湖南省平江县水稻根结线虫病发生及危害评价

[目的]进一步明确湖南省平江县水稻根结线虫病发生危害情况、病原线虫种类及影响水稻发病的因素。[方法]2020年4—6月,采用5点取样法对湖南省平江县24个乡镇400块田块的水稻根结线虫病发生危害情况进行再调查及病原种类鉴定,并对水稻根结线虫病的病情指数与水稻的栽培方式、土壤类型之间的关系进行了分析。[结果]平江县水稻根结线虫病的发生较为普遍,发现病害的乡镇已由2018年的5个增加到2020年的15个,其中15个乡镇的病田率为10%~100%,病株率为2%~55%,根结指数为0.4~15.4。分离获得的病原线虫种类均为拟禾本科根结线虫。调查还发现,发病水稻在砂壤、中壤、重壤稻田的根结指数明显高于在黏土和轻壤稻田的根结指数,直播、抛秧栽培方式下发病水稻的根结指数明显高于移栽方式下的根结指数。[结论]平江县水稻根结线虫病呈蔓延趋势。本研究为有效防控平江县水稻根结线虫病提供了依据。     

海南岛象耳豆根结线虫的种类鉴定及其rDNA-ITS序列分析

【背景】植物根结线虫病是世界性分布的土传病害,常造成农作物的重大经济损失。目前分布于热带亚热带区域的象耳豆根结线虫,由于其致病性和分子特征以及与植物互作关系的独特性,被认为是一种对农作物具有潜在危害性的重要病原根结线虫,因而引起国内外植物寄生线虫学者的广泛关注。【方法】用形态学、同工酶技术和分子生物学技术相结合的方法,对从海南岛农作物上采集到的10个根结线虫纯化种群进行分类鉴定。【结果】象耳豆根结线虫在海南岛大面积栽培的10种农作物和南药植物,包括黄瓜、南瓜、苦瓜、丝瓜、葫芦瓜、辣椒、番石榴、海巴戟、沈香和丁香上均有寄生,其形态学、酯酶表型和mtDNA-PCR扩增产物均有别于常见的根结线虫种类;用引物18S和28S扩增象耳豆根结线虫种群的rDNA-ITS区序列,并对其进行克隆、测序和比对分析,结果表明,象耳豆根结线虫4HBJ种群分别与南方根结线虫、爪哇根结线虫和花生根结线虫的同源性均仅为88%左右。【结论与意义】本文准确鉴定了象耳豆根结线虫,首次阐述其对海南岛多种农作物的致害性;阐释了象耳豆根结线虫的形态和分子特征,并明确了其与3种常见根结线虫的系统发育关系。本研究对今后进一步开展象耳豆根结线虫的基础研究和防治工作具有重要参考价值。     

海南岛象耳豆根结线虫的种类鉴定及其rDNA ITS序列分析

【背景】植物根结线虫病是世界性分布的土传病害,常造成农作物的重大经济损失。目前分布于热带亚热带区域的象耳豆根结线虫,由于其致病性和分子特征以及与植物互作关系的独特性,被认为是一种对农作物具有潜在危害性的重要病原根结线虫,因而引起国内外植物寄生线虫学者的广泛关注。【方法】用形态学、同工酶技术和分子生物学技术相结合的方法,对从海南岛农作物上采集到的10个根结线虫纯化种群进行分类鉴定。【结果】象耳豆根结线虫在海南岛大面积栽培的10种农作物和南药植物,包括黄瓜、南瓜、苦瓜、丝瓜、葫芦瓜、辣椒、番石榴、海巴戟、沈香和丁香上均有寄生,其形态学、酯酶表型和mtDNA PCR扩增产物均有别于常见的根结线虫种类;用引物18S和28S扩增象耳豆根结线虫种群的rDNA ITS区序列,并对其进行克隆、测序和比对分析,结果表明,象耳豆根结线虫4HBJ种群分别与南方根结线虫、爪哇根结线虫和花生根结线虫的同源性均仅为88%左右。【结论与意义】本文准确鉴定了象耳豆根结线虫,首次阐述其对海南岛多种农作物的致害性;阐释了象耳豆根结线虫的形态和分子特征,并明确了其与3种常见根结线虫的系统发育关系。本研究对今后进一步开展象耳豆根结线虫的基础研究和防治工作具有重要参考价值。     

