Intraspecific variation in potassium uptake and utilization among sweet potato (Ipomoea batatas L.) genotypes

There is still limited information on growth and potassium (K) accumulation in sweet potato in response to varying K supply levels over time, and the quantification of such characteristics is necessary to screen for high K absorption and utilization-efficient genotypes. In field experiments in 2012, 108 sweet potato genotypes or breeding lines were screened without K or with a 300 kg ha−1 K2SO4 supply. Seven elite genotypes, Xu22, Nan88, Wan5, Wan6, Xu085, Xu083 and Ji22, selected from the 2012 experiments were tested with different K application levels (0, 150, 300, and 450 kg ha−1 K2SO4) in 2013. Significant intraspecific variations among genotypes and responses to K supplies existed in the root dry matter yield and biomass yield, and in K concentrations, accumulations and use efficiencies (KIUEs) of the sweet potatoes in the initial field experiment. In the advanced field experiment, a K fertilizer application increased tuberous root dry matter of sweet potato by increasing the tuber number, and, to a lesser degree, the mean tuber weight. K accumulation levels in the seven elite sweet potato genotypes peaked under a deficient K supply at 100 days after plantation and decreased, to different extents, at maturity. Based on K accumulation at different growth stages under a K deficiency and K accumulation at maturity with different K supply levels, Nan88 and Xu082 were rated as K uptake efficient, and Ji22 and Xu083 as K uptake inefficient. According to the KIUE for tuberous root yield (KIUE-T) under deficient K and adequate K supplies, the genotypes were classified as being efficient or inefficient in K utilization. Genotypes Xu28 and Wan5 were K-efficient and Ji22 was K-inefficient in both experiments. KIUE-T had a significant positive correlation with the relative root weight per plant, with the tuberous root dry matter increasing from expanding stage to maturity, and it had a significant negative correlation with K concentrations in the roots or whole plants at maturity. No significant correlation was found between root dry matter yield and KIUE.