All articles - Reproductive Biology

Topicality and demand of the subject of dissertation. Various techniques of hybridization arc used in crop breeding, including cotton to produce a wide variability in agronomical valuable traits and develop new forms.
Regardless of its implementation hybridization process leads heredity decoding which allow the new plastic genotypes formation with an ability to change and adapt to the new conditions. Hybridization and selection arc considered as a main synthetic method of new varieties development and a success in this largely depends on the choice of crosses method and genotypes of initial forms. Therefore, there is given a special attention for studying the genetic basis and improving of hybridization methods. However, based on the most widely used of hybridization methods arc not always possible to develop varieties having high parameters of composite agronomical traits. Many developed varieties as a result of breeding methods arc genetically become homogeneous, which leads to a reduction of genetic variation and increasing of risk of cpiphytoty outbreaks and decreasing of total productivity (Boroycvich, 1981). Therefore, it is necessary to increase the genetic variability of crops’ agronomic traits by involving of original forms, as well as wild relatives of crops with genetic resistance to various stress factors, diseases and pests.
In increase cotton production through the creation of early maturing, high-yielding having good fiber yield and quality, resistant to various diseases, pests and stress factors, as well as with low level or toxic gossypol in cotton seeds still remain as critical problem in cotton production.
To overcome these problems there need to improving of genetic basis for assessment of existing donors and through the use of various hybridization methods to create new enriched genotypes, promoting positive recombination of polygene in hybrid’ organism for use in applied cotton breeding. Based on the above stated, the study of the genetic aspects of various methods of remote composite intraspecific and interspecific hybridization, based on the comparative evaluation of the effectiveness in order to isolate valuable recombinants and transgressive forms having new genetic variability of traits arc important both scientific and practical point of view.
The dissertation meets the objectives as set out in the Lows of Uzbekistan «On Seed Production» of December by 21, 2007 and «On Breeding achievements» by August 21, 2002 directed to developing and introduction of high-yielding cotton varieties, with a good yield and fiber quality, tolerance to various factors, as well as improving seed production.
Purpose of researches is comparative study of effectiveness of the various methods of intraspecific composite, convergent and inter-specific (3 to 5 species) hybridization revealing the nature of inheritance, form shaping and transgressive variation of traits, total and (+)-gossypol in creation of genetically enriched breeding material and for using in the applied cotton breeding.
Scientific novelty of the dissertation research is follows:
in the system of topcrosscs there used genetic evaluation for combining ability of main agronomic traits cotton varieties with different origins for further using in intraspecific composite and convergent hybridizations;
there established principally dominant inheritance and overdominance type of inheritance (with deviation toward the initial forms with the high agronomic traits) in F| at composite intra-and interspecific hybridization which genetically distinct accessions from the local and foreign selection and wide transgressive variability in F2-F3, facilitating to efficient selection of valuable recombinants;
first identified the inheritance nature and variability of total and (+)-gossypol in the cotton hybrids’ generative parts, developed by involving of American accessions with high (+)- gossypol and local varieties, as well as their correlation with some agronomical valuable traits;
first there held comparative study of economic traits at the different forms of amphidiploid G.thurheri x G.raimondii K-58 (hirsutum type) and K-59 (type harhadense) for free reproduction and after crossing the cultural forms of G.hirsutum L. species, it was established a wide range of variation of agronomic traits at mutant form of K-59 and composite hybrids, derived from it’s participation as compared to K-58 amphidiploid and it’s composite hybrids. It was found out those two types (type G.hirsutum K-58 and type G.harhadense K-59) of amphidiploid G.thurheri x G.raimondii at the free reproduction exhibits similarities with the both cultural tctraploid species; G.hirsutum L. and G.harhadense L., respectively. When they crossed with the cultivated G.hirsutum L. species these amphidiploid forms also behave as natural tctraploids;
it is revealed that, at the composite hybrids produced with the participation of the both forms of amphidiploid (K-58 and K-59) G.thurheri Tod. x G.raimondii Ulhr., as a result of transgressive variation, there is a disturbance of negative correlations between such traits as yield and fiber length, fineness and boll numbers conducive to positive recombinants emergence and increase donor opportunities of amphidiploids;
by comparative study of different methods of remote intra-and interspecific hybridization revealed the genetic nature of inheritance nature and variation degree of the main agronomic traits in composite hybrids, as well as their effectiveness in allocating recombinants having a new genetic variability of traits;
it is revealed that the possibility of breaking some negatively correlated traits by different methods of composite intra-and interspecific hybridization and selection of recombinants combining early maturity and high productivity, high fiber output with its quality and 1000 seed weight, etc.;
it is confirmed that the effectiveness of used methods such as a composite intraspecific and interspecific crosses, to increase positive transgressive variation and segregation genetically enriched recombinants having new combination of high levels of positive parameters of agronomic traits that were recommended and used to develop valuable initial material and new cotton varieties;
the obtained theoretical data on inheritance nature, hcritability and agronomic traits morphogenesis, levels of total and (+)-gossypol and their correlation with other agronomical valuable traits at developed hybrids could be successfully used in the field of fundamental research, and created unique hybrids, forms, progenies, lines and varieties could be used in applied cotton breeding.
