatment was replicated five times (n 5=5), for a total of 30 experimental plots. Legume species were hairy indigo (Indigofera hirsuta), sunn hemp (Crotalaria juncea), cowpea (Vigna unguiculata), alfalfa (Medicago sativa), and aeschynomene (Aeschynomene americana). Biomass production, N concentration, and nodule characteristics as well as their impact on soil N were measured over a 1-year span in both warm and cool seasons. Overall, both cowpea and hairy indigo produced more biomass and, as a result, higher tissue N compared with those of the other legumes at both 60 and 150 days after planting. However, no impact on soil N was observed. Additionally, all legumes were unable to survive in the cool season, resulting in no measurable biomass at 150 days after planting. These results are relevant for citrus growers aiming to enhance soil fertility through cover crops in southeast Florida. While several legume options are available for the warm season (e.g., cowpea, hairy indigo, and sunn hemp), suitable legume species for the cool season have yet to be identified. [ABSTRACT FROM AUTHOR]

Advance glycation end products (AGEs) are the main reason for diabetic complications. Persistent hyperglycemia and non‐enzymatic glycation increase the rate of AGEs formation. Natural functional food‐based approaches are mainly under investigation these days to discover new treatment options. We focused to investigate potential of medium polar fractions of Citrus paradesi. The peels fractions were analsyed for phytochemical profile, FTIR, HPLC‐DAD, and LCMS‐QTof, and biological investigation including antioxidant assays, α‐glucosidase inhibition, and Anti AGEs inhibition was performed. LCMS‐QTof confirmed the presence of flavonoids and polymethoxylated flavonoids including naringin, narirutin 4‐O‐glucoside, hesperidin, naringenin‐7‐O‐rutinoside hexamethoxyflavone, 3,5,6,7,8,3′,4′ heptamethoxyflavone were major compounds. A significant antioxidant activity was recorded in case of chloroform fraction compared to ethyl acetate fraction. Similarly a substancial AGEs inhibition in oxidative mode (IC50 0.23 mg/mL) and non‐oxidative mode (IC50 0.10 mg/mL) was observed in chloroform fraction, whereas ethyl acetate fraction was only active in oxidative mode (IC50 0.69 mg/mL). A moderate α‐glucosidase inhibition (IC50 1.23 mg/mL) was noticed in total extract, while significant activity was recorded in chloroform fraction (IC50 0.78 mg/mL). It was concluded that medium polar fraction of C. paradesi possesses antidiabetic and anti‐AGEs potential that can be due to presence of flavonoids and polymethoxylated flavonoids. [ABSTRACT FROM AUTHOR]

Citrus spp. are recalcitrant to in vitro shoot regeneration and we report an improved in planta protocol for genetic transformation of rough lemon that bypasses shoot regeneration in tissue culture. The features of the protocol were the use of an Agrobacterium suspension with an OD600 nm = 0.6–1.0 supplemented with 100 μg acetosyringone, gentle shaking of embryo axes pricked at shoot apical meristems (from 2-day-old germinating seeds) at 70 rpm during agro-infection, followed by growth and development of plantlets at 30 °C. PCR screening of 2-month-old T0 plants revealed the presence of an amplicon corresponding to the β-1,3-glucanase gene in the primary branches of 25 plants with a transformation efficiency of 7.74%. PCR analysis of the secondary branches of these plants after 18 months showed chimerism, i.e., the coexistence of transformed and untransformed branches in all 25 plants. Quantification of β-1,3-glucanase expression in the transformed secondary branches by qRT-PCR showed that plant number 32 had maximum (3.71-fold) relative transgene expression. The qRT-PCR analysis of all four tertiary branches arising from the transformed secondary branch of plant number 32 showed no significant differences in expression among themselves and from the transformed secondary branch, suggesting restoration of the transformed branches with uniform expression and dissociation of chimerism. Scanning electron microscopy examination of leaves from secondary and tertiary branches that uniformly expressed the transgene showed a smooth, waxy surface with non-significant variation in stomata, which had a narrow opening and a mean pore length of 4.22 ± 0.25–5.09 ± 0.36 µm. In contrast, the leaves of untransformed branch had a rough surface and a significantly large stomatal opening with a mean pore length of 7.82 ± 0.67 µm. The micro-morphological characteristics of the leaves confirmed the dissociation of chimerism in the transformed tertiary branches of plant number 32. The study demonstrates identification of chimerism after in planta transformation using PCR technique, and the novelty relates to monitoring dissociation of chimerism in transformed tertiary branches of T0 generation using qRT-PCR analysis and its corroboration by electron microscopy. The protocol for genetic transformation in plants described in the present study can be used for trait improvement by transgenesis. [ABSTRACT FROM AUTHOR]

Citrus represents one of the main fruit crops grown in the world, highlighting the 'Tahiti' acid lime tree. The objective was to compare rootstock varieties combined with this scion to identify those with the best agronomic performance and precocity of production, in addition to Phytophthora gummosis resistance. The experiment was carried out in Capitão Poço, northeast region of Pará, and the following seven rootstock genotypes were evaluated: 'Sunki Tropical', 'BRS O S Passos', 'BRS Bravo', 'BRS Donadio', 'Citrandarin Indio', 'BRS Matta', and 'LVK x LCR-038'. A randomized block experimental design was used, with three replications and 10 plants per plot. The evaluated characteristics were: plant height (m); crown volume (m³); number of ripe fruit per plant; total yield of ripened fruit per plant (kg plant-1); cumulative fruit yield (fruit kg plant-1); and average productive efficiency (fruit kg m-3 of crown). The average productive efficiency was high. For early selection, the best rootstocks in terms of yield, stability and adaptability were Sunki Tropical, BRS O S Passos, and Cintradarin Indio. The fruit number had the greatest direct effect on fruit yield, and crown pruning was directly harmful. Further studies to understand the complex interaction of G x E for BRS Donadio and Sunki Tropical should be carried out. [ABSTRACT FROM AUTHOR]

The citrus industry in Florida faces a destructive endemic disease, known as huanglongbing (HLB), associated with Candidatus Liberibacter asiaticus (CLas), a phloem-limited bacterium, and transmitted by the Asian citrus psyllid (ACP). Rootstocks are regarded as critical to keep citrus production commercially viable and help trees cope with the disease. Although most scions are susceptible, some rootstocks are HLB-tolerant and may influence ACP infestation and CLas colonization and therefore the grafted tree tolerance. This study aimed to elucidate the relative influence of rootstock and scion on insect vector infestation and CLas colonization under natural HLB-endemic conditions. Seven commercial rootstock cultivars with different genetic backgrounds were grafted with 'Valencia' sweet orange (Citrus sinensis) or were self-grafted (non-'Valencia') and planted in an open field where ACP and CLas were abundant. ACP infestation was determined weekly during periods of leaf flushing, and leaves and roots were analyzed every 3 months to determine CLas titers. Trees with 'Valencia' scion were more attractive to the psyllids than non-'Valencia' scions. This was also associated with a higher number of bacteria and a larger abundance of foliar HLB symptoms. The influence of the rootstock on the psyllid attraction of grafted 'Valencia' scion was less evident, and leaf CLas titers were similar regardless of the rootstock. Among the non-'Valencia' scions, Carrizo had the lowest and US-942 the highest leaf CLas titers. Root CLas titers also varied among cultivars, and standard sour orange roots harbored more bacteria than some trifoliate orange hybrid rootstocks such as US-942. In some trees, CLas was detected first in the roots 4 months after planting, but root CLas titers remained low throughout the study. In contrast, leaf CLas titers increased over time and were considerably higher than root titers from 7 months until the end of the study, 15 months after planting. Overall, the results of this study demonstrate a greater relative influence of the scion than the rootstock on ACP infestation and CLas colonization during the early stages of infection. This suggests that other cultivar-specific traits, such as the ability to tolerate other stresses and to absorb water and nutrients more efficiently, along with influences on the scion phenology, may play a larger role in the rootstock influence on the grafted tree tolerance during the later stages of HLB progression. [ABSTRACT FROM AUTHOR]

