Complex Fungal Rotting of Pea Seeds

Summary Poor stands of peas due to fungal rotting were observed in field experimental plots in widely separated pea‐growing districts. The rotting was not due to seed‐borne Ascochyta pisi or Mycosphaerella pinodes which were apparently absent from the seed. Isolations from surface sterilized cotyledons of several varieties of peas grown in sterilized and unsterilized soil showed an abundance of common moulds and several pathogenic fungi, namely: a Fusarium of the section Roseum, Fusarium culmorum and Botrytis cinerea. Isolations from surface sterilized rotting stems from five experimental centres at harvest time indicated the presence of a great variety of fungi including a number of species of Fusarium. Many of these, including all the common moulds such as Penicillium, were non‐pathogenic to the cotyledons. Fusarium avenaceum was found to be highly pathogenic to the cotyledons; F. solani var. Martii showed some signs of causing rotting; Botrytis cinerea was highly pathogenic. Several non‐pathogenic species of Fusarium were obtained. Tests with numerous stock cultures show high pathogenicity of the following fungi to pea cotyledons: Botrytis cinerea from Lactuca, Rosa and elsewhere. Fusarium avenaceum from Triticum. Fusarium culmorum from Triticum, Dianthus and Callistephus. Fusarium species from Vicia faba and Tulipa. Helminthosporium sativum from Triticum. Ophiobolus heterostrophus from Oryza. Sclerotinia species from Lactuca. Fusarium Graminearum from Triticum. It is suggested that loss of stand in pea crops due to rotting of the cotyledons by these and other fungi is probably more important than diseases caused by Ascochyta and Mycosphaerella and foot‐rots in the late stage.