6个相似穿孔线虫种群的形态特征及rDNA-ITS序列分析

运用光学显微镜对相似穿孔线虫进行观察及测量其主要特征;采用线虫通用引物18S和28S对6个相似穿孔线虫种群进行rDNA-ITS区进行了序列扩增,获得片段长度大约850 bp,克隆测序后使用UPGMA法进行聚类分析和构建系统发育树。结果表明:6个相似穿孔线虫的相似度高达99.3%,其中1RS、2RS、3RS和6RS 4个种群与来自台湾的KJ845638.1、广州的KF234224.1和马来西亚半岛的FJ455830.1在一个小类群中,表明它们之间的亲缘关系较近;而4RS和5RS种群在另一个小类群中。本研究为深入相似穿孔线虫不同种群间的形态差异与系统发育关系、及两者之间的关系等研究提供科学的理论依据。     

海南地区螺旋粉虱种群mtDNA-COI和rDNA-ITS1基因的序列及系统发育分析

螺旋粉虱Aleurodicus dispersus Russell在海南是一种重要的农林害虫。本研究对海南地区不同螺旋粉虱种群的mtDNA-COI和rDNA-ITS1基因片段进行了测定并对其系统发育进行了分析。mtDNA-COI和rDNA-ITS1的序列比较发现, 海南16个县市螺旋粉虱种群的mtDNA-COI序列基本一致, 只有文昌番石榴Psidium guajava种群的序列发生变异, 在476 bp位点的碱基C突变为碱基T。不同螺旋粉虱种群的rDNA-ITS1序列也无差异。基于mtDNA COI序列的不同螺旋粉虱种群的系统发育树表明, 已传入我国海南地区的螺旋粉虱未发生明显的遗传分化; 研究还发现海南的螺旋粉虱种群与台湾的种群遗传距离最近, 表明海南地区的螺旋粉虱可能由台湾传入的。基于mtDNA-COI和rDNA-ITS1序列构建的不同粉虱种群的系统发育树表明, 粉虱科分为复孔粉虱亚科（Aleurodicinae）和粉虱亚科（Aleyrodinae）, 这一结果与其他研究结果一致。     

贵州白背飞虱灯下种群发生动态区域性比较研究

为明确贵州省白背飞虱Sogatella furcifera (Horváth)全年世代尤其主害代发生危害规律,采用灯光诱测的方法系统地研究了近4年来贵州省4个不同稻区的白背飞虱灯下种群发生动态并进行了区域性对比,结果如下：三都稻区和惠水稻区的白背飞虱灯下始见日多在4月中下旬,锦屏稻区和道真稻区的灯下始见日稍晚,在4月下旬至5月中旬,各稻区灯下主峰日与始见日和始盛日均呈显著正相关;4稻区年度诱虫量差异较大,三都稻区的灯下虫量最多,而锦屏稻区最少,各稻区灯下种群中,白背飞虱的雌雄性比均大于1;在第3代灯下虫量上,三都与道真存在显著差异,在第6代虫量上三都与惠水、锦屏也存在显著差异,其他各代虫量间不同稻区并无显著差异。     

病原线虫对褐飞虱寄生状况调查

褐飞虱Nilaparvata lugens在浙北稻区常年发生严重,在中晚稻后期常暴发成灾.病原线虫是褐飞虱短翅型成虫的主要寄生性天敌之一.由于短翅型成虫数量与下一代发生和为害动态关系密切,故研究线虫对该虫主害代前一代短翅型成虫的寄生情况,有助于剖析褐飞虱成灾的规律,也可为增强线虫这一重要生物因子对该虫的控制作用提供依据.作者调查了浙江安吉1985～1998年线虫对褐飞虱主害代前一代短翅型成虫的寄生情况,讨论了线虫对该虫主害代的控制作用.结果如下.     

