Generation mean analysis of Turcicum leaf blight resistance in maize

Turcicum leaf blight (TLB) caused by Exserohilum turcicum is an important disease of maize in India. Generation means analysis was undertaken to analyze the genetic basis of resistance to TLB, using parents, F₁, F₂, BCP₁ and BCP₂ generations of four different cross combinations of TLB resistant and TLB susceptible maize genotypes (Cross 1: CM138 x NAI147; Cross 2: CM139 x NAI147; Cross 3: CM139 x SKV18; Cross 4: CM139 x SKV21). Of these four, the first three were evaluated under artificial inoculation at UAS-ARS, Naganahalli (Karnataka) while the last was evaluated at VPKAS Farm at Hawalbagh (Uttarakhand) during Kharif-2008. Statistical analyses of the data, includes scaling test, joint scaling test and goodness-of-fit of generation means. Different models failed to fit the data for Cross 1 indicating presence of complex non-allelic interactions. Additive, additive x additive, additive x dominance and dominance x dominance genetic effects were important in the Cross 2. A model with additive, dominance, additive x additive, dominance x dominance effects best explained the genetic effects in Cross 3. Additive, additive x dominance and dominance x dominance effects were most important for expression of TLB in the Cross 4 at Hawalbagh. Thus, the analysis revealed that the nature of inheritance of TLB resistance could be population-specific. Although various types of gene effects were observed, the general tendency was predominance of additive genetic component, indicating that specific breeding procedures like recurrent selection could aid in improving TLB resistance.