Search

Objective: was to select quinoa accessions as possible positive reaction differentials to mildew that identify the variability of Peronospora Variabilis Gaum as a pathogen collected in five departments and evaluated in Cusco. Material and methods: mildew samples were collected from the altiplano (Puno), inter-Andean valleys (Cusco, Apurímac, Ayacucho), and coast (Arequipa), obtaining 175 mildew samples. The installation of the experiment was with 100 accessions of quinoa from the Germplasm Bank of EEA Andenes in cultivated fields during two productive campaigns. For its evaluation, quinoa descriptors were used and agronomic characteristics, yield, reaction to mildew (P. Variabilis), ALJDPC (area under the disease growth curve), and saponin percentage were evaluated. In addition, virulence tests and severity evéduations were performed after inoculating quinoa accessions with mildew in the greenhouse. Results: the morphoagronomic evaluation allowed selecting the following genotypes cis possible differentials with a positive reaction to mildew: RR.GG.41 for isolates from Ayacucho, RR.GG.09 for isolates from Apurímac, RR.GG. 16 for isolates from Apurímac and Arequipa, RR. .GG.57 for isolates from Puno and Apurímac, RR.GG.26 for isolates from Ayacucho and Apurímac, RR.GG.38 for isolates from Cusco cind Arequipa RR.GG.43 for isolates from Puno cind Arequipa, RR. GG .76 for isolates from Cusco and Arequipa and the quinoa accessions RR.GG. 11, RR.GG.22, RR.GG.55, RR.GG.64 for the 142 isolates obtciined from the 175 samples of the five departments Conclusions: the identification of twelve possible differential plants allows knowing the variability of the pathogen in the coastal, inter-Andean, and high plateau valleys. [ABSTRACT FROM AUTHOR]

Quinoa crops in the Peruvian highlands are affected by mildew disease, which can cause losses of up to 90 % of production. The objective of this study was to evaluate the effect of strains of Trichoderma sp and efficient microorganisms (EM) in the control of mildew and yield of quinoa. In the experimental field of the International Potato Center (IPC) Camacani of the National University of the High Plateau of Puno department, in the agricultural campaign 2016-2017, there were sowed control seeds and others pelletized with eight treatments: four Trichoderma sp strains, three doses of EM (5 %, 10 %, and 15 %) and a mixture of Trichoderma sp and EM strains (15 %), later there were made four foliar applications of each one of the eight treatments to 1x107 ufc.ml-1, in each critical moment of the phenological cycle. It was determined the area under the curve of the disease progress (AUDPC) and the yield. All treatments applied significantly favored the reduction of the pathogen and crop yield. The most effective treatment in the reduction of mildew was Trichoderma sp TETQ-3 strain, followed by EM at 5 % with AUDPC of 586.19 and 586.44 respectively, which is equivalent to 53 % less than the control. In terms of yield, ME at 5 % increased production by 208 %, from 1256 kg/ha to 3872 kg/ha. The use of these microorganisms represents an alternative of sustainable use for the biocontrol of phytopathogens and growth promotion in quinoa crops. [ABSTRACT FROM AUTHOR]

Quinoa crop (Chenopodim quinoa Willd.) is native to the Peruvian Andes, nutritious food and it has become very important for agroexport. In Piura, the downy mildew disease appeared causing economic losses, were set as objectives: detect the primary inoculum, describe the symptoms and evaluate the effect of defense inductors in the control of downy mildew. The direct detection methodology was used to observe oospores, the treatments were; Biosar, 3Tac, Agromos + Soil set, Action FP/Pare, Metalosate and control, Area Under the Disease Progress Curve (ABCPE) was evaluated, comparisons of means were made of the Tukey test (α = 0.05). Oospores were detected in all the quinoa samples, being with greater number the var. INIA-altiplano with 96 and with lower var. passankalla with 8 oospores/100 units of seed. As a symptom, yellowish spots were observed on the upper side and gray sporulation on the underside of the leaves. The highest value of ABCPE was obtained by the control with 2,161.02; the lower values and that better controlled the mildew disease in quinoa, they were obtained with Action FP/Pare (0.5 / 0.5 L / 200L water) and Agromos + Soil set (0.25 + 0.25 L / 200 L water), with 939.8 and 1040.7 respectively. [ABSTRACT FROM AUTHOR]

