**7. Conclusion**

resources, molecular genetic diversity, population diversification and strata, and the extent of linkage disequilibrium (LD) for the cotton genome were characterized [10; 11; 12; 23; 24].

302 World Cotton Germplasm Resources

Efforts also identified several SSR markers associated with main fibre quality traits along with donor accessions, bearing "golden" QTLs useful for MAS programs [23; 24]. As a result, a successful MAS program has been established in Uzbekistan that facilitated to mobilize novel haplotypes of important fibre quality QTLs from donor accessions preserved in cotton germplasm collection to commercial cultivars. In that fibre trait-associated DNA markers were used as a tool to manipulate the transfer of QTLs during a genetic hybridization [38; 46; 47].

The MAS program, extensively utilized during past decade in Uzbekistan that involved several donor (germplasm accessions) and recipient (commercial cultivars) germplasm not only improved and developed novel MAS cultivars through mobilization of novel untapped loci but also created novel germplasm resources useful for cotton breeders and future cotton breeding [Table 1; 10; 38; 46; 47]. Several first generation MAS-derived cultivars were devel‐ oped and submitted for State Variety Testing Committee of Uzbekistan for future commerci‐ alization that are being field-trailed for improved agronomic and fibre qualities across the Uzbekistan regions. Moreover, as a ongoing effort, Uzbekistan researchers initiated a genepyramiding approach to combine major fibre quality traits into single genotype of several commercial Upland cotton cultivars of Uzbekistan using these effective molecular markers as

a breeding tool and donor genotypes from cotton germplasm collections [38; 46; 47].

quality traits useful for MAS programs [8; Abdullaev et al., 2014 unpublished]

As a continuation of efforts to characterize cotton germplasm resources at the molecular level, about 300 *G. barbadense* (so called extra long staple fibre Pima cotton) accessions with wide geographic origin covering 17 countries worldwide were recently genotyped with SSR markers to estimate molecular diversity, phylogeny, population structure, and linkage disequilibrium level. These Pima cotton accessions were exchanged with USDA-ARS at Shafter, California, evaluated for major agronomic, morphological and fibre quality traits in the Uzbekistan or/and CA growing environments, and used for molecular mapping of fibre

Use of cotton germplasm resources and their characterization at the molecular level further helped us to select the most diverse *G. hirsutum* accessions to create nested association mapping (NAM) panel. The creation of NAM populations is efficient approach to enhance power [48] of association mapping in cotton [10; 49]. Currently, a panel of 4000 F2:3 generation NAM population individuals has been developed from genetic crosses between 20 most diverse *G. hirsutum* accessions and Uzbek cultivar Namangan-77, a genetic standard for *G. hirsutum.* NAM population individuals are also being genotyped with a large number of SSR markers and evaluated for major agronomic characteristics in different environments of Uzbekistan to conduct fine association mapping studies [22; Abdurakhmonov et al., 2014, unpublished].

Currently, genotyping of additional cotton germplasm accessions from major collections using widely available SSR markers is in progress that will help to characterize and organize the entire cotton germplasm resources of Uzbekistan. In perspective, we also aim to apply novel molecular tools such as SNP platforms and genotyping-by-sequencing (GBS) technologies to Due to the importance of cotton production for the country and the historic expertise on cotton farming and production developed during the past century, Uzbekistan has prioritized and promoted the breeding programs, leading to a collection of one of the richest cotton germplasm resources in the world. Developed and maintained by several leading cotton research institu‐ tions in Uzbekistan, cotton germplasm collections preserve over 25,000 major cotton germ‐ plasm accessions of *Gossypium* species, wild, primitive, pre-domesticated landraces stocks, cultivar and breeding lines, mutants, genetic and cytogenetic stocks, and various types of within and between cotton gene pool hybrids. These resources were collected from the centres of origins of *Gossypium* species during scientific expeditions and through germplasm exchange with world germplasm centres, and developed by scientists and breeders of Uzbekistan for the past century. Consequently, these germplasm resources were the basis for the development of Uzbekistan's main commercial cultivars with early maturity and high productivity, making cotton profitable in the northernmost cotton growing country. This greatest achievement and commitment of cotton breeders timely responded and solved many past and current problems of cotton production as well as it will help to sustain the cotton production in Uzbekistan in the future.

Although each cotton collection has its own specific goals and objectives for preserved materials, there is a huge need for conducting joint re-inventory for clarification of redundan‐ cies between some of collections. There is a need for building short-term and long term cold storage rooms for all collections available in the country to better preserve the collection for future generations and cotton production. Moreover, although initial efforts have been made, coordinated efforts are needed to create a unified electronic database to systematize the germplasm records for all collections that will help for better utilization of the accessions in the breeding programs.

There are over 5,000 novel germplasm resources that were developed for past decade of collaborative efforts on molecular genetic characterization of cotton germplasm resources and establishment of modern MAS and GM programs. The modern cotton genomics and bioin‐ formatics programs in combination with conventional cotton breeding efforts will further enhance the characterization and utilization as well as efficient documentation and systemat‐ ization of the germplasm resources in Uzbekistan.
