Assessment of heterosis based on parental genetic distance estimated with SSR and SNP markers in upland cotton (Gossypium hirsutum L.)

Abstract

Background: Heterosis has been extensively utilized in different crops and made a significant contribution to global food security. Genetic distance (GD) is one of the valuable criteria for selecting parents in hybrid breeding. The objectives of this study were to estimate the GD between parents using both simple sequence repeat (SSR) markers and single nucleotide polymorphism (SNP) markers and to investigate the efficiency of the prediction of hybrid performance based on GD. The experiment comprised of four male parents, 282 female parents and 1128 F₁, derived from NCII mating scheme. The hybrids, their parents and two check cultivars were evaluated for two years. Performance of F₁, mid-parent heterosis (MPH), and best parent heterosis (BPH) were evaluated for ten agronomic and fiber quality traits, including plant height, boll weight, boll number, lint percentage, fiber length, fiber strength, fiber uniformity, fiber elongation ratio, micronaire, and spinning consistent index.

Results: Heterosis was observed in all hybrids and, the traits like plant height, boll number, boll weight and lint percentage exhibited higher heterosis than the fiber quality traits. Correlations were significant between parental and F₁ performances. The F₁ performances between three hybrid sets (Elite×Elite, Exotic×Elite, and Historic×Elite) showed significant differences in eight traits, including boll number, lint percentage, fiber length, fiber strength, fiber uniformity, fiber elongation ratio, micronaire, and spinning consistent index. The correlation of the GD assessed by both SSR and SNP markers was significantly positive. The cluster analysis based on GD results estimated using SNP showed that all the female parents divided into five groups and the F₁ performance between these five groups showed significant differences in four traits, including lint percentage, micronaire, fiber strength, and fiber elongation ratio. The correlation between GD and F₁ performance, MPH and BPH were significant for lint percentage and micronaire.

Conclusions: Our results suggested that GD between parents could be helpful in heterosis prediction for certain traits. This study reveals that molecular marker analysis can serve as a basis for assigning germplasm into heterotic groups and to provide guidelines for parental selection in hybrid cotton breeding.

Keywords: Genetic distance; Heterosis; SNP; SSR; Upland cotton.

Fig. 1

Clustering of 1128 F₁s into five groups using genetic distance based on SNP markers

Fig. 2

Boxplots showing the distribution of F₁ performance for ten traits for the Elite×Elite, Exotic×Elite, and Historic×Elite hybrids and parent performances

Fig. 3

Boxplots showing the distribution of F₁ performance for ten traits for the groups I, II, III, IV, and V and parent performances

Fig. 4

Heterosis performance of F₁ hybrids. a: boxplots showed the mid-parent heterosis for all the analyzed traits. b: boxplots showed the better-parent heterosis for all the analyzed traits. PH: plant height, BW: boll weight, LP: lint percentage, BN: boll number, FL: fiber length, FS: fiber strength, MIC: micronaire, FU: fiber uniformity, FE: fiber elongation, SCI: spinning consistency index

Fig. 5

Correlation matrix between parental performance and F₁ performance and heterosis