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HERITABILITY OF A RAW COTTON BOLL MASS IN GEOGRAPHICALLY SEPARATED F2 HYBRID POPULATIONS
Kodirova Mohidilhon Rustamovna, junior researcher,
Institute of Genetics and Plant Experimental Biology, Academy of Sciences of the Republic of Uzbekistan E-mail: [email protected] Kahharov Izzatulla Tilavovich, Ph.D., senior researcher, Institute of Genetics and Plant Experimental Biology, Academy of Sciences of the Republic of Uzbekistan E-mail: [email protected] Mutalova Mamura Karimjanovna, junior researcher,
Institute of Genetics and Plant Experimental Biology, Academy of Sciences of the Republic of Uzbekistan
HERITABILITY OF A RAW COTTON BOLL MASS IN GEOGRAPHICALLY SEPARATED F2 HYBRID POPULATIONS
Abstract. The article presents analysis of heritability estimate by a raw cotton boll mass in a population of geographically separated cotton F2 hybrids. Efficacy of selection by a raw cotton boll mass was demonstrated to depend on individual peculiarities of the genotypes hybridized.
Keywords: Cotton, heritability, genotype, selection, population, cotton mass.
Cotton breeding at the final stage is based on selection, which is a continuation of genetic studies, that is, hybridologic analysis of Fx and F2 hybrid swarms. Analytical selection is based on individual selection from genetically heterogeneous populations of cotton older generation hybrids, lines and cultivars. In natural settings the cultivar heterogeniety results from natural hybridization between genotype populations, natural mutations and their crossing. One and the same culture is known to have various environment dependence traits. Some traits more depend on growth environment; the others are governed by a genotype. Heritability estimate is routinely calculated by fractional value from 0 to 1 or in percent from 0 to 100. The higher the heritability estimate, the stronger is heritable dependence of the trait [5; 6].
The three main components of the genotypic variation proposed by Wright (according to Brubeyker) [3] are: 1) additive genetic variation; 2)dominancy related deviation; 3) interaction or epistatic deviation. Estimates of herita-bility for various traits, in addition to estimates of their genetic correlations, can be used to identify indirect selection patterns which appear more efficient than the direct selection for trait to be improved [1; 2; 4]. Thus, as most authors report, heritability estimate is a real value to be used as sustainable method for selection, and prediction of the process efficacy, which is essential for selection process planning.
Quantitive traits of cotton in the second generation have a complex nature of heredity. On the one hand, it is connected with the genetic variability, on the other, with the paratypic one. Paratypic variability makes study on hereditary variability of traits difficult.
To assess selection value of the polymorphic and polygenic F2 hybrids, we studied heritability estimate of economically valuable trait of cotton, such as mass of a raw cotton boll in F2 hybrids. Types of cotton of various origins, such as Na-mangan-77 (a product of individual selection from natural hybrid of C-6526 genotype population obtained in its turn by crossing 159-fwith (05152) punctatum subspecies), Kupay-sin (a product of radiation and multiple individual selection), Kelajak (a product made on the basis of L-38 line, obtained by crossing of intraspecific geographically separated L-6161 G.hirsutum and Bulgaria G.hirsutum 146 breeds), UzFA-705 and UzFA-713 (made by radiation of dry seeds of L-38 line by 60CO gamma-rays and multiple individual selection), and Australian selection 75007-11 breed served as materials for study.
Heritability value in the hybrid combinations by a raw cotton boll mass, as it can be seen in (table 1), has different variability. In hybrids heritability estimate by size of cotton bolls ranged from 0.18 to 0.53 (from 18 to 53%), indicating that by the size of cotton boll some hybrid swarms undergo significant environmental effect, the others have high heritable character.
Section 1. Biology_
Table 1. - The coefficient of heritability of the mass of raw cotton of one box in hybrid populations of F„
Namangan -77 Kupaysin Kelajak 75007-11 UzFA-705 UzFA-713
Namangan -77 - 0,44 0,52 0,18 0,33 0,27
Kupaysin 0.50 - 0.41 0.36 0.45 0.36
Kelajak 0.44 0.42 - 0.43 0.44 0.39
75007-11 0.33 0.53 0.48 - 0.38 0.35
UzFA-705 0.31 0.40 0.45 0.30 - 0.38
UzFA-713 0.21 0.46 0.28 0.30 0.35 -
The highest genotypic character of variability by the trait above was demonstrated by hybrid swarms 75007-11 x Ke-lajak (0.48, 48%), Kupaysin x Namangan-77 (0.50, 50%), Namangan -77 x Kelajak (0.52, 52%) and 75007-11 x Kupaysin (0.53, 53%). Effect of genotypes and environment can be seen equal for variability of a raw cotton boll mass in F2 hybrids. The environment appeared to mostly affect the size of bolls of Namangan-77 x 75007-11, UzFA-713 x Naman-gan-77 and Namangan-77 x UzFA-713 with the heritability estimates 0.18(18%), 0.21(21%) and 0.27(27%), respectively. Mean heritability estimates in other hybrid combinations by a cotton boll mass ranged from 0.30 to 0.47(from 30 to 30 to 47%). Thus, as it can be seen, a raw cotton mass in F2 hybrids is affected by the environment factors more significantly than by the genetic ones. High heritable variability by the trait above
was demonstrated in the hybrid swarms with higher genetic enrichment and adaptability to the environment. Reciprocal differences in the trait heritability estimates can be attributed to the origin of initial parent forms. As a whole, selection by a raw cotton boll mass is ineffective.
Thus, F2 hybrids behavior is connected with the environmental effects on manifestation of a trait and with a response of polygenic system of the hybridized forms to specific conditions of cultivation. However, response of polygenic system to the environmental effects in various genotypes is inadequate. This can be confirmed by high typical heritable variability of a raw cotton boll mass in geographically separated hybrid swarms, where breeds of domestic selection and a breed of nondomestic selection served as the female parent.
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