Response of grafted and non-grafted melon plants to effluent and boron under greenhouse conditions

Because of the scarcity of water resources in and and semi-arid regions, the use of marginal water, such as treated sewage effluent, for irrigation is on the rise. Marginal water often contains relatively high salt and boron concentrations. Melons grafted onto Cucurbita rootstocks may be more tolerant to excessive boron concentrations than non-grafted plants. Therefore, the objective of the present study was to determine the effects of effluent and boron on boron uptake, growth and yield of grafted and non-grafted melon plants. Non-grafted melon plants (cv. Arava) and melon plants grafted onto the commercial Cucurbita rootstock 'TZ-148' were grown in pots filled with Perlite in a heated greenhouse and were irrigated with fresh water or effluent. The two irrigation waters contained boron at five concentrations, ranging from 0.2 to 10 mg/L. Increasing boron concentration in the irrigation water increased boron concentration in the plant tissue, with most of the boron accumulating in the leaves. Boron accumulation in non-grafted plants was higher than in grafted ones. Fruit yield decreased with increasing boron concentration, and in this respect, the non-grafted plants were more sensitive to boron level than the grafted ones. Using effluent for irrigation decreased the plant's sensitivity to excess boron concentrations. Thus melon plants grafted onto Cucurbita rootstock were more tolerant than non-grafted ones to high boron concentrations, and this could be explained by the decreased boron uptake by the Cucurbita rootstock. The use of effluent water for irrigation, however, markedly reduced the sensitivity of the melon plants to excess boron concentrations in the irrigation water. It can be concluded from these results that grafted melons irrigated with fresh or effluent water tolerate excess boron.