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Fusarium solani (F. solani) is one of the most important pathogenic fungi, that cause Fusarium dry rot and Fusarium wilt in potato, responsible for low potato yield globally. However, the mechanistic understanding regarding the biocontrol of F. solani remains largely unknown. Here, we investigated the plant growth-promoting and antagonistic capability of Bacillus sp. PM31 against phytopathogen F. solani. The Bacillus sp. PM31, isolated from field-grown potato was analyzed for plant growth-promoting and extracellular enzyme activities. The strain PM31 exhibited phosphate, zinc, and potassium solubilization, nitrogen fixation, siderophore, exopolysaccharides production, and extracellular enzyme activities. The mycelial growth of F. solani was inhibited by strain PM31 with inhibition coefficient of 47.5. Under the storage conditions, inoculation of strain PM31 minimized the development of dry rot symptoms by 57% as compared to uninoculated diseased tubers. Under greenhouse conditions, inoculation of strain PM31 enhanced potato plant growth under fungal stress, while reduced the development of wilting, foot rot, chlorosis, and necrosis of inoculated potato plants by 92%, 75%, 64%, and 82%, respectively, as compared to diseased plants. Results inferred that the inoculation of native antagonistic Bacillus sp., PM31, could aid in global food security through biocontrol of important potato diseases viz. Fusarium dry rot and Fusarium wilt. [ABSTRACT FROM AUTHOR]

Large quantities of fertilizers, mainly nitrogen (N), phosphorus (P), and potassium (K), are used in China's crop production; however, whether N, P, and K still limit yield under the current high input remains unknown. In addition, it is not clear whether magnesium (Mg) potentially limits crop production. To address these issues, a national survey of the soil nutrient status and farmers' fertilization practices was conducted in China to determine the soil N, P, K, and Mg status and current fertilization practices. In addition, various experiments, including optimized NPK (OPTNPK) and Mg fertilizer combined with OPTNPK (OPTNPK + Mg) in comparison with farmers' practices (FFP), were performed across China to identify the potential for reducing NPK application and the need for Mg application in crop production. The survey data from 2699 questionnaires indicated that (1) all soil samples were not deficient in NPK, but 73.0% were limited by Mg. (2) The average N, P (in P2O5), K (in K2O), and Mg (in MgO) balances were 422.6, 334.1, 326.3, and −22.6 kg ha−1, respectively. Only 15.7% of all farmers applied Mg fertilizer. (3) NPK fertilization can be reduced by an average of 28.8% without reducing the crop yield and quality. (4) For most crops, the application of Mg fertilizer increased the crop yield by 5.5–40.6% and improved the quality. However, different crops under different conditions had different responses to Mg fertilization. These results indicate that reduced NPK inputs and increased Mg inputs are equally important for the healthy development and sustainability of China's agriculture. [ABSTRACT FROM AUTHOR]

The riparian zone is an important ecological corridor connecting the upstream and downstream rivers. Its highly complex biological and physical environments significantly affect the biogeographical pattern of species and various ecosystem functions. However, in alpine riparian ecosystems, the distribution patterns and drivers of arbuscular mycorrhizal (AM) fungi, a group of functionally important root-associated microorganisms, remain poorly understood. In this study, we investigated the AM fungal diversity and community composition in near-bank (wetland) and far-bank (alpine meadows) soils along the Niaqu River in the Nam Co watershed, and assessed the relative importance of abiotic and biotic filtering in shaping these distributions. Overall, 184 OTUs were identified in the riparian ecosystem, predominantly belonging to the genus Glomus, especially in the downstream soils, and Claroideoglomus in near-bank soils. AM fungal colonization, spore density, and a diversity showed an overall increasing trend along the river, while the extraradical hyphae declined dramatically from the middle of the river. AM fungal communities significantly varied between the wetland and alpine meadows in the riparian zone, mainly driven by the geographic distance, soil water content, soil pH, and plant communities. Specifically, soil pH was the principal predictor of AM fungal community in near-bank wetland soils, while soil water content had a most substantial direct effect in alpine Frontiers in Microbiology 01 frontiersin.org meadows. These findings indicate that abiotic factors are the most important divers in shaping AM fungal communities at the watershed scale, which could be helpful in alpine riparian biodiversity conservation and management. [ABSTRACT FROM AUTHOR]