云南勐海早稻白背飞虱种群动态及虫源地分析

【目的】白背飞虱Sogatella furcifera(Horváth)是勐海稻区重要的迁飞性害虫,对当地水稻的生产造成严重威胁。本试验旨在研究勐海早稻白背飞虱种群发生动态与虫源地位置,明确迁飞种群发生规律,为实施害虫的异地预测预报提供科学依据。【方法】利用HYSPLIT轨迹分析模型和Gr ADS软件,分析2000-2016年灯诱峰期迁入种群的虫源地分布和气象背景情况;通过田间系统调查和雌成虫卵巢系统解剖,研究2013年勐海稻区白背飞虱的种群动态以及各发生世代的虫源性质。【结果】勐海稻区4月的虫源地主要集中在缅甸中部,部分来自于缅甸南部和金三角地区,5月的虫源地集中在缅甸东部,泰国、老挝、越南的北部也能提供部分虫源;灯诱峰期的天气背景主要为风切变、下沉气流、低温屏障和降水;第2代白背飞虱为危害勐海早稻的主害代,时间为4月中旬至5月中旬。【结论】明确了勐海早稻迁入种群的虫源地分布及主害代发生时期,为白背飞虱在当地的防治和异地预测预报提供了技术支撑。     

扬州邗江地区稻纵卷叶螟发生动态及影响因素分析

稻纵卷叶螟Cnaphalocrocis medinalis是扬州邗江地区重要的水稻害虫之一,具有远距离迁飞特性,且长期以来给本地区水稻安全生产带来了巨大威胁.为了明确扬州邗江地区稻纵卷叶螟的田间种群动态,本研究通过田间系统调查发现2010-2020年间稻纵卷叶螟四(2)代为害较轻,五(3)代和六(4)代仍是主害代.四(2)代只有在2010年和2013年形成了明显的高峰,而五(3)代和六(4)代可以形成明显的蛾蜂,且蛾高峰期持续天数均达到了 23 d及以上.五(3)代稻纵卷叶螟产卵高峰期田间虫(卵)量与发生程度正相关,但六(4)代稻纵卷叶螟的相关性较差.对本地区影响稻纵卷叶螟发生原因进行分析发现:月平均温度与五(3)代稻纵卷叶螟的发生程度有着密切的关联,但月平均温度与六(4)代种群的数量没有相关性.同时,田间降雨量与稻纵卷叶螟的发生情况无明显的相关性.此外,不同栽培方式也对稻纵卷叶螟的发生有关系,例如,在手栽稻田和机插稻田中六(4)代稻纵卷叶螟的蛾量要高于直播稻田.     

福建省闽南地区稻水象甲疫情监测与分析

稻水象甲作为水稻生产上的一种毁灭性害虫．近年来已先后侵入许多国家和地区,特别是与福建省一水之隔的台湾等地已严重发生为害。为了摸清该虫是否在福建南部发生,我们自1993年起至1995年对闽南地区(包括厦门市、漳州市、泉州市）进行系统的监测与调查。结果表明：该虫尚未侵入福建的闽南地区。但通过对该虫生物生态学特性以及福建闽南地区的环境气候、生态条件综合分析,该虫随时都有可能入侵闽南地区．并在本地区大发生。     

