Effect of Sugary-1, Brittle-1 and Double Recessive Mutant on Carbohydrate in Developing Kernels of Maize

Abstract

The present study was undertaken to investigate the changes in carbohydrate content in su1, bt1, su1bt1 and normal kernels during the grain filling period. The F2 kernels of single-cross hybrids among near-isogenic lines with the identical genenetic background of the sweet corn inbreds, WI5125 and WI453, were harvested every three days from 16 days after pollination to maturity. These kernels were studied for the determination of fresh weight, dry weight and the amount of reducing sugars, sucrose, water soluble polysaccharides (WSP) and starch. The fresh weight of bt1 and su1bt1 kernels sharply decreased at early stages of development, resulting in a collapsed endosperm appearance characteristic of bt1 and su1bt1 kernels. The su1 kernels showed a wrinkled endosperm appearance at maturity. In bt1 and su1bt1 kernels the accumulation of dry matter did not increase from the early stages and levelled off soon. The amount of reducing sugars and sucrose of bt1 and su1bt1 kernels was much higher than that of su1 and nomal kernels at earlier stages. The sucrose content of bt1 and su1bt1 kernels showed about a five-fold increase compared with that of su1 kernels. The su1bt1 kernels contained about 16% of the WSP content in su1 kernels during the eating period, about three weeks after pollination. The WSP content of su1bt1 ketnels was twice as high as that of bt1 kernels. The starch accumulation in all the mutant kernels was less efficient than in the normal counterpart. One of the important problems in a sweet corn breeding program is to increase a substantial quantity of WSP associated with textural quality along with increasing the sweetness. The results suggest that the su1bt1 makes it possible to improve the eating quality of sweet corn.