Resistance analysis of the rice variety Huaidao 5 against root-knot nematode Meloidogyne graminicola

Meloidogyne graminicola has emerged as one of the most destructive plant-parasitic nematodes affecting rice(Oryza sativa)production worldwide.Resistance to M.graminicola in rice could be the most effective option for its management.However,sources of germplasm with resistance to M.graminicola in rice remain limited.Here,we describe the root attraction,gall formation and genetic analysis of the resistance to M.graminicola in the rice variety Huidao 5.A nematode attraction assay showed that second-stage juveniles(J2s)of M.graminicola were attracted at the root tip of Huaidao 5 within 8 h without a significant reduction in attraction compared to the susceptible rice variety Nanjing 9108.Microscopic observation of the infection revealed that the J2s invaded root tissues 12 h after inoculation,but their subsequent movement to the root tip was hindered in Huaidao 5,resulting in decreased nematode number compared to Nanjing 9108.Additionally,we used the soil and hydroponic culture systems to simulate upland and flooding conditions in the paddy fields respectively,and found that gall number was significantly reduced,and nematode development was clearly suppressed in Huaidao 5.To investigate the genetic basis of this resistance,cross breeding was performed between the Huaidao 5 and Nanjing 9108 varieties.There was no reduction in the resistance of the F_(1) offspring to M.graminicola in the greenhouse or field trials,suggesting that a dominant gene could control resistance in Huaidao 5.In summary,this study provides a detailed characterization of a novel source of resistance to M.graminicola in rice,which is of great potential for use in crop breeding.

Advances in Cotton Breeding for Resistance to Fusarium and Verticillium Wilt in the Last Fifty Years in China

This review summarizes the main advances in cotton breeding for resistance to fusarium and verticillium wilt in the last fifty years in China. The topics discussed include main achievements, experiences, problems and countermeasures for solving.

Quantitative Trait Loci for Resistance Against Fusarium Wilt Based on Three Cotton F_2 Populations

Fusarium wilt （FW） is one of the most common cotton diseases in the world. Identification of QTLs conferring resistance to FW is key for the incorporation of resistance genes into elite cultivars. Two intraspecific （cross between Gossypium hirsuturn L.） and one interspecific （cross between Gossypium hirsutum L. and Gossypium bardence L.） F2 populations were constructed by using a highly resistant cultivar and crossing it to a susceptible cultivar with 154, 79, and 148 offsprings, respectively. Simple sequence repeats （SSR） were used to screen genomic regions closely linked to FW resistance. The results showed that five QTLs associated with FW resistance were detected in two intraspecific populations using a composite interval mapping method under four different conditions. Four of these loci located on Chr. 2/Chr. 17 neighboring markers JESPR304 or CIR305 which explained 13.1 to 45.9% of the phenotypic effect. Furthermore, JESPR304 and CIR305 were previously testified and found to be tightly linked. It is possible that these four QTLs detected under different conditions were the same resistance QTL/gene. We consider that there is the possibility of a major FW resistant gene in intraspecific populations. In the interspecific mapping populations two QTLs were detected on Chr. 9 and Chr. 12/26 which explained great phenotypic variance of 49.4 and 45.7%. As the location of QTLs for FW resistance among the intraspecific and the interspecfic populations were totally different, it is suggested that there may be different resistance mechanisms between G. bardence L. and G. hursutum L. Thus, the present research provides an opportunity to understand the genetic control of resistance to FW in Gossypium hirsutum and Gossypium bardence and to conduct MAS in breeding programs to develop FW resistant cultivars.

