PJB-2018-744
PHYSIOLOGICAL AND GRAIN QUALITY CHARACTERIZATION OF INDIGENOUS AND EXOTIC MAIZE (ZEA MAYS L.) HYBRIDS UNDER HEAT STRESS
Muhammad Irfan Yousaf
Abstract
Heat stress has become one of the major constraints in maize production worldwide. Pakistan is one of the countries in South Asia most affected by heat stress. The present study was designed to determine the heat stress-related characteristics of indigenous and exotic maize hybrids on the basis of morpho-physiological and grain quality traits. The study was done at Maize and Millets Research Institute, Yusafwala-Sahiwal during spring 2017. Hybrids were sown under two heat regimes: (i) normal sowing and (ii) sowing under heat stress (late sowing). Throughout the growth period, the late sown crop experienced 41.0 °C average daily maximum temperature, versus 36.7 °C for the normal sown crop. Hybrids differed significantly (P<0.05) in grain yield and related traits under both conditions. Correlation analysis showed that grain yield had a positive relationship with net photosynthetic rate (r = 0.393), days to 50% tasseling (r = 0.437) and days to 50% silking (r = 0.429), and a negative association with ear leaf angle (r = −0.420) under heat stress. Percentage grain protein and percentage grain oil were reduced under heat stress conditions regardless of the origin of the hybrid. Cluster analysis categorized maize hybrids into three clusters on the basis of their mean performance under heat stress conditions. It further showed that indigenous hybrids (cluster 3), especially KSC-9663, YH-5519, YH-5482, YH-1898 and YH-5507, were more productive and heat tolerant than exotic hybrids i.e. MV-633, MV-600-4, Maxima, SHG-43 and MV-600-2 (cluster 1). Principal component analysis (PCA) and biplot graphs showed that the first five PCs contributed 72% of the total variability among genotypes, and that the main sources of variation were days to 50% tasseling and silking, plant height, percentage of protein and oil, stomatal conductance and photosynthesis rate.
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