Rice root-knot nematode (Meloidogyne graminicola) infestation in rice

Rice (Oryza sativa) is an important staple food crop for majority of human population in the world in general and in Asia in particular. However, among various pests and diseases which constitute important constraints in the successful crop production, plant parasitic nematodes play an important role and account for yield losses to the extent of 90%. The major nematode pests associated with rice are Ditylenchus angustus, Aphelenchoides besseyi, Hirschmanniella spp., Heterodera oryzicola and Meloidogyne graminicola. However, rice root-knot nematode (M. graminicola) happens to be the most important pest and is prevalent in major rice producing countries of the world. In India, the distribution of M. graminicola in rice growing areas of different states has been documented in nematode distribution atlas prepared by All India Coordinated Research Project (Nematodes) and published by Directorate of Information and Publications of Agriculture, Indian Council of Agricultural Research, New Delhi, India during 2010. M. graminicola affected rice plants show stunting and chlorosis due to the characteristic terminal swellings/galls on the roots which ultimately result in severe reduction in growth and yield. Number of eco-friendly management technologies against M. graminicola have been developed and demonstrated, including the use of bioagents for minimising the losses due to rice root-knot nematode. This review is focused on collating information to understand the current scenario of rice root-knot nematodes with greater emphasis on its ecological requirements, damage symptoms, biology, morphology, host range and management strategies.     

Host response of rice genotypes to the rice root-knot nematode (Meloidogyne graminicola) under aerobic soil conditions

Aerobic rice is a production system where adapted rice varieties are established via direct seeding in non-puddled, non-flooded, non-saturated fields and grown under conditions similar to upland conditions. On land cultivated continuously with aerobic rice, a yield reduction has been observed. The rice root-knot nematode Meloidogyne graminicola is considered one of the possible causes of these yield reductions. Resistance to and tolerance for M. graminicola are essential traits for aerobic rice cultivars in alleviating this problem. In our study, the host response of nineteen aerobic, seven upland and four lowland rice genotypes which are either being used in the International Rice Research Institute’s aerobic rice breeding programme or already cultivated by farmers in Asia was evaluated under aerobic soil conditions in an outdoor raised-bed experiment. Our study showed a large variation in susceptibility and sensitivity to M. graminicola infection among the rice genotypes examined. Resistance comparable to the resistant reference genotypes included in the experiment (CG14, TOG5674, TOG7235) was not found but in terms of susceptibility, the upland genotype Morobereken may be an interesting less-susceptible genotype. Tolerance was found and in terms of sensitivity, the high yielding aerobic genotype IR78877-208-B-1-2 may be an interesting tolerant genotype. Our study also allowed the identification of rice genotypes that are either highly susceptible or sensitive to M. graminicola infection and of which the cultivation should be discouraged. On average, M. graminicola caused an almost 30% reduction in yield. Excluding the two susceptible and three resistant reference genotypes included in the experiment, most affected was dry-shoot biomass (23.6% reduction) followed by root length, which was more affected than fresh-root weight (19.8 vs. 8%) and grain filling (17.3%), while plant height and the number of spikelets/panicle were less affected (10.2 and 8.1%, respectively). Neither tillering nor the number of panicles/plant were affected.     

Host response of Oryza glaberrima and O. sativa rice genotypes to the rice root-knot nematode Meloidogyne graminicola in a hydroponic system under growth chamber

The host response of 25 rice genotypes belonging to Oryza glaberrima and Oryza sativa to Meloidogyne graminicola infection was examined in a hydroponic system. The M. graminicola can build up high population densities in a hydroponic system. Resistance to this nematode species was found in O. glaberrima genotypes which supported significantly lower nematode numbers per plant and per unit root than O. sativa genotypes. The M. graminicola-infected O. sativa genotypes showed a higher root galling index than the O. glaberrima genotypes. The hydroponic system is efficient and reliable method to examine the host response of rice genotypes to M. graminicola infection, and can be useful for the fast screening of high numbers of rice genotypes for the selection of M. graminicola-resistant rice germplasm for breeding purposes.     

The role of thionins in rice defence against root pathogens

Thionins are antimicrobial peptides that are involved in plant defence. Here, we present an in‐depth analysis of the role of rice thionin genes in defence responses against two root pathogens: the root‐knot nematode Meloidogyne graminicola and the oomycete Pythium graminicola. The expression of rice thionin genes was observed to be differentially regulated by defence‐related hormones, whereas all analysed genes were consistently down‐regulated in M. graminicola‐induced galls, at least until 7 days post‐inoculation (dpi). Transgenic lines of Oryza sativa cv. Nipponbare overproducing OsTHI7 revealed decreased susceptibility to M. graminicola infection and P. graminicola colonization. Taken together, these results demonstrate the role of rice thionin genes in defence against two of the most damaging root pathogens attacking rice.     

