Effects of the Pilose Allele, H 2 , on a Long Staple Upland Cotton 1

Joshua A. Lee DENSE pubescence on the leaves of Upland cotton (Gossypium hirsutum L.) imparts resistance to the attacks of certain insect pests. Thus Knight (1) found that the "hairy" allele, Hj, when homozygous, increases resistance to the cotton jassid (Empoasca spp.). The pilose allele, H2, not allelic to H1; produces an even more dense pubescence than the Ht allele. Stephens (3) (4), Stephens and Lee (5), and Wessling (6) (7) reported that H2, when homozygous and in combination with Hj and some other characters, provides measurable resistance to the boll weevil (Anthonomus grandis Boh.). Unfortunately, H2 is invariably associated with decreased lint length coupled with increased Micronaire. Simpson (2) noted that the pilose allele had this property when it appeared de novo among his stocks and ascribed its effects on lint to pleiotropism. Reductions in lint length of l/g inch or more were recorded. Ht, according to Knight (1), has no known effects upon lint properties. Thus the foreseeable difficulties in using the aforementioned character complex in attempts to ameliorate the boll weevil problem in the Southeastern cotton-growing region, seemingly, reside mostly with the H2 allele. The marketing structure in the Southeast generally expects locally grown fiber to exceed 1 inch in length. The staple length of the best adapted varieties in this region usually falls within the range of 1 1/32 to 1 1/16 inches. Allowing for a loss of i/g of an inch, this fiber is too short to combine with pilose without suffering an objectionable sacrifice in staple length. If the l/g-inch toll noted by Simpson is the general amount exacted by H2, the so-called long staple cottons in the iysto 11/4-inch range should be long enough to compensate for this loss and give fiber with length acceptable for Southeastern conditions. Some of the findings of Stephens (data unpublished) tended to sustain this hope. Stephens was able to produce pilose cottons of acceptable length by incorporating germ plasm from Gossypium barbadense L. into pilose G. birsutum. The "background" length of these introgressants has not been determined. It could have been as long as ll/2 inchs, since strains which are basically G. hirsutum, but which contain much G. barbadense germ plasm are available in this fiber length range. The Sealand cottons are examples of this type. These "extra-long" cottons are very poor yielders in the Southeast, however; and, a strain with fiber length in the range of l!/g to l/^ inches with reasonably good yield would probably be more easily obtained. Therefore, the effects of pilose on lint within this length interval seemed to offer a study of some pertinence. In 1958 D. C. Harrell of the Pee Dee Experiment Station, Florence, S. C., kindly supplied seed of Earlistaple 7, and Upland strain having a minimum upper-half-mean lingth of 1.20 to 1.25 inches (equals about 1 3/16 inches,