Epicuticular wax and drought resistance of several maize genotypes

Abstract

Several maize genotypes were grown in College Station and Etter, Texas in 1983 and College Station in 1984. Irrigations were scheduled to provide full and limited irrigation plots at each site. Each genotype was also subjected to germination in an osmotically controlled solution using polyethylene glycol (PEG 20,000) and a seedling wilt recovery evaluation. Drought resistance estimates were obtained from field evaluation, germination, and seedling wilt recovery experiments. Epicuticular wax (EW) loads were measured colorimetrically for each genotype at each site. Significant differences of EW load among parental genotypes were observed in six environments during 1983 and 1984. Significant differences of EW load among hybrid genotypes were observed in five of six environments. Genotype x environment interactions for EW load were observed among both parental and hybrid genotypes grown during 1983 and 1984. The genotype x environment mean squares were used to test differences of EW load among genotypes and environments of tests with significant interactions. Highly significant differences were observed among the parental and hybrid genotypes. Also differences among environments were highly significant in all cases. Nonsignificant differences existed between irrigation levels. An increase in EW load of all genotypes was apparent when grown in drier, less humid conditions. Broad sense heritability estimates of .73, .74, and .79 suggest that maize lines can be hybridized and selected for high or low EW loads. Observation of the general combining ability analysis makes it apparent that available lines can be used for breeding material. B73 had a high GCA and CI66 a low GCA for EW load. Evaluation of the genotypes for drought resistance proved to be more difficult than anticipated. Nonsignificant differences among genotypes for drought resistance were observed in field evaluations and the seedling wilt recovery test. Significant differences were observed with the germination evaluation. Comparison of each drought resistance evaluation to the EW load for each genotype resulted in no significant correlation. It is possible that the importance of high EW loads under moisture stressed conditions has been reduced due to the reliance of maize upon man for survival as it evolved.