Screening and identification of candidate Fusarium wilt-resistance genes from pumpkin

Pumpkin(Cucurbita moschata)has been widely used as cucumber(Cucumis sativus L.)rootstock to defend against Fusarium wilt(FW)and increase cucumber yields and profits.However,the resistance genes and mechanisms underlying the FW tolerance in pumpkin are poorly understood.Here we analyzed the transcriptome of pumpkin inoculated with the cucumber FW causal agent Fusarium oxysporum f.sp.cucumerinum(Foc),and obtained 3152 and 4735 upregulated genes induced by Foc at 24h after Foc inoculation compared with at 0h and 24h non-inoculated control,respectively.Next,404 common differentially expressed genes(DEGs)were screened using the criterion log_(2) FPKM(fold change)≥2.In total,206 of 404 DEGs were predominantly expressed in roots,which is the first tissue that Foc contacts and invades.140 DEGs were selected and classified into four groups(pathogenesis resistance,secondary metabolism-related,transcription factor and signal binding)based on their functional descriptions.Then,29 genes having high expression levels were selected to investigate the expression patterns induced by a Foc inoculation.Among them,16 genes were significantly induced by Foc and showed high expression levels at various treatment time points.These candidate genes may act as positive regulators of FW resistance in pumpkin and provide effective resources for improving cucumber FW resistance through breeding programs.

Characterization of salt tolerance and Fusarium wilt resistance of a sweetpotato mutant

The variant LM1 was previously obtained using embryogenic cell suspension cultures of sweetpotato variety Lizixiang by gamma-ray induced mutation, and then its characteristics were stably inherited through six clonal generations, thus this mutant was named LM1. In this study, systematic characterization of salt tolerance and Fusarium wilt resistance were performed between Lizixiang and mutant LM1. LM1 exhibited significantly higher salt tolerance compared to Lizixiang. The content of proline and activities of superoxide dismutase（SOD） and photosynthesis were significantly increased, while malonaldehyde（MDA） and H_2O_2 contents were significantly decreased compared to that of Lizixiang under salt stress. The inoculation test with Fusarium wilt showed that its Fusarium wilt resistance was also improved. The lignin, total phenolic, jasmonic acid（JA） contents and SOD activity were significantly higher, while H_2O_2 content was significantly lower in LM1 than that in Lizixiang. The expression level of salt stress-responsive and disease resistance-related genes was significantly higher in LM1 than that in Lizixiang under salt and Fusarium wilt stresses, respectively. This result provides a novel and valuable material for improving the salt tolerance and Fusarium wilt resistance of sweetpotato.

Progresses in the Mechanism of Resistance to Fusarium Wilt in Cucumber (Cucumis sativus L.)

Fusarium wilt caused by Fusarium oxysporum f.sp. cucumerinum （Owen） is one of the most devastating diseases in cucumber production worldwide. Recent progresses in the mechanism of resistance to Fusarium wilt in cucumber were reviewed in this paper, including pathogenic mechanism of Fusarium oxysporum, the resistance mechanism of cucumber, the heredity of resistance, and the location of resistance genes. Following works should be the location and cloning of resistance genes with molecular biologic methods.

Test on Wilt-Resistance of Simple Hybrides F7 and Beckross Hybrid Lines F6 B1 of <i>G. hirsutum</i>L. of Cotton to New Virulent Isolates of Fungus <i>Fusarium verticillioides</i>and <i>Verticillium dahliae</i>

The article presents the results of studies on the resistance of hybrid cotton lines to a new virulent isolate (strain) of the fungus Fusarium verticillioides upon inoculation of the host plant. Based on the studies, it was found that the complex genotypic resistance of the studied lines, when the host plants are inoculated with isolates of -100 V. dahliae Kleb fungus and 103 Fusarium verticillioides fungi, depends on the degree of resistance of the parental forms and their combination ability.

