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A new synthetic allotetraploid (A1A1G2G2) between Gossypium herbaceum and G. australe: bridging for simultaneously transferring favorable genes from these two diploid species into upland cotton.

Liu Q, Chen Y, Chen Y, Wang Y, Chen J, Zhang T, Zhou B - PLoS ONE (2015)

Bottom Line: Creating synthetic allotetraploid cotton from these two species would lay the foundation for simultaneously transferring favorable genes into cultivated tetraploid cotton.Here, we crossed G. herbaceum (as the maternal parent) with G. australe to produce an F1 interspecific hybrid and doubled its chromosome complement with colchicine, successfully generating a synthetic tetraploid.The synthetic allotetraploid will be quite useful for polyploidy evolutionary studies and as a bridge for transferring favorable genes from these two diploid species into Upland cotton through hybridization.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Crop Genetics & Germplasm Enhancement, MOE Hybrid Cotton R&D Engineering Research Center, Nanjing Agricultural University, Nanjing, Jiangsu, People's Republic of China.

ABSTRACT
Gossypium herbaceum, a cultivated diploid cotton species (2n = 2x = 26, A1A1), has favorable traits such as excellent drought tolerance and resistance to sucking insects and leaf curl virus. G. australe, a wild diploid cotton species (2n = 2x = 26, G2G2), possesses numerous economically valuable characteristics such as delayed pigment gland morphogenesis (which is conducive to the production of seeds with very low levels of gossypol as a potential food source for humans and animals) and resistance to insects, wilt diseases and abiotic stress. Creating synthetic allotetraploid cotton from these two species would lay the foundation for simultaneously transferring favorable genes into cultivated tetraploid cotton. Here, we crossed G. herbaceum (as the maternal parent) with G. australe to produce an F1 interspecific hybrid and doubled its chromosome complement with colchicine, successfully generating a synthetic tetraploid. The obtained tetraploid was confirmed by morphology, cytology and molecular markers and then self-pollinated. The S1 seedlings derived from this tetraploid gradually became flavescent after emergence of the fifth true leaf, but they were rescued by grafting and produced S2 seeds. The rescued S1 plants were partially fertile due to the existence of univalents at Metaphase I of meiosis, leading to the formation of unbalanced, nonviable gametes lacking complete sets of chromosomes. The S2 plants grew well and no flavescence was observed, implying that interspecific incompatibility, to some extent, had been alleviated in the S2 generation. The synthetic allotetraploid will be quite useful for polyploidy evolutionary studies and as a bridge for transferring favorable genes from these two diploid species into Upland cotton through hybridization.

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Chromosome associations in PMCs at Metaphase I of meiosis.a, 25II + 2I; b, 24II + 4I; c, 25II + 2I; d, 23II + 3I + III; e, 24II + I + III. Arrows indicate the univalents and arrowheads indicate the trivalents. Bar = 10 μm.
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pone.0123209.g003: Chromosome associations in PMCs at Metaphase I of meiosis.a, 25II + 2I; b, 24II + 4I; c, 25II + 2I; d, 23II + 3I + III; e, 24II + I + III. Arrows indicate the univalents and arrowheads indicate the trivalents. Bar = 10 μm.

Mentions: We then performed cytological observations of the new synthetic allotetraploid of G. herbaceum × G. australe. All of the cells observed had 52 chromosomes, indicating that they were tetraploid (2n = 4x = 52; Table 1, Fig 3), which further confirmed the authenticity of the new synthetic allotetraploid. The chromosome configurations in the synthetic allotetraploid were variable, with uni-, bi- and trivalents. Of the 49 pollen mother cells observed, most cells (24/49) had two univalents and 25 bivalents, followed by cells (14/49) with four univalents and 24 bivalents. Some cells (9/49) contained three univalents, 23 bivalents and one trivalent. Only two cells had 26 bivalents. The average chromosome configurations were 2.67 uni-, 23.33 bi- and 0.18 trivalents. The number of univalents ranged from zero to four, with two being the most frequent number, followed by four and three. The number of bivalents ranged from 23 to 26, with 25 being the most frequent number followed by 23 and 24 (Fig 3). The high frequency of univalents in pollen mother cells (PMC) at Metaphase I in meiosis explained why the synthetic allotetraploid plants were partially fertile, since due to disordered segregation, univalents were often lost at Anaphase I, leading to the formation of unbalanced, nonviable gametes lacking a complete set of chromosomes.