In order to generate a new variety of quinoa for the northern highlands of Peru and contribute to the competitiveness of this andean grain, this research was carried out between 2013 and 2018. Phases of introduction and evaluation of germplasm, genetic improvement and advanced evaluation of promising materials were carried out. The first two phases carried out in INIA experimental fields and the third in farmer's fields. Phenotypic characteristics, physiological maturity, mildew reaction and grain yield were evaluated. Also, there was opinion of farmers. Quantitative data was analyzed using ANVA and Duncan's test. From the Genetic Compound A, introduced from the central highlands, the new variety of quinoa was generated, called INIA 437 Red of the North. It is accepted by the farmers of the research, It has white grain and semi-sweetness; purple in foliage and panicle; as well as outstanding characteristics of mildew tolerance and productivity, showing less damage to the disease and greater yield than the Witness, White of Junín variety; also It has greater profitability and productive stability than this; being suitable for cultivation in the study area. [ABSTRACT FROM AUTHOR]

The aim of the work was to evaluate the development of Podosphaera xanthii (Castagne) U. Braun & Shishkoff in pumpkin crop during the years 2018 - 2019. The crop (Cucurbita pepo L.) (hybrid pumpkin material, Gray Zucchini) was established on a surface of 1 500 m2 where 25 plants were randomly selected, and three leaves per plant were labeled, in which incidence and severity were evaluated weekly using a degree scale. Weather variables were recorded. These results indicate that P. xanthii is present at 14 days after transplantation in the sowing from February to April; while from May to July, it is present after seven days, coinciding with the rainy season, conditions that indirectly favor the increase of relative humidity (23-63 %), causing the progress of the disease. The development of the disease was similar in both years (2018-2019), but not between the two sowing dates, with the first symptoms appearing seven days earlier, and with a severity of 0-9 %, at the second sowing time (May-July). The comparison of major components showed a relationship of temperature with the incidence and severity of the pathogen, but not with rainfall, since this factor does not condition the emergence of the disease. As an important result for Tehuacán region, it is suggested the month of February as the most appropriate date for planting the crop, with a low incidence and severity of the disease. [ABSTRACT FROM AUTHOR]

Introduction: There are few studies concerning the morpho-anatomical and histochemical alterations caused by powdery mildew in H. macrophylla leaves in the scientific literature. Objective: To describe and analyze anatomical and histochemical aspects of this pathosystem. Methods: More than 90 leaves of H. macrophylla (both healthy and infected leaves by powdery mildew) were collected in the nursery El Jardín del Eden, Rionegro, Antioquia, Colombia. To carry out the identification of the mycopathogen, sections were stained with Lactophenol Blue, and contrasted with specialized taxonomic keys. Transverse fragments 1 cm thick were fixed in a mixture of formalin, alcohol, and acetic acid. These were subsequently dehydrated using an ethanol series, clarified in Xylene, and finally embedded in Paraplast plus® to obtain 5 µm sections. Schiff's periodic acid reaction (PAS) was used to detect structural and reserve polysaccharides, Ruthenium Red for pectins, Ponseau S and Lacmoid for callose, ferric chloride for polyphenols, Sudan Black for lipids and Uvitex 2B-Hematoxylin for chitin. The sections were observed using a Nikon 80i eclipse® photon microscope, with Uvitex 2B-Hematoxylin-stained sections examined by epifluorescence using a UV-2A filter. For the observation and description of the samples by scanning electron microscopy, healthy and infected leaves were fixed and dehydrated in 100 % methanol, critical point dried, and coated with gold. Results: H. macrophylla leaves are isobilateral and homobaric, with adaxial and abaxial epidermis of a single cellular layer. The palisade parenchyma consists of a layer of short cells, while the spongy parenchyma forms 6 to 7 cellular layers. All vascular bundles in the leaf blade are closed collaterals. Abundant idioblasts with raphides may be observed in the mesophyll, and starch is the main reserve carbohydrate present in the tissues. The leaves are hypostomatic and exhibit a paracytic pattern of superficial stomata which possess large substomatal cavities. The morphological data observed indicate that the mycopathogen is related to the genus Erysiphe. The epidermal cells affected by the pathogen exhibit thickened walls, granular cytoplasm, and papillae or cell wall appositions in the outer periclinal walls. With the deterioration of the epidermis, the underlying tissues are affected and become necrotic. Histochemical test indicate that infected plants thicken and reinforce their epidermal cell walls with primary wall materials; primarily cutin, pectins, and callose. When stained with Sudan Black, the presence of dark-colored agglomerates in the cytoplasm of epidermal cells may be related to plant defense mechanisms; and those observed in mesophilic cells to the disorganization of membrane systems. Polyphenols accumulate in the cytoplasm of infected epidermal cells. The fungal material present in epidermal tissues was clearly differentiated when stained with fluorochrome to detect chitin. Conclusions: Species of the genus Erysiphe are causative agents of powdery mildew in H. macrophylla. Necrosis of the epidermal cells is observed in response to the mycopathogen, possibly due to hypersensitive response. [ABSTRACT FROM AUTHOR]

