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SYNOPSISYield comparisons of two corn hybrids, W240 and W255, grown at Wageningen, Netherlands, and Spooner, Wis., showed maximum yields averaging 110 bushels per acre at Wageningen and 68 at Spooner; 5·year averages for W240 were 86.1 and 62.9 respectively. Higher plant populations (28,907 per acre at Wageningen, 11,784 in Wisconsin), uniform rainfall distribution, higher soil fertility, and lower disease incidence contributed to high yields at Wageningen. The stage of maximum maturity required up to 9 more weeks growing season and occurred as much as 6 weeks later at Wageningen than at Spooner.

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.

Numerous genes affect carbohydrate composition of the endosperm of corn (Zea mays L.). The objective of this study was to measure the effect of 10 gene combinations on level, rate of change, and interrelationships of kernel moisture and sugars during the first 4 weeks after pollination as influenced by the modifier complexes of seven adapted sweet corn inbreds. Four genes influencing endosperm carbohydrates, dull (du), sugary‐2 (su2), waxy (wx), and shrunken‐2 (sh2), and one double combination (du wx), each in association with the sugary‐1 alleles (Su1 and su1), were incorporated into adapted sweet corn inbreds to give seven near‐isogenic series. Determinations were made of moisture, reducing sugars, sucrose, and total sugars at four successive harvests. The sh2 gene, and to a lesser extent the du wx combination, show promise for improved kernel moisture and total sugars and for reduced rates of loss of these components as compared to sweet corn presently in use (su1) for processing. In view of the marked differences in the expression of these genes in the inbreds studied here it is desirable to incorporate them into a broad range of germplasm in a search for modifiers that will further improve and utilize their potential in hybrid combinations.

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