Background: Wheat straw is a rich resource worldwide. Straw return is an effective strategy to alleviate soil-borne diseases on monoculture watermelon. Previous studies focus on soil structure, physical and chemical properties; however, little is known about the molecular responses on host plant.Results: No significant difference on the population ofFusarium oxysporumf.sp. niveumrace 1(Fon1) in rhizosphere soil was found between control (no addition of wheat straw) and the treated groups (addition of 1% (T1) or 2% (T2) wheat straw). RNA-Seq analysis showed that 3419 differentially expressed genes were clustered into 8 profiles. KEGG analysis revealed that phenylpropanoid biosynthesis and plant hormone signal transduction were involved in wheat straw induced response in monoculture watermelon. Genes in lignin biosynthesis were found to be upregulated, and the lignin and auxin contents were higher in T1 and T2 compared to the control. Lignin was also enriched and the Fon1 population decreased in watermelon roots treated with wheat straw. The enzyme activities of phenylalanine ammonia-lyase and peroxidase were increased.Conclusions: Our data suggest that the addition of wheat straw enhances the defense response to Fon1 infection in watermelon through increasing lignin and auxin biosynthesis.

Powdery mildew (PM) significantly and negatively affects the yield and quality of melon (Cucumis melo) worldwide. Race 2F is the predominant physiological race of the pathogen Podosphaera xanthii in many regions. We used accessions PMR 6 (P₁; resistant to PM) and M1-7 (P₂; susceptible to PM) to analyze the inheritance of resistance to PM (race 2F). The ratio between resistant and susceptible individuals fits a Mendelian segregation ratio of 13:3 in a total of 256 F₂individuals and 1:1 in BC₁P₂. The resistance to PM in PMR 6 was governed by two genes: a dominant (AA) gene with an epistatic effect and a recessive gene (bb). Only individuals with aaBB or aaBb genotypes were susceptible to PM. Two PM resistance loci, Pm2.1 and pm12.1, were mapped on chromosomes 2 and 12 by bulked segregant analysis and secondary mapping by quantitative trait loci analysis with 18 markers. A new marker-assisted selection system to identify melon genotypes resistant or susceptible to PM was developed and tested in 93 melon accessions. Nucleotide diversity (π) and fixation index (Fst) for the two PM resistance loci were estimated using resequencing data of 336 melons from three groups: C. melo subsp. agrestis, Cucumis melo subsp. melo, and the intermediate type. The lowest π was observed in C. melo ssp. agrestis, and the highest Fst value was between C. melo ssp. agrestis and C. melo ssp. melo. The findings provide a promising tool that can be used to accelerate breeding for durable resistance to PM.

Crop rotation affects soil properties and soil microbial diversity and structure. Currently, it is not well understood how soil microbial diversity changes following different crop rotation systems of industrial hemp, an ancient and economically important crop. Therefore, these changes were analyzed in this study. Our results showed that different rotation systems significantly affected the wilt disease incidence, plant height, yield, soil physicochemical properties and soil microbial communities in the greenhouse. The rotation systems used in this study significantly reduced the plant mortality and increased the yield compared with a monoculture system. The levels of alkaline hydrolysis and available phosphorus in the soil decreased significantly compared with a monoculture cropping system. Using MiSeq high-throughput sequencing, we showed that the soil diversity and number of bacteria and fungi were significantly higher for rotation systems and controls compared to the monoculture system. The relative abundance of pathogens increased with a monoculture system. Redundancy analysis suggests that soil properties may also affect the soil microbial composition. Taken together, different rotation systems used in this study significantly decreased the disease incidence, increased plant yields and increased soil microbial diversity compared with monoculture for industrial hemp. We believe that applying these rotation systems is an efficient and eco-friendly approach to control soil borne pathogenic diseases and increase floral yields.

Phytophthora root rot (PRR) is a destructive disease of soybeans (Glycine max (L.) Merr) caused by Phytophthora sojae (P. sojae). The most effective way to prevent the disease is growing resistant or tolerant varieties. Partial resistance provides a more durable resistance against the pathogen compared to complete resistance. Wild soybean (Glycine soja Sieb. & Zucc.) seems to be an extraordinarily important gene pool for soybean improvement due to its high level of genetic variation. In this study, 242 wild soybean germplasms originating from different regions of Heilongjiang province were used to identify resistance genes to P. sojae race 1 using a genome-wide association study (GWAS). A total of nine significant SNPs were detected, repeatedly associated with P. sojae resistance and located on chromosomes 1, 10, 12, 15, 17, 19 and 20. Among them, seven favorable allelic variations associated with P. sojae resistance were evaluated by a t-test. Eight candidate genes were predicted to explore the mechanistic hypotheses of partial resistance, including Glysoja.19G051583, which encodes an LRR receptor-like serine/threonine protein kinase protein, Glysoja.19G051581, which encodes a receptor-like cytosolic serine/threonine protein kinase protein. These findings will provide additional insights into the genetic architecture of P. sojae resistance in a large sample of wild soybeans and P. sojae-resistant breeding through marker-assisted selection.

Wild soybean germplasm is distributed widely in China, particularly in Heilongjiang Province. In this study, 242 wild soybean accessions from four agricultural divisions in Heilongjiang Province were evaluated based on six qualitative and eight quantitative traits. Results showed that a large amount of variation occurred in these evaluated traits. Abundant qualitative traits included the wild type (78.51%), purple flowers (90.50%), needle leaf (39.26%), black seed (83.88%), brown hilum (52.07%), and mud film (87.60). Results of multivariate analysis based on quantitative traits showed that 100-seed weight, seeds weight per plant, number of seeds per plant, number of effective pods, and number of invalid pods were significantly different among samples (p < 0.05). A total of 27 germplasms were screened. Cluster analysis identified the 242 accessions into two groups, not following the geographical distribution pattern, with rich wild soybean resources revealed in the northern site. The present study indicated that wild soybean in Heilongjiang Province should be conserved in situ. The rich genetic diversity revealed in soybeans of different sites in Heilongjiang Province suggested its significant potential utilization in genetic improvement and breakthrough for soybean breeding. This information will help to exploit and conserve wild soybean accessions in Heilongjiang Province.

Sulfur (S) fertilization and rhizobium inoculation are important agronomic practices for improving soybean growth and yield. However, their combined effects on yield components and the resultant impacts on yield need further investigation. Our study aimed to verify the combined effects of S fertilizer and rhizobium inoculant on the yield components and seed yield of soybeans, as well as photosynthesis dynamics during the V5–R6 growth stages. A randomized block design incorporating two factors was employed for field experiments on soybean, involving the application of five rates of sulfur (0, 5.0, 9.8, 14.8, and 19.6 kg S ha⁻¹) with rhizobium inoculation or without. A reduction of 50% in mineral fertilizer according to farmer practice (FP) was applied alongside different rates of sulfur for field experiments on soybeans. The findings indicated that the application of sulfur fertilization significantly enhanced soybean yield by increasing the number of grains per plant (NG) and the number of pods per plant (NP). Maximum grain yield was reached under treatment with an S rate of 19.6 kg S ha⁻¹, which increased NG by 39% more than an S rate of 0 kg S ha⁻¹. Correlation analysis indicated that higher photosynthesis was closely associated with increased yield components. This study demonstrated that applying S fertilizers could improve soybean production by combining the appropriate sulfur concentration and rhizobia inoculation.