In vitro Screening of Fusarium Wilt-resistant Germplasm Resources of Red Edible Seed Watermelon( Citrullus lanatus ssp. vulgaris var. megalaspermus Lin et Chao)

[ Objective] This study aimed to establish an appropriate technology system for in vitro screening of Fuzarium wilt-resistant germplasm resources of red edible seed watermelon and obtain variants resistant to fusaric acid, thus providing resistant materials for breeding Fusarium wilt-resistant red edible seed watermel- on. [ Method] Using Zhongxin No. 1 red edible seed watermelon advemitious buds as screening materials and fusaric acid （FA） as a stress agent, in vitro screen- ing of Fusarium wilt-resistant red edible seed watermelon clonal variants and identification of Fusarium wilt-resistance of the germplasm resources of red edible seed watermelon were performed. [ Result] The results showed that the appropriate FA for in vitro screening of Fusarium wilt-resistant red edible seed watermelon vari- ants was 15 mg/L. In vitro screening system for Fusarium wilt-resistant red edible seed watermelon variants was established preliminarily and FA-resistant regenera- ted plants were obtained. Among the 36 germplasm resources of red edible seed watermelon, there were 2 highly resistant materials, 6 moderately resistant materi- als, 11 slightly resistant materials and 17 highly susceptible materials. [ Conclusion] This study confirmed preliminarily that in vitro screening method is effective for obtaining resistant materials of red edible seed watermelon.

Identification of Molecular Markers Linked to the Wilt Resistance Gene FuJ7(t) in Flax

A cross between wilt resistant flax variety Jinya7 and susceptible variety Jinya1 wasmade for mapping wilt resistance gene(s). The inoculation test of F1 and F2 progeny provedthat the resistance of Jinya7 to wilt is controlled by two dominant genes. With 48 EcoRⅠ/MseⅠ primer combinations, amplified fragment length polymorphisms (AFLP) analysis wasperformed on two parents and their F2 resistance and susceptibility bulks. A total ofabout 3300 distinguishable bands were amplified, of which three bands had stabledifferences. The genetic linkage analysis of the three polymorphic DNA fragments withthe resistance gene(s) was made in the F2 segregating population derived from the crossbetween Jinya7 and Jinya1. The DNA fragment AG/CAG was found closely linked to one of thewilt-resistant genes, which with a genetic distance of 5.2cm, was tentatively named FuJ7(t).The cloned fragment AG/CAG was sequenced and then converted successfully to a sequencecharacterized amplified region (SCAR) marker, which can be used more conveniently in theidentification and marker-assisted selection for the wilt resistance gene FuJ7(t) toflax wilt.

Studies on Cotton Breeding Resistant to Fusarium and Verticillium wilt Diseases

Both Fusarium and Verticillium wilts are important soil-borne diseases,which can not be effectively controlled by chemical fungicides.The two diseases,especially Verticillium wilt,have

Utilization and Inheritance of Watermelon Resistance to Fusarium oxysporum f.sp.niveum Introduced from Bottle Gourd

Sugar Baby susceptible to Fusarium oxysporum f.sp.niveum was crossed with high resistant male parents D3-1 and D3-2,respectively.F1 hybrids showed high resistance.The segregation ratios of resistance to susceptibility of F2 and of BC1 hybrid population from Sugar Baby tallied with 3:1 and 1:1,respectively.The results indicated that the resistance to Fusarium wilt was a kind of dominant inheritance controlled by mono-gene or mono-segment DNA.Furthermore,5 hybrid combinations with fine character were bred.Among them,3 were high resistant to Fusarium wilt,and 2 were medium resistant.

Induction of Tolerance to Fusarium Wilt and Defense-Related Mechanisms in the Plantlets of Susceptible Berangan Banana Pre-Inoculated with Pseudomonas sp.(UPMP3) and Burkholderia sp.(UPMB3)