Citrus (Citrus spp. L.), which has high nutritional and economic value, is one of the most commonly grown fruits in Turkey. In spring 2020, large aerial galls (tumors) were observed on trunks and main branches of mandarin (Citrus reticulata cv. Satsuma) and lemon (Citrus limon cv. Kutdiken) trees grafted to sour orange (Citrus aurantium L.) in commercial citrus orchards in Hatay and Mersin provinces of Turkey. Disease incidence was 0.2–1.0% in the orchards inspected. Six bacterial isolates were obtained from young tumors on King's B (KB) medium. Several biochemical and morphological characteristics of all isolates were consistent with the description of the tumorigenic bacterium Agrobacterium tumefaciens (= Agrobacterium biovar 1). Identification of these isolates was confirmed by comparison with reference isolates of Agrobacterium tumefaciens (Syn. Rhizobium radiobacter) using MALDI-TOF MS analysis. The pathogenicity of the isolates was confirmed on carrot slice and stems from 6-month-old Kalanchoe plants and 2-year-old mandarin (cv. Satsuma) saplings. For molecular identification, the 16S rRNA and virD2 genes were amplified with primer pairs 27F/1492R and VirD2A/VirD2C, respectively and the PCR products were sequenced for representative isolates (CAt21, CAt27). The partial sequences of 16S rRNA (accessions numbers MZ708735 and MZ708734) and VirD2A/VirD2C of the representative isolates (CAt21, CAt27) showed 100% nucleotide identity to the A. tumefaciens isolates available in GenBank. According to symptoms, biochemical characteristics, pathogenicity test and molecular analyses, the causative agent of the disease was identified as Agrobacterium tumefaciens (= Agrobacterium biovar 1). To our knowledge, this is the first report of Agrobacterium tumefaciens (= Agrobacterium biovar 1) on citrus in Turkey. [ABSTRACT FROM AUTHOR]

The establishment of minimum growth conditions is essential for in vitro germplasm conservation. Changes to the basic medium and carbon source concentrations are important factors for reducing plant growth in vitro. This study adjusted a protocol for the in vitro conservation of 'Florida Rough' lemon plants. Microcuttings (approximately 1 cm) from plants that were previously cultivated in vitro were inoculated into test tubes with 10 mL of woody plant medium (WPM) at different concentrations (1/1, 1/2 and 1/4) and supplemented with 0, 12.5, 25 and 50 g.L-1 of sucrose, solidified with 7 g.L-1 agar and adjusted to pH 5.8. The experiment was completely randomized in a 3 x 4 factorial design with 15 replications and was maintained under controlled conditions for 360 days. After this period the plant height in cm (PH), the plant dry mass in g (PDM) and the 21 numbers of green leaves (NGL), senescent leaves (NSL) and microcuttings (NM) were evaluated. The variables that best explained the observed behavior of the 'Florida Rough' lemon plants were NGL and PH, with values of 61.63 and 35.08%, respectively. The original concentration of the WPM with the addition of 25 g. L-1 of sucrose yielded the best 'Florida Rough' lemon plant growth reduction in vitro while maintaining the physiologically health of the plants. [ABSTRACT FROM AUTHOR]

Citrus black spot (CBS) symptom expression on sweet oranges has been reported to be affected by the fruit developmental stage and inoculum concentration in greenhouse conditions. However, there is little information concerning the period in which the fruit is susceptible in commercial orchards. This study assessed the influence of fruit age and inoculum concentration of Phyllosticta citricarpa on CBS intensity and fruit drop in the field. Two field trials were conducted in commercial 'Valencia' orchards in São Paulo state, Brazil. Fruit were inoculated from October (petal fall stage) to July (c.6.5 cm diameter), with 101, 103 and 105 pycnidiospores/ml. CBS symptoms and fruit drop were observed in higher levels for fruit inoculated from October to February than from March to July. In both trials, when fruit were inoculated 10 times from October to July or single‐inoculated in November or December, high CBS severities of 11%–22% were observed and the proportion of fruit remaining on the tree was 48%–77%; in contrast, noninoculated fruit had severity below 1.1% and 90% remained on the tree. Inoculations in November or December of green fruit with 1.5–3.0 cm diameter using 105 pycnidiospores/ml were associated with higher CBS intensity and fruit drop and shorter incubation period than inoculations with lower concentrations. This work provides a better understanding of fruit stages and P. citricarpa inoculum concentrations most related to symptom expression and losses under natural conditions and may be helpful for improvement of CBS management in the São Paulo citrus belt. [ABSTRACT FROM AUTHOR]

Citrus plants are grown in diverse regions of the world, from subtropical to semi-arid and humid tropical areas. Through mechanisms essential for their survival, they adapt to the environmental conditions to which they are subjected. Although there is vast literature on adaptation of citrus plants to individual stresses, plant responses to interaction among different types of stresses have not been clearly examined. Abiotic or biotic stresses, or a combination of these stresses, result in reorganization of plant energy resources for defense, whether it be for resistance, tolerance, or prevention of stress. Plants generally respond to these stress factors through production of secondary metabolites, such as volatile compounds, derived from different biosynthesis and degradation pathways, which are released through distinct routes. Volatile compounds vary among plant species, meeting the specific needs of the plant. Simultaneous exposure to the stress factors of water deficit and herbivory leads to responses such as qualitative and quantitative changes in the emission of secondary metabolites, and compounds may accumulate within the leaves or predispose the plant to more quickly respond to the stress brought about by the herbivore. The genetic makeup of citrus plants can contribute to a better response to stress factors; however, studies on the emission of volatile compounds in different citrus genotypes under simultaneous stresses are limited. This review examines the effects of abiotic stress due to water deficit and biotic stress due to herbivory by Diaphorina citri in citrus plants and examines their connection with volatile compounds. A summary is made of advances in knowledge regarding the performance of volatile compounds in plant defense against both stress factors, as well as the interaction between them and possible findings in citrus plants. In addition, throughout this review, we focus on how genetic variation of the citrus species is correlated with production of volatile compounds to improve stress tolerance. • To survive, citrus plants have evolved to cope with biotic and abiotic stresses. • Defense mechanisms include the production of secondary metabolites, such as volatile organic compounds. • Plant responses can be enhanced through the interaction between herbivory by D. citri and water deficit. • There is limited knowledge regarding plant responses to multiple stress factors such as water deficit and ACP herbivory. • Developing resilient cultivars that can withstand multiple stress factors is crucial in the face of climate change and HLB. [ABSTRACT FROM AUTHOR]

