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The use of resistance inducers is a promising development in the management of plant diseases, owing to their ability to control a broad spectrum of pathogens and improve the efficacy of fungicides. This study evaluates different sources of phosphonates (potassium, manganese, copper), a formulation prepared from the by‐products of the coffee industry (Greenforce CuCa), as well as the effects of their application, alone or in association with fungicide, in the management of two important coffee fungal diseases in Brazil: leaf rust and brown eye spot, caused by Hemileia vastatrix and Cercospora coffeicola, respectively. The effect of these products on defoliation, productivity and chemical composition of coffee beans (content of trigonelline, chlorogenic acid, caffeine and total soluble solids) was evaluated. Among all the alternative products tested individually, potassium phosphonate (P2O5—33.6% + K2O—29%) stood out, particularly for rust control, which was similar to the results of fungicide treatments. Treatments with fungicide, Greenforce CuCa and cuprous oxide, individually, caused less plant defoliation. Regarding the chemical composition of the coffee beans, the manganese phosphonate treatment showed the highest values for trigonelline, chlorogenic acid, caffeine and total soluble solid content. The results of this study show that resistance inducers can be useful in disease management, may come to eventually replace traditional fungicides and can also contribute to the beverage quality. [ABSTRACT FROM AUTHOR]

Brazil is the major coffee producer in the world, with 2 million hectares cropped, with 75% of this area with Coffea arabica and 25% with Coffea canephora. Coffee leaf rust (CLR) is one of the main diseases that cause yield losses by reducing healthy leaf area. As CLR is highly influenced by weather conditions, this study aimed to determine the best linearization model to estimate the CLR apparent infection rate, to correlate CLR infection rates with weather variables, and to develop and assess the performance of weather-based infection rate models to be used as a disease warning system. The CLR epidemic was analyzed for 88 site-seasons, while progress curves were assessed by linear, monomolecular, logistic, Gompertz, and exponential linearization models for apparent infection rate determination. Correlations between CLR infection rates and weather variables were conducted at different periods. From these correlations, multiple linear regressions were developed to estimate CLR infection rates, using the most weather-correlated variables. The Gompertz growth model had the best fit with CLR progress curves. Minimum temperature and relative humidity were the weather variables most correlated to infection rate and, therefore, chosen to compose a CLR forecast system. Among the models developed, the one for the condition of high coffee yield at a narrow row spacing was the best, with only 9.4% of false negative occurrences for all the months assessed. [ABSTRACT FROM AUTHOR]

IAC 125 RN was derived from a cross between the coffee cultivar Villa Sarchí and the Hibrido de Timor CIFC 832/2. The coffee trees are short and resistant to races 1 and 2 of the nematode Meloidogyne exigua and to all races of coffee rust, Hemileia vastatrix, present in Brazil. Brazil. [ABSTRACT FROM AUTHOR]

The Pucciniomycete fungus Hemileia vastatrix causes leaf rust on coffee trees. The pathogen is responsible for considerable yield losses in susceptible coffee cultivars if appropriate management strategies are not implemented. Rapid spread and epidemics of rust fungi are usually associated with the emergence of new races of the pathogen that overcome resistance or with the emergence of more aggressive populations of the pathogen. In Brazil, coffee production is dominated by susceptible cultivars of Coffea arabica and Coffea canephora. We assessed aggressiveness in 46 populations of H. vastatrix from Minas Gerais and Espírito Santo, two of the most important coffee-producing states in Brazil. We observed a significant difference in the incubation period between the populations from Minas Gerais and Espírito Santo when 183 single-pustule isolates were inoculated onto Catuaí Vermelho IAC 44, a susceptible C. arabica cultivar. Variation in aggressiveness components was observed between and within localities. Isolates with longer incubation periods also tended to have longer latent periods, although there was only a low correlation between these two aggressiveness components ( r2 = 0.34, P = 2.2 × 10−16). Low-sporulating isolates also had significantly longer incubation and latent periods. The H. vastatrix population from Minas Gerais and Espírito Santo is structured by the formation of groups of individuals with differential level of aggressiveness. Our results indicate that the variation in aggressiveness of the Brazilian H. vastatrix population may be associated with the geographic coffee-producing areas. [ABSTRACT FROM AUTHOR]

