Analysis of Cotton Secondary Metabolites under the Interaction between Verticillium dahliae and Upland Cotton

[Objective] The aim of this study is to investigate the cotton differential metabolites in the interaction between Verticillium dahliae and cotton plant, and to explore new clues for the further study on the defense mechanism of cotton against V. dahliae. [Method] To obtain the cotton root, stem and leaf samples of the pathogen treated and healthy controls, the upland cotton cultivar CCRI 24 was selected as tested cotton material in this paper, and inoculated with V. dahliae conidia or sterile water by injuring root at the 2-true-leaf stage. The 70% (volume fraction) methanol extracts of these samples were separated and detected by ultra-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS), and the metabolite data were obtained by the online XCMS software. Through multivariate statistics and student’s t-test, the differential metabolites were investigated. The types of metabolites were putatively identified based on the comparison of the experimental molecular mass and the monoisotopic accurate molecular mass of cotton metabolites. [Result] The efficiency of negative ion mode was higher than that of positive ion detection mode in the cotton metabolites in UPLC-ESI-MS analysis. 576 ions mainly distributed in cotton root were found in the cotton seedling tissues including root, stem and leaf, which were the distinguished differential metabolites between V. dahliae treatment and healthy control. Among them, 77 ions were identified as sesquiterpenoids, diterpenoids, flavonoids, carbohydrates, aliphatics and phenols. In addition to sesquiterpenes, 17 compounds, including caffeic acid, astragalin, isoastragalin, dillenetin, ent-catechin, gossypetin 8-rhamnoside, gossypicyanin, herbacetin 7-glucoside, leucocyanidin, quercetin 3'-glucoside, quercetin 3-glucoside, quercetin 7-glycosides, α,2',3,3',4,4',6-heptahydroxychalcone 2'-glucoside, melibiose, sucrose, sucrose 6-phosphate and 1-tetratriacontanol, had not been reported in the literatures on the interaction between V. dahliae and cotton, which may be the novel pathogenesis-related metabolites on cotton Verticillium wilt. [Conclusion] The putative pathogenesis-related metabolites of cotton Verticillium wilt may play an important role in the interaction of cotton defense against V. dahliae, which provides an important clue for exploring the new resistant mechanism of cotton to Verticillium wilt.     

Induction of resistance against pine wilt disease caused by Bursaphelenchus xylophilus using selected pine endophytic bacteria

Pine wilt disease (PWD) is the most destructive disease threatening pine worldwide. The disease is mainly caused by the pine wood nematode, Bursaphelenchus xylophilus, which is vectored by pine sawyer longhorn-beetles, Monochamus spp. This study aimed to select resistance-inducing pine endophytic bacteria for management of PWD. To set up a defence-related genes expression pattern for screening, four chemical inducers (salicylic acid, γ-aminobutyric acid (GABA), β-aminobutyric acid and α-aminobutyric acid) were tested in vitro on pine calli and in vivo on pine seedlings. Treatment with GABA had the greatest reduction in PWD severity on pine seedlings. The pattern of defence-related gene expression in calli treated with GABA was used to select potential resistance-inducing bacterial strains. In addition, 92 bacterial strains were isolated from pine tree needles and stems and were tested for expression of defence-related genes in pine calli in vitro. Among the tested strains, 13 showed a similar pattern to GABA treatment in at least four tested defence-related genes and were selected for the seedling assay. From the seedling assay, three bacterial strains (16YSM-E48, 16YSM-P180 and 16YSM-P39) showed significant reduction in PWD severity compared to the untreated control. Moreover, among the selected strains, cell-free culture supernatant of strain 16YSM-P180 significantly reduced PWD severity in inoculated pine seedlings. The selected strains were identified based on the 16S rRNA sequence as Pseudomonas putida 16YSM-E48, Curtobacterium pusillum 16YSM-P180 and Stenotrophomonas rhizophila 16YSM-P39. These selected strains are suggested as potential alternatives for management of PWD by induction of systemic resistance.     

