Development of trispecies backcross populations using a 2(ADD) hexaploid bridging line to introgress genes from A-genome diploids into upland cotton

Authors: Sacks, Erik; Robinson, Arin

Submitted to: World Cotton Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/4/2007
Publication Date: 8/1/2008
Citation: Sacks, E.J., Robinson, A.F. 2008. Development of trispecies backcross populations using a 2(ADD) hexaploid bridging line to introgress genes from A-genome diploids into upland cotton. World Cotton Research Conference Proceedings. September 10-14, 2007, Lubbock, TX, USA. 2008 CDROM

Interpretive Summary: Genetic diversity among upland cotton (Gossypium hirsutum) varieties is low and efforts to increase the diversity by introducing novel genes from related species are desirable. One example of this problem is the lack of resistance to reniform nematode, a microscopic-sized worm feeding on cotton roots, in upland cotton but the presence of such resistance in the related species, G. arboreum, also known as Asiatic cotton. To increase diversity in upland cotton and introduce resistance to reniform nematode, three resistant varieties of G. arboreum were successfully mated with a hybrid of upland cotton and a wild cotton species, G. aridum. The resulting three-species hybrids were then mated to an elite upland cotton variety. Breeding lines derived from these progenies (offspring) will likely be useful for developing cotton varieties with nematode resistance as well as improved yield and fiber quality.

Technical Abstract: Introgression of genes from A-genome diploid Gossypium species into tetraploid upland cotton is desirable but post-zygotic breeding barriers, in addition to ploidy differences, make the task difficult. G. arboreum L. and G. herbaceum L. accessions that had been previously identified as resistant to reniform nematodes were crossed as females to a 2[(AD1)D4] hexaploid bridging line used as a male parent. The long-term objectives were to introgress nematode resistance genes and widen the narrow genetic base of upland cotton. Initially, 25 crosses were made with five diploid accessions and the fruit were allowed to develop without embryo rescue, yielding one hybrid with accession A2-190. In a subsequent ovule culture experiment, 70 crosses were made with six A-genome diploid accessions and the number of seedlings per fruit that germinated in-vitro differed among the accessions, ranging from 0.8 to 5.1. However, seedling growth was weak and only five seedlings from A2-100 and six from A2-113 were grown to flowering size in a greenhouse. Like the D4 parent, the hybrids had purple cup-shaped flowers and were photoperiod sensitive. A day length neutral bridging line would be advantageous. Pseudobackcross populations were made for the three hybrids using MD51ne and Deltapine 16 upland cultivars. The BC1 population derived from A2-190 exhibited diverse and sometimes transgressive segregation for flower and fiber traits and were mostly day neutral. Inbred lines derived from BC1 or BC2 generations should be good candidates for replicated field testing to identify novel genes for improved yield, fiber quality, pest resistance and tolerance to abiotic stresses.