Diversification of rootstock varieties, with consequent reduction in phytosanitary risks, has great importance to the sustainability of citrus cultivation in the south of Brazil. This study evaluated the performance of 42 rootstocks in the nursery phase to generate 'Valencia Late' sweet orange seedlings. Therefore, nucellar seedlings from the rootstocks under study were analyzed in relation to plant height, stem diameter, mortality rate and percentage of bud set after grafting. The experimental design was completely randomized with four replications of 20 sample units. Not adapted genotypes had high mortality rates, and the ones of both hybrids LCR x CTSW - 009 and LVK x LCR - 038 were 100% and 90%, respectively. Other 13 genotypes had mortality rates above 30%, and 'Sunki' mandarin was the female genitor of ten of them. 'Swingle' citrumelo was the rootstock with the highest development (plant height and stem diameter), associated with low mortality rate. In relation to the other rootstocks, the best results were the fast grafting diameter, associated with low mortality rate obtained by hybrids HTR - 053, LRF x (LCR x TR) - 005, CLEO x TRBN - 245, CLEO x TRSW - 287, and citrandarins 'Indio', 'Riverside' and 'San Diego', as well as Trifoliate orange and 'Rangpur' lime. In addition to Trifoliate orange, which is widely used in Rio Grande do Sul, these rootstocks have great potential in citriculture in the south of Brazil. [ABSTRACT FROM AUTHOR]

Summary: In Citrus, the response to environmental floral inductive signals is inhibited by the presence of developing fruits. The mechanism involves epigenetic activation of the CcMADS19 locus (FLC orthologue), encoding a floral repressor.To understand how this epigenetic regulation is reverted to allow flowering in the following season, we have forced precocious sprouting of axillary buds in fruit‐bearing shoots, and examined the competence to floral inductive signals of old and new leaves derived from them.We have found that CcMADS19 is enriched in repressive H3K27me3 marks in young, but not old leaves, revealing that axillary buds retain a silenced version of the floral repressor that is mitotically transmitted to the newly emerging leaves, which are able to induce flowering.Therefore, we propose that flowering in Citrus is necessarily preceded by vegetative sprouting, so that the competence to respond to floral inductive signals is reset in the new leaves. [ABSTRACT FROM AUTHOR]

The EFSA Panel on Plant Health performed a pest categorisation of Diaphorina citri (Hemiptera: Liviidae) (Asian citrus psyllid) for the EU. D. citri is a key pest of citrus in several countries as it is a vector of serious bacterial pathogens, the putative causal agents of Huanglongbing (HLB) also known as citrus greening. Eggs are laid on tips of growing shoots on and between unfurling leaves. Females may lay more than 800 eggs during their lives. Nymphs pass through five instars. The life cycle requires from 14 to 49 days, depending upon the season. There is no diapause, but populations are low in winter. It overwinters as an adult which may live for several months. The species completes 9-10 generations/year; however, under protected conditions, up to 16 generations have been recorded. Commission Implementing Regulation (EU) 2019/2072 (Annex IIA) regulates D. citri, as a quarantine pest not known to occur in the EU territory. Fruits and plants for planting provide potential pathways for entry into the EU. Climatic conditions and the availability of host plants provide conditions to support establishment in the EU. The introduction of D. citri would have an economic impact in the EU through direct but mainly indirect effects due to potential transmission of HLB. Phytosanitary measures are available to reduce the likelihood of entry. D. citri satisfies the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest. D. citri does not meet the criteria of occurring in the EU, nor plants for planting being the principal means of spread, for it to be regarded as a potential Union regulated non-quarantine pest. [ABSTRACT FROM AUTHOR]

Arid and semiarid regions are vulnerable to water deficits and salinity. Citrus plants are sensitive to saline stress and require the use of tolerant scion-rootstock combinations. Thus, this study aimed to evaluate and classify citrus scion-rootstock combinations with respect to their tolerance to salinity during seedling formation in a protected environment. An experiment was conducted in a randomized block design with a 5 x 12 x 2 factorial scheme corresponding to five levels of water salinity (0.8, 1.6, 2.4, 3.2, and 4.0 dS m-1) applied in 12 citrus rootstocks grafted with two scion varieties: 'Tahiti' acid lime and 'Star Ruby' grapefruit. The scion-rootstock combinations were evaluated for accumulated dry matter and survival index at 330 days after sowing the rootstocks. Salinity exerted different effects on the dry matter formation of scion-rootstock combinations. 'Star Ruby' was less sensitive to salinity, particularly when the rootstocks were the hybrids from 'Sunki of Florida' mandarin (TSKFL) with 'Troyer' citrange (CTTR) -- 013 (TSKFL x CTTR -- 013), common 'Sunki' mandarin (TSKC) with 'Argentina' citrange (CTARG) -- 019 (TSKC x CTARG -- 019), TSKC with 'Swingle' citrumelo (CTSW) -- 031 (TSKC x CTSW -- 031), and the trifoliate hybrid (HTR) - 069, as well as the varieties Volkamer lemon and Santa Cruz Rangpur lime. When grafted with 'Tahiti' acid lime, the rootstocks displaying the less sensitive to salinity were TSKFL x CTTR - 013 and TSKC x CTARG - 019. [ABSTRACT FROM AUTHOR]

This study evaluated oviposition of citrus leaf miner (CLM), Phyllocnistis citrella Stainton (Lepidoptera: Gracillariidae), in different Citrus genotypes and related genera to search for resistance sources of type antixenosis or no preference for oviposition. Initially, we screened 23 genotypes and we used lime 'Rugoso' (Citrus jambhiri Lush.) as the susceptibility standard. Based on the number of eggs and pupae found on the plants, five genotypes were most promising to significantly reduce pest population: trifoliata 'Limeira' (Poncirus trifoliata), hybrids M x P222 [Citrus sinensis × Tangor Murcott (Citrus sinensis × C. reticulata)], C x R4 (Citrus sunki × P. trifoliata) and C x R315 (C. sunki × P. trifoliata) and tangerine 'Sunki' (C. sunki). In the preference test for oviposition with choice, trifoliata 'Limeira' and hybrid C x R315 were the least preferred genotypes by CLM, while in the no choice test, the effect of the genotypes was less evident, with a difference only between trifoliata 'Limeira' (less oviposited) and lime 'Rugoso' (more oviposited). Thus, trifoliata 'Limeira' and hybrid C x R315 are potential sources of antixenosis resistance and could be used in breeding programs to incorporate CLM resistance factors in improved genotypes. [ABSTRACT FROM AUTHOR]

The industrial production of citrus plants for ornamental use (ornacitrus) began in Italy at the end of the 1960s due to the need for many citrus nurseries to adapt their activities in a time of crisis for citriculture. Nowadays, the ornamental citrus nursery sector is a well-established industry in many European countries such as Portugal, Spain, Greece, and southern Italy. In Italy, nursery production of ornamental citrus plants has become prominent due to the gradual shutdown of many commercial citrus orchards. Currently, Italy maintains its leadership with more than 5.5 million ornacitrus plants produced annually. Ornamental citrus production regards mainly different cultivars of Citrus and Fortunella species, with lemon as the lead species. In this paper, the contribution of breeding and cultural techniques to the innovation of the sector is reported and discussed. This review aims to give an updated scientific and technical description of a sector with large competitive potential that remains still largely unexplored, pointing out its strengths and weaknesses. [ABSTRACT FROM AUTHOR]

Brazil is the world's largest sweet orange producer, but production in the state of Acre is small and does not meet the local demand, despite having climatic conditions that are adequate for its cultivation. The objective of this study was to evaluate the behavior of the 'Pera' orange using different rootstocks under the edaphoclimatic conditions of Rio Branco, Acre, Brazil. We grafted the scion of the 'Pera' orange onto nine citrus rootstocks: 'Cleopatra' mandarin, TSKFL x CTTR - 013, LVK x LCR - 038, TSKC x CTQT 1439 - 004, LVK x LVA - 009, 'Indio'citrandarin, 'Santa Cruz Rangpur' lime, TSKFL x CTC - 25 - 002, and TSKC x CTSW - 038. The experiment was organized in a random block design with three replicates and two plants per parcel. The following characteristics were evaluated: compatibility between scion and rootstocks, tolerance to drought, production and fruit quality. There was an effect of the rootstocks on the behavior of the 'Pera' variety. The 'Santa Cruz Rangpur' lime, 'Indio' citrandarin, and the hybrid LVK x LCR - 038 rootstocks presented the best performance of the 'Pera' orange. Therefore, they constitute an alternative to the 'Rangpur' lime and may be incorporated into the current 'Pera' orange production system of the region. [ABSTRACT FROM AUTHOR]

