CONICET | Buscador de Institutos y Recursos Humanos

Species of the genus Trichoderma are economicallyimportant as biocontrol agents, serving as a potentialalternative to chemical control. The applicability of Trichodermaisolates to different ecozones will depend on thebehavior of the strains selected from each zone. The presentstudy was undertaken to isolate biocontrol populations ofTrichoderma spp. from the Argentine wheat regions and toselect and characterize the best strains of Trichoderma harzianumby means of molecular techniques. A total of 84 outof the 240 strains of Trichoderma were able to reduce thedisease severity of the leaf blotch of wheat. Thirty-sevenstrains were selected for the reduction equal to or greater than50 % of the severity, compared with the control. The percentagevalues of reduction of the pycnidial coverage rangedbetween 45 and 80 %. The same last strains were confirmedas T. harzianum by polymerase chain reaction amplificationof internal transcribed spacers, followed by sequencing.Inter-simple sequence repeat was used to examine thegenetic variability among isolates. This resulted in a total of132 bands. Further numerical analysis revealed 19 haplotypes,grouped in three clusters (I, II, III). Shared strains, withdifferent geographical origins and isolated in different years,were observed within each cluster. The origin of the isolatesand the genetic group were partially related. All isolates fromParana´ were in cluster I, all isolates from Loberı´a were incluster II, and all isolates from Pergamino and Santa Fe werein cluster III. Our results suggest that the 37 native strains ofT. harzianum are important in biocontrol programs and couldbe advantageous for the preparation of biopesticides adaptedto the agroecological conditions of wheat culture.

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