Evaluation of Salt Tolerance in Sorghum (Sorghum Bicolor) Genotypes

Abstract

Sorghum is a drought-tolerant crop with high potential to improve productivity and livelihood of communities living in Arid and Semi-Arid lands (ASALs). While sorghum is largely adapted to diverse agro-ecological conditions, saline soils which is largely predominated by sodium chloride (NaCl) is a major abiotic threat to production in the ASALS. Laboratory and greenhouse studies were conducted at Egerton University, Njoro (0o22‘11.0‖ S, 35o55‘58.0‖ E) to screen sorghum genotypes for salt tolerance. The experiments were laid out in a Completely Randomized Design (CRD) with treatment combinations of sorghum genotypes tested over four levels of NaCl concentrations 0, 3, 5 and 7 dSm-1. The salt solutions treatments were prepared in hydro-A and hydro-B nutrient solutions to provide the required plant nutrients. A laboratory study to test for the effects of NaCl on seed germination and seedling establishment was determined for 250 sorghum genotypes in a growth incubator maintained at a temperature of 23oC using Petri dishes lined with Whatman‘s filter papers. The data from this experiment were subjected to R4.2.0 for ANOVA and SPSS V. 20.0 for hierarchical cluster analysis of sorghum for salt tolerance. The results from this experiment showed a significant correlation (P ≤ 0.001) between number of root hairs, root length and shoot length among the genotypes and NaCl concentrations. Cluster analysis showed BM 17, GBK 000049, GBK 000038, and BM 29 genotypes to be highly salt tolerant. Root hairs were shown to be a good parameter for screening for salt tolerance. Three salt tolerant and three salt sensitive genotypes were selected from the laboratory experiment and planted in plastic pots in the green-house using vermiculite as a growth media to determine the morphological and ion uptake responses of sorghum genotypes to NaCl concentrations. The data from this experiment were subjected to R4.2.0 for ANOVA. Sorghum genotypes showed significant variation (P ≤0.001) in their growth and shoot/root Na+ uptake at the different NaCl concentrations. BM 17 genotype was significantly tolerant to NaCl concentrations with low salt injury index of below 2 when compared to the highly salt sensitive EST 41. The salt tolerant genotypes seemed to absorb and store more Na+ in their roots and restrict their excess transit to the shoots while salt sensitive genotypes transported more Na+ to the shoots. The results suggest salt exclusion as a mechanism of salt tolerance in sorghum. BM 17, BM 17, GBK 000049 and GBK 000038 were identified as the salt tolerant genotypes which provide a basis for crop improvement for enhanced resilience and improved productivity in ASAL regions.