The Effect of Foliar Application of Cycocel on Quantitative Traits Related to the Yield of Mung Bean (Vigna radiata) Genotypes under Water Deficit Conditions

Drought is one of the most important non-living stresses that has an adverse effect on crop production and their quality and leads to osmotic, ionic, and nutritional limitations as well as growth delay, metabolic disorders and oxidative stress in plants. Iran has a dry and semi-arid climate and the occurrence of drought stress during the growth period of plants is inevitable. Presently, the production of legumes in the country is mostly under rainfed conditions and drought stress is one of the main factors reducing the yield of legumes. Mung bean is a small grain of valuable legume. Evaluation of the performance of different cultivars is considered a starting point in identifying drought-resistant cultivars. Cycocel is one of the most important growth retarders for tampering with growth and performance. Therefore, the present study was conducted to investigate the effect of foliar application of cycocel on quantitative traits of mung bean (Vigna radiata) genotypes under water deficit conditions.

In order to investigate the effect of foliar application with cycocel and water requirements on quantitative traits of mung bean (Vigna radiata) genotypes, experiental desing of split-split plot based on a randomized complete block design with three replications in research farm of the Ferdowsi University of Mashhad. Experimental factors included 3 levels of drought (non-stress, mild stress, and severe stress), 3 levels of cycocel foliar spraying (0, 400, and 800 mg/L), and 2 levels of mung bean cultivars (Hendi landrace and Zarbakhsh). Statistical analysis was performed using SAS 9.4 and comparing the means was based on the LSD method at a 5% probability level. 

The experimental results showed that the effect of drought stress, cycocel, genotype, and the interaction of drought stress and cycocel as well as drought stress and genotype on the number of pods per plant were significant. The results showed that drought stress reduced the number of pods in the plant and cycocel increased it. The number of pods in the plant of the Hendi landrace genotype decreased more than that of the Zarbakhsh genotype due to drought stress. Also, drought stress, cycocel, genotype, and the interaction of drought stress and cycocel as well as drought stress and genotype on the number of seeds in the pod, were significant. The results showed that cycocel increased the number of seeds per pod, while drought stress decreased the number of pods per plant. It was also found that at all levels of drought stress, the Zarbakhsh genotype had more seeds in pods than the Hendi landrace genotype. Drought stress, cycocel, genotype, and the interaction of drought stress and cycocel as well as drought stress and genotype had a significant effect on the 1000-seed weight. The results showed that the 1000-seed weight increased due to the application of cycocel, while drought stress decreased this trait. In addition, it was observed that the 1000-seed weight of the Hendi landrace genotype decreased more than the Zarbakhsh genotype due to drought stress. Drought stress, cycocel, genotype, and interaction between drought stress and cycocel had a significant effect on grain yield. The results showed that the grain yield in the Zarbakhsh genotype was significantly higher than in the Hendi landrace genotype. It was also observed that drought stress decreased and the application of cycocel increased grain yield. Drought stress, cycocel, and genotype had a significant effect on biological performance. Drought stress caused a significant decrease in biological yield. The use of cycocel increased the biological performance and increasing the concentration of this substance increased the biological performance. The results of variance analysis of data showed that the effect of drought stress, cycocel, genotype, and the interaction of drought stress and cycocel, drought stress and genotype as well as cycocel and genotype on harvest index were significant. In addition, it was observed that the harvest index of the Hendi landrace genotype decreased more than the Zarbakhsh genotype due to drought stress.

According to the results of this study in the presence of drought stress, it showed a decrease in yield and its components. Among the studied mung bean cultivars, the Zarbakhsh cultivar showed superiority in tolerance to water shortage conditions compared to other cultivars. The use of cycocel reduced the negative effects of drought stress on the plant. It appeared that the use of cycocel under drought stress conditions improved the plant better plants performance.