Bioestimulantes na indução de resistência a patógenos em feijão guandu

Abstract

Pigeon pea (Cajanus cajan) is a legume used as mulch, in order to retain more moisture in areas with low rainfall, for green manure and in human and animal food. Studies report the presence of fungi associated with pigeon pea seeds. Among the methods of controlling pathogens in seeds, the induction of resistance in plants has been studied as an alternative to the use of chemical agents with promising results. The objective of this work was to determine the effect of resistance elicitors to the incidence of pathogens in pigeon pea seeds and plants, as well as in the fungicidal/fungistatic power of the elicitor in vitro on Fusarium sp.. The experiments were carried out at the Phytopathology and Laboratory. in a greenhouse at the Centro de Ciências Agrárias, UFPB. The following treatments were used: T0 = Control, T1 = Fungicide, T2 = AgroMos®, T3 = Liqui-Plex® Bonder, T4 = Liqui-Plex® CaMg+B, T5 = Liqui-Plex® Fast, T6 = Sheet Top® Aminoagro , T7 = Master Potassium®, T8 = Master RR Ultra ® and T9 = Viusid® Agro. To assess the physiological and sanitary quality of the seeds, health, germination and emergence tests were performed. To verify the effect of treatments on isolates in vitro, treatments were added in PDA culture medium, poured into Petri dishes, adding a 5 mm disk of fungal colony. The in vivo control was carried out in a greenhouse, where the incidence, gas exchange and activity of the enzymes peroxidase (POD), polyphenoloxidase (PPO) and phenylalanine ammonia lyase (FAL) in pigeon pea plants were evaluated 30 days after seeding. The results observed were, the highest occurrence of Aspergillus sp. (21.5%) was observed in treatment T5. Treatments T5, T7 and T9 were efficient in reducing A. niger. Regarding the incidence of Cladosporium sp., it was observed that treatments T5, T6, T7, T8 and T9 were efficient, causing a significant reduction of the pathogen. Treatments T7, T8 and T9 provided promising results for the variables of germination, first count, dead seeds and germination speed index. In the emergency test it was observed that most treatments did not interfere in the variables evaluated, except for treatments T4 and T7. In the in vitro test, treatments T1, T2, T5, T6 and T8 showed the best results regarding inhibition of the average colony diameter (DMC), mycelial growth velocity index (IVCM) and percentage of inhibition of mycelial growth ( PIC). To control the incidence of Fusarium sp. (Figure 2), treatments T3, T5, T6, T7, T8 and T9 proved to be efficient in controlling the incidence of the pathogen. For peroxidase activity (POD), the T4 treatment stimulated the activity of this enzyme, showing the highest result. The elicitors used are efficient in reducing the incidence of A. niger and Cladosporium sp. in pigeon pea seeds. Treatments T7, T8 and T9 stand out, providing increments in the analyzed physiological variables. Treatments T2, T5, T6 and T8 are efficient in controlling mycelial growth in the in vitro test. Treatments T3, T8 and T9 are efficient in controlling Fusarium sp. sporulation. Treatments T3, T5, T6, T7, T8 and T9 reduce the incidence of Fusarium sp. in pigeon pea plants. The treatments do not interfere with gas exchange in pigeon pea plants. Only T4 treatment induces peroxidase enzyme activity in pigeon pea plants.