Disease Development Caused by Ascochyta rabiei on Chickpea Detached-Leaves in Petri Dishes

Abstract

A study using detached-leaves aimed to improve selection method. The improving method was done by scoring both disease symptom and lesion size. The research was begun by selecting agar concentration and dose of conidia that could distinguish response of very susceptible or resistant chickpea genotype. The result was used to determine disease severity (DS) and disease incident (DI) of eight genotypes that were previously tested in the field. Results of the tested agar concentration and dose of conidia showed that 1.5% and 2% agar were good to determine susceptible or resistant genotype; while 1 × 105 or 5 × 104 conidia dose was suitable for inoculation. The formula of DS (no. of leaflets in category × category value/Total no. of leaflets ×10) × 100, and DI (no. leaflets with pycnidial lesions + no. leaflets with necrotic lesions)/Total no. of leaflets × 100 successfully measured genotype response. The lesions development on detached leaves of the susceptible cultivar (Lasseter) began as circular, pale-colored areas, extending to the area covered by the drop of inoculum, then became light brown and finally dark brown. However, the response of resistant line (FLIP508) was restricted in area (and often confined to a tiny speck) surrounded by chlorosis or drying of the tissue.