Starch composition and its granules distribution in wheat grains in relation to post- anthesis high temperature and drought stress treatments

High temperature (HT) and drought stress (DS) pose serious limitations to wheat (Triticum aestivum L.) grain development, which strongly influences grain yield and quality. In this study, we investigated changes in starch characteristics and starch granules of the high-yielding winter wheat cultivar Zhengmai 366 in response to HT and DS, both alone and in combination. HT, DS and the combination of these stressors led to a significant reduction in the proportion of A-type starch granules (>9.9 mu m) to B-type starch granules (<9.9 mu m), and the effects of HT and DS were significantly additive. The volume proportion of A-type starch granules (>9.9 mu m) was positively correlated with the contents of AM, AP and starch as well as the grain yield (thousand grains weight) and was negatively correlated with the ratio of AM to AP, whereas there was a contrary correlation between the volume proportion of B-type starch granules (<9.9 mu m) and these values. HT, DS and HT plus DS led to a significant reduction in the content of AP and starch and grain yield, but these treatments had less of an impact on AM content. DS reduced the size of the small starch granules, while HT reduced the size of the large granules. The changes in morphology and size distribution of starch granules led to a reduction in starch content under both stress conditions, consequently reducing grain yield. HT plus DS had a much greater influence on starch characteristics and yield than HT or DS alone.