| Pepper is one of the major vegetable crops, with a wide range of uses and significant economic value. Heterosis utilization is currently the main means of pepper breeding, but not all hybrids will exhibit the desired heterosis. Therefore, exploring the possibility of prediction of heterosis is of great significance to heterosis utilization in pepper breeding. In this study,22pepper inbred lines were used to generate14F1hybrids. Phenotypic and genetic differences among the inbred lines were analyzed using phenotypic traits and SSR markers, respectively. Mid-parent heterosis and high-parent heterosis were measured for the hybrids. Meanwhile, correlation between the performance of heterosis and the genetic differences was evaluated for the inbred lines and their respective hybrids. The main results are as the following.1. Twenty-two phenotypic traits were measured for the22pepper inbred lines. Spicy and fruit shoulder are the largest variable traits with the coefficients of variation were75.15and76.76, respectively. The number of fruits per plant was the largest variable quantitative trait with the coefficient of variation of77.46. The Euclidean distance between the22pepper inbred lines was from1.49to9.36, with an average of5.58. The22pepper inbred lines were divided into four groups by cluster analysis, exhibiting a high degree coincidence with the pepper fruit traits.2. Genetic differences between the inbred lines were assessed using107pairs of SSR primers. Among them, eight pairs of primers had no amplification products,68pairs of primers had mono-polymorphic amplification products, and31pairs of primers had polymorphic amplification products. In addition to CAK30detecting three alleles, only two alleles were detected for each of the other30polymorphic SSR markers. The Euclidean distance between the22pepper inbred lines was from2.65to6.32, with an average of4.97. Cluster analysis divided22inbred lines into7groups. The results of principal coordinates analysis were similar with that of the cluster analysis, but the principal coordinate analysis more clearly demonstrated the genetic differences between the inbred lines.3. According to the phenotypic data of the inbred lines and their hybrids, heterosis was calculated for each hybrid. As for the yield, the mid-parent heterosis ranged from39.85%(11L25×11L26) to197.81%(11L74×11L235) with an average of133.98%, and high-parent heterosis variation ranged from28.07%(11L25×11L26) to176.87%(11L165×11L172) with an average of109.22%. As far as the first node of flowering, the mid-parent heterosis ranged from2.86%to18.30%with an average of2.86%, and high-parent heterosis ranged from-15.79%to28.57%with an average of3.48. As for the number of fruit per plant, the mid-parent heterosis ranged from-52.59%to50.77%with an average of11.71%, and the high-parent heterosis ranged from-70.91%to40.00%with an average of-9.56%.4. Simple correlation analyses were conducted between the genetic distances calculated by the phenotypic data among the inbred lines, and the mid-parent heterosis determined by the traits of each hybrid. The results showed that the genetic distance based on phenotypic traits exhibited significant positive correlation with the yield obtained (r=0.56, p=0.039), and fruit weight (r=0.57, p=0.035), respectively, which suggested that the larger differences of phenotypic traits exhibiting between the inbred lines would result in greater heterosis of yields and fruit weights for their hybrids. Correlation analyses were further performed between the phenotypic data based genetic distance and the high-parent heterosis. Significant negative correlations were observed between the genetic distances and the heterosis of fruit number per plant (r=-0.56, p=0.039) and flesh thickness (r=-0.73, p=0.003), respectively.5. Simple correlation analyses were further conducted between the genetic distance based on SSR markers and the mid-parent heterosis of each trait. Significant positive correlations were observed between the SSR based genetic distance and plant height (r=0.60, p=0.024) and width (r=0.78, p=0.001), respectively. Similarly, analyses on the correlation between the genetic distance based on SSR markers and the high-parent heterosis of each trait also demonstrated that the SSR based genetic distances were positively correlated with plant height (r=0.59, p=0.026) and width (r=0.72, p=0.004)... |
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