Ecological effect and the utilization rate of K nutrient for different K use efficiency cotton genotypes

This project was implemented by Huazhong Agricultural University. It is important to identify cotton genotypes with higher nutrient efficiency and understand the mechanisms of response to K deficiency among genotypes to help in breeding high K efficiency genotypes. We selected a high K use efficiency genotype 103 and a low K use efficiency genotype 122 from 86 varieties and four different families in the last five years. Based on the two genotypes selected, experiments were conducted with the objectives to: (1) study their differences of agricultural character responses under K deficiency conditions, (2) study the genotypes which are more efficient in K uptake and utilization of soil K, and (3) discover the ecological effect of applying K fertilizer for different K efficiency cotton genotypes. A hydroponic experiment was conducted to find out the difference in K+ absorption mechanism between K-efficient cotton genotype 103 and K-inefficient cotton genotype 122 in low K conditions after growing them under low K stress treatment (2 mg/L) and normal K treatment (20 mg/L) with four treatments. The K concentrations used were 0.015, 0.03, 0.06, 0.12, 0.24, and 0.48 mmol/L.

Results showed that under normal K treatment, the K absorption pattern of the two cotton genotypes was significantly different. The value of Km (constant of K absorption dynamic equation) was 0.14 mmol/L for K-efficient genotype 103 and 1.13 mmol/L for K-inefficient genotype 122, which indicated that genotype 103 has higher affinity to K+ than genotype 122. Values of Vmax (maximum K absorption volume) were 3.76 umol/hr/g RFW (ratio of unit fresh tissue weight) for genotype 103 and 12.2 umol/hr/g RFW for genotype 122. This implied that high-affinity K transporter proteins might contribute to K absorption from environment or K channels which could work in low K condition for genotype 103. As for genotype 122, its low K affinity and high Vmax implied that there might be other ion channels in charge of K absorption. Values of Km were 0.21 mmol/L for genotype 103 and 0.36 mmol/L for genotype 122, indicating that both of the two genotypes have high affinity to K+ in the environment, but genotype 103 had a higher affinity to K+. The data demonstrated that genotype 103 have better low-K adaptability than genotype 122. This research also explained the difference in low K resistance between two cotton genotypes from the perspective of K absorption kinetics. Hubei-37