Marker Assisted Selection for Fiber Quality Improvement in Mutation Breeding Programme of Cotton

A total of 34 cotton genotypes were screened for fibre quality traits. Out of these, four genotypes; FH-883, FH-631S, CIM-707 (Gossypium hirsutum L., an allotetraploid species) and Ravi (G. arboreum, a diploid species) contrasting for lint quality traits were selected. The genotypes, CIM-707 (fibre length above 30 mm) and Ravi (fibre length 17 mm) were irradiated with gamma rays (125, 150, 200, 250 and 300 Gy), and were also treated with EMS (1, 1.5 and 2%). Both mutagens adversely affected the germination percentage of cotton seed. EMS-treated M1 population was much better than irradiated M1 population with respect to germination and plant growth. Moreover, ploidy level also affected the germination percentage. Staple length of M2 plants derived from the Ravi variety was in the range of 13-17.5 mm, while of M2 plants derived from CIM-707 was in the range of 22-31 mm. EMS and gamma irradiation can successfully be used for creating variation among cotton germplasm and hence mutation is a valuable tool for fibre quality improvement. After surveying 520 RAPDs and 435 SSRs, a genetic linkage map was constructed using 117 F2:3 lines derived from a cross FH-631S x FH-883. Twenty loci were mapped into four linkage groups (LG) spanning around 230.2 cM with 5% of the cotton genome coverage. The average genetic distance was 11.5 cM between two adjacent loci. Low level of polymorphism between the two parents might be the result of narrow genetic base, as reported in multiple investigations. LG1 to LG4 were assigned to chromosome 20, 10, 18, and 15, respectively. QTLs for fibre traits were identified using SMA, IM and CIM at LOD > 2 with WinQTLCart. In total, 16 putative QTLs were identified for fibre traits including fibre length, fibre fineness, fibre strength, fibre length uniformity, short fibre index, fibre elongation, and fibre colour. Out of these, nine fibre QTLs were detected on A-subgenome, while seven on D-subgenome, which suggest that fibre traits result from gene interaction of both the subgenomes of cotton. (author)