摘要
为了建立一种简单易操作的室内香蕉穿孔线虫侵染寄主的致病性测定体系,本研究在(25±1) ℃ 下,通过室内试管石英砂培养的方法,以金丰1号番茄为寄主,以不同接种量和接种处理时间接种不同种群,检测线虫繁殖率、根系病害严重度和植株生长量,以分析不同种群的致病力差异。结果显示:以50、100、150和200条/株分别接种4个不同种群雌虫(HN6、SZ-FZ、GJ-LY323和DBSR)至30 d苗龄植株上,在接种9、16、23和30 d后进行观察分析,发现香蕉穿孔线虫主要侵染番茄根系的皮层细胞并在根系内发育繁殖;不同接种量和接种时间对番茄的致病存在差异,线虫繁殖率、根系病害严重度随接种量和时间的增加而增加,而植株生长量则减少;在以150条/株接种23 d后,各项指标差异最显著,能区分不同种群间的致病性;对香蕉穿孔线虫8个种群以150条/株接种30 d苗龄植株23 d后,发现其致病力从大到小依次为SZ-SWK>HaiN-YJ> HL-XY>SZ-FZ≥GJ-LY323>DBSR>HN6>ML-HG。以上结果表明番茄是香蕉穿孔线虫的良好寄主,在室内以150条/株接种量接种30 d苗龄的番茄,在接种23 d后分析线虫繁殖率、根系病害严重度和植株生长量3项指标可以评估不同种群的致病力差异。
香蕉穿孔线虫(Radopholus similis(Cobb, 1893)Thorne,1949)是全球十大植物病原线虫之
番茄(Lycopersicon esculentum)具有生命周期短、容易被高效转化、易于自交留种、相对较小的基因组等这些生物学性状,使其成为功能基因组学研究的理想模式植物之
本研究用于致病性测定的8个供试香蕉穿孔线虫种群及其来源见
序号 No. | 种群编号 Population coding | 寄主 Hosts |
---|---|---|
1 | HN6 | 巴西蕉 Musa AAA Giant Cavendish cv.‘Baxi’ |
2 | SZ-FZ | 粉掌 Anthurium andraeanum |
3 | SZ-SWK | 散尾葵 Chrysalidocarpus lutescens |
4 | GJ-LY323 | 柑橘(芦柑) Citrus reticulata |
5 | DBSR | 大巴水溶 Anubias nana |
6 | HL-XY | 天鹅绒竹芋 Maranta arundinacea |
7 | ML-HG | 红果 Crataegus pinnatifida |
8 | HaiN-YJ | 姜黄(郁金) Curcuma longa |
供试的番茄品种为金丰1号番茄,番茄种子购于广州长合种子有限公司。种植番茄的介质为石英砂(直径1~1.5 mm),购于先科联园林花卉有限公司。
在玻璃培养试管(直径2.5 cm,高15 cm)中装入约1/3高度的干燥石英砂,在125 ℃ 20 p.s. i(约137.8 kPa)高温高压下灭菌2次,每次灭菌1 h,2次灭菌间隔8 h。番茄种子放到无菌水中浸泡1 d(促进发芽)后,用无菌水洗涤3次,75%的乙醇处理1 min、 12.5% NaClO消毒30 min,再用无菌水洗涤7次,每次2 min,将番茄种子放在铺有湿润滤纸的9 cm直径培养皿上,在(25±1) ℃条件萌发7 d后,挑选长势相同的幼苗移栽到装砂的玻璃培养试管中,在(25±1) ℃、光照强度为1 200 lx、16 h光照和8 h黑暗交替的光照培养箱中培养,期间以每2 d浇水1次,湿度维持在约3%(w/w),培养23 d (4叶龄)后接种线虫。
挑取香蕉穿孔线虫雌虫至一离心管中,制备线虫接种悬浮液,用无菌水洗3次,参考丁莎
将香蕉穿孔线虫雌虫(SZ-FZ、GJ-LY323、DBSR和HN6)以200条/株的数量接种到植株根部,分别于接种后9、16、23和30 d对接种的根系进行观察和拍照,选取有病害症状的根组织进行染色并观察根内线虫,初步确定供试香蕉穿孔线虫侵染番茄根系后,再选取相同处理的根组织,制作石蜡切片,观察根系的组织病理学变化。植物根系染色方法参考冯志
将香蕉穿孔线虫雌线虫(SZ-FZ、GJ-LY323、DBSR和HN6)分别以50、100、150和200条/株的接种量,接种于番茄植株根部,于侵染9、16、23和30 d后,观察和拍照记录植株表现的症状,测量植株高度、根系鲜质量,分离统计线虫数量并调查统计病害严重度。病害严重度分级参照文献[
选取寄主来源不同的香蕉穿孔线虫HN6、SZ-FZ、GJ-LY323、DBSR、SZ-SWK、HL-XY、ML-HG和HaiN-YJ 8个种群,以150条/株的接种量接种于番茄植株根部,23 d后统计植株高、根系鲜质量、植株根系病害严重度、根际线虫数量和根内线虫数量,结合各参数分析不同种群的致病性差异,检测所采用接种方法和条件的适用性。
线虫的分离方法参照改良的贝曼漏斗分离法和Kapla
香蕉穿孔线虫4个不同寄主来源的种群(SZ-FZ、GJ-LY323、DBSR和HN6)接种番茄植株后,番茄根系均表现出明显的症状,但发病程度有差异(

