Effects of simple and double grafting melon plants on mineral absorption, photosynthesis, biomass and yield

The Spanish type cultivar ‘Piel de Sapo’ (Cucumis melo L. var. saccharinus), has a limited compatibility with the Cucurbita maxima × Cucurbita moschata hybrids currently used as rootstocks. Double grafting can be used to improve compatibility between rootstock and scion by means of an intermediate rootstock compatible with both. Non-grafted, single, and double grafted melon plants of the cultivar Piel de Sapo were evaluated for water, nutrient absorption, photosynthesis activity, biomass production in early phases, as well as for yields and fruit quality in a long term trial. The hybrid ‘Shintoza’ (C. maxima × C. moschata) was used as rootstock, and the cantaloupe type melon cultivar ‘Sienne’ as an intermediate scion. Grafting did not affect net photosynthetic values, yet increased water use efficiency (35%). Double grafted plants increased aerial dry weights (66% and 31% with respect to non-grafted and simple graft plants, respectively), and also increased capacity for uptaking beneficial minerals (between 61% and 13% and particularly for NO3−, P, K, Ca, Mn, and Zn) with respect to non-grafted and single grafted plants. The quantum efficiency PSII photochemistry values increased in double grafted plants (12%) with respect to the control plants. Consequently, double grafting on a vigorous rootstock such as ‘Shintoza’, with an intermediate scion, results in improved mineral and water absorption and achieves an increase in ion influx to the scion – so enabling an increase in light photosynthetic reaction and biomass. Double grafted plants increased fruit yield when compared to simple grafted and non-grafted plants (12% and 56%, respectively) and did not affect fruit quality in terms of °Brix and colour. In conclusion, double grafting presents several beneficial aspects that are counter-balanced by the extra cost of the technique. The difference in yields reflects compatibility problems.

► To improve compatibility between rootstock (Cucurbita maxima × Cucurbita moschata) and scion (melon “piel de sapo”), double grafting (C. maxima × C. moschata/melon ‘Sienne’) can be used, by means of an intermediate rootstock compatible with both of them.
► Non-grafted, single, and double grafted melon plants of the cultivar ‘Piel de sapo’ were evaluated for water and nutrient absorption; photosynthesis activity and biomass production in early phases; and for yields and fruit quality in a field trial.
► Grafting did not affect net photosynthetic values, but significantly increased water use efficiency and quantum efficiency PSII values.
► Double grafted plants showed higher capacity in nutrient and water uptake and as a consequence were superior in plant growth, fruit yield, and in marketing quality.