Isolation, Incidence, and Virulence of Ascochyta Spp. Of Peas From the Soil

Ascochyta pinodella, cause of footrot, and Ascochyta pinodes, cause of blight, of peas were isolated from field soil by heating the soil to 100 C for 12–15 h followed by plating the soil on a medium containing rose bengal and chlortetracycline. A. pinodella was present in most soils where peas were growing and also in some soils where peas had not been grown for 1 to 5 years. Soil cultures of A. pinodella were weakly virulent but by host passage, re-isolated cultures produced typical symptoms of footrot on young plants. A. pinodes was isolated less frequently from soil; however, cultures were strongly virulent and inoculated plants showed typical disease symptoms in 5 days. Although infected seed has been considered to be the main source of inoculum, the frequent isolation of A. pinodes and A. pinodella from soil demands a re-appraisal of the epidemiology of this disease complex.