A comprehensive understanding of rice straw (RS) and biochar (BC) addition affecting soil quality, enzyme activities, bacterial community structure and grain yield is crucial. The objective of this study was to examine the dynamics of the soil microbial community impacted by the application of rice straw and biochar, and to understand the relationship between the microbial communities, soil enzymes, nutrients and grain yield of paddies. We conducted a field experiment with organic amendments under the direct seeding of paddies. The bacterial community structure in the rhizosphere was characterized using high-throughput 16S rRNA sequencing. The results showed that RS amendment increased grain yields by 8.5 and 9.9% more than with BC and the control without organic amendment (CK), respectively (p < 0.05). The abundance of bacteria associated with nitrate reduction in RS was higher than that in BC and CK, which further showed the significance of the RS-treated soil bacteria in rice nutrient utilization. A cladogram plotted using linear discriminant analysis effect size showed that Proteobacteria (Alphaproteobacteria), Acidobacteria, Firmicutes, Verrucomicrobia and Epsilonbacteraeota in the RS-treated soil increased in comparison with CK. Pearson’s correlation analysis showed that enzymes activities (cellulase activity and protease activity), soil nutrition content (soil hydrolyzable nitrogen), and bacterial phyla (Nitrospinae) were positively correlated with grain yield, suggesting that the RS-treated soil improved enzyme activities, soil nutrition content, and bacterial abundance, which in turn increased grain yield. The results indicated that RS-treated bacterial communities combined with soil enzymatic activities strengthen the transformation of nutrients, suggesting that the interactions play an important role in enhancing the grain yield of paddy rice. These results provide new insights and a theoretical basis for studying the changes in soil microbial communities with the application of RS and BC in Northeastern China.

Rice blast is a fungal disease that seriously threatens rice production. It is of great significance to identify blast resistance genes and clarify their functions in rice varieties. In this study, 11 rice blast resistance genes in 80 Japonica rice varieties in northern China were investigated, including their resistance to rice blast. The results demonstrated that Pita, Ptr, Pib, Pik, and Piks were most widely found, accounting for 48.8, 48.8, 41.3, 20.0, and 18.8% of the tested varieties, respectively. Pi5-G2 at the Pi5 locus and Pik-G5 and Pik-G8 at the Pik locus were also commonly found, and these alleles accounted for 30.0, 10.0, and 3.8% of all the tested varieties, respectively. Pizt was identified only in two cultivars, and alleles Pi2, Pi9, and Pigm at the Piz locus on chromosome 6 were not detected. We found that Pi5 and Pita were relatively conserved, but the alleles of Pik were abundant. Besides Pik, Pikm, and Piks, we also found 10 new haplotypes, and Pikp and Pikh were not found in the japonica rice varieties in northern China. Among the tested varieties, 5 did not carry any of the tested genes, 30 carried only one blast resistance gene, 27 carried two, 14 carried three, and 4 carried four. The resistance of varieties carrying three or four resistance genes was better than those carrying none of the resistance genes or only one or two. There were no significant differences in the resistance characteristics among varieties from different provinces. Our study provided a reference for the molecular breeding of rice blast resistance.

This study assessed the impact of planting techniques and short-term organic additions on soil quality, enzyme activity, and bacterial community composition. Biochar (BC) amendment substantially enhanced the ACE, Chao 1, and Shannon indices in direct-seeded rice (DS). Principal coordinate analysis (PCoA) and dissimilarity distances confirmed significant differences in the rhizosphere bacterial community composition associated with planting methods and organic applications. At the phylum level, transplanting (TT) significantly increased the abundance of Proteobacteria, Planctomycetes, Bacteroidetes, Firmicutes, and Verrucomicrobia, whereas DS significantly reduced the abundance of Acidobacteria, Chloroflexi, Actinobacteria, Gemmatimonadetes, and WPS-2. Rice straw (RS) application was associated with increased Proteobacteria, Acidobacteria, Chloroflexi, and Gammaproteobacteria, while BC application improved Bacteroidetes, Firmicutes, and Verrucomicrobia. Planting methods and organic amendments were also observed to affect soil enzyme activities and physicochemical properties. DS was associated with an increase in microbial biomass nitrogen (MBN) and carbon (MBC), cellulase activities (CA), total phosphorus (TP), available nitrogen (AN), and available potassium (AK), while TT significantly increased urease activities (UA). Compared to BC and the control (CK), RS significantly increased CA, AN, and available phosphorus (AP). RDA ordination plots were used to examine the interactions between soil bacterial communities and soil physicochemical properties; planting techniques and organic additions had different effects on soil bacterial communities. Compared to RS and CK, BC enhanced MBN, MBC, UA, and AK. According to Pearson’s correlation analysis, Chloroflexi levels were positively associated with those of organic carbon (OC), MBN, and MBC. OC, TP, MBN, and CA positively correlated with gemmatimonadetes. In conclusion, these data reveal that planting practices and short-term organic inputs alter soil’s physicochemical parameters, enzyme activity, and microbial community composition.