Effects of agrochemicals on the beneficial plant rhizobacteria in agricultural systems.

Conventional agriculture relies heavily on chemical pesticides and fertilizers to control plant pests and diseases and improve production. Nevertheless, the intensive and prolonged use of agrochemicals may have undesirable consequences on the structure, diversity, and activities of soil microbiomes, including the beneficial plant rhizobacteria in agricultural systems. Although literature continues to mount regarding the effects of these chemicals on the beneficial plant rhizobacteria in agricultural systems, our understanding of them is still limited, and a proper account is required. With the renewed efforts and focus on agricultural and environmental sustainability, understanding the effects of different agrochemicals on the beneficial plant rhizobacteria in agricultural systems is both urgent and important to deduce practical solutions towards agricultural sustainability. This review critically evaluates the effects of various agrochemicals on the structure, diversity, and functions of the beneficial plant rhizobacteria in agricultural systems and propounds on the prospects and general solutions that can be considered to realize sustainable agricultural systems. This can be useful in understanding the anthropogenic effects of common and constantly applied agrochemicals on symbiotic systems in agricultural soils and shed light on the need for more environmentally friendly and sustainable agricultural practices.

Environmentally stable common bean genotypes for production in different agro-ecological zones of Tanzania.

Genotype by environment interaction (GxE) complicates the process of selecting genotypes suitable for quantitative traits like seed yield in beans, hence slows down the development and release of varieties by breeding programs. GxE study on seed yield in beans enables identification of stable genotypes across sites and best site(s) for discriminating the tested genotypes in terms of seed yield. The purpose of this study was to evaluate the influence of the environment, genotype, and genotype by environment interaction on seed yield stability and adaptability of common bean landraces, lines, and improved varieties across three different agro-ecologies in Tanzania. The 99 common bean genotypes (Landraces, lines, and improved varieties) were planted following alpha lattice design in three replications each contained five blocks with 20 plots. Soil properties from the experimental sites, days to 75% flowering, Seed yield, 100 seed weight, number of seeds/pod, and number of pods/plant were recorded. Data on seed yield and its components were analyzed using Additive main effect and multiplicative interaction (AMMI), genotype main effects plus genotype × environment interaction (GGE), and yield stability index (YSI). The AMMI revealed very highly significant (P ≤ 0.001) effects of genotypes, environmental, and genotype × environment interaction on all the traits. AMMI analysis revealed that genotype main effects accounted for 39.3% of the total sum square of seed yield, whereas the environment and genotype × environmental interaction accounted for 31.4% and 26.8 % respectively. Genotype main effects largely influenced the variation in days to 75% flowering (55.5%), number of pods/plant (49.2%), number of seeds/pod (73.3%), and 100 seed weight (71.2%). Among soil properties recorded, available soil phosphorus, soil pH, soil exchangeable K, Ca, and Na had a strong positive association with common bean seed yield, while soil organic carbon and total nitrogen exhibited a strong negative association with seed yield. GGE revealed that E1 (TARI-Selian) was the most discriminative and representative site for common bean genotypes seed yield. Based on the yield stability index, the most stable and high seed yielding genotypes were ACC 714, Selian 14, Selian 9, Katuku, and Msolini. The identified high seed yielding and stable genotypes can be further tested in participatory variety selection involving farmers and later on released as varieties and can also be used for different breeding purposes in different agro-ecologies of Tanzania.

Linking rhizosphere bacterial diversity and soil fertility in tobacco plants under different soil types and cropping pattern in Tanzania: A pilot study.

Tobacco (Nicotiana tabacum L.), one of the major crop plants in Tanzania, cropping affects the level of soil fertility, but the reason has not been known. Plant rhizosphere plays an important role in affecting soil fertility through changing microbial composition. We planned a pilot study to understand the changes in microbial composition and soil nutrients in the rhizosphere soils of tobacco in three agro-ecological zone, namely Sikonge, Tabora and Urambo in Tanzania. This study assessed bacteriota composition using 16S rRNA sequencing and soil fertility in the rhizosphere of tobacco plants. The results showed that bacterial diversity in tobacco rhizosphere soils belonged to Proteobacteria phyla, associated significantly (p < 0.05) with solubilization of insoluble P, K and S. The solubilization of P, K and S in soils facilitates the availability of these nutrients to the tobacco plants (a heavy feeder crop) allows low levels of these nutrients in the soils for the subsequent crop. The Proteobacteria phyla also associated with an increase in soil N content through fixation. Therefore, bacteria diversity in tobacco rhizosphere influence solubilities of macronutrients (P, K, S) and quickly up taken by the tobacco plant and reduces their levels in soils, some bacteria involved in fixing N and increases total N in the soil.

