Indução de resistência em algodoeiro no controle de doenças

Abstract

Brazil is among the five largest cotton producers in the world, but one of the factors that limit the production of the crop are fungal diseases, standing out fusariosis (Fusarium oxysporum f. sp. vasinfectum (Fov)) e ramulose (Colletotrichum gossypii var. cephalosporioides). The use of alternative technologies to the use of synthetic fungicides are efficient in reducing the population of pathogens, disease severity and consequently reducing losses. Among these technologies, resistance inducers with the potential to reduce the severity of diseases stand out. Thus, the objective of this work was to evaluate the efficiency of biotic and abiotic resistance elicitors as a component in the management of diseases in the cotton crop algodoeiro (Gossypium hirsutum L). The experiments were carried out in the Phytopathology Laboratory and in the experimental area in Chã do Jardim, Areia, PB. For the seed health tests, seeds of five cotton cultivars produced in the municipalities of Remígio (BRS Rubi and BRS Aroeira), Itaporanga (BRS Aroeira) and Ingá (BRS Verde) in the state of Paraíba and the cultivar BRS 368 RF ceded were used by EMBRAPA cotton. The treatments used were: AgroMos® (3 mL L-1), Agrosilicon (3 g L-1), Top Folha® Aminoagro (1.5 mL L-1), Amino Plus® (1.5 mL L-1), Potassium Phosphite (3 mL L-1), Lique Plex® Bonder (1.5 mL L-1), Lique Plex® CaMg+B (1.5 mL L-1), Lique Plex® Fast (1.5 mL L-1) and control (ADE). For seed health, the fungicide Captana (240 g 100 kg-1 of seeds) was used and for the field and greenhouse experiments, the fungicide Azoxystrobin (400 mL/ha) was used.The sanity, germination and emergence of the seeds were evaluated, being 200 seeds per treatment, distributed in twenty repetitions of ten seeds for the sanity and four repetitions of 50 in the germination and emergence tests. In the field experiment, seeds of the cultivar BRS Aroeira obtained by small producers in the city of Remígio were used. The height, width and stem diameter of plants of cotton were evaluated and at 90 days gas exchange and chlorophyll a, b and total evaluations were carried out, well as the enzymatic activity of Peroxidase (POX), Polyphenoloxidase (PPO) and Phenylalanine ammonia lyase (FAL). In vitro, the mycelial growth of Fov and its sporulation were evaluated. For the greenhouse experiment, the interaction between the pathogen and cotton plants was evaluated, whose seeds were treated with the elicitors described. After 24 hours of inoculation with the pathogen, the cultivars BRS Rubi and BRS Aroeira (Remígio) BRS Verde (Ingá) and BRS 368 RF (EMBRAPA) were evaluated for plant height, stem diameter, chlorophyll a, b and total, fluorescence chlorophyll and infection rate. The resistance elicitors used were efficient in controlling fungi in seeds and in the severity of ramulose and fusariosis in cotton plants, showing a positive increase in morphological, physiological and biochemical characteristics.