Colonization of Fusarium Wilt‐Resistant and Susceptible Watermelon Roots by a Green‐Fluorescent‐Protein‐tagged Isolate of Fusarium oxysporum f.sp. niveum

Abstract

Interactions between watermelon and a green fluorescent protein (GFP)‐tagged isolate of Fusarium oxysporum f.sp. niveum race 1 (Fon‐1) were studied to determine the differences in infection and colonization of watermelon roots in cultivars resistant to and susceptible to Fusarium wilt. The roots of watermelon seedlings were inoculated with a conidial suspension of the GFP‐tagged isolate, and confocal laser scanning microscopy was used to visualize colonization, infection and disease development. The initial infection stages were similar in both the resistant and susceptible cultivars, but the resistant cultivar responded differentially after the pathogen had penetrated the root. The pathogen penetrated and colonized resistant watermelon roots, but further fungal advance appeared to be halted, and the fungus did not enter the taproot, suggesting that resistance is initiated postpenetration. However, the tertiary and secondary lateral roots of resistant watermelon also were colonized, although not as extensively as susceptible roots, and the hyphae had penetrated into the central cylinder of lateral roots forming a dense hyphal mat, which was followed by a subsequent collapse of the lateral roots. The initial infection zone for both the wilt‐susceptible and wilt‐resistant watermelon roots appeared to be the epidermal cells within the root hair zone, which the fungus penetrated directly after forming appressoria. Areas where secondary roots emerged and wounded root tissue also were penetrated preferentially.

Gene expression patterns and dynamics of the colonization of common bean (Phaseolus vulgaris L.) by highly virulent and weakly virulent strains of Fusarium oxysporum

“…In Medicago truncatula inoculation of a resistant cultivar resulted in the delay of symptom development and reduction of the disease severity with respect to the inoculation of a susceptible cultivar, but no correlation could be found with the degree of colonization of the root parenchyma and central cylinder ( Ramírez-Suero et al, 2010 ). In watermelon, the pathogen can colonize the lateral roots in compatible interactions, but it is unable to penetrate the taproot when infecting a resistant cultivar ( Lü et al, 2013 ). A more complex interaction has been recently reported in the infection of chickpea with F. oxysporum f. sp.…”

“…The vast majority of microscopy analysis of plant colonization by F. oxysporum have been related to the details of particular interactions ( Bishop and Cooper, 1983 ; Czymmek et al, 2007 ; Nahalkova et al, 2008 ; Li et al, 2011 ), or the differences in the colonization of susceptible and resistant cultivars ( Bishop and Cooper, 1983 ; Zvirin et al, 2010 ; Jiménez-Fernández et al, 2013 ; Lü et al, 2013 ). Almost no attention has been paid to the study of differences in plant colonization based on the virulence of the infecting strains.…”

Analysis of the defence-related mechanism in cucumber seedlings in relation to root colonization by nonpathogenicFusarium oxysporumCS-20

“…The FOC‐BN infection progressed more quickly than CS‐20 colonization, and the xylem vessels of the taproot were seriously infected after 5 dpi. Similar trends were observed with the pathogen of F. oxysporum infection (Lü et al ., ). The development of the roots treated with CS‐20 was normal compared with the control roots, indicating that CS‐20 had limited influence on cucumber growth, although it might play a mutualistic role within its host.…”

Fusarium oxysporum colonizes the stem of resistant tomato plants, the extent varying with the R-gene present

“…Several reports show that F. oxysporum strains are able to colonize the interior of the plant despite the presence of a functional resistance response. For example, in incompatible interactions with common bean F. oxysporum strains colonize the plant up to the basal region of the stem (Garces-Fiallos et al 2017;Buruchara and Camacho 2000), whereas F. oxysporum colonization of resistant pea or watermelon is restricted to the roots and sometimes the crown (Bani et al 2012;Lu et al 2014).…”