Study of morphological diversity and relationships among traits in some long-day morphotypes of Iranian onion (Allium cepa L.) landraces

Assessment of genetic diversity and identification of important traits in a population is a basic pre-requisite for the choice of parents in breeding programme. Therefore, in order to study of genetic diversity in some Iranian onion morphotypes and using its results in breeding programs, seeds of 23 morphotypes were planted using a randomized complete block design with three replications in East Azarbaijan Agricultural and Natural Resources Research and Education Center in 2010 and 2011. Combined analysis of variance indicated that there were great diversity among morphotypes for the studied traits. Cluster analysis, using ward’s method, grouped the morphotypes into three groups. Grouping based on morphological traits showed relative correspondence between genetic diversity and geographical pattern. In principal component analysis, the first three principal components accounted 79.70% of the total phenotypic variation. Morphotypes with higher values for the first component, would have higher yield and the morphotypes with lower values for the second component, would have higher quality. Morphotypes with higher values for the third component also would have higher dry matter percentage. Path analysis showed that bulb length had the largest significant positive direct effect (0.6) on bulb mean weight. Direct effect of bulb diameter was also significaint on bulb mean weight (0.22). The highest indirect effect of leaf length via bulb length was 0.55. Therefore, selection of plants with higher leaf length and higher bulb length and diameter could be more useful in breeding for increased yield in these population. ‘Qirmiz Rey-2’ and  and ‘Gogan-2 pomegranate shaped qirmiz Azarshahr’ were superior morphotypes of this experiment. Due to the low percentage of dry matter, the morphotypes under study are not suitable for processing industry but suitable for fresh-market.