GENETIC RESOURCES OF BLACKBERRY WILD SPECIES IN MICHOACAN, MEXICO

Blackberry production is steadily increasing in Mexico, where the state of Michoacan is the largest producer in the country with 8,400 ha planted. The limited genetic base of cultivated blackberries in Michoacan has been based on cultivars (‘Cherokee’, ‘Comanche’, ‘Kiowa’) deployed by the University of Arkansas breeding program in the 90s and more recently the Brazilian cultivar ‘Tupy’. The widespread planting of single cultivars of blackberry in Michoacan has resulted in the development and improvement of better agronomic management practices, but it also has the consequence that the crop is threatened by new and established pests and diseases that are difficult to control by conventional methods. The recent outbreak of Flower Bud Necrosis (NFB) caused by unknown factors in orchards planted with the cultivar Tupy caused severe yield losses and is becoming one of the most economically important factors affecting the crop. A multi-disciplinary effort (by plant geneticists, physiologists and pathologists) is currently in progress to study and develop integrated control practices. For potential crop genetic improvement for diseases such as Downy mildew (DM) caused by Peronospora sparsa and other genetic traits we have identified at least six species of wild blackberries (Rubus adenotrichos Schltdl., R. humistratus Steud., R. cymosus Rydb., R. pringlei Rydb., R. pumila Focke, and, R. sapidus Schltdl.) within the geographical region, and their spatial distribution has been mapped using GIS technology. Furthermore, morphological variability analysis reveals an important intermixing between species, while R. cymosus and R. adenotrichos are clearly distinguished from other species. Wild blackberries could be a potential source for introgression of important agronomic traits into commercial cultivars, and disease resistance. Our goal is to further explore and use the local genetic resources of Rubus species in Michoacan. We are currently screening the germplasm of wild species for DM resistance, and investigating the genetic and morphological basis of DM resistance. In addition, we are also studying the floral biology and ploidy level of each species to develop suitable schemes of controlled crosses.