Prediction of industrial tomato hybrids from agronomic traits and ISSR molecular markers

Abstract

ABSTRACT. Heterosis is a highly relevant phenomenon in plant breeding. This condition is usually established in hybrids derived from crosses of highly divergent parents. The success of a breeder in obtaining heterosis is directly related to the correct identification of genetically contrasting parents. Currently, the diallel cross is the most commonly used methodology to detect contrasting parents; however, it is a time-and cost-consuming procedure. Therefore, new tools capable of performing this task quickly and accurately are required. Thus, the purpose of this study was to estimate the genetic divergence in industrial tomato lines, based on agronomic traits, and to compare with estimates obtained using inter-simple sequence repeat (ISSR) molecular markers. The genetic divergence among 10 industrial tomato lines, based on nine morphological characters and 12 ISSR primers was analyzed. For data analysis, Pearson and Spearman correlation coefficients were calculated between the genetic dissimilarity measures estimated by Mahalanobis distance and Jaccard's coefficient of genetic dissimilarity from the heterosis estimates, combining ability, and means of important traits of industrial tomato. The ISSR markers efficiently detected contrasting parents for hybrid production in tomato. Parent RVTD-08 was indicated as the most divergent, both by molecular and morphological markers, that positively contributed to increased heterosis and by the specific combining ability in the crosses in which it participated. The genetic dissimilarity estimated by ISSR molecular markers aided the identification of the best hybrids of the experiment in terms of total fruit yield, pulp yield, and soluble solids content.

Genetic divergence among processing tomato hybrids and formation of new segregating populations

“…The hybrid Granadero stood out as the highest average genotype for the variables YT, YC, FT and SS by being isolated from the other hybrids in the experiment (Table 3). In the current literature, there are widely variable results regarding processing tomato fruit yield, indicating the existence of differential behaviors of the genotypes in a wide range of Brazilian soil and climate conditions (Aragão et al, 2004;Figueiredo et al, 2016a;Santos et al, 2011;Schwarz et al, 2013).…”

“…These authors recommended the selection of some hybrids for release as commercial cultivars and other hybrids for use as base populations to obtain new elite inbred lines with disease resistance. Figueiredo et al (2015;2016a) worked to improve processing tomatoes and evaluated ten elite lines, their crossings and two processing tomato hybrids for yield and postharvest fruit traits. These authors observed high genetic variability among the inbred lines, experimental hybrids and commercial hybrids and concluded that the best hybrids can be selected for release with the commercial hybrids.…”

“…In this sense, the creation of new breeding programs for processing tomato crops, aimed that improving germplasm and better adaptions to the soil and climate conditions of Brazil, can provide elite inbreed lines and superior tomato hybrids for the processing industry (Figueiredo et al, 2016a;. The genetic variability availability in commercial processing hybrids can be utilized in the formation of new segregating populations with adequate genetic variability for the selection of new elite inbred lines.…”

“…However, as a consequence, there has been a low genetic gain obtained with intrapopulational breeding strategies (Gonçalves et al, 2008;Figueiredo et al, 2016a), which have opted for strategies that seek to recombine existing genetic variability in order to form segregating populations of wide genetic variability and to encourage the selection of transgressive genotypes (Figueiredo et al, 2016b).…”

“…In the global ranking of tomato producers for processing purposes, Brazil ranks ninth for fruit production and second for fruit yield in the world; in highly technical crops, yields can be over 100 tons of fruit per hectare (Vilela et al, 2012). The prominent position of Brazil in tomato production is due in large part to the adoption of hybrids at the expense of open pollinated cultivars (Figueiredo et al, 2016a;Santos et al, 2011).…”