Analysis of Genetic Characteristics and Heterosis for Corolla Phenotypic Traits in Natural Hybrids of Rhododendron

Abstract

【Objective】By analyzing the genetic variation characteristics and heterosis of natural hybridization in Rhododendron, a theoretical basis is provided for hybrid breeding and new variety selection of Rhododendron.【Method】Thirty-six natural hybrids of Rhododendron delavayi and Rhododendron irroratum were taken as the research materials. The phenotypic traits of Rhododendron corollas such as inflorescence shape, flower color, corolla diameter, and number of floret were analyzed, and their genetic diversity, coefficient of variation and heterosis were studied.【Result】The inflorescence shapes mainly were divided into three types, among which flat inflorescences accounted for 83.33%, and the flower color differentiation was most obvious, with pink accounting for 61.11%, and white and light yellow accounting for a relatively small proportion. The differentiation of the corolla throat spots and corolla honeydew spots in hybrids was also obvious. The colorful ribbed stripes on the back of corolla were differentiated from the deep red and light yellow of the parent into the pink, deep red, purplish red and light yellow. The pink ribbed stripes were the most common, accounting for 58.33%. The corolla posture was differentiated into three types: fully wavy, wavy on the edge, and nearly flat. Among them, there were more plants with wavy edges on the corolla, accounting for 86.11%. By calculation, it could be inferred that the Shannon-Wiener diversity of corolla color, corolla throat spot and corolla honeydew spot was higher than 1.0. The frequency distribution of quantitative traits in the corolla followed a normal distribution, it was in conformity with typical genetic characteristics of quantitative traits. The coefficient of genetic variation ranged from 11.17% to 26.7%. The heterosis index of corolla diameter was positive (106.66%), while the heterosis index of other trait indicators was negative, ranging from88.91% to 98.97%. The index of the pedicel length was the smallest. The HH was between 11.11% and 55.56%, while the LL was between 13.89% and 58.33%. The HH of the corolla diameter was the highest.【Conclusion】Therefore, the corolla phenotypic traits of the natural hybrids of Rhododendron delavayi and Rhododendron irroratum have rich variation characteristics, with the potential for breeding excellent germplasm. The hybrids have a certain degree of HH, and phenotypic traits like corolla diameter exhibit excellent traits. However, some traits also have a certain proportion of LL, and the rate of deterioration is also relatively high.

Keywords

• genetic characteristics
• heterosis
• phenotypic trait
• natural hybrid
• rhododendron corolla