Correlation of photothermal quotient with spring wheat yield
The effect of photothermal quotient at anthesis and maturity on kernel m-2, kernel weight (KW) and kernel yield were examined in experiments involving three different genotypes such as: Chakwal-50, Wafaq-2001 and GA-2002 sown at five different sowing times (Planting windows) for two years (2008-09 and 2009-10) at the National Agricultural Research Center (NARC) Islamabad. Photothermal quotient (PTQ) was calculated at anthesis (PTQ1) and maturity (PTQ2) for two years. A direct relationship was observed between photothermal quotients, kernel m-2, kernel weight and kernel yield for all planting windows and genotypes. The maximum value (213.15) of photothermal quotient was recorded when crop was grown on 28th Oct, 2008 (PW2) during the first year and minimum value was observed (143.82) for PW5 (25th Dec, 2009) during the second year. Decrease in photothermal quotient was observed from PW2 to PW5, whereas correlation analysis depicted positive and significant association with individual kernel weight, kernel m-2 and kernel yield with PTQ. The correlation coefficient (r) between kernel m-2 and PTQ1 was 0.5103, while the correlation between PTQ2, individual kernel weight (0.6375) and yield (0.6507) exhibited significance. The outcomes of photothermal quotient and the relationship established through these experiments between kernel m-2, KW and kernel yield and PTQ may be used as a road map to minimize yield losses and select genotypes and managements according to availability of climatic resources.
Keywords: Wheat, photothermal quotient, kernel weight, solar radiation, environment