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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 Kodirova Mohidilhon Rustamovna, junior researcher,
Institute of Genetics and Plant Experimental Biology, Academy of Sciences of the Republic of Uzbekistan E-mail: [email protected]
INHERITANCE AND VARIABILITY OF THE TYPE OF BRANCHING WITH GEOGRAPHICALLY DISTANT AND INTERSPECIFIC HYBRIDIZATION
Abstract. This article provides data on the inheritance and variability of the trait "type of branching of cotton" in F1 and F2 hybrids of geographically distant and interspecific forms of the species Ghirsutum L. and G. Mustellinum. Keywords: Inheritance, hybrids, unterminated types, geographically distant, hybridization.
There are three types of cotton branching, to name: 1) monopodial branching essentially typical of wild species, but occurring in some cultivated, monocyclic tropical samples of cotton; 2) sympodial branching with terminated and unterminated types of fruit spurs; forms with the unterminated types of sympodial branches depending on length of inter-nodes can be subdivided into I, II, III and IV subtypes; 3) null branching where sympodial branches do not form, and bolls are developed directly in the leaf base.
The "branching type" trait changes in which are easily discernable in works on cotton taxonomy can serve as an example [1]. Presence of transitional forms by any trait should have made us conclude of polymeric character of its inheritance [3; 5], but multiple genetic studies of branching type trait, in particular, as a rule, demonstrate its monohybrid character with few exceptions when the trait is inherited by polymery [4; 8]. Based on our previous studies, we concluded that inheritance of sympodia (terminated versus unterminated) is controlled by S-s genome. I, II and III subtypes of the unterminated type of sympodia are determined by polymeric, that is, additive genes, genes promoters of simpodia growth. The branching type inheritance apparently involves 4 independent combined S-s gene alleles, such as S1-s1, S2-s2 and S3-s3 interacting by epistasis and polymery type [6].
Aiming at study on inheritance and variability of branching type, we included forms of the terminated and unterminated types of sympodial branches. By types of branching the hy-
bridized forms are stark contrast, to name L-6161 line having the terminated type ofbranching and Yulduz breed with the 1st type of branching, 146.75003-7 breeds and L-2689 line having the 2nd type of branching and L-2777 line with the 3rd type of sympodial branching. Our findings demonstrated that upon hybridization of terminated type (L-6161) with the unterminated one (75007-3, L-2689, L-27777) samples with the unterminated type of sympodial branches specifically dominate in Fx regardless of branching type they had. Upon hybridization of the unterminated and terminated types of branches in F branching type ratio was 1: 2: 1 (where 1, unterminated type making 25%, 2, unterminated II-III type making 50%, 1, terminated I type making 25%). Hybridization of two breeds with similar types of sympodial branches yielded hybrids with the sympodial branches similar to their parent forms. Hybrid combinations resulting from hybridization of L-2777 line with the 3rd type of sympodial branching and 146 breed with the 2nd type of sympodial branching had the 3rd type of sympodial branching. However, other hybrid combinations resulting from hybridization of L-2777 line having the 3rd type of branching with other samples of cotton (Yulduz breed having the 1st type of sympodial branches, 75007-3 and L-2689 breeds having the 2nd types of sympodial branches) the domination of the latter was observed. Thus, in hybrids resulting from hybridization of breeds having the terminated type of sympodial branches with those having unter-minated types of fruit spurs domination of the unterminated
INHERITANCE AND VARIABILITY OF THE TYPE OF BRANCHING WITH GEOGRAPHICALLY DISTANT AND INTERSPECIFIC HYBRIDIZATION
sympodial type could be seen, but regardless of sympodial branching type (I st, II nd, III rd and IV th subtypes of sympodial branches), the hybrids have compact habitus of bush. In hybrid combinations resulting from hybridization between breeds having I st, II nd, III rd and IV th subtypes of sympodial branches domination of breeds having shorter sympodial branches could be observed.
Invariable genetic basis, only form of trait manifestation is established to change. Number of genes in a genotype necessary for determination of a trait is well within the limits of ploidy. Sometimes differences in manifestation forms create an illusion of polymeric inheritance, while essentially
Table 1. - Splitting ratio in
it is monomeric. Our experiments on "branching type" trait demonstrated that practically in all hybrid combinations with involvement of forms both similar and different in origin and manifestation of the trait in Fx into hybridization complete domination of breeds with the unterminated branching could be seen. F2 plants could be divided into distinctly different phenoclasses, the unterminated and terminates branching types in the ratio 3: 1 (Table 1).
