ENVIRONMENTALLY-INDUCED VARIATION IN STARCH AND NONSTARCH POLYSACCHARIDE CONTENT IN WHEAT

Grain samples from cv. Batten wheat were obtained from experiments con ducted in a mobile rainshelter in two seasons, and they were analysed for their contents of starch, arabinoxylan and beta-glucan. Grain beta -glucan content was less than 0.5% in all samples. However, there was a negative relationship between arabinoxylan content and starch conten t. This was not due simply to starch dilution because the variation in arabinoxylan content was only 15% of that in starch content. There wa s also a negative relationship between grain weight and drought, and a positive relationship between amount of arabinoxylan accumulated and drought. These results offer a possible explanation for the observed r elationship in wheat between high arabinoxylan and low Apparent Metabo lisable Energy for poultry, but contrast with the relationship between drought and beta-glucan in barley. Varying levels of nitrogen fertili ser did not affect the relationship between the proportions of arabino xylan and starch, but, by maintaining photosynthesis longer, late-appl ied nitrogen in combination with plentiful water supply caused an incr ease in arabinoxylan weight/grain not seen in other drought-free treat ments. We conclude that good irrigation management, especially from an thesis, is crucial for good feed wheat quality. (C) 1997 Academic Pres s Limited.