ABSTRACT
The use of commercial bacterial inoculants formulated with plant-growth promoting bacteria (PGPB) in agriculture has shown significant prominence in recent years due to growth-promotion benefits provided to plants through different mechanisms. However, the survival and viability of bacterial cells in inoculants are affected during use and may decrease their effectiveness. Physiological adaptation strategies have attracted attention to solve the viability problem. This review aims to provide an overview of research on selecting sublethal stress strategies to increase the effectiveness of bacterial inoculants. The searches were performed in November 2021 using Web of Science, Scopus, PubMed, and Proquest databases. The keywords "nitrogen-fixing bacteria", "plant growth-promoting rhizobacteria", "azospirillum", "pseudomonas", "rhizobium", "stress pre-conditioning", "adaptation", "metabolic physiological adaptation", "cellular adaptation", "increasing survival", "protective agent" and "protective strategy" were used in the searches. A total of 2573 publications were found, and 34 studies were selected for a deeper study of the subject. Based on the studies analysis, gaps and potential applications related to sublethal stress were identified. The most used strategies included osmotic, thermal, oxidative, and nutritional stress, and the primary cell response mechanism to stress was the accumulation of osmolytes, phytohormones, and exopolysaccharides (EPS). Under sublethal stress, the inoculant survival showed positive increments after lyophilization, desiccation, and long-term storage processes. The effectiveness of inoculant-plants interaction also had positive increments after sublethal stress, improving plant development, disease control, and tolerance to environmental stresses compared to unappealed inoculants.
Subject(s)
Agricultural Inoculants , Nitrogen-Fixing Bacteria , Bacteria , Plant Growth Regulators , Plant DevelopmentABSTRACT
Neste trabalho objetivou-se realizar o levantamento e a avaliação dos índices técnicos de qualidade e produção de silagens de gramíneas tropicais em 14 propriedades nas regiões Sudeste e Centro-Oeste do Brasil. Avaliou-se informações referentes à exploração pecuária, à produtividade da planta forrageira, ao teor de matéria-seca da silagem, ao uso de aditivos e à utilização de inoculantes bacterianos, ao tamanho de partícula da silagem, ao pH da silagem, à condutividade elétrica e à densidade do material no silo. Nas propriedades amostradas, observaram-se diferentes níveis de tecnologia e exploração pecuária (leite e corte) na utilização de silagem de gramíneas para alimentação de animais. O tamanho do rebanho variou entre 30 a 40.000 cabeças. A produtividade foi de 8 a 24 t matéria-seca.ano.ha-1 . O teor de matéria-seca variou entre 13,5 a 35,9%. O pH das silagens encontrado nas diferentes propriedades foi de 4,0 a 5,7. A mensuração da condutividade elétrica obteve a amplitude de 680 a 1187 µS.cm-2 . A densidade de matéria-seca no silo foi de 86 a 230 kg.m-3 . A utilização de gramíneas tropicais para produção de silagem é uma prática viável, entretanto pode-se melhorar a eficiência com a exploração do potencial produtivo da planta, a utilização de aditivos e inoculantes, e o desenvolvimento de equipamentos de corte e colheita.(AU)
This work aimed to conduct the survey and evaluation of the technical indexes and quality production of tropical gramineous silage in 14 properties in the Southeast and Midwest of Brazil. It was evaluated information about the livestock, the productivity of the forage, to the dry matter plant content of the silage, the use of additives and the use of bacterial inoculants, to the size of the silage particle, the silage pH, the electrical conductivity and the density of the material in the silage. In the properties sampled, there were different levels of technology and livestock exploration (dairy and beef cattle) in the use of graminaceous silage for animal feed. The herd size was between 30 to 40,000 heads. The productivity was 8 to 24 dry-matter per year. The dry-matter varied from 13.5 to 35.9%. The pH of the silage found in the different properties was from 4.0 to 5.7. The measurement of electrical conductivity obtained the amplitude of 680-1187 µS.cm-2 . The density of dry-matter in the silo was of 86 to 230 kg.m-3 . The use of tropical graminaceous for silage production is a viable pratice, but the efficiency can be improved with the exploitation of the productive potential of the plant, the use of additives and inoculants, and the development of cutting and harvesting equipment.(AU)