Proceedings of the XLVII Italian Society of Agricultural Genetics - SIGA Annual Congress

Verona, Italy - 24/27 September, 2003

ISBN 88-900622-4-X

Poster Abstract - 1.45

EXPRESSIONS LEVELS OF CHS, DFR AND ANS AND ANTHOCYANIN CONTENT IN 19 GENOTYPES OF CITRUS L.

M. P. RUSSO*, P. S. COTRONEO*, A. R. LO PIERO**, A. CONSOLI**, I. PUGLISI**, G. PETRONE**, T. CORALLO*, G. REFORGIATO RECUPERO*

*) Istituto Sperimentale per l’Agrumicoltura, Acireale (CT)

**) DACPA, Facoltà di Agraria, Università di Catania

anthocyanins, orange flesh, Real Time RT-PCR, Citrus spp. L.

Italian orange fruit production is characterized by the presence of anthocyanins, an important class of flavonoids, representing, due to their antioxydant healthy value, the mean of promotion for the marketing of this product. Making use of clonal selection, inside this group, have been differentiated many early and late selections, characterized by anthocyanin content, diversely expressed in flesh and rind. Anthocyanin content has varying expression levels and is strictly dependent on climate conditions.

The aim of this study is to characterise the relationships between the expression of biosynthetic genes CHS (chalcone synthase), DFR (dihydroflavonol 4-reductase), ANS (anthocyanidin synthase) and the anthocyanin content. Evaluation of expression levels of the enzymes was tested by Real Time RT-PCR, in 16 blood oranges selections, in Cadenera, a blond orange cultivar, and in AMOA 8 and OTA 9, two hybrids obtained crossing respectively: Moro orange per Avana mandarin, and Oroval clementine per Tarocco, the elongation factor (EF), present in Citrus at constant level, was used as internal reference.

Anthocyanin buildup in the flesh of fruits picked in mid march was notably varying, from a maximum of 56.4 mg/g tissue in the AMOA 8 hybrid to a minimum of 0.17 mg/g in Tarocco Sciara. On the basis of their content 3 groups were detectable: the first varying from 56.4 to 10.8 mg/g, the second from 6.2 to 1.4 mg/g and the third from 0.67 to 0.17 mg/g. Anthocyanin content was positively related with the expression of biosynthetic genes. CHS, DFR e ANS levels were basically related among them in the different selections.

Real Time RT-PCR results suggested that the expression levels of CHS, DFR and ANS chiefly corresponded to the amount of anthocyanins. The presence of variability mostly marked in anthocyanin content is due to its accretion. This is confirmed by data from Tarocco Messina, a late Tarocco orange selection, which begins later than the others its pigmentation process, having a very low content of anthocyanins, although showing intermediate levels of biosynthetic genes expression. In Cadenera orange no presence of the pigment was detected, even though CHS and ANS expression levels were similar to the ones observed for the group showing the lowest levels of anthocyanins. The low expression of the biosinthetic genes in the blond orange Cadenera suggests that there are other factors controlling red coloration. Recently Kobayashi et al., 2001 suggested that in white cultivars of grape and in their sports with red skin the phenotipic change is thought to be the result of a mutation in some regulatory gene controlling the expression of UDP-glucose, flavonoid 3-O- glucosyltransferase (UFGT).