Genetics of resistance to early blight (Alternaria solani Sorauer) in tomato (Lycopersicon esculentum L.)

The genetic nature of early blight resistance in tomato was studied in three crosses at seedling and adult plant stages. A six generation mean analysis of the cross Arka Saurabh (susceptible) x IHR1939 (resistance) and its reciprocal cross revealed that the resistance to early blight was conferred by recessive polygenes at both seedling and adult plant stages. This polygenic early blight resistance revealed the importance of additive and additive x additive gene effects at seedling stage and higher magnitude of dominance and dominance x dominance gene effects at adult plant stage. Evaluation of parents, F-1, F-2 and backcross generations of IHR1816 (resistance) x IHR1939 (resistance) revealed that the early blight resistance genes in IHR1816 ( Lycopersicon esculentum NCEBR-1) and IHR1939 ( Lycopersicon pimpinellifolium L4394) are independent.