Morpho-physiological Studies, Management and Screening of Tomato Germplasm against Alternaria solani, the Causal Agent of Tomato Early Blight

Early blight (Alternaria solani) is a potential disease of tomato that reduces its production globally both in conventional and tunnel cultivations. Due to variability in pathogenic isolates, prolonged active disease cycle phase and broad host range early blight is very difficult to manage. A. solani isolate collected from tunnel grown under vegetable area, Bahauddin Zakariya University, Multan was subjected to different temperature range, pH levels, light intensity and growth media (in vitro). The results indicated that A. solani grew the maximum at 25 degrees C (7.50 cm) on PDA medium at 6.5 pH (8.34 cm) under continuous light condition (9.00 cm). On PDA medium the pigmentation varied from creamy yellow, brown black to olivacious brown while on HLEA medium it was light brown. Varietal screening of six tomato varieties was carried out against early blight disease. No variety was found resistant. Concerning severity, out of six tomato varieties Roma showed maximum susceptibility (70.50%) while in Nagina it was least (29.38%). Efficacy of three fungicides (Topsin M, Bavistin and Ridomil Gold MZ) at 1 g/L, 2 g/L and 3 g/L concentration and two bio-agents (Trichoderma harzianum and T. viridae) was evaluated against A. solani in vitro and under tunnel cultivation. In in vitro assay Ridomil Gold MZ inhibited A. solani (47.06%) at 2 g/L, while at 3 g/L concentration Topsin M was more effective (64.71%) as compared to control. Comparing both bioagents inhibition percentage (67.78%) was recorded in T. harzianum whereas T. viridae showed less inhibition (59.63%). Under tunnel cultivation, early blight of tomato was significantly reduced by foliar applications of Topsin M and T. harzianium at 3 g/L and 10(8) conidia/mL concentration, respectively comparing with untreated plants. In the light of present study farmers could be suggested the practice of resistance source, combination of management practices and avoidance of environmental conditions favoring the pathogen, thus result in significant production of tomato. (C) 2015 Friends Science Publishers