Assessment of lignin deposit as a criteria for wheat tolerance under salt and drought stresses

Salt stress is one of the important concerns on crop production in arid and semi arid regions of Iran. Wheat production is commonly decreased by salinity through seed size and grain yield. In the present study a recombinant inbred lines (RILs) has been generated by crossing salt tolerant genotypes and of them ١٥٢٦ RILs were screened for seed size under normal growth condition. The selected seeds categorized in ١٢ seed weight classes ranging from ١٨ to ٦٤ miligrams per seed. Finally, ١٠٧ lines have been selected for further assessment. To identify the factors affecting seed size, lignin content measured in endosperm and testa, also the number of endosperm nuclei has been determined ١٢ days after pollination. The results demonstrated that lignin accumulation and number of nucleus in embyro sac significantly influenced seed size. While, there was a negative correlation between lignin amount of endosperm and seed endosperm content. The lignin amount of endosperm with a negative correlation of -٣٤,٤٪ seems to be the most effective factor to decrease seed size. On the other hand, the nucleus number had a positive significant correlation of ٣٣٪ with seed size. It may suggest that the lignin accumulation in endosperm cell walls and the number of nucleus with different direction are the most effective determinants for wheat seed size. To study the effect of seed size on salt tolerance, all wheat selected RILs were planted at normal and saline (٥٠ ds/m) conditions. The results showed that seed size has a more beneficial effect on seed emergence and primairly seedling growth under saline than normal condition. After three leaf stage seed size effect was disappeared. Plant growth response under saline condition showed a proper variation for different physiologic and agronomic triats and accession numbers ٣٨ and ٩٩ have been identified as the most tolerant and susceptible lines, respectively. The results have been confirmed using biplot analysis. The present results suggest that wheat may be improved by pyramiding different quantitative traits responsible for different components of salt tolerance.