Evaluation of five rootstocks on the growth, gas exchanges and chlorophyll fluorescence of Juglans regia L. cv. 'Xiangling'

Our study comparative analyzed the morphological and physiological performance of Juglans regia L. cv. ‘Xiangling’ (JRX) grafted onto five rootstock species originated from China. A wide range of coefficient of variation (CV), 1.155–39.848%, was detected for fourteen indexes among the studied seedlings. CV of plant height, total dry biomass, total leaf area, root/shoot ratio, chlorophyll index, and stomatal conductance was higher than 15.00%, suggesting higher variation. Principal component analysis, hierarchical cluster analysis and subordinate function analysis were used to screen engrafted seedlings for their quality. All three methods produced the same result that seedling quality of ‘Xiangling’ engrafted with the five rootstock species from high to low were – Juglans regia L. cv. ‘Jizhaomian’ (JRJ), JRX, Juglans regia L. cv. ‘Lvxiang’ (JRL), Juglans mandshurica, Maxim., and Juglans hopeiensis Hu.. The evaluation results were highly consistent with the actual growth performance of the engrafted seedlings, it verified the reliability of our results and the evaluation methods. The results demonstrated that JRJ, JRX, and JRL are potential rootstock candidates in the studied walnut planting regions. It would provide important implication for the selection of proper rootstock species for a certain particular walnut variety.