Heat Stress Effect On Kernel Weight of a Flint and a Pop-Corn Maize Hybrid.

Heat stress is an abiotic factor that commonly reduces maize production. 

Heat stress is an abiotic factor that commonly limits crop yield in several productive areas. In this work a flint (Mill522), a semi-flint (2A120HX), and a pop-corn (P802) hybrid were sown at two dates in order to expose them to heat stress at the same calendar time for two weeks at early (EHS) and late (LHS) stages of the effective grain-filling period. Grain yield components and kernel quality traits as oil, protein and starch concentration were quantified. The evolution of kernel weight and those of the endosperm, embryo and pericarp were followed during the post-silking period. Final kernel number per plant of Mill522 and P802 was reduced by EHS and LHS, respectively, whereas 2A120HX did not exhibit significant variations in response to stressful temperatures. Heat stress diminished final kernel weight of Mill522 (EHS and LHS) and 2A120HX (LHS) by a shorter grain-filling period. Contrarily, final kernel weight of P802 was not affected by extreme temperatures at any stages of the grain-filling period. In relation to kernel composition Mill522 and 2A120HX exhibited a higher oil concentration than P802, and only EHS reduced kernel oil concentration of the formers. Although protein concentration was not altered by EHS or LHS, a sowing date x genotype interaction was detected on this trait. Hybrids P802 and Mill522 exhibitted a a higher protein concentrations only at the early sowibng date. Starch concentration also presented a sowing date x genotype interaction. Only P802 and 2A120HX exhibited a kernel starch concentration at late sowing date. Finally, the response of endosperm and pericarp growth to heat stress was similar to that of the kernel weight.