Conclusion
1. There obtained and identified on comparative study base of intraspecific composed and converged hybrids with participation of six registered medium staple cotton cultivars in topcross system and high effects of GCA on the following traits:
«50%-cmcrgcncy-50 % flowering» Yulduz (-0.71); Tashkent-6 (-0.39) and in S-9070 (-0.38); “50% cmcrgcncy-50% maturing” S-9070 (-1.43), and in
Tashkent- 6 (-0.91); one boll weight S-6532 (+ 0.11); 1000 seeds weight S-9070 (+0.51); on productivity Tashkent-6 (+5,28), S-4911 (+4,04) and S-9070 (+2 24); fiber output S-6532 (+1,29); fiber length S-4911 (+0,70) and S-6532 (+0,48); fiber strength S-6532 (+1,57) and S-4911 (+0,91); micronairc S-6532 (+0,24) and Ak-Darya-6 (+0.24). These donors of high valuable traits were used by us for improving of the recurrent varieties by composite and convcrcgcnt hybridization. It was found that involvement of the varieties with a high GCA in convergent hybridization allows improving of the recurrent varieties and developing of a new initial material for cotton breeding:
inheritance nature and variability degree of agronomic traits at intraspecific composite and convergent cotton hybrids revealed the relative efficiency of the studied hybridization techniques during elaboration of new initial material with enriched genotypes of agronomic traits, and recommended to use in geneticselection process;
convergent hybrids F i dominated by early maturity, in terms of productivity and fiber output occurcd overall effect of overdominance, and F2-F3 appeared as positive transgressive forms;
significant effect of the genotype of the parental forms involved in hybridization on the inheritance nature of fiber quality (length, micronairc, strength) had convergent hybrids Fj, as well as their level of recombination in F2-F3 indicating the need for breeding of recombinants on these traits in early generations, taking into account genotype of initial forms;
the inheritance of the wilt tolcrancccs bccamcs not only depending on the pathogen load in soil fungus infections, but also depends on the used hybridization methods. Thus, most high resistance, i.c. negative superdominance on wilt tolerance observed in convergent hybrids F, and F2;
the direction and strength of correlation between the studied traits in intraspecific composite and convergent hybrids varied in depending on crosses type and from genotype of recurrent varieties. At present ease, the greatest number of recombinants with positive combination of high indicator traits which determining fiber quality, as well as its output, length, observed with with composite, particularly with convergent hybridization.
2. For the first time, on the basis of studies on determination the percentage of (+)- gossypol in seeds of genetically different cultivars of Uzbek cotton selection and analysis of variability, inheritance degree of total and (+)-gossypol in the environmentally and genetically remote hybrids and their correlations with economically valuable traits was proved:
the cultivars S-6524, S-6530 and S-6532 which were elaborated involving subspccic of G.ssp.punctatum had the highest level of (+)- gossypol and the «Turon» cultivar which was developed by composite hybridization has a low indicator of the current trait and relatively high level of total gossypol in seeds;
It was determined intermediate inheritance level of (+)- gossypol in the petals and seeds in F| hybrids and wide positive and negative transgressive variability in Ғ2-Ғ3. It was proved that the efficiency of plant selection with high (+)- gossypol in seeds since F2, that confirmed with segregation of constant progenies and lines on trait basis in F4 hybrids;
as a result of research the cross-correlation total and ( +)- gossypol and some agranomically valuable traits was found that between the ( +)- gossypol in the petals and seed exists a weak correlation. The data on correlations of studied traits showed an independent genetic control of (+)-gossypol in the generative organs and independent inheritance of them at cco- geographically and genetically remote hybridization.
