Phenotypic and molecular characterization of a tomato (Solanum lycopersicum) Second Cycle Hybrid and QTL detection in the F2 segregating population

CABODEVILA, V.G.; CACHIARELLI, P.; PRATTA, G.R.

Rosario

Congreso; 4to Congreso Argentino de Bioinformática y Biología Computacional; 2013

Sociedad Argentina de Bioinformática y Biología Computacional

Second Cycle Hybrids (SCH) are produced by intercrossing Recombinant Inbred Lines (RILs) derived from a F2 generation of two homozygous parents (First Cycle Genotypes, FCG). New genotype combinations among selected alleles from FCG can be identified in the segregating population of SCH. The AFLP (Amplified Fragment Length Polymorphism) has been described as a powerful technique to identify molecular markers. Sixty nine F2 individuals from the SCH (ToUNR18xToUNR1) were phenotypied and genotypied. Parents were two selected genotypes from the set of eighteen RILs obtained from an interspecific cross between S. lycopersicum cv. Caimanta (C, a commercial genotype) and S. pimpinellifollium LA722 (P, a wild genotype). C, P, their F1 (CxP), ToUNR1, ToUNR18 and their F1 (ToUNR18xToUNR1) were used as the experimental testers. Ten quantitative phenotypic traits were evaluated: height, weight, diameter, soluble solids, post-harvest life, acidity, shape, firmness, pH and colour. Six AFLP primer combinations were used. The association of markers with the QTL (Quantitative Trait Loci) for each trait was tested using a one way ANOVA. The χ2 test was applied to prove the hypothesis of independent segregation (1:1:1:1, 9:3:3:1, 3:3:1:1) for each pair of fragments that individually adjusted to a Mendelian segregation (3:1, 1:1). A factorial ANOVA considering all combinations of pairs of independent fragments associated to the same phenotypic trait was used to detect putative interloci interactions. Fragments associated with more than one character were accounted as an indicator of pleiotropic effect. One hundred and ten bands resulted from the six primer combinations, 29 of them adjusted to a Mendelian segregation (one of the combinations did not present any Mendelian segregating band). All traits presented normal distribution (verified by the Shapiro-Wilk´s test), except post-harvest life, titratable acidity and pH. The first two were transformed by Log10, and the third was analysed by Kruskal-Wallis test because no transformation was successful. Various QTLs were detected. The highest number of association was detected for height (6 QTL), following by diameter (5 QTL), soluble solids and pH (3 QTL), weight, shape, post-harvest life, acidity and firmness (2 QTL) and colour (1 QTL). No statistically significant interaction was detected by any of the factorial ANOVA. The genetic implication of this finding is that epistasis did not contribute to the traits. Instead inteloci additivity is the predominant gene action. Pleiotropy was detected for eight AFLP bands. Phenotypic and molecular characterization of a tomato SCH allowed detecting eighteen polymorphic AFLP that marked twenty eight different agronomically important QTL.