Effects of Boll Pilosity on Some Traints of ‘Pima’ Cotton1
- Joshua A. Lee2
A genetic stock, E-2, of ‘Pima’ cotton (Gossypium barbadense L.), differs from commercial cultivars of Pima in that the leaves, stems, and fruit (boll) surfaces are densely pubescent, and the fiber is coarser. Because there is no evidence that dense pubescence on leaves and stems of Pima affects fiber traits other than grade, I questioned whether pubescent boll in Pima cotton is accompanied by coarse fiber, as with upland cotton (G. hirsutum L.). The first step in testing that hypothesis was to cross E-2 with the very pubescent, although glabrous-fruited, stock, ‘Pima S-5-H’, and examine an F2 population. All segregates displayed dense pubescence on leaves and stems but segregated for pubescence on bolls. Two contrasting phenotypes were selected for increase, F2 plants with pubescent (F2-HB), and with glabrous bolls (F2-GB). These were grown in replicated experiments with Pima S-5-H (P-S-5-H), commercial Pima S-5 (P-S-5), E-2 with pubescent fruits (E-2-HB), and E-2 with glabrous fruits and stems (E-2-SS). The P-S-5 entries graded lowest in leaf pubescence, 9.3 trichomes per 1 cm transect of abaxial surface of leaf, with the remaining entries distributed from 16.1 to 17.1. The entries were also significantly higher in lint percentage than the remainder, and had significantly larger bolls. Fiber length measures, 2.5 and 50% span, were about the same for all entries. There were some significant differences in length uniformity index, lint tenacity, and elongation, but these did not relate to differences in density of pubescence on various plant parts. The two entries with pubescent bolls, E-2-HB and F2-HB, at 5.9 and 5.8, graded significantly higher in micronaire value (fiber perimeter) than the remaining entries at 5.0 to 5.3.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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