Breeding low-Pi tolerant and Pi-high-efficiency forest tree varieties is one of the effective ways to solve the low phosphorus utilization rate of forest trees and the lack of available phosphorus in forest soil. The evaluation system of low phosphorus tolerance of different families of Choerospondias axillaris was established to evaluate different phosphorus efficiency types and screen low-Pi tolerant and Pi-high-efficiency germplasms, and thus providing a reference for the P efficient cultivar breeding.

A pot experiment with low-Pi (0.2 mg·kg^-1) or normal-Pi (16.0 mg·kg^-1) supply was conducted, 28 families of Choerospondias axillaris were collected for the tested materials. The characterization values of seedling height, ground diameter, tissue phosphorus content, root system and other traits of each Choerospondias axillaris family were measured. The index of low phosphorus stress tolerance was calculated for each index. The low phosphorus tolerance index was analyzed by factor analysis, and the comprehensive evaluation value (D) and the comprehensive value of phosphorus efficiency were calculated by integrated affiliation function. Cluster analysis was conducted on the low phosphorus tolerance ability of the tested Choerospondias axillaris families, and the low phosphorus tolerance ability and phosphorus efficiency types were comprehensively evaluated. The regression equation was established to screen the discriminant index of low phosphorus tolerance family, and the evaluation system of low phosphorus tolerance ability was constructed.

Different families of Choerospondias axillaris showed significant growth differences under low phosphorus stress. The indexes of aboveground weight, root surface area, root tissue phosphorus content, seedling height, ground diameter and total root length were determined as the screening indexes for the evaluation system of low phosphorus tolerance of Choerospondias axillaris at seedling stage. The 28 families were categorized into three groups: low-Pi tolerance tolerance type, intermediate type and low-Pi tolerance intolerance type, and there were 6 families with low-Pi tolerance tolerance, 18 with intermediate type and 4 with low-Pi tolerance intolerance type. Additionally, based on the scatterplot of comprehensive P efficiency values, it was found that there were 5 families with P-high-efficiency under both low-Pi and normal-Pi; 7 families with high-efficiency under low-Pi but low-efficiency under normal-Pi; 7 families with low-efficiency under both low-Pi and normal-Pi; 9 families with low-efficiency under low-Pi but high-efficiency under normal-Pi.

The evaluation system of low phosphorus tolerance of different Choerospondias axillaris families was preliminarily established, and two families (LF001, L56) with low phosphorus tolerance&high-efficiency under both low-Pi and normal-Pi were screened out.