Histopathological Observations in Guava Root during Wilting caused by Fusarium Species: A Scanning Electron Microscopy Study

Fusarium oxysporum and Fusarium solani are the two most destructive pathogens causing wilt disease in guava (Psidium guajava L.) commonly known as ‘super fruits’. These pathogens attack mainly on the root region of the plant and cause severe infection. In the present investigation the infection process was studied with scanning electron microscopy (SEM) and it was observed that the root region of the guava plant showed disintegration and necrosis in the epidermal layer, cortex tissue, and in vascular bundles, while the root region of a healthy sapling showed no such changes. The rupturing of the epidermal layer may show the entry of pathogens in the host tissue through the secretion of toxic enzymes/metabolites. These toxins have great potential to cause wilting symptoms in guava plants in the form of necrosis. Wilt disease causes huge losses in guava production in both tropical and subtropical countries. Therefore, there is a need to find the responsible factors. The present study is an attempt to understand the interaction mechanism of phyto-pathogens causing wilt disease.