BALANCE BETWEEN PROTEIN AND STARCH COMPOSITIONS RICE GRAINS

摘要

Two alleles are described at the waxy locus (Sano 1984) - Wxa which maintains amylose content under different temperatures of grain-filling, and Wxb which does not (Larkin and Park 1999). Doongara is the only Australian variety that carries the Wxa allele, and we have observed significant variation in amylose content over many seasons (Figure 1). High temperature and N nutrition are the two factors that contribute the most to rice growth. N nutrition can be managed and its effects on plant growth, harvest index and protein content are known. The effect of N-nutrition on increasing the protein content of rice directly affects several of the cooking properties of the rice (Martin and Fitzgerald 2002). Figure 1 also shows the variability of amylose ina variety carrying the Wxb allele - Amaroo. The variability in amylose content of Amaroo can be explained by temperature differences between seasons. Given that Doongara carries the Wxa, such variability is unexpected. In this study we used a collectionof Wxa carriers, and 2 Wxb carriers to determine if the rate of N nutrition affects the proportion of amylose in the rice grain.