Study on Heterosis for Yield and Yield Contributing Traits in Desi Cotton (Gossypium arboreum L.)

The present investigation entitled “Studies on Heterosis for Yield and Yield Contributing Traits in Desi Cotton (Gossypium arboreum L.) was undertaken with the objective to study the scale of heterosis over mid parent (Average heterosis), better parent (Heterobeltiosis) and standard check (Standard heterosis). The line x tester method of analysis was followed involving four females viz., PA 811, PA 839, PA 808 and PAIG 380 and six males viz. AKA 8, JLA 505, PA 812, AKA 7, PA 08 and Phule Dhanwantry for study of heterosis for various yield and yield contributing characters. The F1’s and theis parents were evaluated in Randomized Block Design with two replications. Observations were recorded on Days to 50 % flowering, Plant height (cm), Number of sympodia, Number of bolls/plant, Boll weight (g), Seed index, Seed cotton yield/plant (g) and Lint index. The magnitude of heterosis was highest for seed cotton yield per plant, which was recorded to the extent of 115.28 % over standard check PKV Suvarna in the cross PAIG 380 x AKA 8 followed by 109.68 % over standard check PKVDH 1.

Enhanced Expression of Plasma Membrane Intrinsic Protein 2 Improves Cotton Fiber Length and Potential Economic Viability of Gossypium Arboreum

Background: Gossypium arboreum is a cotton crop native to tropical and subtropical regions that are naturally resistant to Cotton Leaf Curl Virus (CLCuV). However, its cultivation is unfavorable due to the lower quality and shorter fiber length of cotton when compared to the market leading Gossypium hirsutum. Plasma membrane intrinsic protein 2 (PIP2) is an aquaporin responsible for the transport of water and small molecules across cellular membranes. This fluid transport influences cell elongation and cotton fibre development. Hence, increased PIP2 expression may yield plants with enhanced fiber qualities including length. Methods and Results: To test this hypothesis, G. arboretum was transformed with a PIP2 gene construct (35SCpPIP2)using the Agrobacterium-mediated shoot apex cutting method. Relative expression of the CpPIP2 gene in transgenic plants increased up to 35-fold when compared with non-transgenic controls. Transgenic plants displayed a corresponding increase of staple length (up to 150%) when compared with non-transgenic controls. Transgene integration was examined using FISH and karyotyping and revealed the presence of a single transgene located on chromosome 6. Conclusion: Since G. arboreum is naturally whitefly and CLCuV resistant, this improvement of fiber length evidenced for CpPIP2 transgenic plants renders their crop production more economically viable.

Genome-Wide Introgression and Quantitative Trait Locus Mapping Reveals the Potential of Asian Cotton (Gossypium arboreum) in Improving Upland Cotton (Gossypium hirsutum)

Gossypium arboreum (2n=2x=26, A2), the putative progenitor of the At-subgenome of Gossypium hirsutum (2n=4x=52, AD), is a repository of genes of interesting that have been eliminated during evolution/domestication of G. hirsutum. However, its valuable genes remain untapped so far due to species isolation. Here, using a synthetic amphiploid (AADDA2A2) previously reported, we developed a set of 289 G. arboreum chromosome segment introgression lines (ILs) in G. hirsutum by expanding the backcrossing population and through precise marker-assisted selection (MAS) although complex chromosomal structural variations existed between parents which severely hindered introgression. Our results showed the total coverage length of introgressed segments was 1,116.29 Mb, representing 78.48% of the At-subgenome in the G. hirsutum background, with an average segment-length of 8.69 Mb. A total of 81 co- quantitative trait loci (QTLs) for yield and fiber quality were identified by both the RSTEP-ADD-based QTL mapping and the genome-wide association study (GWAS) analysis, with 1.01–24.78% of the phenotypic variance explained. Most QTLs for boll traits showed negative additive effects, but G. arboreum still has the potential to improve boll-number traits in G. hirsutum. Most QTLs for fiber quality showed negative additive effects, implying these QTLs were domesticated in G. hirsutum compared with G. arboreum and, a small quantity of fiber quality QTLs showing positive additive effects, conversely; however, indicates that G. arboreum has the underlying genes of enhancing fiber quality of G. hirsutum. This study provides new insights into the breeding genetic potential of G. arboreum, lays the foundation for further mining favorable genes of interest, and provides guidance for inter-ploidy gene transference from relatives into cultivated crops.