Multilocation dataset on seed Fe and Zn contents of bean (Phaseolus vulgaris L.) genotypes grown in Tanzania.

There are over a hundred genotypes of Phaseolus vulgaris L. grown and consumed in Tanzania. Currently, identification of bean genotypes containing high seed iron and zinc contents has been the focus globally for common bean iron and zinc biofortification. Diversity in seed iron and zinc contents were investigated in 99 bean genotypes grown in Tanzania to identify high seed iron and zinc-containing genotypes for use in iron and zinc biofortification. Flour obtained by grinding seeds of each bean genotypes was used in the determination of iron and zinc concentrations. Data were subjected to analysis of variance (ANOVA) to determine significant differences among common bean genotypes in terms of seed iron and zinc contents. Additive main effects and multiplicative interaction (AMMI) and genotype plus genotype by environment interaction (GGE) were conducted to determine stability and adaptation across sites (TARI-Selian, SUA, and TARI-Uyole) of bean genotypes in terms of seed iron and zinc contents. Data in this data article show that some landraces had high seed iron and zinc contents compared to release varieties thus can be used for iron and zinc genetic biofortification in common beans breeding programs. For more explanation of the data presented in this data article, please follow the related research article "Environmental and genotypes influence on seed iron and zinc levels of landraces and improved varieties of common bean (Phaseolus vulgaris L.) in Tanzania" [1].

The prebiotic potential of brewers' spent grain on livestock's health: a review.

The increasing interest from the feed as a source of energy towards specific nutrient-yielding compounds in feeds is amongst the latest developments from scientific and industrial communities. Apart from brewers' spent grain (BSG) being relatively inexpensive feed source, nutritious with high crude protein and minerals, recent studies have explored its potential as a source of prebiotics. Prebiotics are certain feeds that are comprised of non-digestive polysaccharides that can be fed to animals and modulate the balance and activities of microbial populations in the gut. The BSG contains arabinoxylans and ß-glucans whereby when consumed by animals, they promote the activity of beneficial bacteria particularly species from three genera of Bifidobacterium, Enterococcus, and Lactobacillus. The increased degradation of fibrous feed accelerates the production of short-chain fatty acids (SCFA) which serve as the primary energy sources for the anaerobic microbes. This elevated concentration of SCFA stimulates numerous physio-biological functions which include intestinal nutrients absorption, glucose balance, improvement of immunity, lipid metabolism, and suppression of pathogens such as Salmonella and Escherichia coli. To capitalize on the prebiotic potential of BSG, certain considerations need to be well taken care of and these include possible microbial dysfunctions such as rumen acidosis, different responses rates of animals due to variations in health status, age, and species as well as feed safety issues especially mycotoxin contamination which can jeopardize its inherited prebiotic benefits.

Identification and Management Challenges Associated with Ralstonia solanacearum (Smith), Causal Agent of Bacterial Wilt Disease of Tomato in Sub-Saharan Africa.

Tomato is the world's most consumed vegetable crop after potato and it is source of vitamins, minerals, fiber, lycopene, ß-carotene and income. Despite its significant importance tomato can heavily be attacked by different pathogens including Ralstonia solanacearum that incites bacteria wilt disease. The disease is very devastating causing a considerable yield loss worldwide. The pathogen can survive in plant debris, infected plants and host weeds and spread from one field to another by irrigation or flood water, soil, farm equipment and workers and weeds which usually grow along waterways and it is difficult to manage due to complication in biology, nature of infestation and wide host range. In areas like the Sub-Saharan Africa where there exists a wide diversity of plant species, the pathogen becomes even more difficult to manage. It is on this basis that this review article, clearly discusses challenges for bacterial wilt disease identification and management in tomato farming systems with respect to the diagnosis methods used, pathogen genetic diversity and host range and pathogen survival mechanisms under different environment. The information will empower the responsible personnel involved in tomato production chain to have clear information about the pathogen and management options available against the disease in Sub-Saharan Africa.