Identification and characterization of a new class of Tomato spotted wilt virus isolates that break Tsw-based resistance in a temperature-dependent manner

The single dominant Tsw resistance gene from Capsicum chinense against the Tomato spotted wilt orthotospovirus (TSWV) is temperature sensitive, i.e. the resistance fails to function at or above 32 °C. This study describes a new class of temperature-sensitive resistance-breaking TSWV isolates that induce Tsw-mediated resistance at T < 28 °C but at T ≥ 28 °C break this resistance. The NSs genes from these isolates were cloned and expressed to be analysed for RNA silencing suppressor (RSS) activity and the ability to induce a Tsw-mediated hypersensitive response (HR) in C. chinense and Capsicum annuum (Tsw+). Unlike in viral infection, transient expression of some of the NSs proteins at standard temperatures (22 °C) did not induce Tsw-mediated HR, although varying degrees of RSS activity were observed. Attempts to express and test the NSs proteins for functionality at an elevated temperature through agroinfiltration remained unsuccessful. The NSs proteins of some TSWV resistance-breaking (RB) isolates were analysed and found to lack amino acid residues that were previously shown to be important for RNA silencing suppression and avirulence. This study describes a new class of resistance-breaking TSWV isolates that may be of importance for breeders and growers and for which the underlying mechanism still remains unknown.     

Evaluation of bacterial biological control agents for control of root-knot nematode disease on tomato

Among 19 bacterial strains isolated in Yunnan from rhizosphere soils and plant tissues, Bacillus methylotrophicus strain R2-2 and Lysobacter antibioticus strain 13-6 exhibited the highest antagonistic activity against the tomato root-knot nematode Meloidogyne incognita in plate and greenhouse pot experiments. The two strains, when applied as soil drenches or seed treatments in greenhouse experiments, reduced root-knot severity and incidence on tomato compared to no-bacteria controls. In tomato field trials conducted in separate years, soil drench treatment with either strain reduced root-knot disease levels and increased yields compared to the control. Levels of disease control and yield enhancement provided by the strains were higher than those using the chemicals abamectin and carbofuran. This is the first report of B. methylotrophicus being used as a biocontrol agent against a plant parasitic nematode and the first demonstration that B. methylotrophicus and L. antibioticus can suppress disease caused by root-knot nematodes in the field.     

番茄抗青枯病育种研究进展

综述国内外番茄抗青枯病育种的研究进展，包括青枯病菌的病原分化及抗性遗传，接种方法，品种筛选和育种手段，并对育种前景进行了探讨。     

茄子抗黄萎病遗传的初步研究

选取６份对黄萎病具有抗感差异的茄子材料，利用完全双列杂交设计轮配法配制１５个组合，调查人工灌根后的抗病指数。结果表明：抗性遗传不符合“加性－显性”模型，存在上位性作用，且至少受２对显性基因组控制。     

Evaluation of soil enzyme activities and microbial communities in tomato continuous cropping soil treated with jerusalem artichoke residues

ABSTRACT

Jerusalem artichoke (JY) (Helianthus tuberosus L.) has been reported to have a strong inhibitory effect on weed growth and root knot nematodes, but little information is available on the effects on soil ecosystems, especially soil microorganisms and soil enzyme activities. Understanding the dynamics of soil microbes and soil enzyme activities in cropping systems can help determine how agricultural practices influence soil processes mediated by JY residues. This study used a pot experiment, with five-year continuous cropping soil of tomato plants as the experimental material and 2% (w/w) JY residue as the treatment material in the soil. The treatment was compared to continuously monocropped tomato soil that was not treated with JY residues. The results of 16S high-throughput sequencing showed that both fungal and bacterial community structure and composition varied significantly at each stage of JY treatment. The analysis showed that the major phyla in the soil fungal community included Ascomycota, Zygomycota and Basidiomycota. Chytridiomycota was dominant in only the JY-treated soil. At the genus level, the abundances of Mortierella, Cephaliophora, Cryptococcus and Fusarium notably changed at each stage of JY treatment. In the bacterial community in the JY-treated group, the abundance of Proteobacteria increased significantly, while that of Firmicutes decreased significantly, compared to the control group. JY enhanced the activity of soil sucrase and urease. In addition, the soil sucrase activity showed a strong negative correlation with Fusarium and Bacillus. Overall, our results revealed that JY residues changed both the soil bacterial and fungal community composition and the soil enzyme activities.     

