Growth and dry matter partitioning of diverse cotton genotypes

Abstract

As cotton is an indeterminate species, the timing of crop maturity is largely determined by the capacity of the plant to continue the production of new fruiting sites. According to the nutritional hypothesis, the cessation of fruit production (‘cutout’) occurs when the demand on the resource supply by growing fruit increases to a point where no resource remains for the initiation and support of new fruiting sites. Thus dry matter production could impinge both on the timing of crop maturity and yield. The aim of this work was to determine the extent to which cotton genotypes of diverse genetic background varied in their growth determinants and dry matter partitioning and how this related to crop maturity. Two field experiments were conducted, each involving two sowing times to provide variation in effective season length and growing conditions. Growth analysis showed little difference in growth characteristics of eight genotypes that would affect timing of crop maturity. Allometric plots showed that partitioning to the fruit began earlier in early genotypes but there was little systematic difference in the rate of partitioning after the onset of reproductive growth. The timing of crop maturity (60% bolls open) was related to the time when the growth rate of the fruit per unit area was equal to the crop growth rate (CGR). Taken together, the results imply that the key trait driving maturity was the timing of the onset of reproductive growth and the subsequent development of the demand for dry matter.