A phenological study of earliness components in selected upland cotton lines

Abstract

1981 and 1982 in seven early-maturing lines and one full-season cultivar. Morphological, fruiting, flowering, rate of maturity, yield, and fiber quality traits were measured. Differences among lines were found for node of the first sympodial branch, number of sympodial branches, and plant height. Lines which were developed in Texas were more compact in form, produced fewer monopodial branches, and produced the first sympodial branch at a lower node than the other lines. This combination of components was related to early maturity. Fruiting parameters such as days to square recognition, flowering, boll opening, the intervals between these events, and vertical flowering interval showed significant differences among lines. The majority of the variability in days to boll opening was attributed to differences in days from planting to square recognition. The bloom index measure was found to be especially efficient, as it combines both time of occurrence and rate of flowering, two important components of earliness. Differences between the two growing seasons for fruiting and flowering parameters were reduced by conversion of the data to accumulated degree-day units. Differences among lines were found for several rate of maturity and production measures. CAMD-E and CA-1814 had the fastest rate of maturity, but PD-6520 had the best combination of rate of maturity and yield potential. An 8.5 day range in days to 80 percent maturity was found among the lines. Differences were also found for yield potential, lint percentage, fiber quality factors, and for combinations of yield components. Expression of these and the other characters in 1982 were more typical of an average year, compared to 1981, and were attributed to the more typical planting date and growing conditions of 1982 at the test location. Three difference models predicting earliness, based on mean-maturity date, were developed and related to three types of earliness data. Four principal components affecting earliness were recognized. These are a combination of morphological traits affecting plant conformation and the initiation of the reproductive phase, and genotypic potentials for faster rates of flowering, boll maturation, and rate of crop maturity.