3. For the first time, based on comparative study of agronomic traits of amphidiploid G.thurheri Tod. x G.raimondii Ulbr. two forms (hirsitum type -K-58 and harhadense type -K-59) and hybrids derived from G.hirsutum L. varieties revealed:
both studied forms of hirsutum type and harhadense type of amphidiploid G.thurheri Tod. x G.raimondii Ulbr., being functional diploids provided wide combinative variability in the progeny from the free reproduction and crossing with the cultivars of tetrapioid G.hirsutum L., and showed their similarity to G.hirsutum L. and G.harhadense L. tctraploid species, respectively;
as a result of the research a group of unique composite hybrids (F\G.thurherii Tod. x G.raimondii Ulbr.) x G.hirsutum L. confirmed unlimited transgressive variation as the basis of a new form revealing, new gene pool developing for use in applied cotton breeding. Herewith, at bud mutant K-59 observed emergence of phenotypes with higher variability for most agronomic traits compared to K-58;
it was found out that in composite hybrids which obtained by crossing of studied forms of G. thurberi Tod. x G. raimondii Ulbr. amphidiploids (2n=52) and with G.hirsutum L. cultivars were observed relatively rapid improvement on productivity and its components in comparison with freely propagated amphidiploids offspring. Herewith, composite hybrids involving K-58 on boll number in all generations was slower comparied to hybrids derived from K-59;
composite hybrids F, obtained involving two cultivars of cultivated forms on fiber output and length were observed deviation toward the parent with the best expression of the trait. It was revealed that the fiber output and length of the studied composite hybrids susceptible to less variability compared in terms productivity and its components. Relatively high variation was manifested on fiber output in F2, and on fiber length in F2-F3. In freely multiplying offspring of K-59 and its hybrids with varieties in F3 was observed the derivations of more long staple plants compared with hybrids, developed involving K- 58;
free propagating amphidiploids’ offsprings and composite hybrids selected by using of cultural forms showed the least wilt susceptibility compared with the control. Wilt resistance of barbadense type K-59 progenies from the free breeding was higher as compared than offspring of K-58, and higher in composite hybrids F2-F4, obtained involving K-59.
4. Under the general principle of correlation relationships among the studied hybrids were found that composite hybrids F2 amphidiploids’ G.thurberi Tod x G.raimondii Ulbr., both types (K-58 and K-59) with a G.hirsutum L. type Acala sj-5 cultivar showed mainly low positive and negative correlation coefficient values, which in most eases were none significant. In hybrid combination of K-58 x Andijan-60 fiber output and length correlated positively;
5. Based on comparative study of inheritance and variation of agronomic traits in developed 4 genomic [(G.thurberi Tod. X G.raimondii Ulbr.) X G.arhoreum L.] x G.hirsutum L., 5 - genome [(F|K-28 x S-6524 ) x G.harhadense L. hybrids and their backcross hybrids were proved:
the possibility of broad transgress variation and creation genetically enriched recombinants on unique traits;
efficiency of backcrosscs among the composite interspecific earlier generation hybrids for rapid improvement and stabilization of eultuvated forms of cotton;
wide transgress variability presence in 4 and 5 species composite hybrids and their backcross hybrids on productivity and its components starting with F|. In particular, it was confirmed the effectiveness of five species hybridization to increase the boll numbers per plant, boll weight and weight of 1000 seeds at 4 and 5 species and backcrosscs hybridization.
by obtaining recombinants having fiber output 43,1-45,0%, fiber length - 40 mm and above, micronairc of fiber 3.9-4.5 and wilt tolerance it was confirmed the effectiveness of introgressive and transgressive breeding at composite 4-5 species hybridization and their backcross hybrids.