Powdery mildew, caused by Uncinula necator (Schwein) Burrill is one of the most damaging disease affecting grapevines (Vitis vinifera L.) in Mendoza and worldwide, reducing yield and fruit quality. Throughout six growing seasons (2001/02; 2002/03; 2005/06; 2007/08; 2008/09; 2009/10), powdery mildew incidence values (expressed as daily epidemic increment rates) were observed in clusters from flowering to onset of ripening (change of color of the grape berries), in a grapevine planted with the susceptible Chenin cultivar at the EEA INTA Mendoza (Luján de Cuyo). From hourly values of thermal-moisture elements recorded by upper canopy sensors, meteorological variables were calculated in the 15 previous days of each epidemic observation. Using variables which integrate the effects of air temperature and humidity and frequency of light precipitations over the epidemic progress, logistic models were adjusted for estimating the probability of occurrrence of severe, moderate and nil epidemic increment rates, reaching maximum prediction accuracy of 92.5% (two variable models, N=40). Predicted values by the univariate model (selected by Stepwise procedure; prediction accuracy: 87.5%) were validated with the epidemic curve observed during 2000/2001 growing season. These model predictions could complement epidemic observations, giving regional scale to warning systems for improving the decision making process regarding disease chemical control. [ABSTRACT FROM AUTHOR]

The objective of this study was the species-level identification of the causal agent of the black mildew of mamoncillo (Melicoccus bijugatus) in Colombia using collections of black mildew of mamoncillo deposited at the Museo Micológico de la Universidad Nacional de Colombia Medellín (MMUNM). Observation of symptoms and signs, free-hand sections of structures, measurements, and photomicrographs were performed with a Boeco® stereoscope and a Carl Zeiss® Axiostar Plus microscope equipped with a Canon® PowerShot G5 digital camera. This fungus is characterized by foliar black spots up to five millimeters in diameter mostly on the adaxial leaf surface. Hyphae: dark brown, erect or sinuous; hyphopodia: opposite, scattered, arcuate; conidiogenous cell mixed with hyphopodia, usually opposite, ampulliform; mycelial setae: around perithecia, numerous, scattered, erect, with apex 1-2 dichotomous. Perithecia: scattered, verrucose, dark brown; asci unitunicate, evanescent; ascospores: ellipsoid, four-septated, constricted at the septa; cinnamon-brown. The morphological results allowed the identification of the causal agent of black mildew of mamoncillo as the fungus Meliola crucifera. [ABSTRACT FROM AUTHOR]

In this scientific note I analyze two new paradigms in the Cactaceae recruitment and establishment. The first one is related to the facilitation effect given by "nurse objects" (rocks) compared with "nurse plants", which could be enhanced in places where fog deposition and dew formation are highly frequent phenomena. The trophic biology of the rock-colonizing cactus is the second paradigm. Recent studies have discovered and isolated bacteria living into (endophytic) and outside (in the rhizoplane) cactus roots which are responsible for rock weathering and nutrients release. Research on the "hidden" water gains driven by rocks and bacteria isolation and inoculation to cactus seedlings are very important topics in the endemic cactus populations' restoration and recovering plans in arid environments of the Andean western slopes. [ABSTRACT FROM AUTHOR]

