genetic characteristics; heterosis; phenotypic trait; natural hybrid; Rhododendron corolla 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. |