Disparity of Cotton Pollen Dispersal by Honey Bees Visiting Upland and Pima Pollen Parents1
- G. M. Loper and
- D. D. Davis2
In 1982 and 1983, experimental plantings of a genetic-cytoplasmic male sterile and a pollen fertile upland cotton (Gossypium hirsutum L.) as well as a pollen fertile Pima cotton (G. barbadense L.) were established near Safford in southeast Arizona to study cross-pollination using honey bees (Apis mellifera L.). The objective of these studies was to determine whether poor yields in previous interspecific crossing blocks were caused by a lack of pollen transfer, poor bee visitation, or because of plant factors such as poor bloom synchrony. Observations and data on blooming rates, honey bee visitation, pollen deposition (pollen grains/stigma), nectar volume and sugar concentration, boll samples and hybrid progeny ratios were obtained. Flowering of the Pima R line started later than the upland cottons and the early Pima bloom was approximately 40% cleistogamous. Thus, during the first 2 weeks of A-line bloom, Pima pollen availability was minimal. For 5 consecutive weeks in 1982 when honey bee visitation to the A line was adequate (−1.3%), pollen deposition on A-line stigmas adjacent to the Pima R line ranged from 11.8 to 42.4% (x = 25) of the pollen deposition on A-line stigmas adjacent to upland B line. Progeny rows grown from F1 seed of the A × R cross averaged 20.2% Pima hybrids, showing that isolation from B-line pollen was inadequate. In the 1983 study, pollen deposition on the A line adjacent to Pima was low also. The results are documentation of some of the problems of pollen transfer in producing hybrid cotton seed using a G. hirsutum A line and G. barbadense R. line.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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