Effects of crop management patterns on coffee rust epidemics

The effects of crop management patterns on coffee rust epidemics, caused by Hemileia vastatrix , are not well documented despite large amounts of data acquired in the field on epidemics, and much modelling work done on this disease. One main reason for this gap between epidemiological knowledge and understanding for management resides in the lack of links between many studies and actual production situations in the field. Coffee rust epidemics are based on a seemingly simple infection cycle, but develop polycyclic epidemics in a season and polyetic epidemics over successive seasons. These higher-level processes involve a very large number of environmental variables and, as in any system involving a perennial crop, the physiology of the coffee crop and how it affects crop yield. Crop management is therefore expected to have large effects on coffee rust epidemics because of its immediate effect on the infection cycle, but also because of its cumulative effect on ongoing and successive epidemics. Quantitative examples taken from a survey conducted in Honduras illustrate how crop management, different combinations of shade, coffee tree density, fertilization and pruning may strongly influence coffee rust epidemics through effects on microclimate and plant physiology which, in turn, influence the life cycle of the fungus. We suggest there is a need for novel coffee rust management systems which fully integrate crop management patterns in order to manage the disease in a sustainable way.     

咖啡锈病流行的空间动态

对病害流行过程格局动态的分析结果表明,咖啡锈病的空间分布格局,不论是水平的还是垂直的方向,都随着病情的加重而由核心分布逐渐向均匀分布转化。严重度小于0.07时,病害中心最为明显;严重度达到0.3以后,病害中心消失。病害在垂直方向由下而上进行扩散。根据这些特征作出如下推论:咖啡锈病主要是以雨水为短距离传播媒介,雨季来临前喷药可获得较好的防治效果。防治咖啡锈病的策略,应该是控制病害中心,防止其扩散和蔓延;这种防治策略的实施,以掌握在严重度为0.07时最为理想。在严重度达0.3以前进行病情调查样株要多些,0.3以后可以适当减少,以节省人力和时间。     

云南咖啡锈菌小种鉴定

为明确云南咖啡锈菌小种类型,采用国际通用的 19 个咖啡锈菌生理小种鉴定寄主,利用人工接种鉴定的方法,对采自云南咖啡主产区 12 县（市）的 51 份咖啡锈菌进行鉴定,鉴定出 9 个小种,分别为 VIII（v2,3,5）、XXXIII（v5,7 or v5,7,9）、XXXIV（v2,5,7 or v2,5,7,9）、XXXVII（v2,5,6,7,9）、XLI（v2,5,8）、XLII（v2,5,7,8 or v2,5,7,8,9）、New race（v2,5,6,7）、New race（v1,2,5,7 or v1,2,5,7,9）、New race（v1,5,7 or v1,5,7,9）,这 9 个小种均为国内首次鉴定,其中小种 XXXIII、XXXIV、New race（v2,5,6,7）、New race（v1,5,7 or v1,5,7,9）、New race（v1,2,5,7 or v1,2,5,7,9）、XLI 和 XLII 均侵染 Catimor7963,小种 XXXVII 侵染 CatimorT5175。     

咖啡种质资源抗锈性初步鉴定

采用田间自然鉴定的方法，于2010～2012年在云南省瑞丽市对15个品种96份种质进行抗锈性鉴定和评价。研究结果表明：供试种质资源中，免疫型(I)26份，抗病型(R)6份，中抗型(MR)13份，中感型(MS)9份，感病型(S)43份；抗锈性强的种质资源中，卡蒂姆的抗锈性明显强于其他品种，免疫型材料占该类型抗锈材料的80%。     

A new source of resistance against coffee leaf rust from New-Caledonian natural interspecific hybrids between Coffea arabica and Coffea canephora

The development of cultivars resistant to coffee leaf rust caused by the fungal pathogen Hemileia vastatrix is a priority in coffee breeding. However, only very few descendants of interspecific hybrids between Coffea arabica and diploid relative species have been used as resistance source. Identification of new sources of resistance appeared therefore particularly worthwhile. Hybrid plants derived from interspecific hybridization between C. arabica and Coffea canephora and found in neo‐natural coffee tree populations of New Caledonia were therefore investigated. Amplified Fragment Length Polymorphism and microsatellites amplification were used to evaluate the genetic diversity of 14 hybrid plants, and rust resistance was evaluated by inoculation with a panel of rust races representing a large variability in virulence. An important genetic diversity was characterized in hybrid plants originating from introgressions into C. arabica from various C. canephora progenitors. On the 14 plants tested for leaf rust resistance, eight appeared resistant to all races investigated. Such plant material should represent a highly valuable resource for C. arabica breeding against coffee leaf rust.     

Coffee rust genome measured using flow cytometry: does size matter?

The genome size of most rust species is unknown due, in part, to technical constraints, especially the difficulty in accessing spores to extract the nuclei for cytometry. Using the urediniospores of coffee rust, Hemileia vastatrix, an improved methodology involving flow cytometry was developed for accurate measurement of the nuclear genome size. The results revealed that the genome of this primitive rust fungus is unusually large – measuring 1C‐value = 0·75 pg (733·5 Mb) – significantly bigger than other species quantified thus far in the more advanced rust lineages. The evolutionary consequences and the potential ecological constraints of this large genome size are discussed in relation to the epidemiology of coffee rust.     