This study is aimed at assessing the ability of two endophytic bacteria originally isolated from healthy oil palm roots, Pseudomonas sp. （UPMP3） and Burkholderia sp. （UPMB3） to induce resistance in susceptible Berangan banana against Fusarium oxysporum race 4 （FocR4）. Increased accumulation of resistance-related enzymes such as peroxidase （PO）, phenylalanine ammonia lyase （PAL）, lignithioglycolic acid （LTGA）, and pathogenesis-related （PR） proteins （ehitinase and β-1,3-glucanase） has been observed in plantlets treated with endophytic bacteria UPMP3 and UPMB3 singly or as mixture under glasshouse conditions. Pre-inoculation of banana plantlets with UPMP3 showed a significant reduction in Fusarium wilt incidence 72 d after challenged inoculation with FocR4. UPMB3 was less effective in suppressing Fusarium wilt compared to UPMP3, whereas, the mixture of both endophytes showed an intermediate effect. Based on these results, it is concluded that UPMP3 could be a promising biological control agent that can trigger resistance against Fusarium wilt in susceptible Berangan banana.

Identification and resistant characterization of legume sources against Meloidogyne incognita

Root-knot nematodes(RKNs;Meloidogyne spp.) are becoming a serious problem in legume production. This study identified Vigna genotypes exhibiting resistance to M. incognita(RKN) and characterized the modes of the resistance to M. incognita. In total, 279 accessions from 21 Vigna species were screened for resistance based on a galling index(GI) and an egg mass index(EI). Seven accessions were highly resistant to RKN with GI≤25, namely JP74716(V. mungo var. mungo;cultivated black gram), JP107881(V. nepalensis), JP229392(V. radiata var. sublobata;wild mungbean), Aus TRCF118141(V. unguiculata subsp. unguiculata;cultivated cowpea), Aus TRCF306385(V. unguiculata subsp. unguiculata), Aus TRCF322090(V. vexillata var. vexillata;wild zombi pea) and JP235929(V. vexillata var. vexillata). JP229392 and Aus TRCF322090 were the most resistant accessions having EI values of 18.74 and 1.88, respectively. Continuous culture of M. incognita on both JP229392 and Aus TRCF322090 resulted in a weakness in pathogenic ability for this RKN. The resistance in JP229392 and Aus TRCF322090 to RKN appeared to be antibiosis that was associated with reduced nematode penetration, retardation of nematode development and impeding giant cell formation. The Vigna germplasm resistance to RKN identified in this study could be utilized as gene sources for the development of RKN-resistant Vigna cultivars.

基于BSA-seq技术对西瓜抗枯萎病生理小种1的基因定位

西瓜枯萎病是由尖孢镰刀菌西瓜专化型(Fusarium oxysporum f.sp.niveum)引起的土传真菌病害,是西瓜生产的限制因子。本研究以西瓜抗病种质“V13-9-3”和感病种质“W16-1”为亲本,构建了“W16-1”דV13-9-3”的F1、F2群体。苗期人工接种结果显示:F1植株表现抗病,F2群体的抗病∶感病分离比为3∶1,表明西瓜枯萎病生理小种1的抗性遗传受显性单基因控制。利用BSA技术,采用SNP指数和InDel指数法,将西瓜抗枯萎病基因Fon-1定位在1号染色体上2.20 Mb和2.32 Mb区域内,将这2种方法的定位结果取交集,最终将目标抗病基因区域缩小在2.20 Mb之内,该区域包含8个非同义突变基因和1个移码突变基因。利用荧光定量PCR检测这9个突变基因在接种枯萎病菌5 d和10 d后的表达量变化,发现抗病亲本“V13-9-3”中有7个基因的表达量显著高于感病亲本“W16-1”。研究通过结合SNP指数和InDel指数分析可以快速进行基因初定位,为西瓜抗枯萎病的分子机理研究提供理论依据。

