Detection and Location of Seed‐Borne Inoculum of <i>Didymella bryoniae</i> and its Transmission in Seedlings of Cucumber and Pumpkin

Abstract

Abstract Of the 91 tested cucurbit seed samples from thirteen countries nine from four countries were found to be infected with Didymella bryoniae . The pathogen is located on and in the seed coat including the perisperm and in the tissue of the cotyledons. Primary seedling infection occurred on the radicle, hypoctyl and cotyledons. Infection of the radicle generally caused pre‐emergence tot while infection on the hypocotyl and cotyledons developed furthere inoculum for infection of the first true leaves and the stem. Experimentally, all the isolates of D. bryoniae could infect cucumber ( Cucumis sativus ), oriental melon ( Cucumis melo var. makuwa ), pumpkin ( Cucurbita pepo ) and watermelon ( Citrullus vulgaris ) at different growth stages; the susceptibility of cucumber and pumpkin was markedly influenced by previailing humid conditions.The blotter method was found more suitable for detection of seed‐borne infection than the agar plate method.