Ripening of grain maize in England: varietal differences in ripening patterns

Summary

Changes occurring during ripening in dry weight and percentage dry-matter content of grain and rachis (cob) have been studied in Inra 200, and comparable data obtained for a U.S.A. dent hybrid, Minnesota 803, a Canadian flint × dent hybrid, OX 302, and a range of European flint × dent hybrids (Prior, Kelvedon 59A, De Kalb 202, Maris Carmine, Pioneer 131 and Anjou 210).

In Minnesota 803, OX 302 and, to a lesser extent, Prior, loss of water from the grain was more rapid than in Inra 200 during later stages of ripening. OX 302 reached a harvestable stage (40% grain water content) 10–12 weeks after silking, about 7 days earlier than Inra 200 in favourable seasons, and nearly 14 days earlier when conditions for ripening were less satisfactory. The patterns of changes occurring in the cob were quite different from those in ripening grain. Maximum dry weight of cob was reached when the grain was in the milk stage, and then declined throughout the period of rapid grain development; in the ripe ear, cob dry weight was 15–20% below its earlier maximum. At comparable grain water contents, the cob in Inra 200 was wetter than in Prior, Minnesota 803 and, even more markedly, OX 302. In contrast, water content in the cob of Maris Carmine and Anjou 210 was slightly higher than in Inra 200. The possible relationship between the differing varietal trends in ripening grain (and cob) and resistance to stalk rot is discussed.

The dry weight of the cob in ripe ears of Inra 200 was barely half that found in OX 302 and Minnesota 803, and lower than in other European flint × dent hybrids. Shelling percentage in ripe ears of Inra 200 was 88–90; it was 84–86 in other European flint × dent hybrids, about 80 in Minnesota 803 and 75 in OX 302. Mention is made of the relevance of this information to choice of variety for production of ground ear maize.