Study the Effect of Withholding Irrigation and Brassino-Stroidids Hormone before Harvesting on Quantity and Quality Characteristics of Baluchistan Onion in Iranshahr

Background and Objectives The storage life of onion is an essential factor to marketing this product in the winter season. The storage life of onion depends on different factors of which withholding of irrigation before harvest is the most important. On the other hand, Brassinosteroids (BRs) are widely distributed in the plant kingdom, with pleiotropic effects, as they influence varied developmental processes like growth, germination of seeds, rhizogenesis, flowering, stem elongation, pollen tube growth, leaf epinasty, ethylene biosynthesis, proton pump activation, gene expression and photosynthesis. Therefore, studying the effects of withholding irrigation and Brassinosteroied on quantitative and qualitative characteristics of onion seems to be necessary.
Materials and Methods In order to evaluate the effect of withholding irrigation and Brassinosteroied hormone before harvesting on yield and postharvest life of Baluchistan onion, a split plot experiment in a randomized complete block design with three replications was conducted in Iranshahr’s Institute of Agricultural Research and Education in 2015-2016. This experiment was performed to evaluate three factors, water withholding at three levels (one, two and three weeks before harvest time) and spraying Brassinosteroied in four levels (0, 0.5, 0.75 and 1 μM). Different traits such as Bush height, diameter, length, weight, edible layer of bulb and neck diameter, post-harvest life, dry matter percentage and yield were measured.
Results Agronomic traits and post-harvest life of onion increased by increasing the hormone concentration to 0.75 μM. The highest yield observed in 0.75 μM of Brassinosteroied treatment was about 42 t/ha and in the treatment with one week of withholding irrigation before harvesting was about 39 t/ha. The lowest yield observed in without hormone treatment was about 33 t/ha and in the treatment with three weeks of withholding irrigation before harvesting it was about 36 t/ha. The maximum post-harvests observed in two weeks of withholding irrigation before harvesting and 0.75 μM of hormone treatments were about 60 and 50 days, respectively. The lowest post-harvest lives observed in one week of withholding irrigation before harvesting and without hormone treatments were about 33 and 43 days, respectively.
Discussion Withholding irrigation can decrease the amount of water in bulbs and increase post-harvest life because of reducing post-harvest diseases. On the other hand, Brassinostroides can induce growth and photosynthesis rate and alleviate the adverse effects of abiotic stress in plants. These are important reasons to increase quantitative and qualitative traits in this product.