Evaluation of Thellungiella halophila ST7 for improving salt tolerance in cotton

Background Gossypium hirsutum (upland cotton) is one of the principal fiber crops in the world. Cotton yield is highly affected by abiotic stresses, among which salt stress is considered as a major problem around the globe. Transgenic approach is efficient to improve cotton salt tolerance but depending on the availability of salt tolerance genes. Results In this study we evaluated salt tolerance candidate gene ST7 from Thellungiella halophila, encoding a homolog of Arabidopsis aluminum-induced protein, in cotton. Our results showed that ThST7 overexpression in cotton improved germination under NaCl stress as well as seedling growth. Our field trials also showed that ThST7 transgenic cotton lines produced higher yield under salt stress conditions. The improved salt tolerance of the transgenic cotton lines was partially contributed by enhanced antioxidation as shown by diaminobenzidine (DAB) and nitrotetrazolium blue chloride (NBT) staining. Moreover, transcriptomic analysis of ThST7 overexpression lines showed a significant upregulation of the genes involved in ion homeostasis and antioxidation, consistent with the salt tolerance phenotype of the transgenic cotton. Conclusions Our results demonstrate that ThST7 has the ability to improve salt tolerance in cotton. The ThST7 transgenic cotton may be used in cotton breeding for salt tolerance cultivars.

Alterations in the Antioxidant Metabolites in Cotton Leaf Curl Disease Infected and Healthy Cotton Leaves

The upland cotton (Gossypium hirsutum) belongs to the family Malvaceae and cultivated since ancient times in warmer parts of the world. Pakistan is the 4th largest cotton producing country and prominent cotton yarn exporter of the world. Cotton is the major source of natural fiber and significantly contributes to the economy of Pakistan. There are many factors (biotic and abiotic) affecting the cotton yield in Pakistan. The cotton leaf curl disease (CLCuD) is one of the biotic factors and endemic in the most cotton growing areas of the country. The antioxidant enzymes and antioxidant biochemical metabolites play important role during stress. The present study was planned to compare the antioxidant enzymes and metabolites from healthy and CLCuD infected cotton leaves. Antioxidant enzymes activities including catalase, peroxidase and peroxidase were measured through different antioxidant assays and different antioxidant metabolites were also determined. During stress condition antioxidant metabolites serve as signal for the activation of antioxidant enzymes. Present study revealed that antioxidant enzymes were significantly higher in the infected cotton leaves as compared to the healthy cotton leaves. While the amount of antioxidant metabolites like total phenolic contents (TPC) and total flavonoid contents (TFC) were higher in healthy cotton leaves as compared to the infected leaves.

Preliminary Study Mechanism of Ethylene Induced Abscission Zone Formation and Function of GhArfGAP in Upland Cotton Boll Stalk

Background: With the continuous growth of population, the demand for fiber is also rising sharply. As one of the main fiber plants in the world, cotton fiber yield of upland cotton is affected by boll abscission, which is related to the formation of abscission zone. Therefore, we explored the formation of the abscission zone of upland cotton.Result: The formation of abscission layer of cotton boll stalk was promoted by exogenous ethylene. It was found that both the number of Golgi apparatus and the number of stacking layers increased in the dissociated cells. The GhArfGAP gene family in upland cotton was screened by bioinformatics method, and the species and evolutionary relationship of GhArfGAP gene family were analyzed. qRT-PCR showed that the expression patterns of GhArfGAP13,GhArfGAP15, GhArfGAP25 and GhArfGAP34 in cotton were spatiotemporal specific. Subcellular localization suggested that GhArfGAP25 played a role in Golgi apparatus . The expression of GhArfGAP25 in transgenic Arabidopsis increased in the root, stem and leaf.Conclusions: Ethylene could induce the formation of abscission zone in upland cotton. GhArfGAP13,GhArfGAP15,GhArfGAP25,GhArfGAP34 might regulate the changes of Golgi apparatus in abscisson zone.Taken together the findings provide new ideas for the study of cotton abscission formation.

