''Didymella pinodes'' (syn. ''Mycosphaerella pinodes'') is a hemibiotrophic

fungal A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately from ...

plant pathogen Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomy ...

and the causal agent of ascochyta blight on pea plants. It is infective on several species such as '' Lathyrus sativus'', ''

Lupinus albus ''Lupinus albus'', commonly known as the white lupin or field lupine, is a member of the genus ''Lupinus'' in the family Fabaceae. It is a traditional pulse cultivated in the Mediterranean region. Description The white lupin is annual, more ...

'', ''Medicago spp.'', ''Trifolium spp.'', ''

Vicia sativa ''Vicia sativa'', known as the common vetch, garden vetch, tare or simply vetch, is a nitrogen-fixing leguminous plant in the family Fabaceae. It is likely native to North Africa, Western Asia and Europe, but is now naturalized in temperate and ...

'', and ''Vicia articulata'', and is thus defined as broadrange pathogen.

Symptoms

Symptoms include lesions on leaves, stem and pods of plants. The disease is difficult to distinguish from blight caused by '' Ascochyta pisi'', though ''D. pinodes'' is the more aggressive of the two pathogens.

Epidemiology

The disease cycle starts with dissemination of ascospores after which germination pycnidia rapidly develop. Pycnidiaspores quickly disperse by rain splashes are responsible for reinfection over short distances. Consequently, production of

pseudothecia An ascocarp, or ascoma (), is the fruiting body ( sporocarp) of an ascomycete phylum fungus. It consists of very tightly interwoven hyphae and millions of embedded asci, each of which typically contains four to eight ascospores. Ascocarps are mos ...

is initiated on senescent tissues. After rainfall, ascospores are released from the pseudothecia and disperse by wind over long distances.

Disease management

Useful levels of resistance remain to be determined and the application of fungicidal sprays was reported to be uneconomical. Furthermore, reports showed that insensitivity arises against chemicals such as strobilurons after continuous application. Thus, cultural management is the preliminary option to control the disease progress by minimizing inoculum carry over as well as survival of inoculum on crop residues and in soil, and avoiding initial infection from arial inoculum. Furthermore, burying of infected residues declines pathogen survival, however, crop rotation and tillage regimes have little influence on disease severity. Delayed sowing by 3–4 weeks reduces ascochyta blight severity by more than 50%, however, such measures are not feasible at higher latitudes, because of a shorter growing season.

Host resistance

So far, only incomplete resistance is available in the pea germplasm and quantitative differences are highly influenced by environmental conditions, plant age and physiological characteristics of plants. Tall cultivars with more erect growth suffer lower ''D. pinodes'' infection. Susceptibility increases with earliness and along with maturity of plants. Besides morphological traits, a proteomic and metabolomic study pinpointed molecular markers contributing to resistance. Disease severity of leaves was also reported to be lower when pea plants are associated with rhizobial bacteria that presumably provoke so called induced systemic resistance.

References

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