BACTERIAL DIVERSITY IN COMMON BEAN PRODUCTION SYSTEMS MANAGED WITH COVER CROPS IN THE BRAZILIAN CERRADO

Abstract

The Brazilian cerrado is a region of fundamental agronomic importance of the country’s grain and fiber yields. This biome is also known for its huge biological diversity of soils and for dividing borders with the Amazon rainforest and the Pantanal wetlands. However, intensive agriculture has led to the loss of soil diversity and to the buildup of several soil-borne pathogens that are main constraints for sustainable agriculture. The objective of this work was to investigate changes in the bacterial diversity on the common bean rhizosphere in a commercial field, rotated with different fall cover crops grown in a no-tillage system. We made inferences on grain yield observing if bean plants could host distinct bacterial taxa, according to the previous crop. The study was developed in a commercial area in Planaltina – DF, from 2017 to 2021. The experimental field had over than 20 years of cultivation with up to three annual crops supported by center pivot sprinkling irrigation. Soybean and maize were the main summer crops, with the following cover crops implemented in the fall: crotalaria (Crotalaria spectabilis), white oat (Avena sativa), brachiaria (Urochloa ruziziensis), millet (Pennisetum glaucum), a mix of cover plants composed of millet, crotalaria, forage turnip (Raphanus sativus) and buckwheat (Fagopyrum esculentum). The bacterial metagenome estimated by 16S sequencing revealed responses to the treaments by XX genera including Streptomyces, Nococardioides, Bacillus, Burkholderia, Rhizobium, Azospirillum and Agrobacterium. Such genera play relevant ecosystem services such as plant growth promoters, biocontrol agents and improve plant nutrition with phosphate solubilization and nitrogen fixation. We observed that different bacteria are recruited according to the previous cover crop. The performance of these growth-promoting bacteria is stimulated in soils with low nutrient availability, and this activity can be used as an efficient bioindicators of environmental quality.