图1 香蕉穿孔线虫对番茄根系的危害症状
Fig.1 Symptoms of Lycopersicon esculentum roots infected by Radopholus similis
A-D:寄主来源分别为粉掌(SZ-FZ)、柑橘(芦柑)(GJ-LY323)、大巴水溶(DBSR)和巴西蕉(HN6)的香蕉穿孔线虫种群以200条/株接种的番茄根系;1-4:分别为接种9、16、23和30 d后的番茄根系;CK为健康对照组。A-D: Different populations of R. similis: A. SZ-FZ from Anthurium andraeanum, B. GJ-LY323 from Citrus reticulata, C. DBSR from Anubias nana, D. HN6 from Musa AAA Giant Cavendish cv. ‘Baxi’; 1-4: The tomato root system of 9 d, 16 d, 23 d, 30 d post infection with 200 nematodes per plant; CK: Control tomato root system without inoculating nematodes.
香蕉穿孔线虫侵染发病的根系经品红染色制片(

图2 感染香蕉穿孔线虫(SZ-FZ)的番茄根的品红染色和石蜡切片(横切面)
Fig.2 Fuchsin staining and paraffin section of Lycopersicon esculentum roots (cross section) infected by Radopholus similis (SZ-FZ)
A~D:分别为接种9、16、23和30 d番茄根系品红染色结果;E:未接种线虫的健康根组织;F~H:线虫侵染后根组织。c:根系皮层细胞;ep:根系表皮细胞;s:根系中柱;cav:线虫感染引起的空腔;n:线虫的横截面;e:线虫虫卵的横截面;比例尺= 200 μm。A-D:Staining of Lycopersicon esculentum roots after 9 d, 16 d, 23 d and 30 d of nematode infection, respectively; E: Paraffin section of healthy root tissue without inoculation nematode; F-H: Paraffin section of root tissue after nematode infection; c: The root cortex; ep: The root epidermis; s: The root stele; cav: Cavity caused by nematode infection; n: Nematode cross-section; e: Cross section of nematode eggs; scale bars = 200 μm.
在(25±1) ℃条件下,将SZ-FZ、GJ-LY323、DBSR和HN6 种群分别以50、100、150和200条/株的接种量接种于番茄植株根际,于接种9、16、23和30 d后观察其根系病害症状。接种处理后的番茄根系病害严重度随接种时间和接种量的增加而增加(

图3 香蕉穿孔线虫侵染番茄后番茄根系病害严重度
Fig.3 The disease severity of Lycopersicon esculentum roots infected by Radopholus similiss
A-D: 分别为侵染9、16、23和30 d后的结果。SZ-FZ、GJ-LY 323、DBSR和HN6:来源寄主分别为粉掌、柑橘(芦柑)、大巴水溶和巴西蕉的香蕉穿孔线虫种群;图中数据为10次重复的平均值±标准误;图中同一接种量处理内不同小写字母表示在0.05水平上差异显著。下同。A-D: Results of 9 d, 16 d, 23 d, and 30 d after nematode infection, respectively; SZ-FZ, GJ-LY323, DBSR and AHN6: R. similis populations originated from Anthurium andraeanum, Citrus reticulata, Anubias nana and Musa AAA Giant Cavendish cv.‘Baxi’, respectively; disease severity: a numerical representation of the severity of plant root damage, which classified into 0-5 six levels from low to high according to the lesion area on the roots; the data in the figure was the mean ± standard error of 10 repetitions; the different lowercase letters in the same inoculation dose treatments showed significant difference at the level of 0.05 (DMRT). The same as below.
线虫的繁殖量随接种时间的增加而增加,然而不同接种量条件下,线虫的繁殖量存在差异(