A new synthetic allotetraploid (A1A1G2G2) between Gossypium herbaceum and G. australe: bridging for simultaneously transferring favorable genes from these two diploid species into upland cotton.

Liu Q, Chen Y, Chen Y, Wang Y, Chen J, Zhang T, Zhou B - PLoS ONE (2015)

Chromosome associations in PMCs at Metaphase I of meiosis.a, 25II + 2I; b, 24II + 4I; c, 25II + 2I; d, 23II + 3I + III; e, 24II + I + III. Arrows indicate the univalents and arrowheads indicate the trivalents. Bar = 10 μm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4400159&req=5

pone.0123209.g003: Chromosome associations in PMCs at Metaphase I of meiosis.a, 25II + 2I; b, 24II + 4I; c, 25II + 2I; d, 23II + 3I + III; e, 24II + I + III. Arrows indicate the univalents and arrowheads indicate the trivalents. Bar = 10 μm.
Mentions: We then performed cytological observations of the new synthetic allotetraploid of G. herbaceum × G. australe. All of the cells observed had 52 chromosomes, indicating that they were tetraploid (2n = 4x = 52; Table 1, Fig 3), which further confirmed the authenticity of the new synthetic allotetraploid. The chromosome configurations in the synthetic allotetraploid were variable, with uni-, bi- and trivalents. Of the 49 pollen mother cells observed, most cells (24/49) had two univalents and 25 bivalents, followed by cells (14/49) with four univalents and 24 bivalents. Some cells (9/49) contained three univalents, 23 bivalents and one trivalent. Only two cells had 26 bivalents. The average chromosome configurations were 2.67 uni-, 23.33 bi- and 0.18 trivalents. The number of univalents ranged from zero to four, with two being the most frequent number, followed by four and three. The number of bivalents ranged from 23 to 26, with 25 being the most frequent number followed by 23 and 24 (Fig 3). The high frequency of univalents in pollen mother cells (PMC) at Metaphase I in meiosis explained why the synthetic allotetraploid plants were partially fertile, since due to disordered segregation, univalents were often lost at Anaphase I, leading to the formation of unbalanced, nonviable gametes lacking a complete set of chromosomes.

Bottom Line: Creating synthetic allotetraploid cotton from these two species would lay the foundation for simultaneously transferring favorable genes into cultivated tetraploid cotton.Here, we crossed G. herbaceum (as the maternal parent) with G. australe to produce an F1 interspecific hybrid and doubled its chromosome complement with colchicine, successfully generating a synthetic tetraploid.The synthetic allotetraploid will be quite useful for polyploidy evolutionary studies and as a bridge for transferring favorable genes from these two diploid species into Upland cotton through hybridization.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Crop Genetics & Germplasm Enhancement, MOE Hybrid Cotton R&D Engineering Research Center, Nanjing Agricultural University, Nanjing, Jiangsu, People's Republic of China.

ABSTRACT
Gossypium herbaceum, a cultivated diploid cotton species (2n = 2x = 26, A1A1), has favorable traits such as excellent drought tolerance and resistance to sucking insects and leaf curl virus. G. australe, a wild diploid cotton species (2n = 2x = 26, G2G2), possesses numerous economically valuable characteristics such as delayed pigment gland morphogenesis (which is conducive to the production of seeds with very low levels of gossypol as a potential food source for humans and animals) and resistance to insects, wilt diseases and abiotic stress. Creating synthetic allotetraploid cotton from these two species would lay the foundation for simultaneously transferring favorable genes into cultivated tetraploid cotton. Here, we crossed G. herbaceum (as the maternal parent) with G. australe to produce an F1 interspecific hybrid and doubled its chromosome complement with colchicine, successfully generating a synthetic tetraploid. The obtained tetraploid was confirmed by morphology, cytology and molecular markers and then self-pollinated. The S1 seedlings derived from this tetraploid gradually became flavescent after emergence of the fifth true leaf, but they were rescued by grafting and produced S2 seeds. The rescued S1 plants were partially fertile due to the existence of univalents at Metaphase I of meiosis, leading to the formation of unbalanced, nonviable gametes lacking complete sets of chromosomes. The S2 plants grew well and no flavescence was observed, implying that interspecific incompatibility, to some extent, had been alleviated in the S2 generation. The synthetic allotetraploid will be quite useful for polyploidy evolutionary studies and as a bridge for transferring favorable genes from these two diploid species into Upland cotton through hybridization.

Show MeSH
Related in: MedlinePlus