Characterizing Maize Genotypes for Salt Tolerance Using Morphological and Ionic Traits at Seedling Stage

Maize crop is the third most important cereal crop, mostly grown for food, feed and fodder purpose. In spite of the fact the crop is susceptible to salt stress but exhibits a considerable genotypic variability for salt tolerance. The present study was carried out to determine to which extent the maize genotypes with contrasting morphological traits respond to salt stress. Seven days old seedlings of thirty maize genotypes were exposed to NaCl stress of EC less than 4 (control), equal to 8 and 12 dS m-1 for further 28 days in a temperature controlled greenhouse. The salt stress imposition was completed in two increments every other day from the date of planting. At the age of 35 days, the seedlings were evaluated for contrasting morphological traits. The genotypes exhibited considerable variations for each of the 10 measured morphological and ionic traits. PCA was employed to identify the most suitable morphological trait to be used as selection criterion for salt tolerance. Based on the PCA results, dry shoot weight (DSW) was used to classify thirty maize genotypes into salt-tolerant-T, moderately tolerant-MT and salt sensitive-S groups. Two (2) out of thirty genotypes i.e. SB-9617 and FH-949 had the highest average of percent dry shoot weight (PDSW) values > 70%  were classified as salt tolerant (T). The fifteen (15) genotypes showed average of PDSW values in the range of 55-69.9 % were classified as moderately tolerant (MT) by indicating the sequence order of salt tolerance as YH-1898 > MMRI-yellow > S-2002 > FH-988 > FH-1292 > HC-12 > MS-2018 > NCEV-1270-7 > Pahari > Pearl White > FH-1114 > NCEV-1270-3 > Iqbal > NCEV-1297 > DK-6724. However, thirteen (13) out of total thirty (30) genotypes attained the average PDSW values <55% were classified as salt sensitive (S) following the sequence order as NCEV-1530-9 > Composite > FRI-22 > Azam > MS-2015 > P-1543 > Neelum > Afgoi > Malka-2016 > MS-1501 > HNG > NCEV-1270-5 > NCEV-7004. It was also noticed that the declared salt tolerance was positively correlated with dry shoot weight (DSW), shoot length (SL), stem diameter (SD), fresh shoot weight (FSW), fresh root weight (FRW), dry roots weight (DRW), root length (RL), leaf area per plant (LA), number of leaves per plant (NL) and K+/Na+ ratio. The highest positive Pearson correlation coefficients were determined in LA vs SD (r=0.900), DSW vs SD (r=0.899), SL vs DSW (r=0.891), SL vs FSW (r=0.890) and DSW vs FSW (r=0.887). Additionally, the salt tolerant (T) group of genotypes maintained higher K+/Na+ ratios compared to moderately tolerant (MT) and salt sensitive (S) groups. The results clearly showed that dry shoot weight (DSW) could be viable option to classify maize genotypes into different salt tolerance groups and to identify the most suited and best adapted salt tolerant genotype for cultivation in saline soils. Furthermore, this scientific information could help the plant scientists to improve and develop the new salt tolerant cultivar.