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Genetic Amelioration of Gossypium arboreum through Introgression of Genes from G. hirsutum

V.N. Kulkarni and B.M. Khadi

ABSTRACT

G.arboreum cultivated in India is known for short staple, weak and course fibre. However, it has been considered as resistant to sucking pests and abiotic stress compared to G.hirsutum. The paucity of genetic resources to improve fibre properties in G.arboreum has prompted to resort for introgression of genes from G.hirsutum. The G.arboreum (2n=2x=26 AA) was colchiploidised (2n=4x=52 AAAA) and crossed with G.hirsutum (2n=4x=56 AADD). The resultant F1 was backcrossed to G.arboreum (2n=4x=52 AAAA). The BC1 F7 lines resulted from such cross were evaluated in three cotton growing situation in India to assess the genetic gain over the diploid parent and controls. The introgression has resulted into improved boll features of G.arboreum with boll weight more than 3.0 g and more than 35 per cent four loculed bolls as compared to 2.4 and 16.7 per cent respectively of its G.arboreum parent PA 140. There was significant genetic gain for seed index with genotypes having as high as 10.5 g. On the contrary, PA 140 and local G.arboreum checks possessed only 6.2 g of seed index. Transgressive BC1F7 intrerspecific derivatives were noticed for Ginning out turn with more than 40% GOT where as, GOT around 35 per cent was evident in PA 140 and other local G.arboreum checks. There were significant genetic gains in fibre properties of introgressed G.arboreum derivatives with fibre length as high as 28.4 mm. Fibre micronaire as low as (4.2), strength greater than 25 g/tex as 3.2 mm gauge (ICC mode) and elongation up to 7.0 per cent. The improvement of fibre properties of G.arboreum were quite significant because the G.arboreum parent and control possessed fibre length, around 22.0 mm, micronaire around 5.5, tenacity around 18.0 g/tex at 3.2 mm gauge and elongation between 5 to 6 percentage. The genetic diversity analysis based on 14 economic characters exhibited formation of one big cluster of introgressed derivatives, which was separate from either of the two parents and checks. However, few introgressed derivatives found more near to G.hirsutum parent than G.arboreum. The results of the experiments confirmed the introgression of genes for different economic characters like boll features and fibre properties. Further, the data indicated the possibility of greater ā€˜Dā€™ genome involvement in long and fine fibre properties of G.hirsutum than ā€˜Aā€™ genome. The results are first of its kind in diploid cotton breeding.





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Document last modified 04/27/04