Comunidade microbiana do solo e podridão radicular em meloeiro em diferentes sistemas de manejo

Abstract

This study aimed to quantify the microbial community of soil cultivated with muskmelon and evaluate the incidence of root rot in muskmelon at the no-tillage (NT) and conventional tillage (CT) systems associated with soil coverages.Two experiments (two muskmelon crop cycles) were conducted in a naturally infested area with soilborne pathogens. The incidence of root rot was evaluated in both crop cycles, while the microbial community was quantified only in the first crop cycle.The experiments were conducted at the AgrícolaFamosa s farm, located between the cities of Tibau-RN and Icapuí-CE, in the Northeast region of Brazil.The randomized block design was used with split-plot.At the main plots evaluated two planting systems with and without soil revolving (NT and CT) and the subplots consisted of seven soil cover crops (Sunn hemp; Pearl millet; Sunn hemp + Pearl millet; Corn + Brachiaria; Spontaneous vegetation, Spontaneous vegetation + Black polyethylene film and Soil without vegetation).At the conventional tillage system, the plant materials were dried and incorporated into the soil, while in the no-tillage system were maintained on the ground.It was realized six soil samplings (Fallowed area; Green manure implementation; Muskmelon transplantation and at 20, 40 and 60 days after transplantation-DAT) in each subplot for quantification of total bacteria, fungi, Bacillus spp. and Pseudomonas fluorescens. For isolation and cultivation of microorganisms, serial dilutions were prepared and transferred to plates containing the desired solid medium for each analyzed group.After fruits harvest, all melon plants were collected from subplots, washed and analyzed for the incidence of root rot.The soil microbial communities (total bacteria, fungi, Bacillus spp. e Pseudomonas fluorescens) varied according to the tillage systems (no-tillage and conventional tillage) at the different epochs of sample collection during the muskmelon cycle. The sunn hemp cultivation associated with no-tillage in muskmelon provided greater amount of colony forming units (CFU) of total bacteria compared to the conventional tillage.The planting systems and soil coverages did not affect the amount of total fungi and Pseudomonas fluorescens. The microbial community of soil cultivated with muskmelon is influenced by the planting and soil coverage systems.The incidence of root rot in muskmelon was lower in the no-tillage system pre-cultivated with Sunn hemp, Pearl millet and Spontaneous vegetation. Fusarium solani, Macrophomina phaseolina, Monosporascus cannonballus e Rhizoctonia solani were the pathogens that occurred in muskmelon, being the first fungus the most frequent in both planting systems. The incidence of root rot in muskmelon depends on the cropping and planting systems