CC BY
0OBTAINING TRANSLOCANT PLANTS ON COTTON AND THEIR CYTOGENETIC CHARACTERISTICS
Laposova M.Kh.
National University of Uzbekistan named after Mirzo Ulugbek https://doi. org/10.5281/zenodo. 13884948
Abstract. It is important to suggest that cytogenetically marked cotton lines are an indispensable toolfor studying the cytogenetic problems of this plant. Translocant cotton lines are used for cytological identification of individual chromosomes of the genome, since the chromosomes of metaphase I of the genome are very small in size and difficult to identify with monochrome and differential staining.
Keywords: translocant, chromosome, identification, cytogenetic collection, line.
It is not a secret that Secale Cereale L. was used by Lee et al. worldwide as a source of genes for agronomic improvement and resistance enhancement. In this study, a stable wheat-rye substitution line and 3 major 1RS.1BL translocation lines were selected by crossing the Chinese rye landrace Aigang and the wheat cultivar Mianyang11. The substitution and translocation lines were identified by molecular cytogenetic analysis. The results of PCR, fluorescence in situ hybridization and acid-polyacrylamide gel electrophoresis showed that the substitution line had one pair of 1R chromosomes, named RS1200-3, and the other 3 translocation lines had one pair of 1RS.1BL translocation chromosomes. They were named RT1163-4, RT1217-1 and RT1249. While inoculated with stripe rust isolates, these 4 lines showed high resistance to several species of Puccinia striiformis f. Tritici pathotypes are virulent in sp Yr9. In addition, the different resistance response between them showed that rye has a diversity of resistance genes to stripe rust in wheat. These 4 lines showed better agronomic performance than their parent wheats. GS indices also showed the genetic diversity of 1RS in the same rye variety. This study suggests that rye varieties may have untapped variations that can be used for wheat improvement [5].
Besides that, due to Du et al. [2] identified genes against powdery mildew in the 6RLKU arm of a wheat-rye minichromosome line. The 6RLKU chromosome was derived from the minichromosome segments between L2.8 and L2.5 of the arm. After irradiation, the 6RLKU minichromosome was divided into two small segments. They are called 6RLKumi119 and 6RLKumi200. These fragments are involved in the formation of small segments of wheat-rye translocation chromosomes 6DS/6RLKumi119 and 6DS/6RLKumi200, respectively. The 6RLKumi119 segment was confirmed to contain a powdery mildew resistance gene. A total of 16 markers were developed specifically for 6RLKumi119, their material was cloned and sequenced. BLAST nucleotides from chromosome 6R of Secale cereal L. Lo7 showed gene similarity of 91 -100% in 14 of 16 sequences. A small segment of the translocation chromosome 6DS/6RLKumi119, i.e. 6RLKU, has more genes resistant to powdery mildew, which allows its use in agriculture.
It should be suggested that firstly Yamahita [9] presented an exchange scheme based on chromosome identification, according to which, if the analyzed tester line is translocated on different chromosomes, then the hybrid plants can be classified as tetravalent, bivalent, and producing hexavalent by homogeneous chromosome exchange. If the analyzed tester line has an identical translocation, then the conjugation of chromosomes of the hybrid generation occurs in a
normal state, if their translocation occurs only on one chromosome and occurs in different genetic loci, then tetravalent and bivalent ones are formed.
Later, a new method was developed in Gose related to the study of the exchange of homologous chromosomes, according to which Brown M.S. [1] proposed a double hybrid analysis of lines. The following features are taken into account: "if 23 bivalents are for med in the critical cells of meiosis of the hybrid generation with the participation of two translocation lines, then one of them is hexavalent; if two translocations belong to different chromosomes, then 22 bivalent and two tetravalent; if both translocations belong to the same chromosome, 26 - by the similarity of bivalent breaks; finally, 24 bivalent and one tetravalent state can arise". Simple chromosomal translocations were used in these genetic studies in the USA. In the Cytogenetic Collection of UzNU there are two lines associated with translocations in three non-homologous chromosomes, also arising as a result of the participation of 21 bivalent, one tetravalent and one hexavalent different chromosomes. Nine homozygous translocation lines from the Cytogenetic Collection of UzNU were studied by chromosome numbering and their identification with a test set of translocation lines.
Moreover, in these genetic studies in the USA, simple chromosomal translocations were used. In the Cytogenetic collection of UzNU there are two lines associated with the exchange of three non-homologous chromosomes, which also arose as a result of the participation of 21 bivalent, one tetravalent and one hexavalent different chromosomes. A new cytogenetic collection was created at the National University of Uzbekistan named after Mirzo Ulugbek, which includes 33 translocation lines of G. hirsutum, 95 primary monosomies of Ghoza (half of which occurred from generations) [6]. The identification of monosomic and translocation lines of the Cytogenetic collection, unique in Uzbekistan, is relevant using translocation lines of the tester kit created in the USA.
According to M.F. Sanamyan, nine homozygous translocation lines were studied in the Cytogenetic Collection of UzNU by chromosome numbering and their identification using a translocation line tester [10-14]. When conjugation was detected in hybrids of the translocation line during meiosis, interlinear differences arose in the studied hybrid combinations and the number of chromosomes participating in the exchange. In recent years, the emergence of various environmental problems has led to an increase in the need for cotton fiber.