We aimed to determine the rate of Candidatus Liberibacter asiaticus (C Las) DNA disappearance from Huanglongbing (citrus greening disease)-affected citrus trees after bacterial death from heat treatment. Using the leaf disc sampling method, we followed C Las qPCR Ct values in leaves of potted 'Valencia' orange trees after a heat-treatment that eliminated viable C Las. Although titer declined, C Las remained detectable 5 months after treatment. These results warn caution in interpreting experiments that use C Las titer to assess effects therapeutic treatments on diseased plants. Residual DNA may be detectable for 6 months, but the time to decay depends on pretreatment titer. • Heat treatment eliminated living C Las from citrus plants. • DNA of C Las remained detectable for 5 months. • HLB therapy assessment should consider residual bacterial DNA. [ABSTRACT FROM AUTHOR]

The physicochemical properties of citrus fruit play critical roles in its maturity and quality determination. Hence, this study investigated the effect of canopy position on physicochemical properties of ‘Marsh’ grapefruit across different production regions at harvest and after storage at 7.5 °C for 3, 6, and 9 weeks. The study also evaluated the use of BrimA as an adoptable internal quality and maturity parameter for ‘Marsh’ grapefruit. Fruit from inside canopy (IC) and outside canopy (OC) were harvested from KwaZulu-Natal (KZN) and Mpumalanga (MP) provinces in South Africa. Titratable acidity was determined by titration and calculation of the sugar/acid ratio (TSS/TA) was established while BrimA was derived from sugar and acid with tongue sensitivity index. Colour indices were measured using calibrated colorimeter while sugars were measured using high performance liquid chromatography (HPLC). At harvest, IC fruit from MP province were more luminous than the OC fruit while inverse results were recorded for fruit from KZN. At harvest, IC fruit had higher percentage of titratable acidity (TA) (2.73%) than OC fruit (2.40%) from MP, with opposite results from KZN. The BrimA showed a strong and positive correlation with TSS/TA (r = 0.9364). Overall, our result suggested that canopy position affect some physicochemical properties of ‘Marsh’ grapefruit. However, harvested fruit displayed a high level of maturity and quality over the period of cold storage. BrimA could potentially be used as an index of internal quality of grapefruit but further studies into the subject is required. [ABSTRACT FROM AUTHOR]

Naturally occurring coumarins 7-isopentenyloxycoumarin, auraptene, and umbelliprenin are able to modulate the biosynthesis of melanin in murine Melan-a cells probably through the interaction with selected biological targets like estrogen receptor β and aryl hydrocarbon receptor. Such a modulation strictly depends on the individual structure of the coumarin: the presence of a 3,3-dimethylallyloxy side chain is a structural determinant for tanning activation whereas a farnesyl one leads to the opposite effect. The parent compound with a free OH group, umbelliferone, did not provide any interaction. Other coumarins assayed, having shorter chains and/or being substituted in other positions, and prenyloxypsoralens, were not active or not further investigated in this context being cytotoxic at low doses. [ABSTRACT FROM AUTHOR]

This study aimed to characterise and discriminate 44 authenticated commercial samples of citrus essential oils (EO) from seven species (bergamot, lemon, bigarade, orange, mandarin, grapefruit, lime) by analysing the non-volatile oxygenated heterocyclic compounds (OHC) by UHPLC/TOF-HRMS, multivariate data analysis (PCA, PLS-DA) and metabolomic strategies; the OHC fraction includes coumarins, furocoumarins, and polymethoxylated flavonoids. Two different approaches were adopted: (i) targeted profiling based on quantifying 18 furocoumarins and coumarins, some of which are regulated by law, and (ii) targeted fingerprinting based on 140 OHCs reported in citrus essential oils, from which 38 discriminant markers were defined. This approach correctly discriminated the Citrus species; its “sensitivity” to relatively low adulteration rate (10%) was highly satisfactory. The proposed method is complementary to that of analysing the citrus EO volatile part by GC techniques. [ABSTRACT FROM AUTHOR]

Sour rot is a major postharvest disease of citrus fruit and is caused by the fungal pathogen Geotrichum citri-aurantii . A lack of chemicals certified for the control of this disease has led to the consideration of alternative methods and strategies, such as the use of yeasts as biocontrol agents. The purpose of the present study was to test the ability of yeasts isolated from leaves, flowers, fruit, and soil, and six Saccharomyces cerevisiae isolates to control citrus sour rot, to assess the mechanisms of action of the yeast isolates that were demonstrated to be effective for biocontrol, and to identify the most effective yeast isolates for the biocontrol of G. citri - aurantii. In in vivo assays, three yeast isolates (ACBL-23, ACBL-44, and ACBL-77) showed a potential for controlling sour rot in citrus fruits, both preventatively and curatively. Most of the eight yeast isolates that were assessed for a mechanism of action did not produce antifungal compounds in an amount sufficient to inhibit the growth of the pathogen. Additionally, nutrient competition among the yeast strains was not found to be a biocontrol strategy. Instead, killer activity and hydrolytic enzyme production were identified as the major mechanisms involved in the biocontrol activity of the yeasts. Isolates ACBL-23, ACBL-44, and ACBL-77, which controlled sour rot most effectively, were identified as Rhodotorula minuta , Candida azyma, and Aureobasidium pullulans , respectively. To our knowledge, this is the first report of the potential of C. azyma as a biological control agent against a postharvest pathogen and its ability to produce a killer toxin. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the influence of the growing environment on the in vitro conservation of citrus genotypes obtained from the Active Citrus Germplasm Bank of Embrapa Cassava and Fruit. The study used multivariate statistic tools in order to improve the efficiency in the analysis of the results. Approximately 1-cm of length microcuttings from plantlets derived from ten genotypes previously cultured in vitro were inoculated in test tubes containing 20 mL of WPM culture medium supplemented with 25 g L-1 sucrose, solidified with 7 g L-1 agar and adjusted to a pH of 5.8, and maintained under three environmental conditions for 180 days. The experiment was carried out in a completely randomized design in a split-plot in the space, with 15 replications. The results indicate that the principal component analysis is an effective tool in studying the behavior of different genotypes conserved under different in vitro growing conditions. The growing conditions of 22?1?C, a light intensity of 10 ?mol m-2.s-1 and a 12 hours photoperiod was the most adequate for reducing the growth of in vitro conserved plants, increasing the subculture time interval while keeping the plants healthy. [ABSTRACT FROM AUTHOR]

4'-Geranyloxyferulic and boropinic acid have been recently found as phytochemicals exerting promising pharmacological effects as cancer chemopreventive, anti-inflammatory, neuroprotective, and anti-Helicobacter pylori agents. An RP HPLC-UV/Vis method for the qualitative and quantitative analysis of these oxyprenylated derivatives in handmade citrus-based typical Italian liqueurs like limoncello, arancello, and mandarinetto was successfully performed. Concentration values showed a great variation between the different liquors, limoncello, from Abruzzo region, being the richest one both in 4'-geranyloxyferulic acid (1.68 ± 0.03 µg/ml of liquor) and boropinic acid (0.16 ± 0.01 µg/ml). Only in two cases boropinic acid was not detected. [ABSTRACT FROM AUTHOR]

