فهرست مطالب سمیه صوفی نیا

Lathyrus sativus L. is an annual plant from the legume family, used as a very valuable protein source for livestock and poultry, as well as for human nutrition. This genus has several useful agronomic characteristics such as high grain yield capacity and high protein content of its grains. Legumes produce economic performance in different environmental conditions and have a high potential for use in marginal areas with low rainfall. In fact, this has made it a popular crop in subsistence agriculture, especially in developing countries. The greatest importance of grass pea is related to the high resistance of this plant to harsh environmental conditions, such as drought, low soil fertility, and resistance to pests and plant diseases, which makes its production and cultivation economical. Salinity stress is an important abiotic stress that has harmful effects on plant performance and product quality and is a limiting factor for plant growth. Although salinity stress can occur in all growth stages of the plant, but considering that the initial establishment of the plant has a great impact on the final performance. Salinity stress in the seedling stage can be one of the most harmful stages for the plant. To improve the salinity tolerance in crops, genetic diversity between and within species can be used through selection and breeding. The purpose of this experiment was to investigate the response of early-maturing grass pea genotypes to different levels of salinity by evaluating some agronomic traits and identifying salinity-tolerant genotypes.

In order to evaluate the response of grass pea early maturing genotypes to salinity stress, 26 genotypes were studied as factorial experiment on based randomized complete block design with two replications at Research Farm of Plant Production and Genetics Department, Faculty of Agriculture, University of Maragheh. The salinity treatments were applied to four levels (0, 40, 80, 120 mM) of NaCl and different seedling and agronomic traits such as shoot fresh weight, shoot dry weight, fruit fresh weight, fruit dry weight, number of grains, number of grains per pod, plant height, leaf angle to the stem, leaf length, leaf width, number of leaves, number of shoots, location of the first shoot from the soil surface, root length were evaluated. Also, during the experiment, the date of flowering, the date of pod formation, the date of pod filling and the date of grain maturity were also recorded for each pot. Before data analysis, the assumptions of data variance analysis were checked with tests of normality and homogeneity of variances, and mean comparisons were made using Duncan's method at the 1% probability level. For the grouping of genotypes, cluster analysis was done by Ward's method and Euclidean distance measure using standardized variables. In order to determine the contribution of each trait in the total variation, reduce the amount of data and better interpret the relationships, principal components was used.

The difference between genotypes and salinity levels was significant in most seedling traits and with increasing salinity, the dry forage yield was decreased. Genotypes 19, 14, 13, 21, 10, 7, 25, 15, 24 and 12 were the best genotypes in terms of dry forage yield in seedling stage. Also, in the agronomic traits, differences between genotypes and salinity levels were significant in most traits. In general, the yield attribute decreased with increasing salinity. In cluster analysis with Ward’s alghorithm, the genotypes were divided into three clusters. The first cluster with the genotypes 8, 23, 11, 21, 7, 20, 2, 22, 3, 10 and 26 had the best genotypes for yield improvement. In principal component analysis, the first four principal components explainaed 82.08% of total variation. Based on the results, the first component could be identified as a component of biological yield and the second component as a forage yield. Thus traits of shoot length, root length, seedling length and the ratio of shoot length to root length were significant for the effect of genotype, salinity and the interaction of genotype × salinity at the probability level of 1%. The traits shoot dry weight, root dry weight and seedling dry weight had a significant effect of salinity at the probability level of 1%, and the trait of the ratio of shoot dry weight to root dry weight had not significant difference for any of the effects. Genotypes 19, 14, 13, 21, 10, 7, 25, 15, 24, and 12 were the best genotypes in terms of dry forage yield in seedling stage. In field traits, the difference between genotypes and salinity levels was also significant in most of the traits. In cluster analysis by Ward's method, the genotypes were divided into three clusters. The first cluster with genotypes 8, 23, 11, 21, 7, 20, 2, 22, 3, 10 and 26 had the best genotypes for yield improvement. In principal components analysis, the first three main components explained 82.08% of the total variation. The first component accounted for 38.31%, the second component for 25.31% and the third component for 19.74% of the total variation. Based on the obtained results, the first component can be named as the biological yield component and the second component as the forage yield.

The difference between genotypes and salinity levels was significant in most seedling traits, and dry forage yield decreased with increasing salinity. Thus, the characteristics of shoot length, root length, seedling length, and the ratio of shoot length to root length were significant for the effect of genotype, salinity, and the interaction of genotype in salinity at the probability level of 1%. The traits dry weight of shoot, dry weight of rhizome and dry weight of seedling had a significant effect of salinity at the probability level of 1%, and the trait of the ratio of dry weight of shoot to root had no significant difference for any of the effects. The results of seedling stage showed that genotypes 2, 6, 10, 13 and 26 (local) had high yield and genotypes 1, 3 and 5 had the lowest forage yield. The field results showed with the increase of salinity levels, a decrease in yield was observed.

Generally, with increasing salinity, forage yield decreased. The genotypes 10, 20, 22 and 23 the most tolerant genotypes and genotypes 16, 17, and 18 were identified as the most sensitive genotypes.