Clubroot caused by Plasmodiophora brassicae is an economically important disease of crucifer crops throughout the world and is a major threat to the quality and yield of cabbage (Brassica oleracea var. capitata L.) in China. Host resistance is essential for clubroot management. Although two cabbage lines (clubroot-resistant line CR21 and clubroot-susceptible line CS54) have been identified through screening 80 cabbage accessions, the molecular mechanisms underlying differential responses to clubroot remain elusive. Herein, RNA-seq analysis was performed to characterize the transcriptomic changes in CR21 and CS54 at 3 days after P. brassicae inoculation (DAI). In total, 1,057 and 4,741 differentially expressed genes (DEGs) were found in CR21 and CS54, respectively. Moreover, 541 genes were up-regulated in CR21, but showed either no significant change or were down-regulated in CS54. Gene Ontology (GO) analysis showed that most DEGs were involved in metabolism, transport, signal transduction, and defense. Compared with the identified putative defense response genes in Arabidopsis thaliana, 165 resistance-related DEGs were obtained, including PAMPs-triggered immunity (PTI)-related genes and Effector-triggered-immunity (ETI)-related genes. Interestingly, the co-supported defense response DEGs contained the defense-related genes, wound response genes, RBOHB, WRKY28, TIR-NBS-LRR class (RPS4 etc.), pathogenesis-related (PR) gene (Bo7g005050), lipid transfer protein class (LTP1 etc.), plant hormone-related genes, ethylene signaling transduction (HRE1-like gene and EIN3), ABA signaling (PP2C and PYL13), and cell wall modification related genes (EXP17 and PME44, beta-1,3-glucanase and cytochrome P450 genes). Taken together, this study provided a comprehensive insight into transcriptomic responses to P. brassicae infection in two different cabbage lines, and identified several candidate genes that might contribute to clubroot resistance in cabbage and other Brassica crops.

The smut fungus Ustilago esculenta infects Zizania latifolia and induces stem expansion to form a unique vegetable named Jiaobai. Although previous studies have demonstrated that hormonal control is essential for triggering stem swelling, the role of hormones synthesized by Z. latifolia and U. esculenta and the underlying molecular mechanism are not yet clear. To study the mechanism that triggers swollen stem formation, we analyzed the gene expression pattern of both interacting organisms during the initial trigger of culm gall formation, at which time the infective hyphae also propagated extensively and penetrated host stem cells. Transcriptional analysis indicated that abundant genes involving fungal pathogenicity and plant resistance were reprogrammed to maintain the subtle balance between the parasite and host. In addition, the expression of genes involved in auxin biosynthesis of U. esculenta obviously decreased during stem swelling, while a large number of genes related to the synthesis, metabolism and signal transduction of hormones of the host plant were stimulated and showed specific expression patterns, particularly, the expression of ZlYUCCA9 (a flavin monooxygenase, the key enzyme in indole-3-acetic acid (IAA) biosynthesis pathway) increased significantly. Simultaneously, the content of IAA increased significantly, while the contents of cytokinin and gibberellin showed the opposite trend. We speculated that auxin produced by the host plant, rather than the fungus, triggers stem swelling. Furthermore, from the differently expressed genes, two candidate Cys2-His2 (C2H2) zinc finger proteins, GME3058_g and GME5963_g, were identified from U. esculenta, which may conduct fungus growth and infection at the initial stage of stem-gall formation.

