Discerning morpho-anatomical, physiological and molecular multiformity in cultivated and wild genotypes of lentil with reconciliation to salinity stress

Abstract

One hundred and sixty two genotypes of different Lens species were screened for salinity tolerance in hydroponics at 40, 80 and 120 mM sodium chloride (NaCl) for 30 d. The germination, seedling growth, biomass accumulation, seedling survivability, salinity scores, root and shoot anatomy, sodium ion (Na+), chloride ion (Cl-) and potassium ion (K+) concentrations, proline and antioxidant activities were measured to evaluate the performance of all the genotypes. The results were compared in respect of physiological (Na+, K+ and Cl-) and seed yield components obtained from field trials for salinity stress conducted during two years. Expression of salt tolerance in hydroponics was found to be reliable indicator for similarity in salt tolerance between genotypes and was evident in saline soil based comparisons. Impressive genotypic variation for salinity tolerance was observed among the genotypes screened under hydroponic and saline field conditions. Plant concentrations of Na+ and Cl- at 120 mM NaCl were found significantly correlated with germination, root and shoot length, fresh and dry weight of roots and shoots, seedling survivability, salinity scores and K+ under controlled conditions and ranked the genotypes along with their seed yield in the field. Root and shoot anatomy of tolerant line (PDL-1) and wild accession (ILWL-137) showed restricted uptake of Na+ and Cl- due to thick layer of their epidermis and endodermis as compared to sensitive cultigen (L-4076). All the genotypes were scanned using SSR markers for genetic diversity, which generated high polymorphism. On the basis of cluster analysis and population structure the contrasting genotypes were grouped into different classes. These markers may further be tested to explore their potential in marker-assisted selection.

Fig 1. Seed germination percentage (a), salinity tolerance score (b), seedling survival percentage (c), root length (d), shoot length (e), root fresh weight (f), shoot fresh weight (g), root dry weight (h) and shoot dry weight of lentil genotypes raised (i) under 120 mM NaCl, in hydroponic conditions.

Bar represents dispersion among observations and square represents mean value.

Fig 2. Changes in stellar region and vascular bundles in cross-sections of stem in tolerant and sensitive Lens species raised under control (0 mM) and (120 mM NaCl) saline stress in hydroponics.

E-Epidermis, COR-SC—Cortical-Schlerenchyma, COR-PR- cortical parenchyma, PH = Pholem, END = Endodermis, S-V = Stellar-Vascular bundle, COR-V = Cortical -Vascular bundle. Bar in each figure represents 100 μm.

Fig 3. Changes in stellar region and vascular bundles in Root cross-sections of tolerant and sensitive Lens species raised under control (0 mM) and (120 mM NaCl) saline stress conditions raised in hydrophonics.

E = Epidermis, COR- SC = Cortical-Schlerenchyma, COR- PR = Cortical Parenchyma, PH = Phloem, RH = Root Hair. Bar in each figure represents 100 μm.

Fig 4. Na⁺, K⁺, Cl^- contents in root and shoot of Lens species at different levels of salt stress (0, 40, 80 and 120mM NaCl) at seedling stage under hydroponic conditions.

Fig 5. Fluorescent root images of tolerant breeding line (PDL-1), sensitive cultigen (L-4076) and tolerant wild accession (ILWL-15) for detection of H₂O₂ under 120 mM NaCl stress conditions in hydrophonics.

Bar in each figure represents 1 mm.

Fig 6. Effects of salt stress (120mM NaCl) on activity of antioxidant enzymes APX (a), GPX (b), SOD (c), catalase (d) and proline concentration (e) in root and shoot of Lens spices raised in hydrophonics.

Fig 7. Percent reduction in pods and seed yield per plant in contrasting lentil genotypes grown under three salt concentrations during 2013–14 and 2014–15.

Fig 8. Changes in Na⁺ (a and b), K⁺ (c and d) and Cl^- (e and f) content in root and shoot of contrasting lentil genotypes at vegetative stage in control (EC<1.0) and saline stresses (40, 80 and 120 ECiw) under field conditions.

Circles are the actual observations and line represents mean value.

Fig 9. Changes in Na⁺ (a and b), K⁺ (c and d) and Cl^- (e and f) content in root and shoot of contrasting lentil genotypes at reproductive stage in control (EC<1.0) and saline stresses (40, 80 and 120 ECiw) under field conditions.

Circles are the actual observations and line represents mean value.

Fig 10. UPGMA tree based on dissimilarity index of 30 SSR markers for 162 lentil genotypes.

Fig 11. Structure plot with K = 3 depicting model based population, using structure with 30 SSR markers.

The number in the bracket represents origin of accessions as follows: Argentina (1), Bangladesh (2), Crotia (3), France (4), ICARDA (5), India (6), Italy (7), Jordan (8), Lebnon (9), Palestine (10), Slovania (11), Spain (12), Syria (13) and Turkey (14).

Fig 12. Correlation between genetic similarity index and taxonomic distance for total sodium per cent of 162 genotypes at 120 mM NaCl concentration.