Analysis of seed traits and selection of superior provenances of Rhododendron delavayi from different provenances

To investigate the morphological characteristics and germination traits of Rhododendron delavayi seeds from six provenances in Guizhou Province, analyze the variation and genetic characteristics of seeds from different provenances, and to provide technical support for the breeding of superior varieties.

The morphological traits (seed length, width, thickness, length-to-width ratio, flattening rate, seed dimension index, and thousand-seed weight) and germination traits (radicle length, germination rate, germination potential and germination index) of seeds from the six provenances were subjected to variability and heritability analysis, correlation analysis, and cluster analysis. The seed quality from different provenances was comprehensively evaluated using principal component analysis.

The results showed that the morphological characteristics of R. delavayi seeds from different provenances exhibited extremely significant differences (P<0.01). The coefficient of variation for seed morphological traits exceeded 10.00%, with the smallest variation observed in thousand-seed weight. The coefficients of variation for seed dimension index, seed thickness, and length-to-width ratio all exceeded 30.00%. The broad-sense heritability of morphological traits was greater than 0.87. The germination traits of seeds from different provenances also showed significant differences (P<0.05). Seeds from the Bailidujuan management area exhibited the longest radicle length (5.17 mm), the highest germination rate (77.50%), and the greatest germination potential (20.00%). Correlation analysis indicated that seed length and length-to-width ratio were significantly (P<0.05) or extremely significantly (P<0.01) negatively correlated with germination rate, germination potential, and germination index. Seed width was significantly (P<0.05) or extremely significantly (P<0.01) positively correlated with radicle length, germination rate, and germination index. The six provenances could be classified into three major categories: the first category included Zhongshan District, Shuicheng District, and Bailidujuan Management Area; the second category included Xixiu District and Hezhang County; and the third category was Changshun County. The comprehensive evaluation of seed quality from different provenances ranked as follows: Zhongshan District > Shuicheng District > Bailidujuan Management Area > Hezhang County > Changshun County > Xixiu District.

In conclusion, the morphological characteristics of R. delavayi seeds are primarily influenced by genetic factors but also exhibit certain variations due to geographical and environmental factors across different provenances. Seeds from Zhongshan District and Shuicheng District were relatively superior and can be further studied as material for breeding and propagation.