Supression of tan spot and plant growth promotion of wheat by synthetic and biologic inducers in field conditions

PERELLO, ANALIA EDITH; DAL BELLO, G

ANNALS OF APPLIED BIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2011 vol. 158 p. 267 - 274

0003-4746

Tan spot of wheat caused by Pyrenophora tritici-repentis (Ptr) is a major leaf spot disease. No single control measure is likely to be successful in controlling tan spot and a fully integrated system of disease management is more likely to achieve a long-term solution. Research to improve control efficacy has focused on fungicide improvement, resistant cultivars, the use of biological control agents (BCAs) mixtures and combinational approaches involving BCAs and plant resistance stimulants with complementary modes of action. Various biotic and abiotic agents can stimulate wheat defence mechanisms and so benefit resistance to Ptr infection. Among them, Trichoderma spp. have been widely used as antagonistic fungal agents against several pathogens as well as plant growth enhancers. Also, the synthetic agents acibenzolar- S-methyl (ASM) and thiomethoxam (TM) have provided broad-spectrum disease and pest control and additionaly enhanced plant vigor against several fungal diseases.The aim of this research was to evaluate the effectiveness of two Trichoderma harzianum strains and two substances of synthetic origin (acibenzolar-S-methyl, thiomethoxam) on the suppression of tan spot and plant growth promotion of wheat plants. When BCAs, ASM and TM were applied to field plots on wheat cultivar Klein Escorpion, the severity of tan spot disease was reduced, and plant height, fresh weight, dry weight of shoots, and dry weight of roots were increased in comparison with control. When applied prior to Ptr inoculum, ASM, TM and the strain Th1 of T. harzianum caused a reduction in necrotic lesions greater than 50 % compared to the control treatment.Treatments of seed with TM resulted in a significant enhancement of plant heigh. Applying ASM, foliar fresh weight significantly increased by 45 %, whereas the seed-coating with Th1 and TM, effectively increased foliar fresh weight from 29 to 50 %. ASM alone or combined with Th1 increased dry weight to above 60 %, whereas the effects of TM and Th1 on dry mass showed an increase that ranged from 57 to 25 %. Plants treated with Th1, and both synthetic compounds achieved up to 6 fold increment in root dry weight over the control. Keywords: Pyrenophora tritici-repentis, tan spot, wheat, biological control, SAR, plant growth .