Effect of chitosan and zeolite on growth and yield of sesame (Sesamum indicum L.) under different irrigation conditions in Yazd

Sesame (Sesamum indicum L.) is an annual plant, with self-pollinating flowers which belongs to the Pedaliaceae family. This crop is one of the most important oilseed plant in Iran with 6500 and 42 thousand hectares cultivated area in Iran and the world (Golestani and Pakniyat, 2007). India, Sudan, Myanmar and China are the main production centers of this crop (Rajeswari et al., 2010). Water deficit stress reducing photosynthesis, stomata closure due to reduced plant growth, lack of assimilates for grain filling and lower grain filling period of plants (Reddy et al., 2004). Chitin is polysaccharides found in nature and has multiple applications in industry, medicine and agriculture (Wang et al., 2003). Chitosan is a glucosamine polysaccharide derived from chitin that more than 50% of acetyl groups refer has removed. Zeolites are a group of natural porous minerals that acts as a molecular sieve with its crystal structure practices and allow some passage of some ions and block the passage of some others, due to open channels in their ionic lattice.
A split plot factorial experiment was conducted in a randomized complete block design with three replications at the Research field of Yazd Center of Agriculture and natural resources, Yazd, Iran (31°N 54°E and 1220 m above sea level with sandy loam soil, 7/67 pH = and organic matter) during 2012 growing season. Treatments were three irrigation regimes (irrigation at 50, 65 and 80 percent depletion of plant available water in the soil, as the control, average stress and severe stress) placed in the main plots and foliar application in four levels (concentrations of chitosan with 0.4 percent and 0.05 percent, distilled water (control) and one percent acetic acid (This material is the solvent of chitosan and may affect traits separately)) and zeolite application (not application and use 4.5 tons per hectare) arranged as sub-plots. After determining the moisture content (TDR), field capacity and wilting point, experimental applied. Mean comparisons were performed by Duncan’s multiple range test (DMRT) using in SAS 9.2.
Results showed that the interaction effects of all treatments were significant on grain and oil yield, number of seeds per pod and height of the first pod from the ground application of zeolite at the average stress level of irrigation led to 85 percent and 67 percent decreases in oil and seed yield, respectively, averaged over all levels of foliar application. It was also observed that non application of zeolite in average stress level decreased 70 percent of total dry weight, 10 percent oil percentage and number of pod per plant 4 times in comparison with using this mineral material in normal level. Zeolite did not affect the number of pod per plants significantly under controlled condition. By increasing water deficit stress, number of pod per plant was reduced. Zeolite increased number of pod per plant in both moderate and severe water deficit stress condition (29%). Maximum pod length (2.3 cm) was observed in controlled condition which was (30%) higher than severe stress (2.2 cm).
We concluded that Chitosan and zeolite as growth enhancer materials increased yield of sesame under water deficit stress. Results also showed that water deficit stress reduced oil yield, height of first pod and seed in pod that reduce yield being through impact on yield components. Zeolite and chitosan could reduce negative effects of water deficit on plants and improve crop yield and its yield components.