During the past years there has been an increase in the number of tomato greenhouse facilities in Michoacan. The expected high yield for some of these greenhouses has not been attained due mainly to the presence of tomato diseases, which in many cases, the identity of the pathogen is unknown. The objectives of this research were to determine the incidence and the etiology of the main diseases affecting greenhouse grown tomato in central Michoacan. Sampling was carried out in six commercial tomato greenhouses located in four municipalities from March to October 2007. The main diseases detected were wilting of young and mature plants, late blight, bacterial speck and powdery mildew. The identified pathogens were Phytophthora infestans, Oidiopsis taurica, Rhizoctonia spp., Fusarium oxysporum, Oidium neolycopersici and Pseudomonas syringae pv. tomato. Late blight caused by P. infestans and mildew caused by O. neolycopersici were the most important diseases detected due to the high disease incidence and severity. [ABSTRACT FROM AUTHOR]

With the objective of evaluating the sensitivity of various cultivars of melon to Clethodim herbicide during December 2003 to June 2004, six experiments were conducted in greenhouse conditions in EEFBM. The cultivars evaluated were cantaloupe (cv. Hymark, Mystic Eastern, Western and Torrione Laser) honey dew (cv. Orange Flesh, Honey Brew and Tan Dew), dorado (cv. Golden Prince and Golden Nesta), toad skin (cv. Piñonet and Sancho); Tendral (cv. Green Late) and Gali (cv. Solar King). Each cultivar was evaluated at 36, 48, 60, 72 and 84 clethodim g / ha; a control treatment without herbicide was included. We found that a percentage of clethodim caused damage below 20% (considered minor) in all melon cultivars with a slight increase with increasing doses. Phytotoxicity symptoms consisted of chlorosis on the edge of the leaf blades, corrugated blades and leaf buds. Although there was no significant interaction between cultivars by clethodim dose, the late cultivars Nesta and Green seemed the least affected by this herbicide, while the cantaloupe cultivars were slightly more susceptible. The cultivars were recovered two weeks after application. Other variables such as number of leaves and guides, leaf area, biomass of stems and leaves were not affected by the clethodim. Under the conditions of this evaluation and from the viewpoint of selectivity, it is suggested that use of clethodim in doses ranging from 36 to 84 g ai / ha in the melon cultivars tested is appropriate. [ABSTRACT FROM AUTHOR]

The marigold (Calendula officinalis) is an herbaceous plant used by its beautiful yellow or orange flowers, in bordures, gardening and as cut flower. It is largely diffuse in the world, not only for the beauty of his flowers or his use in cosmetic, but for being resistant, of easy cultivation and for it low demanding in environmental conditions. In Mendoza it is very used as ornamental plant and every year is affected by a disease called powdery mildew. In Argentina there are mentioned as etiological agents of the disease different species of the generous Erysiphe, and Oidium erysiphoides. Nevertheless the teleomorphic form wasn't described until 1991 in Corrientes and Córdoba. There, it was reported as Sphaerotheca fusca. In 2004 in Mendoza, it was observed over marigold cultures a severe powdery mildew attack. Studying the problem, over the typical powder of the disease, the presence of black bodies was observed. This motivated to determine the etiology of the disease in Mendoza. Several samples of marigold plants affected were taken at different places. At the laboratory, morphological and morphometric studies permitted the identification of Podosphaera fusca (=Sphaerotheca fusca) as causal agent of the powdery mildew of the marigold in Mendoza. [ABSTRACT FROM AUTHOR]