• Cumulative fruit yield was decisive for identify promising rootstocks to 'Pera';. • Rangpur, Volkamer x Rangpur, Maravilha Sunki and Indio induced higher yield to 'Pera';. • Florida Sunki x citrange 13–012 and Sunki x Swingle-041 perform similar to Rangpur. • The citrus rootstocks induced no significant change on the fruit's quality. In tropical cohesive soils of Brazil, 'Rangpur' lime provide high fruit yield to 'Pera' sweet oranges. However, the predominance of a single rootstock puts the citrus industry in this region at risk. To identify promising rootstocks for diversification of 'Pera' sweet orange orchard's in the tropical cohesive soils of Brazil, a trial was established with 37 citrus rootstocks on the northeast coast of Brazil. The horticultural performance, fruit yield up to the tenth year, and physic-chemical fruit quality attributes were evaluated. The rootstocks induced changes in the tree size, cumulative fruit yield fresh mass and size of fruit, but had not significant influence on chemical fruit quality. The Hierarchical Cluster Analysis allowed group rootstocks into three classes, in which the accumulated fruit yield was the attribute that most contributed. A group with 15 rootstocks was chosen due to the best productive performance and fruits with 193.75–218.5 g, 57.36–62.65% of juice with 9.85–13.08° brix, which meets the requirement of the Brazilian market. Among these 15, the hybrid of 'Volkamer' lemon (VKL) with 'Rangpur' lime (RL), 'Maravilha Sunki' mandarin, 'Indio' citrandarin and the local selection of RL stood out by inducing the highest yield. VKL × RL – 030 produced fruits later, but favored the highest fruit yield at the tenth year. Trees grafted on these four rootstocks and also onto RLCNPMF, TSKC × CTQT1434 – 001, MXWL × LHA – 004, 'Santa Cruz' Rangpur, 'San Diego' citrandarin,– 004 and trifoliate TRH-208 had greater production regularity across the harvests, although the last three showed lower cumulative yield. The earliest fruit bearing was induced by TSKFL × CTC13 – 012, followed by the 'Sunki' mandarin hybrids TSKC × CTQT1434 – 001, RL, TSKC x TRFD -007 and TSKC x CTSW-041. It is concluded that the most promising rootstocks for diversification of citrus orchards under rainfed condition on the northeast coast of Brazil are VKL x RL-030, 'Maravilha Sunki' , 'Indio', TSKFL × CTC13 – 012 and TSKC × CTQT1434 – 001, RLCNPMF – 004, TSKC x TRFD -007, TSKC x CTSW-041 and MXWL × LHA – 004. [ABSTRACT FROM AUTHOR]

Gas exchange and hydraulic features were measured in leaves of three different Citrus species (Citrus aurantium L., Citrus limon L., Citrus × paradisii Macfad) infested by Phyllocnistis citrella Staiton, with the aim to quantify the impact of this pest on leaf hydraulics and, ultimately, on plant fitness. Infested leaves were characterized by the presence on the leaf blade of typical snake-shaped mines and, in some cases, of a crumpled leaf blade. Light microscopy showed that leaf crumpling was induced by damage to the cuticular layer. In all three Citrus species examined: (a) the degree of infestation did not exceed 10% of the total surface area of infested plants; (b) control and infested leaves showed similar values of minimum diurnal leaf water potential, leaf hydraulic conductance and functional vein density; and (c) maximum diurnal values of stomatal conductance to water vapour, transpiration rate and photosynthetic rate (An) were similar in both control leaves and the green areas of infested leaves. A strong reduction of An was recorded only in mined leaf areas. Our data suggest that infestation with P. citrella does not cause conspicuous plant productivity reductions in young Citrus plants, at least not in the three Citrus species studied here. [ABSTRACT FROM AUTHOR]

Molecular markers were used to evaluate genetic similarity among 36 citrus accessions (C. sinensis, C. reticulata, C. limon and cultivars) of the Greek national clonal germplasm repository located in Poros. In total, nine RAPD and five ISSR primers produced 262 loci, of which 236 were polymorphic. Both techniques were proven to be equally analytical with an average discrimination power above 0.9. The RAPD and ISSR markers were highly correlated and clustering among them had high correspondence. Citrus accessions formed separate clusters according to their species, even though sweet orange and mandarin cultivars revealed high affinity, while lemons were more divergent. C. sinensis genotypes had the highest intragenetic affinity suggesting that cultivated oranges have a narrow genetic base. On the contrary, the C. reticulata group was the most variable. In general, Greek varieties exhibited a distinctive genetic background that could be discriminated from foreign established cultivars using the mentioned molecular techniques. This information could facilitate their use in future Citrus spp. breeding programs. [ABSTRACT FROM AUTHOR]

Isolates of Citrus tristeza virus around the world differ widely in their biological properties. These properties may depend on strain mixtures within individual trees. Monoclonal Antibody 13 (MCA13) is an antibody that detects almost all the severe strains causing Quick Decline and Stem Pitting CTV syndromes. The objectives of this work were: I) to determine the percentage of CTV isolates reactive to the MCA13 antibody in each Colombian region evaluated and II) to analyze the genetic diversity of isolates from these regions. In almost all the regions evaluated, CTV MCA13 reactive isolates were identified; however, only one was found in Mompox area. The coat protein gene was amplified by reverse transcription-polymerase chain reaction (RT-PCR) and analyzed by single strain conformational polymorphisms (SSCP) patterns. In this work, at least twelve different dsRNA electrophoretic profiles and seven SSCP different electrophoretic patterns were identified. At least two different isolates were shown to be a mixture of strains. Non reactive strains to MAC13 from the Mompox region could be the best candidates for a Tristeza disease cross-protection program. [ABSTRACT FROM AUTHOR]

Abstract: The selenium contents of a total of 62 unifloral honeys from Erica spp., Castanea sativa, Eucalyptus spp., Lavandula stoechas, Citrus spp. and Echium plantagineum honeys collected in Portugal were determined by fluorometry after reaction with 2,3-diaminonaphthalene. The selenium levels of the honey samples studied were low, ranging from <1.0 to 2.91μg/100g fresh weight. The honeys from Erica spp., C. sativa and E. plantagineum presented the highest selenium values from all the honeys studied (median values 1.69, 1.51 and 1.51μg/100g fresh weight), and the honeys from Eucalyptus spp., L. stoechas and Citrus spp. presented the lowest values (median values 1.33, 1.28 and 1.20μg/100g fresh weight). The selenium content of Erica spp., was significantly higher than that observed for the Eucalyptus spp., L. stoechas and Citrus spp. and the selenium level of the Eucalyptus spp., was also significantly lower than that observed C. sativa and E. plantagineum honeys. From these results it can be concluded that honey is a marginal source of Se for the Portuguese population. [Copyright &y& Elsevier]

Water and soil salinity affects the growth, development and production of fructiferous species, such as citrus. The use of tolerant rootstocks can guarantee the agribusiness of citrus under such conditions. Thus, the sensibility to salinity during the phase of rootstock formation of varieties and selected hybrids was studied. The experiment was carried out in a greenhouse, with five levels of irrigation water salinity [control, tap water with electrical conductivity (ECw) of 0.41 dS m-1, and water with ECw of 1.0, 2.0, 3.0 and 4.0 dS m-1] and seven genotypes, in a randomized block design and five replications each consisting of four plants, during 150 day period. Growth and physiologic variables were evaluated. Significant effects of genotypes and salinity in the variables were observed. The most expressive reduction was found for total dry matter with unit increase of ECw. A linear reduction was observed in hybrids LVK x LVA-009 and TSK x TRENG-256. Among the evaluated genotypes ′Volkamer′ lemon was the least sensitive to saline stress. [ABSTRACT FROM AUTHOR]

