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 - 1.28

DIFFERENTIAL EXPRESSION OF ISOFLAVONOID GENES DURING CICER-ASCOCHYTA INTERACTION BY REAL TIME PCR

C. ROSATI

ENEA, C. R. Trisaia, S.S. 106, km 419+500, 75026 Rotondella (MT), Italy

isoflavonoid pathway, plant-pathogen interaction, leguminous plants, Real Time PCR

Chickpea (Cicer arietinum) is a leguminous crop extensively cultivated in the Mediterranean area. Ascochyta blight, caused by the fungus Ascochyta rabiei, is the most serious fungal disease affecting chickpea, with yield losses higher than 50% in susceptible varieties. To investigate of view the early steps of Cicer-Ascochyta interaction leading to isoflavonoid phytoalexins biosynthesis from the molecular point, the expression of flavonoid and specific isoflavonoid genes was studied in the varieties Principe and Sultano, respectively susceptible and resistant to Ascochyta. The chickpea sequences of genes coding for chalcone synthase (CHS), chalcone isomerase (CHI), chalcone reductase (CHR), isoflavone synthase (IFS) and isoflavone reductase (IFR), known to be expressed during Cicer-Ascochyta interaction, were used to design specific primers and probes for Real Time PCR. The first two genes belong to the general flavonoid pathway, while the latter three encode proteins specifically involved in the synthesis of isoflavonoid phytoalexins, accumulated at different levels upon Ascochyta infection. The expression of such genes was monitored at 1, 3, 9 and 24 hours after inoculation with Ascochyta inoculum and blank solution, and compared with expression at time zero. Gene expression data were further normalized with respect to the expression of EF-1alpha gene. For chr, chs and ifr, the accumulation of transcript peaked 3 hours after inoculation. Qualitative and quantitative differences in gene expression patterns were found between the two varieties. CHS, the key enzyme in phenylpropanoid-flavonoid pathways, was constitutively expressed at high levels, though its transcript abundance was not affected by inoculation. Moreover, ifr was more expressed in the resistant variety Sultano than in Principe, and chi was showed a peak 3 hours after inoculation only in Sultano. On the other hand, chr was expressed at higher levels in the susceptible variety Principe than in Sultano, pointing out a negative correlation with mechanisms of resistance. A cross population Principe x Sultano is being bred to extend analyses to segregating progenies and validate the presented preliminary data.