Evaluation of yield and agronomic components by triallel cross and selection of high essential oil yielding hybrids in Basil

Abstract

The basil (genus Ocimum) is a medicinal and fragrant herb or shrub with a wide range of applications as an ornamental plant, culinary ingredient, flavoring agent, and bioactive fragrance ingredient in foods cosmetics, and household items. Basil essential oil is in high demand, especially for novel high-quality oils with distinct aromas and chemical properties. The objectives of this study were, i) to increase the essential oil yield of better quality by gathering different genes responsible for the above economic characters scattered among different genotypes belonging to the same species or in other species of basil, and ii) the estimation of nature and amount of different genetic parameters. In the Ocimum, the single crosses and their corresponding three-way crosses/hybrids developed during the cropping season 2017–18 (single crosses) and 2018–2019 (three-way crosses). The three-way crosses/hybrids were evaluated in the field experimental trials during the 2019–20 at the CSIR-CIMAP, Lucknow (India) research farm. The analysis of variance (ANOVA) worked out for general and specific line effects for the eleven traits, and they were found highly significant for all the eleven traits. All the three-way crosses exhibited high variations for oil yield and yield contributing characters. For all eleven attributes, the additive genetic components of variance (σ2A) were higher than the dominant genetic components of variance (σ2 D), indicating that selection is simple for these attributes. For all the traits in the study, additive × dominance (σ2AD) gene action was higher than additive × additive (σ2AA), and dominance × dominance (σ2 DD), indicating that epistasis component of variance was present. Based on the genetic components of variance and mean performance of oil yield, only two tri-hybrids, C46.1 and C35.1, for the high oil yield and linalool (%), tri-hybrids C14.5 and C24.3 (47.13%), were found better. One tri-hybrid rich in Chavibetol, C26.1 (14.58%), is also selected for the extensive area cultivation in the North Indian plain. In addition, the three-way cross can combine desirable features from three genotypes into a single genotype. In conventional plant breeding, by a three-way cross design, the hybrids can be improved by crossing between an F1 (single cross) (A×B) as a female parent and a genotype (C) as the male parent. The essential oil of promising Ocimum tri-hybrids indicates aromatic compounds, such as methyl chavicol, linalool, β-ocimene, Chavibetol, and camphor content are present in adequate amounts. It is the first report using a triallel mating design in the basil. These tri-hybrids can be recommended for cultivation on a large scale.