INFLUENCE OF GRAFTING AND STEM DISINFECTION METHODS ON THE YIELD OF GREENHOUSE-GROWN SPANISH CUCUMBERS

Cucumber is the most cultivated vegetable in Central Spain greenhouses (Madrid and surrounding areas). Farmers grow cucumber repeatedly on the same soil because they do not have much surface available, so it was a normal practice to disinfect greenhouses with methyl bromide. Since methyl bromide was forbidden, it has been necessary to use other alternatives to continue growing cucumbers in central Spain. Grafting is one of the most promising techniques, and it has been used successfully in these areas not only to overcome soil problems (nematodes mainly), but also to improve yield and quality. The rootstocks used so far (hybrids of Cucurbita maxima × Cucurbita moschata) present no resistance to nematodes, so the aim of the study was to evaluate if soil steam disinfection would complement the use of rootstocks. Two steam disinfection methods were evaluated: sheet steaming and steaming hoods. In both cases soil was steamed for about two hours at 80-85°C down to 35 cm depth. Cucumber cultivar tested was ‘Trópico’, grafted onto commercial rootstock Shintoza (Cucurbita maxima × Cucurbita moschata) and watermelon rootstock Robusta (Citrullus lanatus). Grafting allowed significant increases in production. Higher yield was obtained with Shintoza (almost 44.5 kg•m^-2), 33% more than yield obtained with Robusta and 50% more than non-grafted plants. Steam disinfection did not improve yield, even with non-grafted plants. Plants grafted onto Shintoza produced 285 fruits•m^-2, 47% more cucumbers than non-grafted plants, and these cucumbers had the highest weight, 156 g.