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

Salsomaggiore Terme, Italy - 26/29 September, 2001

ISBN 88-900622-1-5

Poster Abstract

MOLECULAR CHARACTERIZATION OF RED CHICORY (CHICORIUM INTYBUS L.) EXPERIMENTAL POPULATIONS

SOATTIN M.*^,**, LAZZARIN R.**, PARRINI P.*

* Dipartimento di Agronomia Ambientale e Produzioni Vegetali, Università degli Studi di Padova, Agripolis, Via Romea 16, 35020 Legnaro, Padova

pparrini@unipd.it

** Veneto Agricoltura, Centro Sperimentale Ortofloricolo Po’ di Tramontana, Via Moceniga 7, 45010 Rosolina, Rovigo

red chicory, phenotypic mass selection, AP-PCR markers, I-SSR markers

Red chicory (Chicorium intybus L., 2n=2x=18) belongs to the family of Compositae and, among others, it includes the var. silvestre Biskoff to which the red or variegated chicory, also called radicchio, refers. In this species inbreeding is hampered by a sporophytic incompatibility system which, together with the frequently observed severe inbreeding depression, is a major drawback for the genetic improvement of the cultivated types. Since the selection of parental inbred lines suitable for the production of hybrids is not easily feasible, red chicory varieties are usually based on the intercrossing of a number of individuals selected for superior morphological and commercial traits. As a consequence, they are represented by a heterogeneous mixture of highly heterozygous genotypes sharing a common gene pool. Currently used materials of red chicory are known to possess a high variation and adaptation to the natural and anthropological environment where they have originated and are still cultivated. In spite of this, no effort has been made to adopt and exploit molecular markers for characterizing and breeding valuable plant materials amenable to programs of variety selection.

Results on the genetic variability within and relationships between two local varieties of “Radicchio di Verona” (coded as C₀-OP and C₀-OM) and their derivatives from a first (C₁-OP and C₁-OM) and a second (C₂-OP and C₂-OM) cycle of mass selection are presented here. Thirty to forty plants for each population were analyzed by means of AP-PCR and I-SSR markers using primers previously selected for their ability to find homologous binding sites and give reliable polymorphic amplification patterns. In particular, the molecular marker data collection was based on one ten-mer (OP-A1=5’-CAGGCCCTTC-3’), one universal (5’-TTATGAAACGACGGCCAGT-3’) and two inter-microsatellite (I22=5’-CCA(TG)₈-3’ and I33=5’-(AGC)₄T-3’) primers. The original local varieties C₀-OP and C₀-OM showed comparable Dice’s mean genetic similarity estimates and variability coefficients, respectively, of 0.651 (C.V.=25%) and 0.629 (C.V.=26%). After two selection cycles the mean genetic similarity estimates of populations increased up to 0.667 and 0.671 and the C.V. reduced to 19.5% and 20.6%, respectively. Actually, an increase in terms of genetic uniformity was obtained only with the first cycle of selection whereas the second one was not effective since C₁ and C₂ populations showed comparable estimates of Nei’s genetic diversity (0.302 vs. 0.313 for C₁-OP and C₂-OP and 0.275 vs. 0.277 for C₁-OM and C₂-OM). As expected, most of the total variation (85%) was within population, being the proportion of the among selection-derived populations genetic diversity as low as 15% (G_ST=0.149). Despite two cycles of selection, the amount of genetic diversity detected in C₂-OP and C₂-OM was still very high compared to that found in the C₀ populations. The diversity index (H_S) values calculated at each marker locus ranged from 0.122 (I33/5) to 0.494 (M13/2) and it was higher than 0.3 for eight out of 14 loci. The low genetic differentiation among OP and OM selections over all loci was confirmed by the gene flow estimate that was as high as Nm=2.852. According to a contingency test, four out of 14 marker loci did not show any significant difference in terms of allele frequency neither between C₀ and C₁ nor between C₀ and C₂ populations whereas the rest of markers loci revealed significant changes demonstrating an involvement on selected traits.

The overall results confirm the high variability that can be found within red chicory populations and underline the difficulties that plant breeders encounter in selecting distinguishable, uniform and stable varieties.