苦瓜枯萎病抗病与感病品种根际土壤的微生物数量消长动态分析

以28个苦瓜品种为材料,通过苗期人工接种枯萎病鉴定其抗性强弱,结果显示,28个苦瓜品种枯萎病发病程度出现较大差异,共获得高抗材料1份、感病材料11份。苦瓜根际微生物生物数量消长动态差异分析结果表明,土壤中尖孢镰刀菌数量与苦瓜抗、感品种枯萎病发生的相关性存在差异,枯萎病的发生与土壤中尖孢镰刀菌数量呈极显著正相关。抗病品种土壤微生物数量结构优于感病品种。抗病苦瓜品种根际微生物群落的丰富度和多样性更高,其真菌的Sobs、Shannon和Chao1指数分别高出36.93%、25.89%和38.58%,细菌的Sobs、Shannon和Chao1指数分别高出13.63%、12.91%和26.52%。感病苦瓜品种土壤中的pH、铵态氮、硝态氮、速效磷和有机质含量在幼苗期均高于抗病苦瓜品种,根际微生物组成受pH、氮素、有效磷等因素的综合影响。

海南黄瓜抗枯萎病嫁接砧木筛选研究

为筛选适宜海南冬春季节黄瓜抗枯萎病的嫁接砧木品种,对收集的21种砧木进行黄瓜枯萎病抗性鉴定,以易感砧木种质‘全福太郎’为对照,采用人工接种尖孢镰刀菌黄瓜专化型,鉴定各砧木的黄瓜枯萎病抗性。通过测定不同砧木的发病率、病情指数、根系活力、叶绿素相对含量、相对电导率、丙二醛含量等生理指标,结合新引进的病害严重程度指数曲线下面积(AUDRC)综合评价不同砧木对黄瓜枯萎病的抗性。结果表明,不同砧木对黄瓜枯萎病的抗性表现不同,病情指数评价指标表明,‘双力铁甲’‘金甲砧’‘创凡一号’为抗性砧木,‘金甲砧’AUDRC指标表现最好;生理指标中,根系活力表现较好为‘双力铁甲’‘金甲砧’‘创凡一号’;叶绿素含量较高的品种为‘金甲砧’‘创凡一号’‘日系冬之助’,显著高于对照组;相对电导率较低,为‘青根砧王’‘创凡一号’;丙二醛含量较低的为‘双力铁甲’‘金甲砧’‘创凡301’,显著低于其他砧木。依据病情指数、根系活力、SPAD、REC、MDA等生理指标,‘双力铁甲’‘金甲砧’‘创凡一号’为抗性砧木。研究表明,‘金甲砧’为21个砧木品种中综合抗黄瓜枯萎病最好的砧木。

甜瓜抗枯萎病资源筛选及抗病生理指标相关性分析

为明确黑龙江地区甜瓜枯萎病生理小种,探究枯萎病胁迫下甜瓜生理指标变化,完善甜瓜枯萎病抗病评价体系,利用表型鉴定结合分子标记辅助选择(MAS,marker-assisted selection)对24份甜瓜资源进行抗病筛选。结果表明,黑龙江省尖孢镰刀菌甜瓜专化型Fm-1为1号生理小种。分子标记辅助选择共筛选出抗病资源15份,感病资源9份,具有较高的筛选效率。其中野生型资源1314抗性最强,发病率仅为10%;栽培种22-152的感病程度最高。利用筛选的两个抗性极端材料在幼苗期接种病原菌并于根部取样,测定抗病生理指标并进行相关性分析。结果表明,枯萎病胁迫下的抗病和感病材料生理指标响应差异显著,过氧化氢酶(CAT)、苯丙氨酸解氨酶(PAL)、超氧化物歧化酶(SOD)和过氧化物酶(POD)活性与发病率呈极显著负相关;丙二醛含量和相对电导率与发病率呈极显著正相关。综上,利用功能性分子标记可在早期实现精准筛选甜瓜抗枯萎病品种,相对电导率和CAT及PAL活性可作为抗枯萎病评价的首选指标。

