Investigation and mass selection on Gholy-Ghesseh Local onion

In order to congregate the desirable genes in local onion population of Gholy- Ghesseh, mass selection method was used in this study carried out from 1998-2002 in Kheir-Abad Agricultural Research Center, Zanjan, Iran. In 1998, based on bulb characters , single bulbs were selected and in the next year , planting was conducted in isolated plots providing open pollination. Seeds of selected plants were harvested, combined and used as F1 population which were planted during the 2nd phase of the selection. For evaluation of the selection, seeds obtained from both the phases along with seeds of single plants collected from F2 population and parental (initial ) seeds were compared in an experiment using RCBD layout with 19 treatments and 4 replications in 2002.Single plants were chosen based on number of flowering stems which varied from 1-16 ones. Results showed no significant difference between populations originated from F1 and F2 selection regarding mean bulb weight, bulb diameter, bulb height, number of leaves, leaf weight, plant weight, dry matter %, bulb neck, total biomass, bulb performance, and per cent of sprouting bulbs during storage period, concluding no advance in selection process. But significant positive was observed on sheath length, leaf length and double bulbing. Among the populations, F2 generation showed the highest mean leaf length and leaf sheath which were 55.6 and 13.6 cm respectively but double bulbing was the least(2.1%) in this population compared with the others. Genetic analysis of the studied characters revealed the maximum rate of general heritability h2 b with leaf sheath length which was 0.39. Genetic correlation coefficient of neck diameter was significantly positive comparing with bulb weight, leaf length, leaf weight, sheath length, plant weight and bulb height where as this coefficient was significantly negative when double bulbing compared with the same charactersso it could be concluded that selection for reduction of double bulbing must be based on more vigorous plants while for thin neck bulbs such plants should be avoided. Presence of significant negative genetic correlation between double bulbing and neck bulb- being important economic characters of onion- confirmed the idea that simultaneous mass selection of these two characters is not efficient in onion breeding. Genetic and phenotypic correlation of bulb weight,was significantly positive with bulb height, bulb diameter and plant weighton the other hand correlation of neck diameter was negative with bulb diameter but positive with bulb heightthereby selection of bulbs with higher diameter but lower length could be effective for improvement of bulb neck and bulb performance. Path analysis showed that plant weight had the highest direct and significant influence on bulb performance but indirect effect of leaf weight via plant weight and of bulb diameter via leaf weight were also considerable.