Coffee leaf rust is the most limiting disease for coffee cultivation in Brazil. Despite its importance, relatively little is known about the genetic diversity of Hemileia vastatrix, the rust causal agent. In this work, the DNA from 112 monopustule isolates from different geographic locations and coffee genotypes were analysed by amplified fragment length polymorphisms ( AFLP). The objectives were to assess the influence of the host and geographic origin on the diversity and population differentiation in H. vastatrix. The fungal population showed a low level of genotypic diversity. Gene diversity ( h) was 0·027 and the hypothesis of random mating in the total population was rejected, but evidence for recombination was found for two subpopulations (São Paulo and Paraná). The analysis of molecular variance revealed that 90% of the genetic distribution of the pathogen occurs among isolates within the subpopulation (states or host of origin). There was no correlation between geographic and genetic distance ( r = −0·024, P = 0·74), which together with the high number of migrants and the low degree of differentiation in populations of H. vastatrix, is consistent with the fact that the inoculum is probably easily dispersed by wind over long distances, allowing dispersal of the pathogen among coffee growing areas in Brazil. Therefore, it is difficult to predict the durability of resistant sources to coffee rust. The recommendation for the breeding programmes is thus to incorporate multigenic resistance as a control strategy. [ABSTRACT FROM AUTHOR]

Abstract: Geoinformation techniques were applied to develop predictive models to study the areas of risk to soybean rust (Phakopsora pachyrhizi Sydow) in soybean (Glycine max L.); coffee leaf rust (Hemileia vastatrix Berk & Br) in coffee; and black Sigatoka (Mycosphaerella fijiensis var. difformis) in banana, considering Brazil''s climatic characterization and the distribution of soybean, coffee and banana crops. Temperature and rainfall data were obtained for the period from 1950 to 2000, for which observational data are available, and of simulations for 2020, 2050 and 2080 using the SRES A2 climate change scenarios. Using principal components analysis, a single variable was generated based on 57 variables, in order to determine an index explaining 87%, 88% and 90% of the variability of soybean, coffee and banana crops, respectively, in municipal districts across Brazil. The climatic model was used to generate the zoning of the three plant diseases, using temperature and leaf wetness as input. Areas of favorability for the diseases were plotted against the main coffee, soybean and banana growing areas in Brazil. This methodology enabled the visualization of the changes in areas favorable for epidemics under possible future scenarios of climate change. [Copyright &y& Elsevier]

The coffee leaf miner, Leucoptera coffeella, is the most important pest of Coffea arabica plantations in Brazil, and all cultivars are susceptible to the insect. However, distinct reactions have been observed in other species, such as C. congensis and C. canephora. In this work, the occurrence of antixenotic response was surveyed in individuals of Coffea species, selected for resistance to the leaf miner at both field and laboratory conditions. Tests performed on young plants from C. arabica cultivars Icatu Precoce IAC 3282, Mundo Novo IAC 515-20, Tupi IAC 1669-33 and Catuaí Amarelo IAC 62 demonstrated that these were preferred for oviposition when pooled with seedlings from C. canephora cv. Apoatã IAC 2258. Apoatã was also preferred over C. racemosa for oviposition. Similar results were observed in tests using detached leaves, and higher amount of eggs was counted in the cv Obatã IAC 1669-20 and Catuaí Vermelho IAC 81, and lower oviposition frequency was observed in C. canephora cv. Guarini IAC 1598. C. congensis showed an oviposition frequency between C. arabica and C. canephora. Also, the results suggest that the frequency of oviposition is co-related with the plant resistance level, during larvae infection. [ABSTRACT FROM AUTHOR]