6. As a result of studies of correlations in composite 4-5 species and backcrosscs hybridization of F2 hybrids it was revealed the effectiveness of used methods in interruption of such negatively correlated traits as «fiber output» and «fiber length» from medium positive (r=+0,39) up to high positive (r=+0,62), «fiber length» and «micronairc» -medium positive (r=+0,55), as well as «fiber length» and «fiber strength» -medium positive (r =+0,56 and r=+0.50).
7. Based on intraspecific composite and convergent, eco-geographically and genetically remote and 3-4-5 species and backcrosscs hybridizations were developed the following new breeding progenies, lines and varieties of upland cotton:
by composite and convergent hybridization way-L-7966, L-214/05; CC-896/05; CC-896/28; CC-991/05; CC-991/09; KC-1/05; КС-1/08; КС-1/18; KC-1/35; KC-1/51; KC-1/77, S-231-233/07, L-234-235/07, L-236-237/07, L-242-243/07, L-244-245/07, L-482-483/07, L-484-485/07, L-666-667/07, L-397-398/07, L-802-803/07, L-814-815/07, L-230/05;
cco- geographically and genetically distant hybridization - cultivar S-7300, S-7301, the progenies S-5344, S-5361. HPG-1;
composite 3 - specific hybridization -cultivar «Sulton», «Jarkurgan», S-7276, S-7277, as well as a number of lines;
8. Using the remote intra-and interspecific hybridization it was elaborated unique introgression hybrids, genetically enriched cotton recombinants, progenies, lines, and varieties «Sulton», «Jarkurgan», S-7276, S-7277, S-7300, S-7301 having positive combination of high agronomic traits. Cultivar «Sulton» was included in the State register from 2011 and for the period from 2008 up to 2014 it was sown on the area of over than 275,5 thousand hectares.
9. The following rcccomcndations were given for practize and future studies:
use of method convergent hybridization, allowing improving of agronomic valuable traits of recurrent parent and registered medium staple cotton cultivars and receiving a positive transgressive variability;
as an initial source in convergent crosses use cotton varieties with high General combination ability (GCA) on the following: on early maturity- Tashkent-6 and S-9070; boll weight - S-6532; weight of 1000 seeds S- 9070; on productivity -Tashkent-6, S-4911 and S-9070; fiber output -S-6532; fiber length - S-4911 and S-6532; fiber strength - S-6532 and S-4911; and for micronairc - S-6532 and Ak-Darya-6.
for use as an initial source in cotton genetics and breeding research such new cotton selection progenies as well as the lines: KS-1/05; K.S-1/08; K.S-1/18; KS-1/35; KS-1/51; and KS-1/77, L-7966, L-214/05, S-214/05, SS-896/05; SS-896/28; SS-991/05 and SS-991/09 with early maturity, productivity, wilt tolerance, fiber output and quality.
to use in cotton genetics and breeding researches both USA accessions BC3S,-47-8-l-17, BC3S|-l-3-6-15 with 95% of (+)-gossypol level in seeds and lines HPG-1 and others with 90% of (+)-gossypol level, as donors on this trait. Since 2012, developed and studied in the competitive variety testing of Institute the following lines: L-404-05 and L-6970 with high (+)- gossypol level were recommended for testing on ground control of the State Inspection Commission for Agriculture crops variety testing.
widespread use of various forms of synthetic tetrapioids G.thurheri Tod. x G.raimondii Ulbr., 4-5 species composite hybrids [(G. thurheri Tod. x G. raimondii Ulbr.) x G.arhoreum L.] x G.hirsutum L. and [(F t K- 28 x C-6524 ) x G.harhadense L., as well as their backcrosscs for achievement the broad transgress variation, elaboration genetically enriched recombinants on economically valuable traits and their use in practical cotton breeding;
to extend the areas in of early maturing commercialised cotton cultivar «Sulton» and perspective one «Jarkurgan» as well broad testing of such as new varieties S-7277, S-7300 and S-7301 in the republic.