Optimal NaCl concentration for screening popcorn inbred lines for salt tolerance at the germination stage

Approximately 85000 hectares of popcorn, which is a C4 glycophytic and salt-sensitive crop, is cultivated in Brazil. Agricultural land area is decreasing because of increasing population and salinity stress, leading scientists to devise a means to develop salt-tolerant crops using genetic approaches. This study was carried out to determine the most suitable NaCl concentration for screening popcorn inbred lines for salt tolerance. Four NaCl solutions (0, 60, 120, and 180 mmol L-1) were used on four popcorn inbred lines in a completely randomized design. The experimental treatments were replicated four times in a seed-germinating chamber over seven days. Twenty-five seeds from each line were treated with Maxim® before being placed on germination paper and soaked in an appropriate NaCl solution. Significant (p < 0.05) responses of the inbred lines to different NaCl concentrations in terms of shoot length, root length, fresh and dry shoot and root weight, root diameter, root surface area and germination percentage were observed. The salt tolerance index based on dry seedling weight was significantly correlated with the other traits under 60 and 120 mmol L-1 NaCl. The most concentrated NaCl solution (180 mmol L-1) resulted in the greatest reduction in the performance of the inbred lines, indicating that NaCl is toxic to the inbred lines evaluated. Regression analysis indicated that shoot length and root length are the most significant traits for assessing salt stress tolerance in popcorn inbred lines. The results suggest that NaCl solutions of 60 and 120 mmol L-1 could be used for screening salt tolerance in popcorn, as these provide a strong ability to distinguish among the inbred lines studied.