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Differences Between Ascospores and Conidia of Didymella rabiei in Spore Germination and Infection of Chickpea

December 2007 , Volume 97 , Number  12
Pages  1,600 - 1,607

Antonio Trapero-Casas and Walter J. Kaiser

First author: Departamento de Agronomía, ETSIAM, Universidad de Córdoba, Apartado 3048, 14080-Córdoba, Spain; and second author: 3394 Chickory Way, Boise, ID 83706.

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Accepted for publication 2 July 2007.

Studies were performed to compare the germination and infection of ascospores and conidia of Didymella rabiei under different temperature and moisture conditions. Germination of ascospores and conidia on cover glasses coated with water agar began after 2 h, with maximum germination (>95%) occurring in 6 h at 20°C. No germination occurred at 0 and 35°C. Ascospores germinated more rapidly than conidia at all temperatures. Germination declined rapidly as the water potential varied from 0 to --4 MPa, although some germination occurred at --6 MPa at 20 and 25°C. Ascospores germinated over a wider range of water potentials than conidia and their germ tubes were longer than those of conidia at most water potentials and temperatures. The optimum temperature for infection and disease development by both ascospores and conidia was around 20°C. Disease severity was higher when ascospores were discharged directly onto plant surfaces from naturally infested chickpea debris compared with aqueous suspensions of ascospores and conidia sprayed onto plants Disease severity increased as the length of the wetness period increased. When dry periods of 6 to 48 h occurred immediately after inoculation, disease severity decreased, except for the shorter periods which had the opposite effect. Disease severity was higher with ascospore inoculum when no dry periods occurred after inoculation.

Additional keywords:Ascochyta blight, Cicer arietinum.

© 2007 The American Phytopathological Society