Phosphorus use efficiency and genotype × environment interactions in four elite soybean genotypes in Kenya

Abstract

The constraint of low soil phosphorus (P) availability is a significant aspect that affects the production of soybean in sub-Saharan Africa, especially soils that are highly weathered and where the fixation of P restricts access to nutrients in the soils. In the study, the phosphorus use efficiency (PUE) and genotype x environment interaction (GEI) among four elite soybean genotypes (Gazelle, Blackhawk, SB 08, and SB 19) were measured under three phosphorus levels (0, 30, and 50 kg P ha -1) and across phosphorus-deficient environments in western Kenya. PUE assessment was carried out in a split-plot randomized complete block design and to assess GEI in terms of agronomic characteristics such as grain yield, total biomass, and accumulation of phosphorus, multi-environment trials were conducted at three phosphorus deficient locations. The analysis of variance indicated that the effects of phosphorus level were highly significant (p < 0.001) on these characteristics, but the effects of genotype and genotype x phosphorus interactions were not significant, implying that the limitation of nutrients concealed genetic differences suggesting that increased phosphorus availability is necessary before genotypic differences can be fully expressed. The gain in grain yield and biomass was observed to be steady with exposure to phosphorus, evidencing the prevailing role phosphorus supply played in improving crop performance. Genotypic yield differences were not significant, but the yield index, phosphorus efficiency indices, and PCA indicated that underlying physiological strategies included SB 19, which had high phosphorus utilization efficiency, Gazelle, which had high phosphorus uptake and partitioning, and SB 08 that had a balanced response. The environment and genotype × environment interaction (p < 0.05) passed significant to generate the grain yield, time to maturity, days to 50% flowering and the other agronomic traits, whereas environment was considered to explain the most significant part of the variation. AMMI and GGE biplots showed that there were crossover interactions, meaning that there was no best genotype in all the environments. SB 08 was found to be the most stable with AMMI Stability Value, and SB 19 was a mixture of moderate stability and high phosphorus utilization efficiency. The findings illustrate that the output of soybean in phosphorous-deficient systems is mostly determined by the availability of nutrients but the environmental circumstances have strong effects on the genotype performance of soybean. It shows the significance of combining phosphorus regulation with the choice of effective and resilient genotypes to improve productivity and functionality of low-input agriculture.