Greenhouse screening of the saprophytic resident microflora for control of leaf spots of wheat (Triticum aestivum)

Abstract

Ten microorganisms of the epiphytic microflora of wheat leaves in Buenos Aires Province, Argentina, were evaluated under greenhouse conditions as potential biocontrol agents of the pathogensAlternaria triticimaculans, Bipolaris sorokiniana, Drechslera tritici-repentis andSeptoria tritici in two application sequences (prior to or together with the pathogens). The antagonists significantly reduced the expression of the diseases on wheat plants compared with control plants not inoculated with the antagonists. Maximum percentage of reduction of the necrotic lesion area (NLA) (40–55%) ofS. tritici resulted whenCryptococcus sp.,Rhodotorula rubra andPenicillium lilacinwn were sprayed on leaves prior to inoculations with the pathogen.Bacillus sp.,Cryptococcus sp.,Fusarium moniliforme var.anthophylium,P. lilacinum andR. rubra reduced significantly (34–52%) the NLA ofB. sorokiniana in both of the application sequences. The best antagonistic effect againstA. triticimaculans was shown byAspergillus niger, Bacillus sp.,Chaetomium globosum, F. moniliforme var.anthophylium andNigrospora sphaerica, with a NLA reduction from 21% to 35% in the co-inoculation or in the sequential application. All microorganisms exceptN. sphaerica performed better than the control againstD. tritici-repentis. The area under disease progress curve (AUDPC) of the pathogens appeared to progress similarly, but at lower values, in treated plants than in untreated controls. The two yeasts and the bacteria decreased AUDPC to 50–55% ofS. tritici andB. sorokiniana compared with the control in both application sequences, whereas the maximum efficacy againstA. triticimaculans was reached byN. sphaerica andA. niger for the sequential application and byF. moniliforme var.anthophylium for the co-inoculation. If the parasitism occurs also in nature, application of antagonists for biological control might provide the opportunity to compete with the pathogens and regulate their colonization in wheat leaves.