CONICET | Buscador de Institutos y Recursos Humanos

PHENOTYPICAL AND MOLECULAR CHARACTERIZATION OF DURUM WHEAT GENOTYPES IN VERNALIZATION REQUIREMENT BASUALDO J.*, DIAZ M.L.**, CARRERA A.D.*;*** *) Centro de Recursos Naturales Renovables de la Zona Semiárida - CONICET Bahía Blanca, Camino de la Carrindanga Km 7, 8000 Bahía Blanca, Argentina. **) Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur. Bahía Blanca, Argentina. ***) Departamento de Agronomía, Universidad Nacional del Sur. Bahía Blanca, Argentina. Vernalization , gene expression, Triticum turgidum var. durum Vernalization requirement is an adaptive trait that modules flowering time in order to occur under spring favorable environmental conditions. The genetic basis of vernalization in cereals can be described using the two loci VRN-1/VRN-2 model. Vernalization response is also closely associated to level of cold tolerance. Most of the durum wheat cultivated in Argentina comprises spring genotypes but there is an increasing interest in exploring variability in heading time and frost tolerance. The focuses of this study are the determination of variability in vernalization requirement and the molecular characterization of VRN-1 locus, through PCR markers, sequencing and analysis of expression profiles, in a collection of durum wheat from diverse origin. Vernalization response in thirty two genotypes was evaluated by scoring the date of ear emergence under vernalization and non-vernalization conditions. All genotypes showed spring growth habit except MVTD 10-98, which flowered only after vernalization treatment (6 week to 4°C dark and then 21°C, 16 hs ligth). Among spring lines, 11 genotypes delayed heading, four showed early heading, and 16 not differenced from unvernalized plants (Student test). Allelic variation at the VRN-1 locus was examined using primers that amplify coding and regulatory regions from A and B genomes. Polymorphisms were investigated by electrophoresis in agarose and acrylamide gel and sequencing. The promoter region was monomorphic for the vrn-1 winter allele. At the first intron region, VRN-A1 resulted polymorphic with 28 lines carrying Vrn-1 spring allele and four presented vrn-1 winter allele. Genotypes with spring habit and certain vernalization response were described as facultative. They carried vrn-1 winter allele at VRN-A1 locus. Spring genotypes with Vrn-1 allele that delayed flowering after vernalization were interpreted as the effect of additional loci on flowering time of vernalized plants. Gene expression was evaluated in a set of eight genotypes with distinct vernalization sensitivity. Reverse transcription (RT)-PCR reveled different VRN-A1 expression levels according to growth habit, treatments (vernalized and unvernalized plants) and development stages (two and five-leaf). Vernalization induced VRN-1 expression in genotypes with vrn-1 allele at two leaves stage. In non vernalized plants, evidence of VRN1 expression was obtained at five-leaf stage in all the genotypes except the winter one and CBW105 and this agree with a long days to heading period of CBW105. In this genotype, VRN1 expression was just detected at eight- leaves stage. It was possible to interpret the differences in vernalization response in the light of molecular analysis and also to describe facultative materials with partial sensitivity. The observed variability in headings days is an interesting result concerning adaptation to specific environmental conditions.