The objective of this study was to assess whether defence responses in coffee ( Coffea arabica) were linked to a specific developmental stage of the rust fungus Hemileia vastatrix. Histological observations in compatible and incompatible high-yielding Brazilian coffee cultivars showed that the fungus produced ‘pioneer’ haustoria in adjacent and subsidiary stomatal cells soon after entering the stomata, followed by later developed ‘secondary haustoria’ which invade mesophyll cells. In the incompatible interaction between Race II and cv. Tupi, a strong and transient H2O2 generation at infection sites was detected at 39 h post inoculation (hpi) during secondary haustoria formation. In addition, clear-cut differences in defence gene expression between compatible and incompatible interactions were only observed during the secondary haustoria formation. Transcripts of the pathogenesis-related (PR) genes CaPR1b and CaPR10 accumulated to maximal levels at 39 hpi (38- and 86-fold, respectively) in the incompatible interaction, but stayed at low levels in the compatible interaction. In contrast, the CaWRKY1 gene and the CaRLK gene were only induced in the susceptible cultivar. These results indicated that the specific resistance of cv. Tupi was expressed after differentiation of the H. vastatrix secondary haustoria. Analysis showed no evidence of specific recognition of coffee rust at the pioneer haustoria stage, suggesting that haustoria components are not recognized by, or not secreted into, the subsidiary and adjacent cells of the stomata. Additionally, the present study provides new insights into the colonization process of the coffee rust fungus. [ABSTRACT FROM AUTHOR]

Despite the importance of coffee leaf rust (Hemileia vastatrix), population studies of the pathogen are mostly focussed on identification of physiological races and there is no information on the genetic diversity and structure of populations of H. vastatrixin Brazil. In this study, 120 isolates of H. vastatrixwere collected from organic and conventional coffee production systems from two coffee-producing regions in the state of Minas Gerais, Brazil. To test the hypothesis that H. vastatrixpopulations differ between conventional and organic plantations, random amplified polymorphic DNA markers were used to determine the genetic diversity and structure of the populations of H. vastatrixsampled from 12 fields within the two regions. Across all loci, high values of genetic diversity (h= 0.28) and 92 haplotypes were detected. Based on the cluster analysis and θ test, there was no association between origin of the isolate with either cropping system or region. In addition, considering the AMOVA analysis, most of the genetic variance occurred within populations (≈80%). There is evidence of random mating in the population of H. vastatrixin Brazil, which can partially explain the high genetic variability of the pathogen. Therefore, we conclude that genetic diversity in H. vastatrixpopulations in Minas Gerais was high and no clear clustering of isolates was detected that allowed establishment of correlation of pathogen diversity with geographical origin or coffee cropping system. [ABSTRACT FROM AUTHOR]

In this review of coffee leaf rust (CLR) in Brazil, we report: (i) the historical introduction of CLR in Brazil and the first control measures; (ii) favorable environmental conditions and times of year for the disease; (iii) breeding methods and strategies used for developing CLR-resistant cultivars; (iv) the levels, sources, and types of CLR resistance; (v) the development of Brazilian resistant cultivars; and (vi) chemical and cultural control methods. Most plantations are cultivated with susceptible cultivars, such as those of the Catuaí and Mundo Novo groups. Brazilian research institutes have developed dozens of cultivars with different levels of resistance, and significantly increased the planting of new resistant cultivars. The main sources of CLR resistance are genotypes from Híbrido de Timor, Icatu, BA series carrying the SH3 gene, and Ethiopian wild coffees. High CLR resistance is still observed in Sarchimor and SH3-carrying genotypes. Intermediate CLR resistance is observed in Ethiopian wild coffees and in Sarchimor and Icatu derivatives, where qualitative resistance has been supplanted by races of Hemileia vastatrix. Contact, mesostemic, and systemic fungicides are used for chemical control in Brazil. CLR incidence in Brazil begins to increase after the rainy season onset in November, reaches a peak in June, and remains high until August. Thus, chemical control is typically applied from December to April. [ABSTRACT FROM AUTHOR]

