COTTON BOLL RETENTION AND ITS RELATIONSHIP TO LINT YIELD

Fruit retention helps determine cotton (Gossypium hirsutum L.) yield. Study objectives were to (i) characterize genotypic variation in whole-plant boll retention percentage, (ii) determine the relationship between retention and lint yield, and (iii) characterize timing, stage, and frequency of fruiting-form abscission over two seasons in eight field-grown genotypes: normal-, sub okra-, okra-, and super okra-leaf isolines of MD 65-11 and four commonly grown higher-yielding cultivars. Flower production was higher in okra- (238 m-2) and super okra-leaf (323 m-2) than in normal (160 m-2) and sub okra-leaf (164 m-2) isolines, but boll retention was lower in okra- (29%) and super okra-leaf (21%) than in the normal- (42%) and sub okra-leaf (45%), so lint yields did not differ significantly among isolines. The cultivars averaged 16% more flowers, 33% more bolls, and 37% higher lint yield than normal-leaf MD 65-11, but lint yield correlated with boll retention (r = 0.84*; P < 0.05) when super okra- and okra-leaf types were excluded. Genotypes differed slightly in distribution of mature bolls on mainstem nodes and on sympodial branch positions. Deltapine 90 produced fewer bolls (73%) on lower mainstem nodes (8-20) than the other genotypes (86-92%), reflecting its full-season fruiting habit. Distribution of open bolls on sympodial fruiting positions differed between normal-leaf (98% at Positions 1 and 2) and super okra-leaf MD 65-11 (88%). The other genotypes produced 94 to 96% of their bolls at Positions 1 and 2, which differs significantly from both extremes. When seven of these genotypes and three others were grown in the greenhouse and observed for development of squares and bolls, the normal-leaf types shed more small squares (bract width < 2 cm) but fewer bolls than did the okra- and super okra-leaf types.