Abstract
Yield is an important breeding target. As important yield components, boll number per plant (BNP) shows dynamic character and strong heterosis in Upland cotton. However, the genetic basis underlying the dynamic heterosis is poorly understood. In this study, we conducted dynamic quantitative trait loci (QTL) analysis for BNP and heterosis at multiple developmental stages and environments using two recombinant inbred lines (RILs) and two corresponding backcross populations. By the single-locus analysis, 23 QTLs were identified at final maturity, while 99 QTLs were identified across other three developmental stages. A total of 48 conditional QTLs for BNP were identified for the adjacent stages. QTLs detected at later stage mainly existed in the partial dominance to dominance range and QTLs identified at early stage mostly showed effects with the dominance to overdominance range during plant development. By two-locus analysis, we observe that epistasis played an important role not only in the variation of the performance of the RIL population but also in the expression of heterosis in backcross population. Taken together, the present study reveals that the genetic basis of heterosis is dynamic and complicated, and it is involved in dynamic dominance effect, epistasis and QTL by environmental interactions.
Highlights
Studies on quantitative trait loci (QTL) analysis for fiber trait were conducted in cotton[18,19,20]
Liu et al.[15] developed the immortalized F2 (IF2) population based on recombinant inbred line (RIL) population and found that both dominance and over-dominance contributed to heterosis of ‘XZM 2’ hybrid, and dominance played more important role in cotton yield performance
Guo et al.[22] conducted heterotic QTL mapping for yield traits using chromosome segment introgression lines and the results suggested that the over-dominant effect mainly contributed to yield heterosis
Summary
Studies on QTLs analysis for fiber trait were conducted in cotton[18,19,20]. For yield and yield heterosis, Shen et al.[21] detected five QTLs for bolls per plant using RILs population. Liang et al.[16] conducted study of yield heterosis in F2:3 and F2:4 populations derived from a hybrid ‘Xinza 1’ and indicated that partial dominance and overdominance effects at the single locus level and epistasis at two-locus level elucidated the genetic basis of heterosis in Upland cotton. The QTL analysis for yield and yield heterosis is usually studied using the final trait at maturation stage in cotton or other crops These reports overlooked the distinct hQTL actions at different developmental stages. We used previously constructed two Upland cotton BC populations and two RIL populations, and conducted QTL and conditional QTL analysis for boll number per plant as well as heterosis performance under multiple developmental stages and environments. This research will provide new insights into understanding of the genetic basis of dynamic heterosis in Upland cotton
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