Comparison of the epidemiology of ascochyta blights on grain legumes

Abstract

Asochyta blights of grain legumes are caused by fungal pathogens in the genus Ascochyta. Different species infect the different legume species, and in pea three species including Phoma medicaginis var. pinodella have been implicated in ascochyta blight. The impact of the diseases varies between crops, countries, seasons and cropping systems, and yield loss data collected under welldefined conditions is scarce. However, ascochyta blights are considered major diseases in many areas where legumes are grown. Symptoms appear on all aerial parts of the plant, and lesions are similar for most of the species, except for M. pinodes and P. medicaginis var. pinodella. Infected seed, stubble and/or air-borne ascospores are major sources of primary inoculum. Their importance varies between species and also between regions. All Ascochyta spp. produce rain-splashed conidia during the cropping season which are responsible for the spread of the disease within the crop canopy. Only in pea are ascospores involved in secondary disease spread. Limited data suggests that Ascochyta spp. may be hemibiotrophs; however, toxins characteristic for necrotrophs have been isolated from some of the species. Modelling of ascochyta blights is still in the developmental stage and implementation of such models for disease forecasting is the exception.

Control of Leaf Spot Diseases on Ecotypes of Faba Bean (<i>Vicia faba</i> L.) Produced in the Andean Region of Bolivia

“…Reports from other countries agree with this, and indicate that the disease appears on the leaves, stems, pods and grains [22,27]. Given the environmental conditions of the Altiplano, the disease does not develop very quickly and is seen only on the pods and stem during the ripening stage; it is therefore something of a minor problem for this crop.…”

“…The present work shows that the leaf spot disease affecting faba beans in the study region is a complex of fungal diseases caused by hemibiotrophic and necrotrophic pathogens [10,22]. According to the criteria of Damsteegt [6], these diseases were categorized as new (Cladosporium sp.…”

“…The remaining diseases-Lepthosphaerulina and Ascochyta blightappear at low levels during ripening, probably depending on environmental conditions. Temperature and relative humidity are both key factors in the epidemiology of Ascochyta blight [22], which can be considered a minor disease in Bolivia.…”

Aggressiveness Changes in Populations of Didymella pinodes over Winter and Spring Pea Cropping Seasons

“…To address these questions, we analyzed the phenotypic and genotypic diversity in populations of an aggressive foliar pathogen of peas, Didymella pinodes, along the course of an epidemic. D. pinodes is a necrotrophic, polyphagous, polycyclic, homothallic fungus that causes ascochyta blight on winter and spring pea fields worldwide (26,27). This pathogen is known to present individuals differing widely in their abilities to cause disease on peas (28)(29)(30)(31)(32).…”

“…Whereas pycnidia are produced on both green and senescent plant organs, pseudothecia appear only on the senescent parts (33). This fungal pathogen has various ways of persisting in the environment and dispersing over more or less long distances (splashing, wind) (27,34,35). These features are more important for D. pinodes than for pathogens whose modes of reproduction are dissociated, since they help to increase population diversity and have an impact on pathogenicity.…”