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Genetic evaluation and characterization using cluster heat map for assessing NaCl tolerance in tomato germplasm at seedling stage

Fazal Rehman1*, Asif Saeed1, Muhammad Yaseen2, Amir Shakeel1, Khurram Ziaf1, Hassan Munir1, Sultan Ali Tariq3, Muhammad Ahsan Raza1, and Awais Riaz1

Salinity is a serious problem that limits crop growth and yield. The present study used plotting to evaluate 25 tomato (Solanum lycopersicum L.) accessions for various morpho-physiological parameters at the seedling stage and identify significantly salt-tolerant tomato lines at three different salinity levels. The pot experiment had a completely randomized design with three replicates in a factorial arrangement under greenhouse conditions. Tomato plants were exposed to 0 (control), 8, and 12 dS m-1 as NaCl stress at the seedling stage. The morpho-physiological traits, such as root and shoot length, root/shoot ratio, number of leaves, fresh and dry shoot weight, fresh and dry root weight, leaf area, Na+ and K+ concentrations, K+/Na+ ratio, and tolerance index, were recorded to examine salt tolerance. According to principal component analysis (PCA), there were six principal components (PCs) with Eigen values > 1 and 77.2% of total cumulative variability. The PC1 (24.3%) revealed the highest variability followed by PC2 (16.2%). Meanwhile, the PCA biplot and cluster heat map analyses indicated that Subarctic, Raad-Red, Naqeeb, Pakit, Tommy-Toe, and BL-1076 were salt-tolerant, whereas PBLA-1401, PB-017902, CLN-2413, BL-1078, BL-1174, and BL-1079 were the most susceptible accessions based on their performance under stress.

Key words: Cluster heat map, pot experiment, principal component analysis, salinity, Solanum lycopersicum, tomato seedling.

1University of Agriculture, Faculty of Agriculture, Faisalabad 38040, Pakistan. *Corresponding author (fazlpbg@gmail.com).
2University of Agriculture, Faculty of Sciences, Faisalabad 38040, Pakistan.
3Pakistan Agricultural Research Council (PARC), National Agricultural Research Center (NARC), Park Road, Islamabad 44000, Pakistan.

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