Introduction
Onion is one of the most important vegetables in Iran and is cultivated in 51.499 hectares. The cultivated area of this crop in the short-day southern regions is 25.964 hectares, which is equivalent to more than 50% of the cultivated onion area in Iran. Commercial short-day onion cultivars are cultivated in most of these regions, so that large amount of currency is expensed to import short-day onion seed. In addition, the increase in the currency rate in recent years has increased the cost of onion production in short-day southern regions. Therefore, it is very important to produce and introduce short-day onion cultivars. This research was conducted to produce half-sib families through open pollination among nine superior onion cultivars. The best half-sib families were selected in terms of bulb yield and storability.
Materials and methods
This project was carried out in Isfahan and Khuzestan during three crop years (2020-2023). During two crop years of 2020-2022, a polycross genetic design was carried out among nine short-day onion cultivars (Sahar, Paliz, Saba, Savanasweet, Goldeneye, Duster, Impriaterize, Primavera, and Texas Early Grano) in the Isfahan location (Dastgerd Agriculture Research station), and half-sib families were produced. The progenies of half-sib families along with their parents were evaluated in a randomized complete block design (RCBD) with 18 treatments and three replications in Khuzestan location (Behbahan Agriculture Research station) during the crop year of 2022-2023. Seeds were sown in the nursery in early October, and seedlings were transplanted (at the two- or three-leaf stage) in late September. The earliest bulb time was estimated using the bulb ratio and statistical technique of cusums. The studied traits included leaf number and height, bolting percentage, bulb yield, days to maturity, mean bulb weight, mean bulb diameter and height, skin number, total soluble solids, dry matter, and bulbstorage losses. Bulbs were harvested when 50-80% of the foliage top had fallen and collapsed. To calculate dry matter content of the bulb, 10 bulbs were randomly selected from each plot and their weight was determined. After drying complete samples in the oven (65 ̊C) and fixing weights (about 72 h), samples were weighed again, and dry matter was calculated. After harvesting and curing, bulbs were stored under uncontrolled storage conditions (no heating, cooling, or ventilation systems), and after 3 months, postharvest bulb storage losses were determined. The results were analyzed using SPSS v.26. software. Means of significant differences among treatments were determined at the 0.05 probability level using Duncan’s test. Correlation coefficients among traits were calculated using Pearson method.
Results and Discussion
Bulbing occurred in the studied genotypes in a photoperiod of less than 13 h; therefore, all progenies and their parents were short-day genotypes. Palize cultivar produced the highest yield. The difference in bulb yield among this cultivar and Sahar, Saba, Savana sweet, and Goldeneye cultivars and Saba and Texas Early Grano half-sib families was not significant. The doubling bulb was not observed in studied genotypes. The highest bulb dry matter percentage was found in Texas Early Grano cultivar. The decrease in the percentage of bulb dry matter in the Saba cultivar and Savanasweet half-sib families was not significant compared with the Texas Early Grano cultivar. The highest skin number was recorded in the Texas Early Grano cultivar. The decrease in the number of skins in Sahar, Primavera, and Saba cultivars was not significant as compared with that in Texas Early Grano cultivar. The lowest bulb storage losses were observed in Sahar cultivar. The differences in this trait among Paliz, Primavera, and Texas Early Grano cultivars and Paliz, Savanasweet, Duster, Primavera, and Texas Early Grano half-sib families were not significant in comparison to Sahar cultivar. The correlation coefficients among bulb yield with leaf number and height, mean bulb weight and diameter were positive and significant at 1% probability level. Differences in days to maturity were not significant in all genotypes; therefore, final progeny selection was made with emphasis on bulb yield and storage losses. According to these results and comparison of days to maturity ,yield and bulb storage losses in progenies half -sib with maternal parent and parents mean the half-sib, progenies of Saba, Daster, and Texas Early Granohalf- sib families were selected.
Conclusion
The results showed that Texas Early Grano, Saba, and Duster half-sib families with high bulb yields (from 65.18 to 68.29 t ha-1) and good storability (storage bulb losses from 11.79% to 15.41%) are promising genotypes for introducing as short-day indigenous onion cultivars. |