Two surveys (2005/2006 and 2009) were conducted in the state of São Paulo, Brazil, to investigate the incidence of ' Candidatus Liberibacter asiaticus' and ' Ca. L. americanus', two liberibacters associated with citrus huanglongbing (HLB) disease and both transmitted by Diaphorina citri, in orange jasmine ( Murraya exotica), a widespread ornamental tree in cities and villages. The graft-transmissibility of the two species, and their DNA relatedness to citrus-associated liberibacters, were also investigated. Quantitative PCR was applied to PCR-positive orange jasmine and HLB-positive citrus growing in backyards and orchards to assess their inoculum source potentials. Liberibacters were detected in 91 of 786 sampled orange jasmine plants in 10 of 76 sampled locations. PCR-positive trees exhibited yellow shoots and/or dieback symptoms indistinguishable from those on PCR-negative trees. ' Candidatus Liberibacter americanus' was more common in 2005/2006 (96·6%) and ' Ca. L. asiaticus' in 2009 (84·8%). rplJ nucleotide sequences were identical within all populations of either species. Graft transmission succeeded only in homologous host combinations, including ' Ca. L. americanus' (2/10) from/to orange jasmine and ' Ca. L. americanus' (5/18) and ' Ca. L. asiaticus' (5/9) from/to citrus. Symptoms were mild and developed less rapidly in orange jasmine than in citrus, probably as a result of lower liberibacter multiplication rates. Respective titres of ' Ca. L. americanus' and ' Ca. L. asiaticus' in orange jasmine averaged 4·3 and 3·0 log cells g tissue, compared with 5·5 and 7·3 in citrus. The results indicate that orange jasmine does not favour liberibacter multiplication as much as citrus. However, its importance in HLB epidemics should not be underestimated as it is a preferred host of D. citri and is not under any strict tree-eradication programme or measures for insect control. [ABSTRACT FROM AUTHOR]

An experiment was carried out in the greenhouse aiming to evaluate the effect of different substrates and levels of nutrient solution in the formation of Poncirus trifoliata, ‘Troyer’ Citrange, ‘Swingle’ Citrumelo and tangerine ‘Sunki’ citric rootstock grown in containers. The experimental design was a randomized blocks in split plot scheme with three replications. Each sub-plot had twenty containers. The main plots received four levels of nutrient solution (0; 0.25; 0.5; 1.0g L-1 relationship N=1; P=0,14; K=0,34; Ca=1,41; Mg=0,13 and N concentration in the stock solution of 7.2%) applied by water irrigation in a continuous fertilization system in a floating irrigation system. The sub-plots tested four citric rootstocks and two commercial substrates. The nutritive solution was changed at 15-day intervals. The maximum growth and dry mass accumulation, in general, reached with the application of the maximum level of nutritive solution, except the foliar area of ‘Trifoliata and dry mass of the aerial part of tangerine ‘Sunki’. The commercial substrate 1 provided the greater growth and biomass accumulation, independently of stock for grafting and dosages of fertilizers used. [ABSTRACT FROM AUTHOR]

Background: Different monofloral honeys have a distinctive flavor and color because of differences in physicochemical parameters because of their principal nectar sources or floral types. Methods: Honey samples were collected from Apis mellifera colonies forged on 10 floras to analyze the quality of honey in terms of standards laid by Honey Grading and Marking Rules (HGMR), India, 2008 and Codex Alimentarious Commission (CAC), 1969. The honey samples were analyzed for various physicochemical parameters of honey quality control, i.e., pH, total acidity, moisture, reducing sugars, non-reducing sugars, total sugars, water insoluble solids (WIS), ash content, 5-hydroxymethylfurfural content, and diastase value. The antioxidant potential was estimated using Folin-Ciocalteu reagent. Further, honey samples were assayed for antibacterial activities against clinical isolates of Staphylococcus aureus and Escherichia coli using the hole-plate diffusion method. Results: The physicochemical variation in the composition of honey because of floral source shows Ziziphus honey with high pH and diastase values along with low acidity, whereas Helianthus honey contained high reducing sugar and low moisture content. Amomum, Brassica, Acacia, and Citrus contained lowest amount of non-reducing sugars, ash, WIS, and moisture, respectively. Lowest 5-hydroxymethylfurfural (HMF) value was detected in Amomum honey, while highest HMF value was observed with Eucalyptus. The maximum antibacterial and antioxidant potential was observed in Azadirachta and Citrus, respectively. Conclusion: The quality of honey produced by local beekeepers met HGMR and CAC standards, and the chemical composition and biological properties of honey were dependent on the floral source from which it was produced. [ABSTRACT FROM AUTHOR]

Nucleic acid sequence based amplification (NASBA) is a method of amplifying RNA, for the detection of RNA viruses and human pathogenic bacteria. Recently, NASBA has also been employed for the detection of plant diseases caused by viruses and quarantine bacteria. A major citrus pathogen, Xanthomonas citri subsp. c itri (Xcc) , causal agent of citrus bacterial canker, is being studied in depth due to its economic importance, with recent focus concentrating on its viability and survival under different stress conditions and control treatments. In this work, a NASBA protocol using primers for gumD mRNA has been developed to assess the viability of this pathogen under different bacteriocidal treatments. This method is rapid, specific and sensitive, and is able to detect viable bacterial cells, using a hybridization device which allows the visualization of the results in only 30 min. The usefulness of the method has been confirmed with bacterial suspensions subjected to different heat treatments and to sodium orthophenylphenate. [ABSTRACT FROM AUTHOR]

Abstract: The application and informativeness of RAPD, ISSR, IRAP and REMAP markers to study the genetic diversity and relationship among the Citrus and its relative genotypes were investigated. High levels of polymorphism were observed for all four marker systems. The RAPD technique generated the highest number of polymorphic bands and average number of polymorphic band per assay unit. Average limit of the discriminating power was very close to its actual discriminating power of each marker. The highest and the lowest values of effective number of patterns were obtained from the marker REMAP (5.94) and RAPD (4.48), respectively. Correlation between the genetic similarities matrices were estimated from all four markers using the Mantel matrix correspondence test, and results showed significant correlations among the RAPD, ISSR, IRAP and REMAP similarity matrices. The highest correlations were found comparing RAPD and ISSR markers, whereas RAPD and REMAP (r =0.143) markers were poorly correlated. To assess the usefulness of the overall information provided by these marker data for establishing phylogenetic relationships and Citrus germplasm classification, cluster analysis was performed. All four techniques, solely or in combination, discriminated the genotypes very efficiently and generated a high similarity in dendrogram topologies, although some differences were observed. The linkage analysis was conducted based on the segregation of 38 RAPD, 13 ISSR, 19 IRAP and 9 REMAP loci in 96 progeny of an intergeneric cross Citrus sinensis and Poncirus trifoliata. Among the 81 studied loci 65 loci distributed on five linkage groups. Comparing the result obtained with RAPD, ISSR, IRAP and REMAP markers in this study, IRAP and REMAP proved to be as a reliable molecular marker for fingerprinting, mapping and diversity study of Citrus and its relatives. [Copyright &y& Elsevier]