图4 香蕉穿孔线虫接种番茄后线虫繁殖率
Fig.4 The nematode reproductive rate of Radopholus similis after inoculated Lycopersicon esculentum
A-D: 分别为侵染9、16、23和30 d后番茄中线虫的繁殖率。A-D:Nematode reproductive rate of R. similis at 9 d, 16 d, 23 d, and 30 d after inoculated L. esculentum, respectively.
植株株高测量统计结果显示,与对照组相比,接种9 d后,株高具有显著性差异(P<0.05)(

图5 香蕉穿孔线虫接种番茄后植株株高
Fig.5 Plant height of Lycopersicon esculentum after infected by Radopholus similis
A-D: 分别为侵染9、16、23和30 d后番茄株高。A-D: Plant height of L. esculentum after 9 d, 16 d, 23 d, and 30 d of nematode infection, respectively.
植株根系鲜质量测量统计结果显示,与对照组相比,接种9 d后,番茄根系鲜质量显著减少(P<0.05)(

图6 香蕉穿孔线虫接种番茄后植株根质量
Fig.6 Root fresh weight of Lycopersicon esculentum infected by Radopholus similis
A-D: 分别为侵染9、16、23和30 d后番茄根质量。A-D: Root fresh weight of L. esculentum after 9 d, 16 d, 23 d, and 30 d of nematode infection.
综合上述“2.2”、“2.3”结果,根据根系发病症状严重度、线虫繁殖率和寄主生长量3个因素,分析不同种群、接种量和接种时间对香蕉穿孔线虫侵染番茄的影响,可以得出在(25±1) ℃条件下,最佳接种量为150条/株,最佳调查时间为接种后23 d。
(25±1) ℃条件下,以150条/株的接种量接种番茄23 d后观察结果,测定比较8个不同寄主来源的香蕉穿孔线虫种群对番茄致病性(
线虫种 | 植物株高/cm Plant height | 根系鲜质量/g Root fresh weight | 根际线虫数量 Nematodes in rhizosphere sand | 根内线虫数量 Nematodes in root | 病害严重 Disease severity |
---|---|---|---|---|---|
CK | 18.98±0.533a | 0.36±0.015a | 0±0f | 0±0f | 0±0e |
HaiN-YJ | 14.60±0.312de | 0.18±0.012ef | 56.60±3.290b | 140.20±3.912b | 3.90±0.100a |
ML-HG | 16.45±0.466bc | 0.32±0.014b | 31.50±2.504e | 48.90±2.121e | 2.10±0.100d |
GJ-LY323 | 15.24±0.022cd | 0.26±0.017cd | 39.00±2.129cd | 103.00±5.779c | 3.10±0.100b |
SZ-SWK | 13.84±0.299e | 0.16±0.013f | 88.60±3.170a | 174.10±11.845a | 4.10±0.233a |
HL-XY | 14.82±0.633de | 0.19±0.014e | 44.00±3.350c | 138.90±4.357b | 3.80±0.133a |
HN6 | 16.53±0.339b | 0.27±0.015c | 31.90±2.163de | 62.00±3.033e | 2.20±0.133d |
SZ-FZ | 15.09±0.498de | 0.24±0.013d | 44.70±2.329c | 117.50±9.404c | 3.30±0.153b |
DBSR' | 15.44±0.362bcd | 0.26±0.014cd | 38.20±0.814cde | 83.40±4.868d | 2.60±0.163c |
注: 1) CK:不接种线虫的对照组;香蕉穿孔线虫种群寄主来源依次为姜黄(郁金)、红果、柑橘(芦柑)、散尾葵、天鹅绒竹芋、巴西蕉、粉掌和大巴水溶;2) 病害严重程度:植物根系损伤严重程度的数值表示,根据Zhang
Blak
植物线虫对寄主的致病性测定或植物对线虫的抗病性测定主要受接种虫量、接种时间和接种环境条件的影响,处理不当,会对评估结果带来困难。Opoku-Asiama
目前,普遍认为香蕉穿孔线虫不同寄主和地理来源种群的致病力差异,有可能是由于线虫为适应不同的环境而长期不断进化的结
本研究在实验室沙培试管条件下对不同香蕉穿孔种群进行接种测试,明确了该线虫在实验室条件下对番茄的致病性,建立了在实验室条件下香蕉穿孔线虫侵染番茄的致病性接种体系,这可为进一步利用番茄作为模式寄主研究香蕉穿孔线虫的致病机理和防治方法提供重要科学依据,但在大田条件下香蕉穿孔线虫对番茄的致病性有待进一步研究。
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