Assessing potential of resistance source for the enhancement of resistance to Maydis leaf blight (Bipolaris maydis) in maize (Zea mays L.)

Abstract

Maydis leaf blight caused by Bipolaris maydis (Cochliobolus heterostrophus) presently has become a major disease of maize, causing considerable losses in productivity. Out of three races C, 0 and T, race '0' is prevalent in maize tract of India. During last three decades, though considerable breeding research has been carried out to improve the productivity, progress with respect to resistance breeding has been lagging behind with respect to Maydis leaf blight. Work of all these years have led to identification of two resistant source inbred lines namely, CM 104 and CM 105. However, incorporation of maydis resistance from these two sources have been rather discouraging. These two sources though possessed high per se resistance, their capacity to transmit their resistant gene have not been very fruitful under different background germplasm. In order to understand the reason behind such behaviour the genetic study based on combining ability was undertaken, using these and two other inbred lines namely CM 119 (susceptible) and CM 206 (moderately resistant). Using four inbred lines of contrasting resistance level in a diallel making system, gene action studies were conducted. Resistance to Maydis leaf blight was found to be predominantly under the influence of additive gene action along with significant contributions from '8dditive x additive epistasis. However, significant role of dominant gelle action along with epistasis could not be ruled out entirely.