Nitrogen Assimilation and Carbon Metabolism is Affected by Incompatible and Compatible Combination of Grafted Melon

Grafting improved the nitrogen use efficiency (NUE) of scions and enhanced carbon metabolism in leaves. Nevertheless, this positive effect can be lost by incompatible graft combinations. In order to investigate the nitrogen assimilation and carbon metabolism between incompatible and compatible grafts, Kiran (Ki) (Cucurbita melo L.cv.) was grafted onto three different pumpkin rootstocks (TZ (Cucurbita maxima Duchesne x Cucurbita moschata Duchesne), Shimshon (Sh) and 53006 (53). At 130 days after transplant ripe fruits were harvested and plants were cut 1 cm above and below the grafted zone (scion-rootstock) for phloem extraction. Phloem sap and fruits were used for metabolite profiling. The phloem sap of the rootstock revealed that metabolites of the tricarboxylic acid cycle (carbon metabolomics), the biosynthesis of sugar (carbon metabolomics) and amino acids (nitrogen assimilation and metabolism) were higher in cultivar TZ, a compatible combination. While the scion phloem sap metabolite profiles shown the enhancement of sugar metabolism on a Ki/53, a possible incompatible combination. Fruit metabolites revealed an enhancement of quality in Ki/TZ combinations, shown by increased levels of sugars and free amino acids. Further work related to root and leaf hormones will be carried out to provide a better understanding of carbon and nitrogen metabolism in both compatible and incompatible combinations.