Recurrent selection for maydis leaf blight resistance and grain yield improvement in maize.

Leaf blight of maize (Zea mays L.), caused by Bipolaris maydis (Nisik. and Miyake), is one of the major factors limiting maize production in the plain areas of Pakistan, particularly in the North West Frontier Province (NWFP). The objectives of this study were to estimate selection differential, expected and observed response to selection and heritability for maydis leaf blight resistance and grain yield and to determine progress from selection in a maize population. Two cycles of S, recurrent selection were conducted in broad based maize population, Sarhad White (SW). One hundred S, lines were compared with their respective original population (C0) as a check. The experimental material was evaluated under artificial epiphytotics during 2003 and 2004, at NWFP Agricultural University, Peshawar. Selection differentials, expected responses and heritability estimates were determined from the replicated S1 lines performance of the first cycle. The observed progress was estimated from the replicated S1 lines of the second cycle that were generated after recombination of selected S1 lines of the first cycle. Highly significant variations between the cycles were observed for MLB and grain yield. Moderate and high heritability estimates, desirable selection differentials and close correspondence of expected and observed response were manifested for MLB and grain yield. The positive percent deviation of inoculated from uninoculated trials in both cycles (C1 = 71% and C2 = 41%) for leaf blight indicated successful development of blight disease after artificial inoculation, while the negative percent deviation of inoculated form uninoculated trials (C1 = -21 and C2 = -6%) for grain yield indicated the impact of blight disease on grain yield. Blight disease was significantly reduced from 2.9 to 2.3, whereas, grain yield was significantly increased from 2041 kg ha(-1) cycle(-1) to 2527 kg ha(-1) cycle(-1) or 19% cycle(-1). This yield improvement in SW was probably the result of concomitant reduction in the blight disease severity by -26%. These findings suggested that S1 recurrent selection was quite effective in improving disease resistance and grain yield. Nevertheless, some additional cycles of selection may be required to further improving grain yield and resistance level to maydis leaf blight in SW maize population.