Screening of Cucumis metuliferus germplasms resistant to Meloidogyne incognita and effects of its grafting on fruit quality of Laohan melon

Objective To clarify the effects of grafting with Cucumis metuliferus materials resistant to Meloidogyne incognita on the fruit quality of Laohan melon at maturity stage.

Methods Using 11 accessions of Cucumis metuliferus germplasm resources as materials and self-rooted melon as the control, the root-knot index (GI) of roots was determined under pot culture conditions. The results showed that Cucumis metuliferus ZM4 and ZM3 were highly resistant to Meloidogyne incognita, ZM5 was moderately resistant, and ZM1 was lowly resistant. Using the thick-skinned melon 'Laohan' as the scion, and the highly resistant ZM3, ZM4 and moderately resistant ZM5 as rootstocks, the related quality traits of mature fruits were determined under greenhouse conditions.

Results The plant height and scion stem diameter of the grafted seedlings were all higher than those of the self-grafted melon control. The scion stem diameter of L-ZM4 and L-ZM5 was higher than that of the pumpkin rootstock grafted combination. The soluble sugar content of L-ZM3 was higher than that of the control and pumpkin grafted combination. The soluble protein content of the 3 Cucumis metuliferus rootstock treatments was all higher than that of the control and pumpkin grafted combination. The titratable acid content of L-ZM4 was significantly higher than that of the control and pumpkin grafted combination. The total free amino acids content of all grafted combinations was lower than that of the self-grafted control. The central and edge soluble solids content of all grafted combinations was higher than that of the control and pumpkin grafted combination. The single fruit mass of the 3 Cucumis metuliferus rootstock grafted treatments was higher than that of the control, but lower than that of the pumpkin grafted combination.

Conclusion The comprehensive traits including growth potential, fruit quality and nematode resistance of ZM3 and ZM5 grafted seedlings were better than those of self-rooted seedlings and pumpkin grafted seedlings, which are suitable to be used as grafting rootstocks for Laohan melon cultivation.