**6. Genetic diversity analysis of Indian cotton germplasm**

It is increasingly believed that the reason for recent stagnation and/or decline in cotton yield and fibre quality in India was mainly due to declining trend in genetic diversity of released cultivars and breeding stocks, emergence of new menace (such as minor pests become major pests) and a greater than before exposure to environmental hassles such as drought, heat, salinity etc., Research on genetic diversity of cotton cultivars and some of its related species conducted in several global laboratories including India using a range of molecular markers that has clearly shown the narrowness of genetic base of cotton cultivars.

For example, a set of 96 core accessions were screened using the informative polymorphic markers at the CICR, Nagpur. Combination of different type of 46 markers such as simple sequence repeats (SSR), sequence related amplified polymorphism (SRAP) and randomly amplified polymorphic DNA (RAPD) markers were employed to assess the genetic diversity. It was concluded that the available diversity was low and more informative markers are required to understand the genetic diversity among the core accessions [6].

Similarly, the genetic divergence among 19 elite lines of cotton that are more frequently employed in TNAU cotton breeding programs was investigated using morphological (multi‐ variate Mahalanobis D2 statistics) and SSR markers [20]. This study grouped all the 19 *Gossypium* accessions into two main cluster *i.e.*, *G. hirsutum* and *G. barbadense* lines and there were narrow inter-specific genetic diversity. In an another study [21], thirty *G. barbadense* accessions and five *G. hirsutum* cultivars belonging to different institutes of India were genotyped with 88 SSR markers and found to be closely related within the species. Genetic diversity amongst 91 upland cotton accessions (50 maintainer, 'B' and 41 restorer 'R' lines) and three wild species such as *G. aridum, G. thurberi* and *G. anomalum* was analysed using SSR and RAPD markers and also revealed a higher level of genetic relatedness [22].

It should be noted that the low genetic diversity, as mentioned above, was not due to the limitation of marker technology since it was invariably concluded in numerous studies that molecular markers has immense potential in germplasm characterization. For example, all the wild species available in the CICR were efficiently characterized by using simple RAPD and inter simple sequence repeats (ISSR) markers. Further, eleven cotton hybrids along with their parents and 13 cultivars were characterized at the molecular level and specific markers were identified for testing genetic purity. Sequence characterized amplified region (SCAR) markers and specific primers were also designed to identify three cotton hybrids such as Savitha, Shruthi and Surya [6]. Thus, the narrow genetic diversity present in the current cultivars/ hybrids is obviously a great bottleneck for cotton breeding and needs to be widened to meet the demands of both farmers and textile industries.

breeding materials have not been disclosed to the public). Some private sectors that are actively involved in Bt cotton hybrid development and/or cotton research in India include Mahyco, Rasi Seeds, Nuziveedu Seeds, Ganga Kaveri Seeds, Ajeet Seeds, Tulasi Seeds, Prabhat Seeds, Vikram Seeds, Nath Seeds, Vibha Seeds, Bioseeds, Nandi Seeds, Bayer Crop Science, JK Seeds, Dow Agrosciences, Krishidhan seeds, Zurai Seeds, Navkar Hybrids and DuPont India.

It is increasingly believed that the reason for recent stagnation and/or decline in cotton yield and fibre quality in India was mainly due to declining trend in genetic diversity of released cultivars and breeding stocks, emergence of new menace (such as minor pests become major pests) and a greater than before exposure to environmental hassles such as drought, heat, salinity etc., Research on genetic diversity of cotton cultivars and some of its related species conducted in several global laboratories including India using a range of molecular markers

For example, a set of 96 core accessions were screened using the informative polymorphic markers at the CICR, Nagpur. Combination of different type of 46 markers such as simple sequence repeats (SSR), sequence related amplified polymorphism (SRAP) and randomly amplified polymorphic DNA (RAPD) markers were employed to assess the genetic diversity. It was concluded that the available diversity was low and more informative markers are

Similarly, the genetic divergence among 19 elite lines of cotton that are more frequently employed in TNAU cotton breeding programs was investigated using morphological (multi‐ variate Mahalanobis D2 statistics) and SSR markers [20]. This study grouped all the 19 *Gossypium* accessions into two main cluster *i.e.*, *G. hirsutum* and *G. barbadense* lines and there were narrow inter-specific genetic diversity. In an another study [21], thirty *G. barbadense* accessions and five *G. hirsutum* cultivars belonging to different institutes of India were genotyped with 88 SSR markers and found to be closely related within the species. Genetic diversity amongst 91 upland cotton accessions (50 maintainer, 'B' and 41 restorer 'R' lines) and three wild species such as *G. aridum, G. thurberi* and *G. anomalum* was analysed using SSR and

It should be noted that the low genetic diversity, as mentioned above, was not due to the limitation of marker technology since it was invariably concluded in numerous studies that molecular markers has immense potential in germplasm characterization. For example, all the wild species available in the CICR were efficiently characterized by using simple RAPD and inter simple sequence repeats (ISSR) markers. Further, eleven cotton hybrids along with their parents and 13 cultivars were characterized at the molecular level and specific markers were identified for testing genetic purity. Sequence characterized amplified region (SCAR) markers and specific primers were also designed to identify three cotton hybrids such as Savitha, Shruthi and Surya [6]. Thus, the narrow genetic diversity present in the current cultivars/

**6. Genetic diversity analysis of Indian cotton germplasm**

128 World Cotton Germplasm Resources

that has clearly shown the narrowness of genetic base of cotton cultivars.

required to understand the genetic diversity among the core accessions [6].

RAPD markers and also revealed a higher level of genetic relatedness [22].