Developmental and behavioural effects of the endophytic Fusarium moniliforme Fe14 towards Meloidogyne graminicola in rice

The root‐knot nematode, Meloidogyne graminicola, is an important pest of rice in many rice production areas worldwide. The endophyte Fusarium moniliforme strain Fe14, isolated from a disinfected root of rice, has previously shown potential antagonistic activity against M. graminicola. This study shows the effects of Fe14 on M. graminicola behaviour, infection, development and reproduction. The endophyte Fe14 colonisation significantly reduced M. graminicola penetration into rice roots by 55% and increased the male to female ratio nine times. The endophyte also delayed juvenile development into female inside the rice root. These results suggest a suboptimal performance of the giant cell and a cumulative effect of the endophyte on the long‐term root‐knot nematode population development. In split‐root assays, the application of Fe14 at the inducer side significantly reduced nematode invasion at the responder side by 38% and 60% in two independent trials. This result suggests a systemic effect of the endophyte on rice plants. The root exudates from Fe14‐treated plants were either less attractive or had repellent effect on nematode movement. The results, when compared to what was described for other endophytic Fusarium against other nematode species, may indicate a basal response mechanism initiated in the plant by endophytic Fusarium spp. The present study may give leads for unravelling the molecular mechanisms responsible for the induced systemic defence responses in plants.     

Biological control of rice root-knot nematode,Meloidogyne graminicola through mixture of Pseudomonas fluorescens strains

The plant growth promoting rhizobacterium, Pseudomonas fluorescens strains PF1, TDK1, and PY15 were evaluated individually and in combinations for their efficacy against root-knot nematode, Meloidogyne graminicola, in rice plants under in vitro, glass house and field conditions. Culture filtrates of these strains either individually or as mixture inhibited egg hatching and caused mortality of juveniles of M. graminicola in vitro. The efficacy was more pronounced when filtrates of the strain were used as mixtures than as individual strains. Mixtures of P. fluorescens strains signficantly reduced M. graminicola infestation when applied as bacterial suspensions through seed treatment. The higher activity of peroxidase and chitinase enzymes was observed in plants treated with P. fluorescens mixtures than the plants treated with individual strains, two strain mixtures and untreated control. In field trials on rice, talc formulations of the P. fluorescens strains individually as well as mixtures were evaluated as seed treatment, soil treatment and combination of both. A mixture of the three strains was the most effective when applied either as seed + soil treatment or as seed treatment alone. The introduced P. fluorescens strains survived endophytically on rice roots. The application of the P. fluorescens mixture PF1 + TDK1 + PY15 in seed + soil treatment resulted in higher grain yield which provided a 27.3% increase over the control followed by P. fluorescens mixture PF1 + TDK1 + PY15 in seed treatment alone, which increased the grain yield of rice by 24.7% compared to the control.     

Host response of rice genotypes from crosses of high-yielding and drought-tolerant Oryza sativa advanced breeding lines to the rice root-knot nematode Meloidogyne graminicola

The host response to Meloidogyne graminicola infection of 30 advanced breeding lines developed from crosses between high-yielding and drought-tolerant Oryza sativa genotypes was evaluated in outdoor raised beds. None of the advanced breeding lines showed resistance to M. graminicola comparable to the M. graminicola-resistant African rice (O. glaberrima) genotype TOG5674. However, rice genotype IR86815-23-4-1-2 was identified tolerant which showed no yield reduction even when infected with M. graminicola. IR82635-B-B-143-1, IR85733-19-4-1-1, IR85733-19-4-2-4, IR85,735-42-1-4-1 and IR 85735-42-1-4-4 were less sensitive to M. graminicola infection with less than 20% yield reduction compared to other rice genotypes. These rice genotypes could alleviate yield losses in M. graminicola-infested rice fields in regions with limited resources to control M. graminicola and when resistant cultivars are not available.