Aneuploids induced by deficiencies of chromosome 9 and analysis of the time of nondisjunction in cotton

Abstract

MYLES, E. L., JR., and ENDRIZZI, J. E. 1989. Aneuploids induced by deficiencies of chromosome 9 and analysis of the time of nondisjunction in cotton. Genome, 32: 12 -18. Plants of allotetraploid cotton, Gossypium hirsutum L. (2n = 4x = 52), which are monosomic for chromosome 9 or haplodeficient for the long arm of the chromosome, an Ah genome chromosome, produce a high frequency of aneuploid progeny. The aneuploids include monosomes, trisomes, and multiple monosomic and trisomic combinations that are the result of chromosome nondisjunction, which is induced by the deficiency of the long arm of chromosome 9. Loss of chromosomes occurs far more frequently than additions, and chromosomes of the Ah genome undergo nondisjunction at a significantly greater rate than do chromosomes of the Dh genome. Stained paraffin sections of ovules at different stages of development of monotelodisomic 9 and normal plants (TM1) were analyzed to determine the time and probable causes of nondisjunction during megasporogenesis. The most significant difference between mono 9 and TM1 was observed in ovules in stages of development just before and at the time of flowering. The mono 9 female gametophytes had supernumerary nuclei, indicating that chromosome nondisjunction occurs at the mitotic divisions of the embryo sac.MYLES, E. L., JR., et ENDRIZZI, J. E. 1989. Aneuploids induced by deficiencies of chromosome 9 and analysis of the time of nondisjunction in cotton. Genome, 32 : 12-18. Les plantes allotktraploi'des du coton, le Gossipium hirsutum L. (2n = 4x = 52), qui sont monosomiques pour le chromosome 9 ou haplodkficientes pour le bras long du chromosome, un chromosome du gknome Ah, produisent une frkquence klevke de descendants aneuploi'des. Ces aneuploi'des incluent, des monosomes, des trisomes et des combinaisons monosomiques et trisomiques qui rksultent d'une non-disjonction induite par la dkficience du bras long du chromosome 9. Les pertes de chromosomes sont beaucoup plus frkquentes que les additions. Les chromosomes du gknome Ah subissent de la nondisjonction a un taux significativement plus klevk que les chromosomes du gknome Dh. Des ovules de plantes monotklodisomiques 9 et de plantes normales (TM1) ont kt6 prklevks a diffkrents stades de dkveloppement, puis aprks emparaffinement, sectionnement et coloration, les coupes ont fait l'objet d'analyses pour dkterminer le temps et les causes probables de la nondisjonction au cours de la mkgasporogenkse. La diffkrence la plus significative entre les mono 9 et les TM1 a kt6 observke chez les ovules aux stades de dkveloppement qui prkckdent immkdiatement la floraison ou au cours de la floraison. Les gamktophytes femelles des mono 9 posskdaient des noyaux surnumkraires, ce qui indique que la non-disjonction survient lors des divisions mitotiques dans le sac embryonnaire.

Cytogenetic Collection of Uzbekistan

“…In our experiments, we detected a nearly 2 : 1 ratio of the A t -to the D t -subgenome monosomes for all that monosomes of medium sizes to be from A t -genome. The ratio observed us is not significantly different from the ratio given by Myles and Endrizzi [52]. This confirms a greater tolerance of G. hirsutum to loss of the large A t -genome chromosome than the small D t -genome chromosomes.…”

“…These specific mutations were not frequent, but they were specific for the thermal neutron irradiation and very important for cotton genetics as new genetic markers. A similar analysis of chromosome aberrations showed that gamma-irradiation of pollen resulted in 53 translocations in the M 1 out of 331 studied plants, 52 plants with interchanges in the M 2 out of 348 Studied plants and 35 -in the M 3 generation out of 211 studied plants ( Table 2). All translocations were involving of two nonhomologous chromosomes formed quadrivalent associations ( Figure 3).…”

“…Monosomes of medium sizes demand special translocation tests with subgenome and chromosome number assignment of the translocated chromosomes. The analysis of subgenome assignment of unidentified monosomes of medium sizes showed the A t subgenome location [52] and significant deviation from the expected 1:1 ratio of the A t -subgenome monosome number to the D t -subgenome ones. This observation implied that preferential loss of the A t -subgenome chromosome was caused by specific genetic regulation system of chromosome disjunction and was not due to size of monosomes [52].…”

“…The analysis of subgenome assignment of unidentified monosomes of medium sizes showed the A t subgenome location [52] and significant deviation from the expected 1:1 ratio of the A t -subgenome monosome number to the D t -subgenome ones. This observation implied that preferential loss of the A t -subgenome chromosome was caused by specific genetic regulation system of chromosome disjunction and was not due to size of monosomes [52]. In our experiments, we detected a nearly 2 : 1 ratio of the A t -to the D t -subgenome monosomes for all that monosomes of medium sizes to be from A t -genome.…”

The creation of new aneuploid lines of the cotton (Gossypium hirsutum L.) with identification of chromosomes by translocation and SSR-markers

“…Дополнитель-ные исследования внесли уточнения в это соотношение, где из 95 идентифицированных унивалентных хромосом 79 имели А h -субгеномную и только 16 -D h -субгеномную принадлежность (4 : 1) (Edwards et al, 1980b). Это позво-лило считать, что преимущественная потеря хромосом, принадлежащих к А h -субгеному, обусловлена существо-ванием генетической системы регуляции расхождения хромосом, а не их размером (Myles, Endrizzi, 1989).…”