The effects of presowing magnetic treatment on cucumber seeds of the "Japanese" variety on the disease Cucumber mildew produced by Pseudoperonospora cubensis and on plant yield were studied during the blooming and harvest stages in plants sowed in late period (December- February). The magnetic treatments consisted in combinations of magnetic field strength and exposure periods: 120 mT-5min, 120 mT-10min, 160 mT-10 min and 200 mT-3min. The disease appeared naturally in the field, and the infection index and incidence was evaluated. The results showed a significant stimulation of yield and its components by treatments (12-72%) and a reduction in infection index and incidence of disease in the two stages evaluated; the best combinations were 200mT-3mín (12%) and 120 mT-5mín (12.2 %) in the flowering stage and 200mT-3mín (14.8%) in the crop stage for the infection index; the lowest disease incidence values for both stages were detected in the combination of 200mT-3mín. [ABSTRACT FROM AUTHOR]

In order to assess if ants attracted to honeydew-producing Hemiptera switched food sources when offered an additional, considerably rich and abundant food source, we studied the interaction between the plant Solanum lycocarpum (Solanaceae), an efn-lacking shrub, the predominantly diurnal ant Camponotus crassus (Hymenoptera: Formicidae), and two species of membracids (Enchenopa spp.; Homoptera: Membracidae). The study was done during September of 1999 at the Reserva Ecológica of IBGE (ca. 35 km S of Brasilia-DF, Brasil). The results show that ants were attracted both to the experimental food source and to the membracids. Moreover, the mean number of ants visiting the experimental nectary was significantly higher than those visiting the membracids. However, the membracids were never left unattended, which suggests that ants, even though presented with an abundant and rich food source, do not abandon other sources. The latter can be explained due to an increment in the honeydew production rate by the membracids, thus the attention levels of ants does not vary Another possibility is the fidelity of worker ants to a food source and its location. To show that ants switch food sources based on quality and/or quantity, and not merely based of their presence and/or absence, requires future research, both for plants with and without extrafloral nectaries. [ABSTRACT FROM AUTHOR]

Tamarind (Tamarindus indica) is an important crop in the dry tropic region of Mexico. Powdery mildew (Oidium sp.) is a disease that affects this leguminous crop, and causes up to 60% reduction in fruit production. Lesions on leaves are powdery; there is production of a white mycelium with a hyphal net on the foliar surface. Hyphae are hyaline with smooth cell wall, and produce short and erect conidiophores. Conidia are hyaline, unicellular, cylindrical, in chains or singly, with an average length of 27 μm × 14 μm width. Powdery mildew has a strong relationship with the rainy season, the presence of young plant shoots, and dry days; therefore, the highest disease severity occurs during August-October. The damage caused by this disease increases in orchards that have poor agronomic management practices. The current control of the disease is mainly based on the continuous application of systemic fungicides. [ABSTRACT FROM AUTHOR]

The article presents a study on the appearance of the Podosphaera, a section of the Sphaerotheca xanthii, on the cucurbits in northern Sinaloa, Mexico. It is stated that the powdery mildew is one of the most important diseases in the cucurbits in the region. The literature notes of the Golovinomyces cichoracearum as the causal agent of the disease. The aim of the study is to identify and confirm the real cause of the disease. Results show that there is no occurrence of the Golovinomyces cichoracearum among the tested samples of the powdery mildew.

Leveillula taurica (Lév.) Salm. is a pathogenic fungus, at the moment, in expansion in Argentina and particularly in Mendoza. Physalis viscosa (groundcherry) grows spontaneously in several cultures and in its surroundings in Argentina. The finding of L. taurica on camambú a wide spread specie in our country has motivated the present study. The symptoms were characterized by the presence of yellow cuneiform patches in the adaxial face of the leaves corresponding with a white plush on the other leave face. Etiological studies based on the histopa-thology of the diseased tissues and fungal morphology have confirmed the presence of Leveillula taurica (Lév.) Salm on it anamorphic face of Oidiopsis taurica Sal. [= Oidiopsis sicula (Scal)]. Since it was found for the first time in 1996 in Tupungato, the fungus has been spreading itself everywhere in Mendoza. The pathogen attacks camambú from Decem-ber to May. This lengthy attack period could represent and important source of inoculum for susceptible cultures. This paper is the first report of L. taurica on Physalis viscosa not only in Argentina but worldwide. [ABSTRACT FROM AUTHOR]