Assessment of onion breeding selections in storage

Supply of fresh produce of bulb onion in Kazakhstan is confined to the season from late summer to mid-autumn, so over 7-9 months from late-autumn to the next mid-summer season onion is delivered from storage. Improving of postharvest storability of onion accessions has been an essential part of the breeding program of the Kazakh Research Institute of Potato and Vegetable Growing. In the frame of onion breeding program 88 onion accessions were studied in storage. Onion bulbs were stored in polypropylene netted bags, which are placed bulk on the wooden shelves. Storage temperature fluctuated from 2-5 to 10-12°C. In the spring after prolonged storage the results showed that high natural decline in mass (>10,0%) was observed in 18 breeding selections of onion, in 35 selection numbers it was at a level of 6,0-10,0%, low natural decline in mass (<6.0%) were noted in 35 onion accessions. The lowest natural decline in mass was observed for onion breeding selections ON268 - 3.3% and ON208 - 2.3%. The maximum natural decline in onion mass was recorded for selection numbers ON136 - 19.0% and ON174 - 18.3%. Out of the 88 onion breeding selections investigated 25 accessions have no visible infection signs on onion bulbs. The maximum loss from diseases was observed in onion breeding selections ON282 - 22.4% and ON202 - 22.0%. The economic value of studied onion breeding selections was integrated into indices to include mean onion bulb weight at 100 g, natural decline in mass at <6% and the loss from diseases at <10% during prolonged storage and storability rate at >90%. The best distinguished integrated indices of onion bulb storability were documented for onion breeding selections ON208, ON275, ON272, ON180, ON185, ON248 and ON278.