Investigation of the response of new improved alfalfa cultivars to salinity in field conditions

Alfalfa (Medicago sativa L.) is one of the most important forage crops and it produces high quality fodder for all types of livestock and alone can provide energy, protein, minerals and vitamins for livestock. Alfalfa is relatively sensitive to the salinity, but it has a high genetic diversity that can be used to select resistant cultivars. Therefore, the success of selection of alfalfa resistant cultivars requires exploitation of this genetic diversity that can produce more resistant plants to salinity compared to other forage plants, thus cultivar selection is important for alfalfa hay production. The aim of this project was to evaluate the tolerance of new alfalfa cultivars to salinity in field conditions.

This research was carried out in 2017 and 2020 at the Research Farm of East-Azarbaijan Agricultural and Natural Resources Research and Education Center, Tabriz, Iran (Firuz Salar village located 4 km from Azarshahr city). In this study, two synthetic cultivars A and B along with a local ecotype as a control cultivar were compared in saline water and soil conditions. Synthetic A cultivar was selected from 11 ecotypes based on general combining ability test and evaluation of half-sib families, which eventually led to the production of Synthetic A cultivar. Synthetic cultivar B has been produced by selecting superior genotypes from five elite ecotypes. With polycross of selected genotypes in completely isolated conditions, synthetic cultivar B has been produced. Synthetic cultivars and common ecotype and local control were evaluated in a randomized complete block design with three replications. The field was irrigated with saline water of the experimental area. Chlorophyll index, plant height, stem diameter, leaf area index, fresh and dry forage yield in each harvest and their annual total, leaf to stem ratio, protein content, digestibility, ADF, NDF, and the chlorophyll content a and b were measured.

The results showed that there was a significant difference between the studied cultivars for all measured traits at the level of 1% probability and also the effect of harvest was significant for all traits except leaf to shoot ratio. The mean height in both synthetic cultivars A and B was higher than the control cultivar and both were in a statistical group. Similar results were observed for fresh and dry forage yield, leaf area index, stem diameter, leaf to shoot ratio and chlorophyll index and synthetic cultivars were superior to the control cultivar.The average fresh forage yield of synthetic cultivars A and B in each harvest was 18.06 and 17.81 tons per hectare, respectively, which was significantly higher than the average fresh forage yield of the control cultivar (15.24 tons per hectare). For dry forage yield was quite similar and dry forage yield of synthetic cultivars was significantly higher than the control cultivar. Synthetic cultivars were superior to control cultivar in terms of chlorophyll content. It seems that improving the photosynthetic ability of these cultivars is one of the reasons for the high forage yield in these cultivars.

The results showed that there was a significant difference between the studied cultivars for all measured traits. The average fresh forage yield of synthetic cultivars A and B in each crop was 18.06 and 17.81 tons per hectare, respectively, which was significantly higher than the average fresh forage yield of the control cultivar (15.24 tons per hectare). For dry forage yield, quite similar results were obtained and the dry forage yield of synthetic cultivars was significantly higher than the control cultivar. The mean height in both synthetic cultivars A and B was higher than the control cultivar. On average, during the three years of the study, the third and second harvest produced the highest fresh forage yields. It seems the cultivars that have been modified for normal conditions also appear to be better under stress conditions. According to the total results obtained, synthetic cultivars have the necessary potential for