Abstract
F1 populations of half diallel cross were considered for this investigation. Phenotypic component of variation (s2P) was higher than genotypic (s2G), interaction ((s2I) and within error (s2w) components of variation. Trait bulb weight showed the highest values for s2P, s2G, s2I and s2w. The noticeable amount of phenotypic, genotypic, interaction and within error covariation was found in the combination of BW×BY, possibly indicating wide scope of selection for this pair of characters. Genotypic correlations were higher than the respective phenotypic correlations. This situation was also marked in the path coefficient analysis. Bulb yield/plot showed highly significant and positive correlation coefficient with other characters both at phenotypic and genotypic levels. When all the nine characters were included in an index, it exhibited the highest genetic gain as percentage. When a combination of two or more characters was studied in a function, the efficacy was higher than that of direct selection for bulb yield. The combination of five, six, seven or eight characters showed higher percentage of expected gain. Due to significantly correlated with BY and having high positive direct effect at phenotypic level characters viz., LL, BW, PH and NLs is considered as primary yield components. Again combinations of these four characters gave the commendable expected genetic gain of 330.7290% may be considered as important selection index for this material.
Highlights
Onion (Allium cepa L.) a spice crop of Alliaceae family has a close relation with the group of garlic, scallion, leek, chieve (Block, 2010) and Chinese onion (AllergyNet, 2010)
The phenotypic variation was higher than the genotypic, interaction and within error components of variations for all the characters
When four characters leaf length (LL) (1), bulb weight (BW) (4), plant height (PH) (7) and Neck length (NL) (8) or Bulb length (BL) (3), BW (4), PH (7) and bulb yield/plot (BY) (9) associated in different combinations gave more than 300% genetic gain
Summary
Onion (Allium cepa L.) a spice crop of Alliaceae family has a close relation with the group of garlic, scallion, leek, chieve (Block, 2010) and Chinese onion (AllergyNet, 2010). The use of onion is not limited to any climate or associated with nationality. It is used as vegetable as well as spice and an indispensable item in every kitchen for their flavor, aroma and taste in preparation of different dishes. Onion is used for preparing Homeopathic, Unani and Ayurvedic medicines. It has a special flavour and pungency because of having sulfur containing compounds Allyl-propyl disulphide (C6H12S2) found in the bulb scales (Udachappa et al, 2019a). Mila & Parvin (2019) reported that due to lack of quality seeds and improved varieties as well as improper cultural practices the yield level of onion is quite low in Bangladesh than in other countries. Efforts should be made to develop high yielding varieties through breeding research
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