Of note, in all F2 hybrids resulting from hybridization of L-6161 lines having terminated branching type with those having the unterminated type of fruit spurs a plant having transitional types of branching could be seen.
F2 based on sympodia types
№ Material Total number of plants The number of plants with sympodia Х2 Ratio
unterminated type terminated type
1. A-2689 x A 6161 252 191 61 0.08 3.1: 1
2. A-6161 x A-2689 320 243 77 0.15 3.1: 1
3. 75007-3 x A 6161 210 160 50 0.16 3.2: 1
4. A-6161x75007-3 165 118 47 0.80 2.5: 1
5. A-2777 x A-6161 158 121 37 0.21 3.2: 1
6. A-6161 x A 2777 185 140 45 0.2 3.1: 1
7. 146 x A-6161 120 94 26 0.64 3.6: 1
8. A-6161x146 180 138 42 027 3.2: 1
9. ^Agy3 x A-6161 355 266 89 0.13 2.9: 1
10. A-6161 x ^AAy3 350 259 91 0.24 2.8: 1
The findings allow concluding of polymeric character of a trait inheritance when the distribution of transitional and other forms by classes is taken into account or of monomeric one when the diversity can be neglected to unite all plants having terminated branching in one class, and those having unterminated and mixed types of branching (which can be categorized as the recessive) into another to have ratios close to 3: 1 [7; 2].
F1 hybrids obtained from crossing unterminated types of sympodial branches (AN-Bayaut-2-G. hirsutum L x G. Mustel-linum) among themselves were mainly observed compressed bush form, that is, the dominance of the form related to the first type or one-and-a-half type of branching, the ratio the splitting is equal to 1: 2: 1.
Thus, in hybrid combinations obtained by crossing between the forms of the I, II, III, and IV types of sympodial branches, the dominance of forms with a shorter type of sym-
podial branches is mainly observed. We think that the latter is more consistent and natural because the trait inheritance is essentially monomeric; transitional and other forms result from changes in manifestation form of permanent genetic basis. Consequently, general consistencies in the ratios of classes of alternative traits in F2 are preserved, rather extensive diversity of gene- and phenotypes formed as a result of gametal linkage with various potential capabilities for development of the trait can be seen. For that very reason in most cases we obtained heterogeneous populations ofvarious forms preserving geno-typic status upon prolonged self-fertilization.
Thus, number of genotypic and phenotypic classes in the trait manifestation increases by several times along with the respective reduction in percent of identical copies of initial forms practically without any changes in the genetic basis and increase in number of traits in the group of genetic factor to result in nonstandard conclusions.
References:
1. Abdullaev A. A. Variation of some quantitative traits in F2 upon interspecific hybridization. Uzbek Biological Journal, 1971. 4,- P. 64-65.
2. Abzalov M. F. Genetics and phenogenetics of the cotton most significant traits, Summary of Doctoral Dissertation (Agriculture),- M., 1991.- 24 p.
3. Baboev D. M. Variability of cotton in various geographical zones. Summary of Candidate's Dissertation (Agriculture), -Tashkent, 1972.- 21 p.
4. Voytenok F. V Selection of cotton by resistance to wilt.- M., "Kolos" publishing house. 1981.- 90 p.
5. Dospekhov V. A. Methods of field experiments.- M., "Kolos" publishing house. 1979.- 416 p.
6. Musaev D. A., Abzalov M. F., Fatkhullaeva G. N. Identification of new morphological forms in G. hirsutum L. In: Urgent problems of botany in USSR. - Alma-Ata, 1988.- 311 p.
7. Musaev D. A. Genetic collection of cotton and problem oftrait inheritance,- Tashkent, "Fan" publishing house. 1979.- 163 p.
8. Sagdullaev F. Inheritance of branching type in fine-stapled cotton and its correlation with some economically valuable traits. In: Genetic studies of cotton.- Tashkent, "Fan" publishing house. 1972.- 87 p.