咖啡驼孢锈菌 ITS 序列特征及系统发育关系

为了了解咖啡驼孢锈菌 ITS 序列特征及系统发育关系,本研究对来自中国咖啡栽培区的咖啡驼孢锈菌 ITS 序 列进行了克隆。将克隆序列与来自不同咖啡种植区的咖啡驼孢锈菌菌株序列多样性进行了比较,并于 NCBI 数据库中 下载其他锈菌菌株 ITS 序列进行系统发育关系研究。结果表明,来自中国咖啡栽培区的咖啡驼孢锈菌 ITS 序列全长 950 bp。 其中 ITS1 长为 224 bp,GC 含量介于 30.36%~31.25%之间;5.8S 长为 153 bp, GC 含量为 37.25%;ITS2 长 483~485 bp, GC 含量介于 24.12%~25.05%。来自不同咖啡种植区咖啡驼孢锈菌 ITS 核苷酸序列多态性虽然存在一定差异,但是其多 样性十分低且不存在明显的区域分化。在系统发育关系方面,咖啡驼孢锈菌与其他锈菌 ITS 序列差异明显,能独立聚 类成一个分支。     

Genetic analysis of partial resistance to coffee leaf rust ( Hemileia vastatrix Berk & Br.) introgressed into the cultivated Coffea arabica L. from the diploid C. canephora species

The objective of this study was to identify polymorphic molecular markers associated with partial resistance to coffee leaf rust, Hemileia vastarix. A segregating F ₂ population derived from a cross between the susceptible Coffea arabica cv. Caturra and a C. canephora-introgressed Arabica line exhibiting high partial resistance was analyzed. Rust resistance measured as rust incidence (RI) and defoliation (DEF) was evaluated in field conditions in three consecutive years (2003–2005). During the 2003 season, which was characterized by favorable conditions for a rust epidemic, the F ₂ plants exhibited different levels of resistance ranging from very susceptible (50.1% for DEF and 49.5% for RI) to highly partial resistance (9.1% for DEF and 3.7% for RI). Molecular analysis enabled identification of seven polymorphic markers (5 AFLP and 2 SSR) exhibiting significant association with partial resistance. Coexistence of resistance homozygous alleles (RR) at codominant SSR loci was correlated with high resistance. This study is the first attempt to develop PCR-based sequence specific markers linked to partial rust resistance in coffee.     

Modeling spatial variability and pattern of rust and brown eye spot in coffee agroecosystem

The advent of Precision Agriculture has made possible the analysis of complex spatial patterns of plant disease epidemiology considering statements of integrated disease management. The objective of this work was to use geostatistics, statistics and geographical information systems to characterize the structure and magnitude of spatial dependency of rust (Hemileia vastatrix) and brown eye spot (Cercospora coffeicola) incidence and severity in coffee agroecosystem cultivated with Catuai Vermelho IAC-99 (Coffea arabica L.). Evaluations of incidence and severity of rust and brown eye spot were accomplished at 67 georeferenced points arranged in 6.6202 ha of coffee crop, in the years of 2005, 2006 and 2007. Exponential models of covariance enabled the characterization of the magnitude and structure of rust and brown eye spot spatial variability in the evaluated dates. Ordinary block kriging presented satisfactory performance to map rust and brown eye spot outbreaks based on kriging error coefficients. Kriged maps enabled the visualization of intensity of rust and brown eye spot in each evaluation date. Assessments of incidence and severity presented highly statistical correlation based on linear regression models, also confirmed by the spatial variability of kriging maps. Kriging maps of rust and brown eye spot enabled to observe that intensity of disease was dispersed in foci patterns along the coffee plantation, indicating that the current strategy of disease control based in total area may be replaced by site specific disease management, with less environmental impact and sustainability of coffee crop, according to statements of integrated disease management and precision agriculture.     

Race-specificity and inheritance of incomplete resistance to coffee leaf rust in some Icatu coffee progenies and derivatives of Hibrido de Timor

Summary Selfed and cross-pollinated progenies of Icatu coffee plants and derivatives of Híbrido de Timor, with susceptibility or moderate resistance to coffee rust in the field, were tested with Hemileia vastatrix race II and isolate 2 (Is. 2) in the greenhouse or laboratory. Progenies from plants with a susceptible reaction type in the field (scores 8 and 9) all showed homogeneous levels of susceptibility similar to that of the control cultivars Mundo Novo and Catuaí of Coffea arabica. Variation for incomplete resistance was mainly expressed by low or heterogeneous reaction types and also by longer latency periods. Incomplete resistance to race II of some Icatu and Catimor plants, which is overcome by Is. 2, appeared to depend on a partially dominant gene. The expression of this gene may vary also according to the genetic background and some residual resistance to Is. 2 was observed. A few derivatives of Híbrido de Timor were more resistant to Is. 2 than to race II, suggesting the presence of a resistant factor to Is. 2 in this germplasm. Segregation in progenies from other plants with incomplete resistance to race II suggested presence of one or a few genes only, which in homozygous condition or in combination seem to confer near-complete or complete resistance. The results suggest that selection for incomplete resistance, expressed by intermediate reaction types, in Icatu and derivatives of Híbrido de Timor may not provide durable resistance to coffee rust. On the other hand, due to apparent additive gene action, phenotypic selection of plants with a highly resistant reaction type could facilitate the accumulation of several resistance alleles in one genotype, which could provide an efficient barrier against new race formation of the pathogen.