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Gossypium populifolium, native to northwestern Australia, is a recent addition to the U.S. Cotton Germplasm collection. This species is a short trailing vine 1-1.5m long which grows as a herbaceous perennial from an enlarged woody root stock. The corolla is generally white with red petal spots. The calyx is prominent with lobes about as long as the mature capsule, while the bracts are greatly reduced and reflexed. The capsule produces about 6 seeds which appear hairless but have a fleshy, aril on the basal half of the rachis. This dries quickly and is easily broken off after the capsule opens. In spite of extreme morphological differences between this species and G. hirsutum or G. barbadense, it is an excellent pollinator and easily produces hybrids with these species. Hybrids between G. Lifolium and tetraploid cottons have many phenotyli traits intermediate between the parents. Hybrid growth habit is very spreading-erect with long intermodes. Sepal and bract sizes are intermediate but the bracts are flaired into an open cup-like structure in which the capsule sets. The white collora color of the wild species dominates in the hybrid. The triploid hybrid is unusual in that it has some female fertility and will set from 1 to 4 seed per boll when backcrossed with G. hirsutum. The hexaploid is less female fertile than the triploid. Pollen fertility of the triploid was not examined, but the hexaploid has male fertility. Dr. Joshua Lee (personal communication) reported that G. populifolium was diploid (2n = 26). We examined the hybrids cytologically and confirmed this number. In the hybrids the average meiotic MI configuration of 218 microspore mother cells was I(23.1) II(6.1) III(0.88) IV(0.27) with a chiasma frequency of 9.3 per cell. The G. populifolium chromosomes are perhaps the largest yet observed in the genus, being roughly twice the size of the A chromosomes. |
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©National Cotton Council, Memphis TN |
Document last modified Sunday, Dec 6 1998
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