Real-time quantitative PCR (RT-qPCR) is a method with high sensitivity and convenience that has been extensively used to analyze the expression level of target genes. A reference gene with a highly stable expression is required to ensure the accuracy of experimental results. However, the report on appropriate reference genes in arrowheads (Sagittaria trifolia) is still limited. In this study, eight candidate reference genes (ACT5, UBQ, GAPDH, CYP, NAC, IDH, SLEEPER and PLA) were selected. The candidate genes were employed in a RT-qPCR assay in different tissues at different developmental stages of the same tissue (including corm, leaf and leafstalk) in arrowheads. Five statistical algorithms, GeNorm, NormFinder, BestKeeper, delta cycle threshold (ΔCt) and RefFinder, were used to evaluate the stability of these genes’ expressions in order to identify the appropriate reference genes. The results showed that UBQ was the optimum reference gene in leaf, leafstalk, root, stolon and corm, IDH exhibited the most stable expression during the expansion of corm, UBQ and PLA were the most stable reference genes in developmental stages of leaf and leafstalk, respectively. Finally, the reliability of reference genes was further confirmed by the normalization of PDS and EXP1 genes under different arrowhead tissues and developmental stages of corm, respectively. This study constitutes important guidance for the selection of reliable reference genes for analyzing the tissue- and developmental-stage-specific expression of genes in arrowheads.

Straw mulching on wet beds is an effective method to alleviate continuous cropping obstacles in greenhouses. However, this technique cannot be applied in the production of leafy vegetables with high planting density. Straw mulching in furrows is an alternative method in this circumstance. In this study, celery (Apium graveolens L.), a vegetable that prefers a high planting density and wet soil, was used to test furrow straw mulching technology, and the effect of different straw amounts and straw decomposers on soil improvement and celery production was investigated. The results showed that straw mulching in furrows significantly reduced soil conductivity and nitrate nitrogen levels, increased the contents of soil organic carbon as well as phosphorus and potassium nutrients in the bed, and improved celery yield and quality, indicating the significant lateral movement of released nutrients between the furrow and bed. The positive effects of 15,000 kg/ha straw application were more pronounced than those of 7500 kg/ha and 11,250 kg/ha. In addition, straw decomposers accelerated nutrient release and improved celery yield and quality. A decomposer named “ZhuBang” containing Bacillus licheniformis was the most effective. We concluded that furrow straw mulching combined with straw decomposer application is an effective measure for the sustainable production of leafy vegetables in intensive vegetable production facilities.

The rational use of a large amount of straw produced from grain fields is an important issue in major grain-producing areas. On the other hand, due to the long-term preferential applications of chemical fertilizers, soil organic carbon (SOC) content, soil fertility and organic matter levels have decreased, and the soil physical-chemical properties have deteriorated in protected agricultural facilities. In this study, a wet crop, taro (Colocasia esculenta (L.) Schott) and the straw of two main crops [wheat (Triticum aestivum L.) and rice (Oryza sativa L.)] were selected to investigate the effect of row-surface straw mulching on taro yields and soil chemical properties. The results showed that nearly all wheat straw and 74% of rice straw decomposed in one season under wet conditions. Straw mulching significantly increased the taro yield, increased the levels of SOC, soil rapid available nitrogen, phosphorus and potassium, and improved the activities of sucrase and phosphatase in the soil. We conclude that row-surface straw mulching t of wet crops could not only improve the soil properties and crop yields in the protected facility but could also consume considerable straw (wheat: 14,250 kg/ha, rice: 111,00 kg/ha), and the method applied in other areas with similar conditions.

Vegetable growth under plastic tunnels is a steadily growing agricultural sector but is causing environmental problems as a result of this farming system. Rice is one of the most important crops in China, and the rice straw is not only an agricultural residue, but also an important fertilizer resource. Rice straw return into the soil is a common practice in China. However, little is known about the effects of straw mulching on vegetable growth and soil quality under plastic tunnels. A two-season experiment of water spinach was carried out by plastic tunnel cultivation. The results indicated that rice straw decomposition rate was high under plastic tunnels, and rice straw supplies abundant nitrogen, phosphate, potassium and other essential nutrient elements to plants. With rice straw mulching, soil microbial growth and activity, and soil enzymatic activities were increased, and resulting in higher electrical conductivity lower redox potential. In conclusion, Soil organic matter content and soil nutrient availability were improved, and at the same time, the production of water spinach was significantly improved with rice straw mulching under plastic tunnels. Rice straw mulching under plastic tunnels could be a sustainable practice for vegetable growth, especially for aquatic vegetables.