苦瓜枯萎病抗性生理研究及鉴定评价体系构建

通过苦瓜枯萎病抗性生理研究,构建高效精准的苦瓜枯萎病抗性鉴定评价体系,旨在为苦瓜抗枯萎病种质资源筛选及抗病品种选育提供理论基础。以热科2号苦瓜为试验材料,选用灌根法、胚根法和伤根法在苦瓜2叶1心期接种不同浓度的苦瓜枯萎病菌,分析不同接种时间的病情指数和生理响应的差异情况,以及不同接种方法和接种浓度对病害的影响。结果表明,采用灌根法接种1×10^(6)个·mL^(-1)的枯萎病菌,在第25天时病情指数为37.1,显著低于1×10^(7)个·mL^(-1)、显著高于1×10^(4)个·mL^(-1),苯丙氨酸解氨酶活性和叶绿素含量显著低于胚根法,多酚氧化酶活性与可溶性蛋白含量与胚根法相比无显著差异。在苦瓜幼苗2叶1心时采用灌根法接种1×10^(6)个·mL^(-1)的枯萎病菌,25 d时鉴定发病情况,可作为精准高效鉴定苦瓜枯萎病抗性的体系。

枯草芽孢杆菌B579对黄瓜枯萎病的防治及其诱导抗性研究

【目的】探究枯草芽孢杆菌B579对黄瓜枯萎病菌的生防效果及诱导抗性机理。【方法】采用平板对峙试验和温室盆栽试验,检测病原菌生长及形态变化、植物生长量、叶片防御酶活性、丙二醛含量、防御相关基因表达量等指标。【结果】枯草芽孢杆菌B579对黄瓜枯萎病菌具有较强的抑制作用,抑菌圈周围菌丝出现粗细不均、膨胀、断裂等现象。盆栽试验表明B579对黄瓜枯萎病的防治效果为78.80%。B579处理组黄瓜幼苗的株高、茎粗、鲜重、干重分别比对照组增加了13.87%、4.17%、15.15%、12.77%。相比单独接种病原菌(FOC)处理,接种B579再接种病原菌(B579+FOC)处理在第4天和第7天显著提高了黄瓜叶片苯丙氨酸解氨酶(PAL)、多酚氧化酶(PPO)、过氧化物酶(POD)和过氧化氢酶(CAT)的活性,并减少黄瓜叶片丙二醛(MDA)的含量(P<0.05)。实时荧光定量PCR检测结果表明,接种B579再接种病原菌后,黄瓜叶片防御相关基因LOX、PR1、PR3和CAT表达量在第4天和第7天显著高于其他处理(P<0.05)。【结论】枯草芽孢杆菌B579能够通过直接抑制病原菌生长和使黄瓜产生诱导抗性来有效防治黄瓜枯萎病。

冬瓜枯萎病菌的分离、鉴定及冬瓜种质抗性鉴定

冬瓜在瓜类蔬菜生产中占有重要地位,而枯萎病严重威胁冬瓜的安全生产。通过病原菌致病力测定、形态学特征观察、培养特性比较,以及基于翻译延伸因子(TEF-1α)的系统发育分析,对采自广东、广西等地的冬瓜枯萎病病原菌进行鉴定,将引起冬瓜枯萎病的病原鉴定为尖孢镰刀菌冬瓜专化型(Fusarium oxysporum f.sp.benincasae)。在此基础上,选取致病力较强的冬瓜枯萎病菌株,以不同冬(节)瓜资源为材料,采用苗期灌根接种法对所收集的26份小冬瓜资源、47份节瓜资源和74份大冬瓜资源进行抗病性鉴定。结果表明,147份冬(节)瓜资源的抗性鉴定结果差异相对较大,且不同冬(节)瓜资源间的枯萎病发病率存在显著差异,其中26份小冬瓜资源中没有1份高抗材料;47份节瓜资源中有2份高抗材料(JG-25和JG-33),占比4.26%;74份大冬瓜资源中有4份高抗材料(DDG-19、DDG-32、DDG-40和DDG-74),占比5.41%。研究结果为抗枯萎病冬瓜种质资源的筛选及瓜类枯萎病抗性遗传育种提供参考。