Abstract: ‘Swingle’ citrumelo [Citrus paradisi MacFaden× Poncirus trifoliata (L.) Raf.] has been extensively used as a rootstock in several citrus growing regions of the World, including Southern Brazil where ‘Rangpur’ lime (Citrus limonia Osbeck) is still the predominant variety despite being affected by several important pathogens. In this case, ‘Swingle’ citrumelo is used to produce nursery trees to establish new orchards or to be inarched in adult and healthy groves in order to change the rootstock. We report herein a system to produce trees on ‘Swingle’ citrumelo more rapidly by budding onto non-rooted cuttings, as well as assessing potential to rapidly multiply ‘Swingle’ through rooting of non-budded cuttings. Therefore, two potential products are described: budded trees and rooted rootstock cuttings. ‘Valencia’ sweet orange [Citrus sinensis (L.) Osbeck] was budded at different heights on cuttings derived from eight-month old rootstocks. Grafted and additional non-budded cuttings were then treated with indole-3-butyric acid (500mgL−1) or left untreated before rooting. Three types of cuttings were evaluated: softwood, semi-hardwood and hardwood. The use of nursery trees derived from pre-budded hardwood cuttings of ‘Swingle’ citrumelo is an alternative grafting method on this cultivar. Softwood cuttings with one leaf pair were considered the most adequate material for rapid multiplication of ‘Swingle’ citrumelo by cutting. This could be particularly useful for inarching production or conventional budding after transplant of cutting-derived rootstocks. [Copyright &y& Elsevier]

Abstract: The present study is designed to investigate the effect of some natural prenyloxyphenylpropanoids as neuroprotective agents against NMDA-induced toxicity in mixed cortical cell cultures containing both neurons and astrocytes. Excitotoxicity was induced by exposure of cultures to NMDA (100μM) at room temperature in a HEPES-buffered salt solution followed by incubation at 37°C for the following 24h in MEM-Eagle''s supplemented with 15.8mM NaHCO3 and 25mM glucose. Tested compounds were mixed with NMDA. Neuronal injury was measured in all experiments by examination of cultures with phase-contrast microscopy at 20×, 18–20h after the insult while neuronal damage was quantitatively assessed by counting dead neurons stained with trypan blue and by measuring lactate dehydrogenase (LDH) released in the medium. Results showed that only natural prenyloxyphenylpropanoids containing a coumarin nucleus, namely 7-isopentenyloxycoumarin and auraptene, both found in nature from plants belonging to the genus Citrus and other of the family of Rutaceae, including edible ones, exerted a good dose-dependent manner protective effect against NMDA-induced neurotoxicity in particular at concentrations ranging from 1 to 10μM. [Copyright &y& Elsevier]

A new laboratory technique combining shoot-tip grafting in vitro and biological indexing on indicator plants was explored for the detection of citrus exocortis and related viroids. Τhree in vitro laboratory methods were used and compared with the classical biological method. With the classical in vivo method, diagnosis is based on the expression of symptoms on indicators 11–14 weeks after inoculation. In contrast, with the first in vitro method, microindexing in vitro of citron seedlings by graft inoculation, diagnosis was possible 12 days after inoculation; with the second method, microindexing in vitro of citron cuttings by graft inoculation, 20 days after inoculation; and with the third method, microindexing in vitro of citron cuttings by injection inoculation, 40 days after inoculation. Inoculated Etrog citron plantlets grown in vitro and tested by RT-PCR showed the same viroid content as the source plants. Of the three in vitro viroid indexing methods, microindexing on cuttings by grafting was easier and more reliable than microindexing either on seedlings or on cuttings by injection. [ABSTRACT FROM AUTHOR]

The rise in the productivity of sweet orange in Brazil has been related to the use of superior rootstocks and higher tree density, among other factors. In order to investigate whether the cropping system and the land use efficiency would benefit from more intensive cultivation, the performance of Valencia sweet orange was evaluated over nine years on four rootstocks, which induced contrasting vigor, at 513, 696 and 1000 trees·ha−1. Agronomic Institute of Campinas (IAC) 1697 and IAC 1710 citrandarins, and diploid and allotetraploid (4×) Swingle citrumelos were classified as semi-dwarfing, super-standard, standard, and dwarfing rootstocks, respectively. The fruit yield per tree was decreased at higher tree densities, notably for more vigorous rootstocks. Conversely, the cumulative productivity was increased over the evaluation period by 27% at 1000 trees·ha−1, irrespective of the rootstock, and the most vigorous rootstock resulted in 2.5 times higher production than the dwarfing one on average. Most fruit quality parameters were seldom influenced by the tree density, while the rootstock was a decisive factor in improving the quality and the soluble solids content. Dwarfing rootstocks allowed for harvesting 17% more fruit per minute by manual pickers. Because the tree row volume per area is lower with such rootstocks, even at higher tree density, spray volume can be reduced, although appropriate equipment should be developed for better spray coverage on smaller trees. Nine years after planting under strict vector control, the cumulative incidence of huanglongbing-symptomatic trees on IAC 1710 was double that on Swingle 4×. Taken together, the results suggested that the land use efficiency in the citrus industry can be further improved by planting vigorous rootstocks at moderate to high tree densities. Nevertheless, obtaining highly productive semi-dwarfing and dwarfing rootstocks is the sine qua non for making high-density pedestrian sweet orange orchards more profitable. [ABSTRACT FROM AUTHOR]

Brazil is the largest producer of sweet orange and its juice in the world. Extensive cultivated area is located under an Aw climate in the North–Northwest of the state of São Paulo and the Triângulo of Minas Gerais state, being subjected to severe drought events. Although 56% of the orchards are irrigated in these regions, there is a need for drought tolerant rootstocks as an alternative to traditional genotypes such as Rangpur lime and Volkamer lemon, which are susceptible to the endemic citrus sudden death disease (CSD). In this sense, the tree size and production of Valencia sweet orange grafted onto 23 rootstock genotypes were evaluated over a ten-year period in rainfed cultivation at 7.0 m × 3.0 m spacing. Most evaluated types resulted from the cross of Poncirus trifoliata with Citrus, but two interspecific hybrids of Citrus (Sunki mandarin × Rangpur lime hybrids), the Barnes trifoliate orange and a tetraploid selection of Swingle citrumelo were also tested. Tropical Sunki mandarin was used as the reference control. Those hybrids coming from the cross of Sunki × Flying Dragon induced large tree sizes to Valencia sweet orange as well as the other citrandarins, Tropical Sunki mandarin and the Sunki mandarin × Rangpur lime hybrids, whereas only the tetraploid Swingle citrumelo behaved as a dwarfing rootstock, decreasing the canopy volume by 77% compared to that induced by the most vigorous citrandarin 535. The citrandarins 543 and 602 and the citrange C38 induced the highest mean fruit production, 67.2 kg·tree−1, but they also caused pronounced alternate bearing and only the hybrid 543 led to a high production efficiency consistently. Graft incompatibility symptoms were not observed over the evaluation period, and the canopy shape of Valencia sweet orange was also influenced by the rootstocks tested. Two citrandarins and one citrange were selected as the most promising alternative rootstocks for Valencia sweet orange grown under an Aw climate, even though productivity would likely benefit from supplementary irrigation. [ABSTRACT FROM AUTHOR]

