WHITISH-FLESH COLOR MUTATION IN LOQUAT INVOLVES FRUCTOSE BIOSYNTHESIS AND S-LOCUS

Abstract

Loquat (Eriobotrya japonica Lindl.) produces yellowish-flesh and whitish-flesh fruits. A bud mutation with whitish-flesh fruits originating from the yellowish-flesh cultivar ‘Dongting’ was discovered. The white mutant and yellow loquats were collected and used in this study. Two polymorphic bands were obtained with the primers UBC813/535 and OPH01/1719, discriminating between wild and mutant genomes. The deduced amino acids of the two sequences were highly correlated with NAD-dependent sorbitol dehydrogenase (NAD+-SDH) in E. japonica and F-box proteins, S ribonuclease (S-RNase) in P. pyrifolia. Three SNP variances at nucleotide 32, 370 and 461 in the coding sequence of the NAD-SDH gene, were observed in whitish fruit mutants, and the amino acids of the three alleles were also different. In addition, real-time quantitative PCR showed that NAD-SDH and some other carotenogenic genes were considerably suppressed in ripe mutant fruits compared to those in wild fruits. These results suggest that flesh color of loquat might be controlled by at least two loci referring to NAD+-SDH and S-locus, in addition to expression levels of carotenogenic genes. The NAD-SDH might be an upstream gene involved in I²-carotene accumulation in yellowish-flesh fruit and it may be important for flesh color and fructose biosynthesis.