Abstract
ABSTRACT Several traits must be simultaneously considered in selection of tobacco cultivars for meeting the requirements of farmers, manufacturers and consumers. Breeders should have an understanding of associations between economically-important traits in order to devise the best strategy to have response to selection for all them. Utilization of selection indices has been shown to be one of the most efficient strategy for selecting for correlated characters. In tobacco, no reports can be found within the academic literature for multiple trait selection. In this study we demonstrate the efficiency of the Sum of the Standardized Variables Index (SSV) for multi-trait selection in tobacco. The method was evaluated using a collection of thirteen inbred lines and hybrids derived using a diallel scheme. The hybrids, parental lines, and checks were evaluated in two field locations. The traits assessed were yield (YLD), general quality index (GQI), leaf stem to lamina ratio, percent total alkaloids, and percent total sugars. We considered weights according to the economic importance of each trait: 0.4 for YLD, 0.3 for GQI and 0.1 for the remaining characters. The SSV index proved to be efficient and easy to interpret, and could be used to generate genetic gain for almost all characters in the desired direction. General combining ability (GCA) explained the larger part of the variation of the index in the diallel analysis. The mean heterosis estimate was 2.02%. Some hybrid combinations exhibited heterosis levels greater than 10%, indicating that increased attention might need to be given to commercialization of F1 hybrids.
Highlights
A new cultivar will only be widely adopted if it meets the requirements of producers, industry, and consumers
In the case of tobacco, numerous correlated traits are important, making development of new cultivars improved for multiple traits challenging
Selection based upon a numerical index value can be used, whereby important traits are weighted and the index is calculated based upon a linear function of the traits being considered
Summary
A new cultivar will only be widely adopted if it meets the requirements of producers, industry, and consumers. In the case of tobacco, numerous correlated traits are important, making development of new cultivars improved for multiple traits challenging. There are numerous methodologies for application of selection indices been the most efficient called the optimum index or the Smith-Hazel index (Bernardo, 2020). It has as a restriction, the estimation of genetic and phenotypic variances and covariances with high accuracy, which it is not always possible in practice. The present study was carried out with the objective of assessing the efficiency of SSV selection indices involving some important traits in tobacco and, at the same time, evaluates combing ability for measured traits from diallel crosses of flue cured tobacco inbred lines
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