Physiologic and agronomic response of grain sorghum cultivars to drought stress and mycorrhizal fungus in summer cropping

Background and purpose: sorghum is the fifth most important grain in the world and is the main food of more than 500 million people in more than 30 countries. This plant has been introduced as a good substitute for corn in water shortage conditions; Because it has a higher tolerance to drought. On the other hand, choosing a variety adapted to the region and with greater tolerance to drought helps to increase production and reduce water consumption. Also, the use of arbuscular mycorrhizal fungi through the development of the root system, improving the absorption and transfer of nutrients and the production of metabolites and plant hormones has an important role in increasing the tolerance of plants to drought and on quantitative, qualitative, The growth and performance of agricultural plants has a positive effect. Considering the reduction of atmospheric precipitation in Iran and as a result of the water crisis in the country, the need for irrigation water management, especially in the agricultural sector, which is considered to be the main consumer of water, is of considerable importance. On the other hand, due to the fact that mycorrhizal fungi help the crop to absorb water, the above experiment aims to investigate the use of mycorrhiza in reducing the effects of drought stress on the yield and morphophysiological characteristics of three varieties of grain sorghum in moderate weather conditions. Kouhdash Lorestan was done.

Materials and methods: This experiment was carried out in the summer of 2015 and 2016 in Kohdasht city of Lorestan in the form of split-plot-factorial split-plot design with four replications. The main factor includes three irrigation regimes after 80 (control), 120 and 160 mm cumulative evaporation from the class A evaporation pan and sub-factors include mycorrhizal biological fertilizer in two levels of application and non-application of fertilizer and three grain sorghum varieties including Kimia, Payam. and Sepideh were the levels of the factors.

Findings: The results showed that the morphophysiological characteristics of sorghum such as leaf area index, spike length, number of seeds per spike, 1000 seed weight, seed yield, biological yield and harvest index decreased significantly with the increase in the intensity of drought stress. The highest seed yield was obtained under normal irrigation conditions and this trait decreased significantly under severe drought stress conditions. The comparison of the average of the simple effect of the factors showed that the application of mycorrhiza produced the highest seed yield and among the cultivars, Sepideh cultivar was the best and Payam cultivar had the lowest seed yield. The trend of changes in grain yield and leaf proline content with the increase in drought stress followed a significant linear relationship, negative and positive, respectively.

Conclusion: In total, the Sepideh variety with the use of mycorrhiza in the irrigation regime after 120 mm of evaporation without significant difference while producing the most desirable grain yield saves irrigation water can be recommended for the region.