Differences of Cd and Pb Accumulation in Different Cultivars of Phaseolus coccineus L. in Yunnan Alpine Mountain Area

Purpose To reduce the accumulation of cadmium (Cd) and lead (Pb) in Phaseolus coccineus L. in alpine mining area, screening for low accumulation and high-quality P. coccineus cultivars suitable for farmland planting in this areas.

Methods A field experiment was conducted with 10 main cultivars of P. coccineus in Yunnan Province, and representative farmlands were selected around Lanping mining area. The contents of nitrogen (N), phosphorus (P) and potassium (K), vitamin C, protein, total starch, Cd and Pb were measured to explore the differences in mineral nutrients, grain quality, and Cd and Pb accumulation in different cultivars of P. coccineus.

Results There were significant differences in biomass, mineral nutrient content, grain quality and accumulation characteristics of Cd and Pb among different cultivars of P. coccineus. The maximum differences in biomass and yield were 3.88 times and 1.42 times, respectively; the maximum differences of N, P, K content in the grains were 1.42 times, 1.48 times and 1.40 times, respectively; the maximum differences of Cd, Pb content in grain were 1.93 times and 5.71 times, respectively; the maximum differences of Cd, Pb accumulation in grain were 3.76 times and 4.29 times, respectively; the maximum differences in the contents of reducing sugar, vitamin C, protein, soluble sugar and total starch were 1.98 times, 2.09 times, 1.43 times, 1.31 times and 1.42 times, respectively. Cultivar of YN10 showed high yield (2050 kg/hm²) and low Pb (0.17 mg/kg), cultivar of YN03 showed high yield (2048 kg/hm²) and low Cd (0.23 mg/kg). Correlation analysis showed that grain Cd content was significantly or extremely significantly negatively correlated with leaf N content, and root, stem and leaf K content; and it was significantly or extremely significantly positively correlated with total starch and vitamin C content. Grain Pb content was extremely significantly positively correlated with protein content.

Conclusion The absorption of Cd and Pb in P. coccineus is closely related to mineral nutrients and grain quality. Considering the grain yield, heavy metal accumulation, quality, and other factors, cultivars of YN10 and YN03 are more suitable for planting in Lanping Cd and Pb mildly polluted areas.