The Effect of Times and Type of Stress Modulator on Quantitative and Qualitative Yield of Cumin under Rainfed and Irrigated Conditions

A split-plot factorial experiment was conducted with 3 replications to evaluate the impacts of different type and time applications of stress modulators on the yield and yield components of cumin (Cuminum cyminum L.) under rainfed and irrigated conditions during 2016-2018. The studied factors were the cultivation method at 2 levels (rainfed and irrigated conditions) as the main plot and times of foliar applications with 2 levels (vegetative and vegetative + flowering growth stage) and sources of stress modulators with the 4 levels (control, 1.5 M Glycine Betaine (GB), 10-7 mM Brassinosteroids (BRs), and 1.5 mM Sodium Nitroprusside (SNP)). The results showed that irrigated cultivation led to the productions of higher plant heights, more lateral branches, larger numbers of umbrellas and seeds per plant, greater 1000-seed weights, more grain and essential oil yields, and less essential oil contents as compared to the treatments undergoing the rainfed condition. The lateral branches, umbrellas per plant, seeds per plant, and 1000-seed weights were affected by the application times. The foliar applications of Brassinosteroids (BRs) increased plant heights, lateral branches, umbrellas per plant, seeds per plant, 1000-seed weights, and grain and essential oil yields with less essential oil contents compared to those of the control. Under the irrigated condition, spraying of BRs enhanced plant height (7.64%), lateral branches (3.57%), umbrellas per plant (14.3%), seeds per plant (47.4%), 1000-seed weight (3.69%), and grain yield (74.5%), and lowered essential oil content (11.22%) when compared to those undergoing the rain-fed condition. Overall, the modulators for reducing drought stress impacts by elevating the yields and yield components could be classified as BRs>GB>SNP.