Maize starch fine structures affected by ear developmental temperature

Growing temperature is known to affect the grain yield and quality of maize. Two genetically unrelated normal dent maize inbreds, ICI63 and ICI92, with different heterotic backgrounds were grown in a greenhouse with the ears wrapped in temperature control devices set at 25 and 35 degrees C during the grain-filling period. Grain yield, kernel weight, and kernel density were less for ears at 35 degrees C than for those at 25 degrees C. The extent of the loss, however, varied with the variety: 13.1 and 37.9% kernel weight loss and 8.47 and 10.08% density loss for ICI63 and ICI92, respectively. The starch granular shape of ICI63 became more oval-shaped, but there was no shape change for ICI92. As developmental temperature increased, starch granule size decreased and gelatinization temperature increased. With increasing developmental temperature, the true amylose content of ICI63, determined by iodine affinity, decreased 2.39% and that for ICI92 decreased 2.20%; amylose molecular size of both varieties also decreased. Size exclusion chromatography and high-performance anion-exchange chromatography revealed an increased medium branch-chain fraction and decreased long and short branch-chain fractions for ICI63 amylopectin, whereas ICI92 amylopectin had increased long and medium branch-chain fractions and a decreased short branch-chain fraction, when the ear developed at 35 degrees C.