Effects of Two Maize Endosperm Mutants on Kernel Maturity, Carbohydrates, and Germination

The shrunken-2 (sh2) and sugary enhancer (se) genes which modify endosperm carbohydrates in maize (Zea mays L.) show promise as a means of improving quality for human consumption. A major factor limiting their use is the associated low germination of the seed and low seedling vigor. This research was undertaken to measure germination of sh2 and se hybrids as compared to their respective standard counterparts, Sh2 and Se, when seed was harvested at successive stages of maturity, and to examine germination differences as related to corresponding carbohydrate fractions. Hybrids were hand pollinated on the same day, and ears were harvested at approximately weekly intervals on six successive dates beginning 32 days after pollination. Kernel weight, moisture, reducing sugars (RS), total sugars (TS), water soluble polysaccharides (WSP), total soluble carbohydrates (TSC), water insoluble polysaccharides (WlP), tal non-structural carbohydrates (TNC), cold and warm temperature germination, and seedling vigor were determined for seed at each harvest. Although the sh2 gene markedly increased kernel sugars and reduced kernel weight, seed of the hybrid, sh2 (2 ✕ 3), had satisfactory cold.temperature germination when harvested after mid-September, when its moisture content was approximately 50%. Seed of the hybrid, se (8 ✕ 10), also higher in sugar than its standard counterpart, germinated satisfactorily at cold-temperature when harvested at a moisture content of 60%. Cold-temperature germination was negatively associated with kernel moisture, RS, TS, WSP, TSC, and TNC and positively associated with WlP. It usually was not significantly related to kernel weight. Root, shoot, and total seedling length were positively correlated with cold temperature germination. These results indicate that germination at low temperatures simulating those in the field can often be satisfactory for hybrids carrying the sh2 or se genes.