Retardation of pine wilt disease symptom development in Japanese black pine seedlings exposed to simulated acid rain and inoculated withBursaphelenchus xylophilus

Three- or 4-year-old Japanese black pine seedlings were exposed to simulated acid rain (SAR) at pH 3 for two months, then inoculated with a virulent isolate (S 10) of pinewood nematodes. The experiments were repeated three times in 1996–1998. The exposure to SAR killed no seedlings, and retarded the development of disease symptoms in the seedlings inoculated with nematodes. In the experiments in 1996 and 1997, however, cessation of resin exudation, and primary decrease in the xylem conductivity occurred earlier in the seedlings exposed to SAR than in those exposed to tap water as a control. These results imply that acid rain at pH 3 influenced an increase in some resistance of Japanese black pine seedlings to pinewood nematode, and that this improved resistance could potentially overcome damage caused by acid rain. The exposure to SAR did not have any significant effect on the water relations of the seedlings itself, suggesting that retardation of the symptom development after the exposure to SAR could not be attributed to the improvement in the water relations. This work was supported in part by a Grants-in-Aid for Scientific Research from the Japan Forest Technical Association (JAFTA).     

Modeling wildfire risk to northern spotted owl (Strix occidentalis caurina) habitat in Central Oregon,USA

Natural disturbances including wildfire, insects and disease are a growing threat to the remaining late successional forests in the Pacific Northwest, USA. These forests are a cornerstone of the region's ecological diversity and provide essential habitat to a number of rare terrestrial and aquatic species including the endangered northern spotted owl (Strix occidentalis caurina). Wildfires in particular have reduced the amount of late successional forests over the past decade, prompting land managers to expand investments in forest management in an attempt to slow losses and mitigate wildfire risk. Much of the emphasis is focused specifically on late successional reserves established under the Northwest Forest Plan to provide habitat for spotted owls. In this paper, we demonstrate a probabilistic risk analysis system for quantifying wildfire threats to spotted owl habitat and comparing the efficacy of fuel treatment scenarios. We used wildfire simulation methods to calculate spatially explicit probabilities of habitat loss for fuel treatment scenarios on a 70,245 ha study area in Central Oregon, USA. We simulated 1000 wildfires with randomly located ignitions and weather conditions that replicated a recent large fire within the study area. A flame length threshold for each spotted owl habitat stand was determined using the forest vegetation simulator and used to predict the proportion of fires that resulted in habitat loss. Wildfire modeling revealed a strong spatial pattern in burn probability created by natural fuel breaks (lakes and lava flows). We observed a non-linear decrease in the probability of habitat loss with increasing treatment area. Fuels treatments on a relatively minor percentage of the forested landscape (20%) resulted in a 44% decrease in the probability of spotted owl habitat loss averaged over all habitat stands. The modeling system advances the application of quantitative and probabilistic risk assessment for habitat and species conservation planning.     

陇川魔芋病害与抗病高产栽培技术

通过6年来对云南陇川魔芋白绢病、软腐病发生规律的研究,根据陇川当地的生产实际,提出了正桷选地,推广种植红魔芋,种芋切块繁殖,足施底肥,施用石灰,黑色地膜覆盖等系统的魔芋抗病高产栽培技术。