It is known to everyone that the cotton varieties grown in our country belong to the species G. hirsutum. Complete identification of cotton chromosomes helps to determine the location of genes responsible for valuable economic traits. Identification of cotton chromosomes is the source material for creating a new productive variety. Identification of chromosomes of homozygous translocation lines in the cytogenetic collection of UzNU by the method of cytogenetic analysis serves as the basis for obtaining a new stable, fertile line.
The development of a set of chromosome-specific microsatellite-containing BACs and their physical mapping in Gossypium hirsutum L. was studied by Wang et al. [7]. Abstract Fluorescence in situ hybridization (FISH) using a bacterial artificial chromosome (BAC) clone as a probe is a reliable method for cytological examination of chromosomes. It contains a large number of small chromosomes used in many plants. We previously generated eight chromosome-specific BAC clones. Derived from tetraploid cotton, they were used as excellent cytological markers for chromosome identification. By isolating more chromosome-specific BAC clones in tetraploid cotton (Gossypium hirsutum L.), a complete set can be generated to identify all 26
chromosome pairs using this technology. In addition, one BAC containing an EST with high sequence similarity to the ethylene-responsive element binding factor of G. hirsutum was physically localized to the long arm of chromosome A7 using the chromosome A7-specific marker Wc BAC FISH. Analysis of the physical marker positions on comparative chromosomes, BAC-FISH and genetic linkage maps showed that most of the 26 BAC clones were localized at or near the ends of the corresponding chromosomes, and active recombination regions of cotton chromosomes were mainly located in the distal regions. The technology showed us that the MIDDLE chromosomes allow the association of their genetic linkage groups and the reassignment of each chromosome according to the corresponding genetic linkage.
Definitely, BAn experiment by Gan et al. [3] on individual chromosome arrangements and chromosomal diversity using a multi-probe fluorescence in situ hybridization (FISH) system was carried out in the Dt subgenome of tetraploid Gossypium barbadense (AD2), G.thurberi (D1) and G.trilobum (D8). The following two were possible subgenomic donors of tetraploid cottons. The FISH probes contained a set of bacterial artificial chromosome (BAC) clones specific for 13 individual chromosomes in the Dt subgenome. All chromosome orientations tested were confirmed using a centromere-specific BAC probe. Four 45S rDNA loci in D1 and D8 of the cotton Dt subgenome were successfully identified at the end of the short arm of chromosomes 03, 07, 09 and 11 and one 5S rDNA locus in the pericentromeric region of the short arm of chromosome 09. This showed the presence of chromosomal collinearity in D1 and D8 of the cotton Dt subgenome and with them in AD2 MEDIUM. The results provide a basis for understanding the chromosomal structure of cotton and the evolution of polyploidy in the cotton genome.
However, eight homozygous translocation (TT) lines of G. hirsutum marking chromosome 3 of the A genome and chromosome 9 of the D genome of cotton were crossed with G. hirsutum, G. mustelinum and G. tomentosum, all of which are homozygous for standard terminal constructs (tt). Chiasmata frequencies in the G. hirsutum Tt control were compared with G. hirsutum x G. mustelinum and G. hirsutum x G. tomentosum Tt hybrids. Chiasmata frequencies were compared across the core and in individual regions.
Some genomic differences appeared to have arisen between G. hirsutum and G. mustelinum. Chiasmata frequencies across the core of the G. hirsutum x G. mustelinum hybrids were reduced by 1.8-1.9%. Four of the eight TT lines showed a 3.4-10.5% reduction in chiasmata in tetravalent hybrid translocations, suggesting that chromosomes 1, 21, 23, and 24 may have undergone localized genomic differentiation. The two species may naturally differ in the final arrangement of the two chromosomes, since tetravalency independent of experimentally introduced translocations was observed in 13% of two G. hirsutum x G. mucellinum hybrids. Little genomic differentiation occurred between G. hirsutum and G. tomentosum. In G. hirsutum x G. tomentosum hybrids, nuclear-scale assessments showed a very small (0.1 to 0.2%) but statistically significant reduction in chiasmata frequency, and no reduction in chiasmata frequency was observed for specific tetravalent translocations with more sensitive measurements.[4]
What is more important, significant progress has been made in genetic mapping of the tetraploid cotton plant Gossypium hirsutum by Wang et al. However, six linkage groups (LGs) have not yet been assigned to specific chromosomes, preventing the construction of a unified genetic map. In this study, specific bacterial chromosome clones (BACs) were generated in G. hirsutum. For these six LGs, TM-1 was identified by screening a BAC library using linkage group-specific simple sequence repeat markers. These BAC clones hybridized with ten translocation
heterozygotes of G. hirsutum. As L BAC fluorescence in situ hybridization probes, this allowed us to map these six LGs A01, A02, A03, D02, D03, and D08 to chromosomes 13, 8, 11, 21, 24, and 19, respectively. Thus, 13 meologous pairs of chromosomes were identified and a new nomenclature of tetraploid cotton chromosomes was proposed [8]. Thus, in the USA about 60 translocation lines of cotton were created and their identification was carried out, however serial translocation lines were not obtained on all chromosomes. In addition, 33 homozygous translocation lines of a unique cytogenetic collection were created and their identification is being carried out in Uzbekistan.
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