The Effects of Time and Method of Pollination on Seed Set in American Upland Cotton¹

Abstract

T HE flmy-ers of Upland cotton (Gossypium hirsutum L.) are largely self-pollinated, but some natural crossing does occur. The natural crossing is caused primarily by bees, the amount of crossing varying widely from locality to locality (Kime and Tilley,8).3 Cotton breeders must protect flowers from insects in order to be sure of self-pollination or of cross-pollination in the case of emasculated flowers. There has been considerable work done on the effect of time and method of pollination, on the number of bolls set, and on the number of seed obtained. Meade (9) found the number of seed per boll was increased about 10% for Durango and 5% for Acala when emasculation followed by hand pollination was compared to normal open pollination. Kearney (5) found the mean number of seed per boll was higher in localities having large numbers of bees in relation to cotton plant population than in areas where bees were scarce. Hand pollination increased the number of seed per boll in areas of few bees but not in areas where bees were plentiful. Banerji ( 1) found no significant difference in per cent bolls set between open pollinated flowers and hand crossed flowers. Kearney (6) reported that bagged flowers had significantly fewer seed per boll than unbagged. He also reported that pollen extracted from anthers and applied to the stigmas in the evening prior to anthesis showed a very limited ability to effect fertilization.A preliminary experiment was conducted at College Station, Tex., in 1939 to determine the effect of time and method of cross-pollination on the number of

Successful boll development after ovary damage during emasculation of Upland cotton flowers

“…The removal of the corolla and staminal column during emasculation with no ovary damage did not significantly lower boll retention compared to self-pollinated 'Deltapine 90' flowers, Table 2. Successful boll development using the Doak (1934) emasculation technique was reported to range from 50 to 90% (Loden et al, 1950;Brown and Lee, 1976;Lee, 1980;Wilson and Stapp, 1984) and similar results were observed in this study. Removal of the membrane surrounding the ovary did not significantly lower boll retention compared to emasculated flowers that were cross-pollinated.…”

“…Wilson and Stapp (1985) reported 6% boll retention for flowers with damage to the ovary wall compared to 25% boll retention observed in the present study. Boll development will depend on multiple factors, including the location, season, temperature, rainfall, and time of emasculation and pollination (Loden et al, 1950; Douglas and Adamson, 1965; Lee, 1980;Wilson and Stapp, 1984;Dong et al, 2005). Climatic conditions in Mississippi could have been more favorable leading to the higher boll retention observed in the present study.…”

The Role of Endogenous Growth Substances in the Fruiting of Upland Cotton

“…The answer remains unknown, but the following speculations are put foward. It is established that in the absence of fertilization, bolls fail to develop, and are subsequently shed (Lloyd, 1920;Loden, Lewis and Richmond, 1950;Tharp, i960); hence it may be argued that the act of fertilization sets in motion mechanisms directed towards retention and growth. In other words, a nutritional polarity, perhaps of a unique and very particular kind, may be established with fertilization as a necessary prerequisite.…”