Variability, Correlation, and Path Analysis Studies in Lettuce

Abstract

Lettuce (Lactuca sativa L.) is an important crop due to its potential to return profit, nutritional value, and production potential. Twenty-seven genotypes of lettuce procured from the Crop Genetic Resources, Wageningen, The Netherlands, check cultivars Great Lakes and Alamo-1, were planted at the experimental farm of the Dept. of Vegetable Science UHF, Nauni, Solan, India, in Sept. 2008 and evaluated in Apr. 2009 for variability, association between characters, direct and indirect effects of component traits on yield and quality characters, and to identify desirable genotypes. Genotype CGN-10944 had the best yield compared to checks. Genotype CGN-19088 had better β-carotene and iron content but lower yield than checks. There were wide ranges for different horticultural traits, seed vigor index II, and bacterial soft rot disease severity. Moderate to high phenotypic coefficient of variation and genotypic coefficient of variation for gross head weight, net head weight, nonwrapper leaves, iron content, β-carotene, and disease severity exist. The magnitude of heritability for characters was low for 1000 seed weight and high for heading percentage. Genetic advance as percentage of mean (genetic gain) was low for 1000 seed weight and high for β-carotene. Correlation indicated that net head weight was significantly and positively correlated with gross head weight, heading percentage, equatorial diameter, seed vigor index I, and disease severity and significantly and negatively with days to marketable maturity, nonwrapper leaves, and head shape index. Among quality characters β-carotene had a significant positive association with seed germination and negative association with disease severity. Iron content had a positive and significant association with seed vigor index II. Path coefficient analysis indicated that of all characters' positive direct effects for net head weight was contributed by gross head weight, equatorial diameter, disease severity, heading percentage, seed vigor index I, and nonwrapper leaves. Maximum positive indirect effects were observed for equatorial diameter, seed vigor index I, and disease severity via gross head weight. For quality characters genotype CGN-19088 had higher β-carotene and iron contents. Genotypes CGN-04778, CGN-04925, and CGN-20721 had minimum disease severity and were resistant to bacterial soft rot.