QTL analysis of yield and seed number in Citrus

Amount, regularity and low seed content of the crop are important propel ties of scion citrus cultivars, The genetic control of these traits was studied in a progeny derived From the cross Citrus volkameriana x Poncirus trifoliata using molecular marker analysis. Since the traits were not normally distributed, the Kruskal-Wallis non-parametric test was used for quantitative trait loci (QTLs) detection. Most of the QTLs detected correspond to the trait "number of fruits per tree", in agreement with its known physiological complexity. Related traits (fruit number, fruit size and seed number) are controlled by QTLs some of which are located in the same genomic regions, suggesting that undesired associations could be broken to some degree by recombination. QTL analysis over years revealed important effects of genotype-by-environment interaction on QTL detection. This result agrees with the differences found fur the trait means among years, which was found to be related, among other causes, to the alternate bearing of some genotypes and the amount of rain before harvest.