Interaction of Shrunken‐2 with Five Other Carbohydrate Genes in Corn Endosperm1

The interactions of the shrunken‐2 (sh2) gene with waxy (wx), amylose‐extender (ae), sugary‐1 (su1), dull (du) and sugary‐2 (su2) on the carbohydrate composition of maize (Zea mays L.) endosperm were determined. The contents of fructose, glucose, sucrose, water‐soluble polysaccharide (WSP), and starch of whole kernel samples 21 and 28 days after pollination were determined. Percent starch and amylose of mature kernels were determined. The sh2 mutation reduced starch drastically concurrent with a large accumulation of sucrose as previously observed. In homozygous double and triple recessive genotypes, sh2 was epistatic over all other genes for the accumulation of sucrose and reduction of starch. Genotype combinations containing both su1 and sh2 produced the most extreme reduction in starch content, and in all cases sh2 inhibited the large WSP content normally caused by su1. Starch from kernels homozygous for ae alone had 60% amylose. Presence of sh2 in the multiple recessive genotypes inhibited the ae enhancement in percent amylose. With few exceptions those genotypes with wx produced no amylose; those which did were in combination with ae. Genotype combinations containing both wx and sh2, had higher sucrose than normal and the starch, although reduced in quantity, was 100% amylopectin.