• Flush growth was dependent on the scion and rootstock as well as climate influences. • Dwarfing rootstocks induced minor flush shoot intensity and growth rate. • Warmer seasons are critical to insect-vector control due to faster flush growth. • Regression models based on degree-days have potential to support spray applications. Occurrence, intensity, and growth patterns of new shoots (NS) were evaluated in orchards of 'Pera' and 'Folha Murcha' sweet oranges (Citrus × aurantium var. sinensis L.), 'Ponkan' mandarin (C. reticulata Blanco) and Persian lime (C. × latifolia var. latifolia) grafted on nine rootstocks to determine potential impacts of scion-rootstock combinations on NS growth parameters favorable to Diaphorina citri. NS number and the area under flush shoot dynamics were used to compare NS intensities. NS number (dependent variable) and meteorological elements (independent variables) were used through multiple linear regression to describe NS occurrences. NS growth data were compared through non-linear regression based on degree-days. NS occurrence dynamics were similar for all combinations, but the intensity was significantly higher on 'Florida' rough lemon than on 'Flying Dragon' trifoliate. Occurrence of NS on 'Pera', 'Folha Murcha' and Persian varieties associated positively (P < 0.05) with an increase of minimum and average temperatures (avg. adjusted R2 = 0.406; 0.408; 0.403, respectively), whereas on 'Ponkan' was related to the accumulated rainfall (avg. adj. R2 = 0.311). NS grew faster and attained longer lengths during spring (102.7 mm during 34 days) than autumn (71.9 mm during 42 days), except for 'Folha Murcha' which took longer to grow and reached shorter lengths (78.8 mm during 38 days) during spring, and longer lengths during autumn (118.3 mm during 42 days). Logistic models better fitted NS growth data (avg. adj. R2 ≥ 0.94). The adjusted R2 values of regression models developed to predict NS occurrence during the study were not high enough to estimate optimum timing to start insecticide applications for the control of D. citri. However, the adjusted R2 values attained for NS growth can be used to improve timing, and thereby adjust frequency of insecticide applications. [Display omitted] [ABSTRACT FROM AUTHOR]

• Headed nursery trees increased the cumulative fruit yield of sweet orange by 30 %. • Differences in the tree size and yield were larger for less vigorous scion varieties. • HLB incidence was similar regardless of the scion variety and nursery tree standard. • Headed nursery trees have greater potential for orchard resetting than whipped trees. Insect-proof propagation of citrus is recommended to prevent vector-transmitted pathogens such as Candidatus Liberibacter spp. and Xylella fastidiosa. Although larger nursery trees were related to a superior post-planting performance in other perennial crops, there are few studies on citrus. This fact motivated us to evaluate the tree growth, the fruit production, and the huanglongbing (HLB) incidence of four commercial sweet orange varieties ('Valencia Late', 'Hamlin', 'Pera' and 'Folha Murcha') using two nursery tree standards (young whip and large headed trees). Eight years after planting, the tree size was similar between the evaluated treatments, especially for more vigorous varieties. However, large headed trees anticipated and increased the cumulative production by 30 % in average, which can improve the performance of reset trees in particular. Regardless the nursery tree standard and sweet orange variety, the cumulative incidence of HLB was relatively high over eight years. Therefore, a strict control of the vector should be reinforced in the field irrespectively of these factors. [ABSTRACT FROM AUTHOR]

• The toxicity of essential oils (EOs) toward Dermanyssus gallinae was evaluated. • EOs from Cinnamomum cassia and Cinnamomum camphora var. linalooliferum were toxic. • Trans-cinnamaldehyde and linalool were less toxic to D. gallinae than EOs. • The EOs were toxic to the nontarget organism Beauveria bassiana. Dermanyssus gallinae (De Geer) (Acari: Dermanyssidae) is the main ectoparasite associated with laying poultry. This mite is commonly controlled by the application of synthetic chemical insecticides, wich lead to the selection of resistant populations and formation of residues in eggs. Thus, new molecules must be developed to control D. gallinae. This work evaluated the toxicity of essential oils (EOs) from Cinnamomum cassia , Cinnamomum camphora , Cinnamomum camphora var. linalooliferum , Citrus aurantium , Citrus aurantium var. bergamia, Citrus aurantifolia and Citrus reticulata var. tangerine against D. gallinae. Additionally, the chemical profiles of the most bioactive EOs were analyzed by gas chromatography coupled with mass spectrometry (GC–MS) and the major compounds were subjected to new tests using D. gallinae. The most toxic EOs against D. gallinae were evaluated for the nontarget entomopathogenic fungus Beauveria bassiana (Unioeste 88). The EOs from C. cassia (LC 50 = 25.43 ± 1.0423 μg/cm3) and C. camphora var. linalooliferum (LC 50 = 39.84 ± 1.9635 μg/cm3) were the most active in the fumigant bioassay and caused mortality rates of 96 and 61%, respectively. The GC–MS analysis revealed that the major constituents of EOs from C. cassia and C. camphora var. linalooliferum were trans-cinnamaldehyde and linalool, respectively. The pure compounds, trans-cinnamaldehyde (LC 50 = 68.89 ± 3.1391 μg/cm3) and linalool (LC 50 = 51.45 ± 1.1967 μg/cm3), were tested on D. gallinae and showed lower toxicity than the EOs. Thus, the compounds were not the only active substances produced by C. cassia and C. camphora var. linalooliferum ; moreover synergism may have occurred between the substances. The EOs from C. cassia and C. camphora var. linalooliferum were also toxic to B. bassiana (Unioeste 88). Thus, EOs from C. cassia and C. camphora var. linalooliferum are promising candidates for use in D. gallinae control, but cannot be used in conjunction with the fungus B. bassiana. [ABSTRACT FROM AUTHOR]

• The performance of sweet orange 'Pera' on five rootstocks was assessed. • 'Pera' trees on HTR-051 showed the highest yield efficiency. • 'Red Rough' lemon imparted the highest cumulative yield to 'Pera'. • LVK x LCR – 010 conferred lower alternate bearing index to the trees. • Red Rough' lemon and LVK x LCR – 010 conferred yield precocity to 'Pera'. Citrus orchards in the coastal tablelands of Northeast Brazil are almost exclusively composed of 'Pera CNPMF D-6' sweet orange, henceforth 'Pera', grafted on 'Rangpur' lime. Therefore, assessing new rootstocks for 'Pera' in this region is pivotal for diversification purposes, potentially leading to increased competitiveness, yield and fruit quality. In this study, vegetative growth, productive performance, pest attack and fruit quality of 'Pera', grafted on five rootstocks, were assessed over 10 years in Northeast Brazil. The trifoliate hybrid HTR-051 conferred the highest yield efficiency to 'Pera', while 'Red Rough' lemon and LVK x LCR - 010 induced precocity, with yields exceeding 9400 kg ha−1 in the first harvest, as well as the highest cumulative yields. 'Red Rough' lemon, LVK x LCR - 010 and HTR-051 were notable for imparting high weight and total soluble solids to 'Pera' fruit. Regarding pests, the highest densities of citrus rust mite Phyllocoptruta oleivora were found on the fruit of 'Pera' grafted on LVK x LCR - 010, despite low densities of this arthropod over the sampling period. Altogether, our results highlight 'Red Rough' lemon and LVK x LCR −010 as superior rootstocks for excelling in productive performance and fruit quality. In addition, HTR-051 manifests as an excellent option for high-density orchards because it induces dwarfism and high production efficiency. [ABSTRACT FROM AUTHOR]

In a previous work, we in silico annotated protein sequences of Citrus genus plants as putative tryptophan decarboxylase (pTDC). Here, we investigated the structural properties of Citrus pTDCs by using the TDC sequence of Catharanthus roseus as an experimentally annotated reference to carry out comparative modeling and substrate docking analyses. The functional annotation as TDC was verified by combining 3D molecular modeling and docking simulations, evidencing the peculiarities and the structural similarities with C. roseus TDC. Docking with l-tryptophan as a ligand showed specificity of pTDC for this substrate. These combined results confirm our previous in silico annotation of the examined protein sequences of Citrus as TDC and provide support for TDC activity in this plant genus. [ABSTRACT FROM AUTHOR]