Detection of Fungi Causing Fusarium Wilt Disease on Cowpea in Basra Governorate, Iraq, and Its Biological Control

Abstract

This study was conducted during 2023-2024 to identify the fungi causing cowpea wilt disease in Basra Governorate and its biological control. The field survey showed that the highest incidence of Fusarium wilt disease of 13.5% was detected in Nashwa region, followed by Al madina region (12.69%), whereas the lowest incidence (11.74%) was found in Ezz El-Din Salim region. Fusarium isolates were isolated from cowpea roots. Morphological identification was made based on reference keys and molecular identification was performed using the ITS1-ITS4 primers. The sequences of isolates R2, R3, and R7 matched with Fusarium oxysporum reference isolate by 99%, 99% and 98% sequence identity, respectively. The pathogenicity test results revealed that F. oxysporum R7 isolate surpassed other isolates in causing seed mortality of 93.33%, followed by R2 and R3 isolates with 86.66% and 77.33% seed mortality rate, respectively. Trichoderma longibrachiatum had a high antagonistic capacity against F. oxysporum isolates; the degree of antagonism for all isolates was 1 based on the Bell scale. The highest inhibition rate of Bacillus cereus reached 94.25% against R7 isolate, and the lowest was 89.81% against R3 isolate. Saccharomyces cerevisiae achieved the highest inhibition rate of 90.5% against R7 isolate and the lowest rate against R3 isolate (78.32%). The volatile compounds produced by the biocontrol agents inhibited the growth of F. oxysporum isolates. T. longibrachiatum had the highest inhibition rate (96.84%) against isolate R2 and the lowest inhibition rate (93.51%) was against R7 isolate. Whereas, the highest inhibition rate of B. cereus against R2 isolate reached 85.7%, and the lowest inhibition rate was 81.7% against the R7 isolate. Furthermore, the highest inhibition rate of S. cerevisiae was against R3 isolate (89.21%), and the lowest inhibition rate (77.58%) against the R7 isolate.

Keywords:

Vigna unguiculata, Trichoderma longibrachiatum, Bacillus cereus, Saccharomyces cerevisiae, Fusarium oxysporum.