Inter- and intranational spread of ascochyta pathogens of chickpea, faba bean, and lentil

Ascochyta blights of chickpea, faba bean, and lentil are caused by Ascochyta rabiei, A. fabae, and A. fabae f. sp. lentis, respectively, all of which are important seedborne pathogens. Infected seed is important in the long-distance spread and survival of these pathogens. In the last 20-25 years, there has been a steady increase in the exchange of germplasm of cool season food legumes between countries. Seed transmission has been responsible for the introduction of the ascochyta blight pathogens of chickpea, faba bean, and lentil into, and for dissemination within, many countries worldwide. The teleomorphic (sexual) states of the blight pathogens of chickpea, faba bean, and lentil belong to the genus Didymella. These fungi are heterothallic, requiring the pairing of two compatible mating types for successful sexual reproduction. Movement of infected seed of these three crops not only leads to the introduction of virulent pathotypes, but may lead to the distribution of compatible mating types, thus allowing the development of the teleomorph in nature. Storage of chickpea, faba bean, and lentil seed at temperatures of 4 degrees to -18 degrees C in germplasm repositories not only prolongs the longevity of the seed but also of the associated seedborne ascochyta pathogens.