Coffee leaf rust (CLR), caused by Hemileia vastatrix , is a major disease in coffee fields worldwide. In Brazil, fungicides are extensively used for disease control; nevertheless, disease outbreaks can occur if applications are not properly timed. In this study, we evaluated a CLR forecast system (FS) for scheduling fungicide foliar sprays in seven field trials (conducted in five different sites). Two trials were carried out in 2015–16 season and five in the 2016–17 season. The CLR-FS uses the cumulative infection rate based on daily infection rates, accumulated since the beginning of each season, considering minimum air temperature and average relative humidity. The treatments were based on soil drench followed by foliar sprays: T1 - control; T2 - two or three sprays according to the regional calendar of each site; T3 - FS with more conservative thresholds (MC) with three sprays; T4 - FS with less conservative thresholds (LC) with three sprays; T5 - FS LC with two sprays; T6 - same as T3, without soil drench. We assessed CLR incidence monthly and estimated the area under the disease progress curve (AUDPC) for comparison of treatments. In six experiments, the sprays adjusted by the FS showed lower AUDPC than T2. However, all treatments controlled CLR appropriately in seven experiments. In four experiments, treatment T5, with only two foliar sprays, was as efficient as the other treatments with three applications. The CLR-FS used in a less conservative threshold could improve chemical control of CLR; however, regional calibrations may be necessary. • Thresholds of a forecast system for adjusting fungicide sprays timing were assessed. • Two sprays scheduled by the forecast system presented good control performance. • Foliar sprays play an important role in CLR control than soil drench does. • All treatments were ineffective in areas surrounded by severely diseased plants. • Knowledge on how the weather is driving CLR improves control efficiency. [ABSTRACT FROM AUTHOR]

The El Niño Southern Oscillation (ENSO) is an oceanic-atmospheric phenomenon influencing worldwide weather and climate. Its occurrence is determined by the sea surface temperature (SST) anomaly of the 3.4 Niño region in the Pacific Ocean (5°N-5°S, 120°-170°W). El Niño (EN), Neutral (NT), and La Niña (LN) are the three possible phases of ENSO, respectively, for warm, normal, and cold SST anomaly. As in other regions around the world, weather in Brazil is influenced by ENSO phases. The country is the major coffee producer in the world, and production is strongly influenced by weather conditions, which affect plant yield, harvest quality, and interactions with pests and diseases. Coffee leaf rust (CLR), caused by the fungus Hemileia vastatrix , is a major cause of coffee yield and quality losses in Brazil, and requires fungicide spray applications every season. Because CLR is highly influenced by weather conditions, it is possible to use weather variables to simulate its progress during the cropping cycle. Therefore, the aims of this study were to estimate CLR infection rate based on a validated empirical model, which has daily minimum air temperature and relative humidity as inputs, and to assess the extent of ENSO influence on the annual risk of this disease at 45 sites in Brazil. Cumulative infection rates (CIR) were estimated daily from October to June of each growing season and location, based on the prevailing ENSO phase. Differences between the extreme phases (EN-LN) were assessed by the Two-One-Sided-Tests (TOST) method. Analysis of data from eight sites, located mainly in Paraná State, provided evidence of CIR differences between EN and LN phases (G1). Evidence of no difference of CIR between EN and LN was found in 18 sites (G2), whereas 19 sites showed no evidence of differences (G3) due to relatively large variation of CIR within the same ENSO phase. The G1 sites are located mostly in Southern Brazil, where ENSO exerts a well-defined influence on rainfall regime. In contrast, the G2 sites are mainly in Minas Gerais State, which is characterized as a transition region for ENSO influence on rainfall. The G3 sites are located between the northern region of Minas Gerais State and southern region of Bahia State, which is characterized by a subhumid climate that is usually very dry during winter, and where rainfall can vary up to 300% from one year to another, influencing relative humidity and resulting in a high CIR variability. Therefore, ENSO had a well-defined influence on CIR only in Paraná State, a region with minor importance for coffee production in Brazil. No ENSO influence was found in more northerly zones where the majority of Brazilian coffee is produced. This is the first evidence of ENSO-linked regional impact on the risk of coffee rust.