EVALUATION AND UTILIZATION OF TOMATO (LYCOPERSICON ESCULENTUM Mill.) GENOTYPES FOR IMPROVING DISEASE RESISTANCE TO EARLY BLIGHT

Abstract

Early blight disease of tomato caused by Alternaria solani Ellis and Martin
(Jones and Grout) is one of the major diseases of tomato. Recently this disease
has attracted much attention because of the considerable loss in yield inflicted
by it (Kaur et aI., 1993; Oatar and Mayee, 1981). This is a three phased disease
which causes damping off!collar rot, leaf blight and fruit rot symptoms. The
disease appears on foliage normally at fruiting stage of the crop as circular
to angular, dark brown to black spots with concentric rings. On the stem,
dark elongated spots, often target boarded, occur at any point, but are especially
injurious when engirdle the juncture of stem. Fruits are infected usually at
ripe stage, at the stem end. The pathogen remains viable on dry infected
leaves and seeds. Most of the commercial varieties grown presently in the
region are susceptible to early blight disease. The studies, were therefore, taken
up to screen the germplasm against this disease to identify resistant /tolerant
genotypes under field conditions dUring the year 1990, 1992 and 1993 when
the disease appeared in a severe form, which could be used either as commercial
varieties or as a source of resistance in the acceptable varieties.