Global insights into homoeolog gene expression in upland cotton under intraspecific hybridization

Background: Hybridization is useful to enhance yield potential of agronomic crops in the world. Cotton has genome doubling due to alloteraploidy process and hybridization process in coordinate with duplicated genome can produce more yield and adaptability. Therefore, expression of homoeolog gene pairs between hybrids and inbred parents are vital to characterize genetic source of heterosis in cotton.Results: Investigation results of homoeolog gene pairs between two contrasting hybrids and their respective inbred parents identified 36853 homoeolog genes in hybrids. It was observed both high and low hybrids had similar trends in homoeolog gene expression patterns in each tissue under study. An average of 96% of homoeolog genes had no biased expression and their expressions were derived from the equal contribution of both parents. Besides, very few homoeolog genes (An average of 1%) showed no biased or novel expression in both hybrids. The functional analysis described secondary metabolic pathways had a majority of novel biased homoeolog genes in hybrids. Conclusions: These results contribute preliminary knowledge about how hybridization affects expression patterns of homoeolog gene pairs in upland cotton hybrids. Our study also highlights the functional genomics of metabolic genes to explore the genetic mechanism of heterosis in cotton.

QTL mapping of agronomic and economic traits for four F2 populations of upland cotton

Background Upland cotton (Gossypium hirsutum) accounts for more than 90% of the annual world cotton output because of its high yield potential. However, yield and fiber quality traits often show negative correlations. We constructed four F2 populations of upland cotton, using two normal lines (4133B and SGK9708) with high yield potential but moderate fiber quality and two introgression lines (Suyuan04–3 and J02–247) with superior fiber quality, and used them to investigate the genetic basis underlying complex traits such as yield and fiber quality in upland cotton. We also phenotyped eight agronomic and economic traits and mapped quantitative trait loci (QTLs). Results Extensive phenotype variations and transgressive segregation were found across the segregation populations. We constructed four genetic maps of 585.97 centiMorgan (cM), 752.45 cM, 752.45 cM, and 1 163.66 cM, one for each of the four F2 populations. Fifty QTLs were identified across the four populations (7 for plant height, 27 for fiber quality and 16 for yield). The same QTLs were identified in different populations, including qBW4 and qBW2, which were linked to a common simple sequence repeat (SSR) marker, NAU1255. A QTL cluster containing eight QTLs for six different traits was characterized on linkage group 9 of the 4133B × Suyuan04–3 population. Conclusions These findings will provide insights into the genetic basis of simultaneous improvement of yield and fiber quality in upland cotton breeding.

QTL Mapping of Agronomic and Economic Traits for Four F2 Populations of Upland Cotton

Background: Upland cotton (Gossypium hirsutum) accounts for more than 90% of the annual world cotton output because of its high yield potential. However, yield and fiber quality traits often show negative correlations. We constructed four F2 populations of unland cotton, using two normal lines (4133B and SGK9708) with high yield potential but moderate fiber quality and two introgression lines (Suyuan04-3 and J02-247) with superior fiber quality, and used them to investigate the genetic basis underlying complex traits such as yield and fiber quality in upland cotton. We also phenotyped eight agronomic and economic traits and mapped quantitative trait loci (QTLs). Results: Extensive phenotype variations and transgressive segregation were found across the segregation populations. We constructed four genetic maps of 585.97 cM, 752.45 cM, 752.45 cM and 1 163.66 cM, one for each of the four F2 populations.. Fifty QTLs were identified across the four populations (7 for plant height, 27 for fiber quality and 16 for yield). The same QTLs were identified in different populations, including qBW4 and qBW2, which were linked to a common simple sequence repeat (SSR) marker, NAU1255. A QTL cluster containing eight QTLs for six different traits was characterized on linkage group 9 of the 4133B×Suyuan04-3 population. Conclusions: These findings will provide insights into the genetic basis of simultaneous improvement of yield and fiber quality in upland cotton breeding.