Salim Shah S, Khalil Iftikhar Hussain, Iqbal Muhammad
Department of Plant Breeding and Genetics, NWFP Agricultural University, Peshawar, Pakistan.
Pak J Biol Sci. 2007 Oct 15;10(20):3632-7. doi: 10.3923/pjbs.2007.3632.3637.
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.
玉米大斑病由玉米离蠕孢菌（Nisik.和Miyake）引起，是限制巴基斯坦平原地区，特别是西北边境省（NWFP）玉米产量的主要因素之一。本研究的目的是估计选择差、对玉米大斑病抗性和籽粒产量的预期和观察到的选择响应以及遗传力，并确定玉米群体选择的进展。在基础广泛的玉米群体Sarhad White（SW）中进行了两个轮回的S₁轮回选择。将100个S₁株系与其各自的原始群体（C₀）进行比较作为对照。2003年和2004年在白沙瓦的NWFP农业大学，在人工发病条件下对试验材料进行了评价。根据第一个轮回的重复S₁株系表现确定选择差、预期响应和遗传力估计值。观察到的进展是根据第一个轮回选择的S₁株系重组后产生的第二个轮回的重复S₁株系来估计的。在大斑病和籽粒产量方面，两个轮回之间观察到极显著差异。大斑病和籽粒产量表现出中等和高遗传力估计值、理想的选择差以及预期和观察到的响应的密切对应。两个轮回中接种试验与未接种试验相比，大斑病的正偏差百分比（C₁ = 71%，C₂ = 41%）表明人工接种后成功诱发了大斑病，而籽粒产量接种试验与未接种试验相比的负偏差百分比（C₁ = -21，C₂ = -6%）表明大斑病对籽粒产量的影响。大斑病病情显著从2.9降至2.3，而籽粒产量显著从2041 kg·ha⁻¹·轮回⁻¹增加到2527 kg·ha⁻¹·轮回⁻¹或19%·轮回⁻¹。SW群体中产量的提高可能是大斑病病情严重程度同时降低26%的结果。这些发现表明，S₁轮回选择在提高抗病性和籽粒产量方面相当有效。然而，可能需要额外的几个轮回选择来进一步提高SW玉米群体的籽粒产量和对玉米大斑病的抗性水平。
