Molecular characterization and association mapping of agronomic traits in g. barbadense varieties from cotton Germplasm collection of Uzbekistan

Appropriateness and relevance of the dissertation's subject. "According to UN projections, by 2050, the production of food resources should be doubled, which would feed about 9.3 billion people" 1 With the deterioration of the global climate and land degradation is a falling agricultural productivity. To avoid a global environmental catastrophe a radical change in the structure of production and consumption of a number of key natural and agricultural resources, including cotton is needd.
Cotton (Gossypium L.) is one of the most important crops. Experts estimate that by 2030 global demand for cotton products will more than double, while the annual increase in genetic yield of raw cotton, is only 7,1-8,7 kg / ha. At the same time, competition in the world market leads to increased requirements for the quality of cotton fiber.
Most modern cultivated varieties of cotton have a common genetic structure that is not able to fully meet modem requirements. Work on improving the quality of fiber - a very complex process due to the narrow genetic base of modem cultivars of cotton and negative genetic correlation between the quality and yield of cotton fiber. This instruct you to explore the genetic resources of cotton, for use in the selection process of its genetic diversity.
To ensure the high competitiveness of cotton production in Uzbekistan use modem approaches to improving productivity and quality of cotton fiber.
Much of the molecular-genomic research and MAS focused on members of the species G. hirsutum. Another species, unfortunately, neglected, at the same time they have a wealth of genetic potentia For example, it is necessary to focus more attention on the genome of long staple cotton {G.barbadense), a fiber which far exceeds the quality indicators of medium staple cotton.
This dissertation research is to a certain extent to the task of implementation of the Presidential Decree of October 20, 2008 No. PD-4041 "On measures to optimize the acreage and increased production of food crops."
The purpose of research is to study the molecular genetic diversity, population structure and identification of genetic loci associated with valuable traits in cultivated representatives oflong staple cotton (G. barbadense) from the world collection of germplasm of cotton in Uzbekistan.
Scientific novelty of the research is as follows:
assessment of the diversity of a large sample of 288 G.barbadense a ccessions from the cotton germplasm collection of Uzbekistan in two independent cco-geographical conditions (Uzbekistan and the United States) on a range of valuable economic traits;
ecotypes identified with the greatest stability on interesting features in the various cco-gcographical conditions of growth, as well as combining the best features of several indicators of fiber quality and valuable morphological and biological parameters in Uzbekistan, and the United States.
studied the molecular-genetic diversity of G. barbadense accessions using SSR markers and identified informative microsatellite marker loci to analyze the genome of cultured representatives of the G. barbadense-,
revealed the amount of variability and distribution of allele frequencies of SSR marker loci in cultivated G. barbadense germplasm.
studied the genetic diversity at the level of DNA marker loci;
identified the genetic distance, genetic variation and phylogenetic relationships of cultivated accessions of the collection
determined the genetic structure of a population cultivated of G. barbadense verieties;
investigated and determined the genetic structure and genetic differentiation of populations of worldwide G. barbadense L. germplasm collection and the most genetically diverse ecotypes identified.
studied and defined and intrapopulation intcrpopulation genetic differentiation;
assessment of linkage disequilibrium and its decay in the genome of the cultivated G. barbadense species was done;
an associative mapping of valuable traits using germplasm resources of cultivated G. barbadense and found a trait-associated markers have retained a strong association with the fiber traits as in Uzbekistan, and the United States;
verified an integrated genetic map of tctraploid cotton, defined the distance between the new and already well-known trait-associated markers, determined more precisely the location of some QTLsfor agronomic traits on chromosomes;
first tested method «in silica chromosome walking» using complex computer analysis, which revealed a sequences near the SSR marker loci, homologous genes causes the manifestation of some marker-associated traits.
CONCLUSIONS
1. Evaluated of diversity of 288 G.barbadense accessions from the cotton germplasm collection of Uzbekistan in two independent cco-gcographical conditions on a range of valuable economic traits. Determined ecotypes, which have the highest stability on interesting traits in the various eco-gcographical conditions of growth, as well as combining the best performance of several fiber trait and valuable morphological and biological parameters in Uzbekistan, as well as in the USA environments, which arc the first to engage in breeding.
2. Studied molecular-genetic diversity of G. barbadense genome using SSR markers. Revealed 108 polymorphic SSR markers amplified 301 marker locus. Number of loci ranged from 2 to 5 with an average value of 3.5 for one locus SSR markers. In a study 60 (55%) proved to multilocus markers (3 or more loci), the majority of loci (81%) were represented by two and three alleles. It is shown that in the germplasm of cultivated G. barbadense germplasm there arc a large number of new alleles. On the basis of the identified marker a panel is designed to determine the varietal ecotypes and accessions, obtained for each sample a unique genetic profile (DNA barcode).
3. Revealed moderate (~ 33%) total genetic diversity at the level of DNA marker loci ranged over a wide range (0.02-0.71) Identified phylogcntic relationship of G. barbadense accessions on the basis of genetic distances varying between 0.01 - 0.67, with an average value of 0.19. Identified genetic structure of the population, which is represented by two sub-populations, and several genetic groups within population.
4. The high level of intra-variability (67.2%) and moderate intcrpopulation differentiation (32.8%) revealed. Very strong genetic differentiation (0.584) was found between Africa subgroup and and Turkmen subgroup and between African and Uzbek subgroup (0.575). There is moderate genetic differentiation (F.$7 =0.117) between the Uzbek and Turkmen subgroup. In accessions formation was involved African, African-American and American genotypes. The greatest genetic diversity have found in Turkmen varieties. Clearly traced the genetic isolation of the Uzbek and Turkmen varieties and noted the formation of the Central Asian ecotype.
5. Linkage disequilibrium in the genome of the cultivated G. barbadense, at critical values of r2>0.1 and r2>0.2 remained at 8% and 4.3% respectively, according to pairwise combinations of SSR markers.
6. LD decay in the G. barbadense genome, with a minimum threshold of r2>0.05 in on average 24.8cM, and at a high threshold of r2>0.1 LD retained, on average, at a distance of З.ЗбсМ.
7. MLM based association mapping have identified 100 trait-associated markers which retained a strong association with the fiber traits in Uzbekistan, and the United States environments, of which 85 markers identified for the first time. Identified markers arc highly associated (BF<0.15), both with one and with two or more economically valuable traits in both geographical conditions and arc a priority for the MAS program.
8. Specified an integrated genetic map of tetrapioid cotton, where determined the distance between the new and already well-known trait-associated markers and determine more precisely the location of some QTLs for agronomic traits on chromosomes.
9. The method of «in silica chromosome walking» was tested using complex computer analysis and revealed the sequences of 17 genes near the 8 SSR markers. Of these, at least 8 genes substantially coincide with the identified associations marker indication based on a comparison of functions described in the literature.