Salt tolerance index and morpho-physiological characterization of tomato F2 segregating lines under salinity stress

Abstract Background: Salinity is one of the major abiotic stresses that impairs plant growth and development. It is responsible for huge crop yield losses worldwide posing a threat to world food security. The aim of the present investigation is to explore the potential of genetic crosses between a wildtype salt-tolerant tomato and salt-sensitive genotype to develop commercially desirable salinity-tolerant tomato cultivars. Methods: A cross between a salt-sensitive tomato cultivar (CA4-S) and a salt-tolerant wild-type tomato species (LA1606-T) was generated and the resulting F1 plants were selfed to obtain the F 2 seeds. Tomato seedlings obtained from 120 F 2 lines were randomly selected and cultivated in a greenhouse under RCBD. To evaluate the salinity response of segregating progenies, seedlings were irrigated each day with 185 mM NaCl for 82 days and various agronomical traits including leaf chlorophyll content, plant height, number of leaves, leaf length, days to maturity, flower number, fruit number, fruit weight, fruit length, fruit width, fruit set percentage, and total fruit yield were quantified. Main findings: Results presented herein show that all traits examined exhibited diverse ranges of variations, and continuous distribution, typical of quantitative traits among F 2 progenies. The skewness value of total yield (TY) (0.04) and days to maturity (0.09) were very close to 0, signifying that TY and days to maturity tend to follow a normal distribution. The total fruit yield per plant was positively correlated with total fruit number, number of fruits per cluster, fruit set percentage, number of flowers per cluster, fruit weight, fruit number, and chlorophyll content, but negatively correlated with plant height. Conclusion: A salt tolerance index (STI) was developed based on these measurements, and was used to select the most tolerant and sensitive progenies from the F 2 generation. These selected progenies could be selfed and advanced to obtain salt-tolerant cultivars of tomato genotypes, thus helping to address genetic bases of salt tolerance and the prevailing food insecurity in the world.