Histopathological and biochemical aspects of grafted and non-grafted cucumber infected with stem rot caused by Fusarium spp.

Cucumber grafting has been used in Egypt recently to induce soil diseases tolerance. The impact of various grafting techniques on the vulnerability of grafted cucumber seedlings to Fusarium which stimulates the stem rot was investigated. Consequently, the anatomical and physiological studies were carried out on the diseased and healthy grafted cucumber seedlings, comparing with the non-grafted ones. Fusarium equiseti (MW216971.1) caused a severe stem rot of the grafted seedling through affecting the connection area of the different grafting methods, leading to complete seedling death. The hole insertion grafting method significantly exhibited the highest diseases incidence (100%), and mean disease severity index (5) when inoculated with F. equiseti. The pathogen remarkably affected the graft union area causing tissue discoloration and decay. The levels of antioxidant enzymes and total phenols were significantly enhanced in the diseased grafted and self-rooted cucumber. However, the diseased grafted cucumber recorded significantly the highest values of the antioxidant enzymes activities and total phenolic content when compared with the self-rooted ones. The results of SDS-PAGE profile revealed variations in the leaves protein profile of the grafted and self- rooted seedlings in response to Fusarium infection. Taken together, grafting cucumber onto a resistant rootstock using the splice technique can alleviate the stem rot severity caused by Fusarium spp. by enhancing the histological, physiological and molecular defense response of the grafted seedling.