Flowers with Abnormal Numbers of Involucral Bracts in Cotton1

Abstract

A primitive race stock of cotton (Gossypium hlrsutum L.) Texas 703, had 26 to 59% flowers with more than the usual number of three involucral bracts in four seasons in the field at Phoenix, Ariz. The most common variant was a flower with a fourth, almost full‐sized bract, but other flowers had up to seven bract segments. Two cultivars, ‘Deltapine 16’ and ‘Stoneville 7A’, had lower frequencies of flowers with abnormal numbers of bracts. Plants of the race stock and cultivars had only three‐bract flowers in the winter greenhouse. We selected race stock ✕ cultivar F5 progenies that were almost true‐breeding for abnormal (98.9%) and normal (99.5%) numbers bracts. About one‐third of the F4 plants selected for all abnormals in the field had low frequencies of abnormals when cut back and moved into the greenhouse in the fall. The most common variant in the advanced‐generation selections, as in the race stock, was a flower with four bracts; one progeny had 95% four‐bract flowers. Others, however, had lower proportions of four‐bract flowers in relation to other abnormal numbers. Thus, it may be possible to select plants having flowers with more than four bracts. An inheritance study of selected F3 parents and four hybrid generations suggested that abnormal bract number is conditioned by three or four pairs of genes that show additive, intra‐allelic, and interallelic effects.