Rhizosphere soil microbial communities substantially impact plant growth by regulating the nutrient cycle. However, dynamic changes in soil microbiota under different tree ages have received little attention. In this study, changes in soil physicochemical properties, as well as bacterial diversity and community structures (by high-throughput Illumina MiSeq sequencing), were explored in pomelo trees of different ages (i.e., 10, 20, and 30 years) under red and paddy soils cultivated by farmers with high fertilizer input. Moreover, soil factors that shape the bacterial community, such as soil pH, AP (available phosphorous), AK (available potassium), and AN (available nitrogen), were also investigated. Results showed that pH significantly decreased, while AP, AK, and AN increased with increasing tree age under red soil. For paddy soil, pH was not changed, while AP was significantly lower under 10-year-old pomelo trees, and AK and AN contents were minimum under 30-year-old pomelo trees. Both soil types were dominated by Proteobacteria, Acidobacteria, and Actinobacteria and showed contrasting patterns of relative abundance under different tree age groups. Bacterial richness and diversity decreased with increasing tree age in both soil types. Overall, bacterial community composition was different under different tree ages. RDA analysis showed that soil pH, AP, and AN in red soil, and pH and AP in paddy soil showed the most significant effects in changing the bacterial community structure. A random forest model showed Sinomonas and Streptacidiphilus in red soil, while Actinoallomurus and Microbacterium in paddy soil were the most important genera explaining the differences among different age groups. The ternary plot further revealed that genera enrichment for Age_30 was higher than that for Age_10 and Age_20 in red soil, whereas specific genera enrichment decreased with increasing tree age under paddy soil. Co-occurrence network revealed that bacterial species formed a complex network structure with increasing tree age, indicating a more stable microbial association under 20 and 30 years than 10-year-old pomelo trees. Hence, contrasting patterns of changes in soil physicochemical properties and soil microbial communities were recorded under different tree ages, and tree ages significantly affected the bacterial community structure and richness. These findings provide valuable information regarding the importance of microbes for the sustainable management of pomelo orchards by optimizing fertilizer input for different ages of trees. [ABSTRACT FROM AUTHOR]

Non-point source pollution from the Agri-sector (especially nitrogen (N)) due to the application of conventional urea with heavy rates not only depleted the water quality of Erhai Lake but also declined the nitrogen use efficiency (NUE) of different crops grown in the Erhai Lake Basin, Dali, Yunnan, China. It is imperative to mitigate the total nitrogen and its forms (nitrate (NO3−)-N and ammonium (NH4+)-N) loading to the surface and subsurface water flow through optimum fertilizer management for crop production in the region. To achieve this goal, a balanced crop nutrition system was practiced with different fertilizer types for rice-broad bean crop rotation system. The crop nutrition system consisted of No Fertilizers (CK), Conventional Fertilizer Practice (CF), Conventional urea as environmental Fertilizer (T1), Refined Organic Fertilizer applied solely (T2), Refined Organic Fertilizer applied with conventional urea (T3), Refined Organic Fertilizer applied in T2 was increased 4 times (T4), Refined Organic Fertilizer applied in T3 was increased 4 times but the same amount of conventional urea (T5), and Controlled Release Fertilizer (CRF) application (T6). The same rate of nitrogen (20% lower than CF) was applied in T1, T2, T3, and T6. All the former mentioned treatments were compared to CF with respect to different variables. In case of crop production, T6 gave maximum rice grain yield (9.9 t ha−1) and broad bean yield (5.1 t ha−1). Treatments T1 and T5 were at par for rice grain yield (7.8 t ha−1) and this quantity was not significantly lower than CF. Treatments T6, T5, and T1 were observed 29%, 47%, and 46%, respectively lower in TN loading to the surface and percolating water than the CF. Conventional urea and refined organic fertilizer combined with conventional urea at reduced nitrogen rates can be a reliable option for crop production in the Erhai Lake Basin with optimum yield under the rice-broad bean crop rotation system. CRF at reduced nitrogen rate can be a better option for higher yield and lower NO3–N, NH4+-N and total nitrogen losses to the surface runoff and leached water. [ABSTRACT FROM AUTHOR]

Endophytic bacteria are useful for their safe services in plant growth improvement and for ameliorating abiotic and biotic stresses. Salt-tolerant plant-growth-promoting Kocuria rhizophila 14asp (accession number KF 875448) was investigated for its role in pea plants under a saline environment. Salt stress (75 mM and 150 mM NaCl) was subjected to two pea varieties, peas2009 and 9800-10, in a greenhouse under a complete randomized design. Different parameters such as plant growth promotion, relative water content, chlorophyll, antioxidants, and mineral contents were analyzed to elucidate the extent of tolerance persuaded by PGPB (plant-growth-promoting bacteria). Exhibition of adverse effects was noticed in uninoculated varieties. However, inoculation of K. rhizophila improved the morphological parameters, antioxidant enzymes, and minimized the uptake of Na+ in plants under various saline regimes. Pea variety 9800-10 exhibited more tolerance than peas2009 in all traits, such as root and shoot length, fresh and dry biomass, chlorophyll contents, and antioxidant enzymes. Our results showed that halotolerant K. rhizophila inoculation plays a vital role in enhancing plant growth by interacting ingeniously with plants through antioxidant systems, enduring saline conditions. [ABSTRACT FROM AUTHOR]