香蕉枯萎病菌4号小种致病力分化的初步研究

自2003年6月至2010年1月,我们通过采集或交流的方式共得到海南、广东、福建、云南和广西等省区的35个市县的56个Fusarium oxysporum f.sp. cubense Race 4菌株,并通过盆栽伤根淋灌法接种巴西蕉苗,系统性地评价了56个Race 4菌株的致病力。实验结果表明：供试的56个Race 4菌株表现出了很明显的致病力分化,其中,强致病力的菌株有29个、中致病力的有9个、弱致病力的有18个,分别占供试菌株的51.79%、16.07%、32.14%。     

油柿叶片离体再生体系的建立

以油柿叶片为材料开展了离体培养研究,旨在建立其再生体系,为转基因操作奠定基础。结果表明,油柿叶盘在MS（1/2N）+IBA0.1mg/L+ ZT3.0mg/L培养基上,经前期暗处理3周后移至正常光照下培养的再生效果最好,其不定芽再生率和外植体平均不定芽数最高,分别为80.5%和（4.1±0.8）个。再生苗接种于添加IAA和IBA各0.5mg/L的MS(1/2N)培养基上,4周时生根率可达92%,成功地建立了油柿叶片的离体再生体系。     

紫外线杀灭营养液中黄瓜枯萎病病菌试验

设计、试制了一种可以用于无土栽培循环营养液消毒的紫外线消毒系统,并对其杀灭黄瓜枯萎病病原菌的性能和效果进行了实验室研究。先将黄瓜枯萎病病原(Fusarium oxysporum f.sp.cucumerinum)菌株接种于PDA培养基上,培养后将其加入到营养液中进行紫外线照射。通过对紫外线照射前后的病原浓度进行计数,发现紫外线对黄瓜枯萎病病原有较好的杀灭效果。在营养液紫外线透射率(T10)为96.65%、病原浓度为6.87×102conidia/ml、最大流量为36 L/min时,灭菌率为100%;在营养液紫外线透射率(T10)为95.42%、病原浓度为1.14×105conidia/ml、最大流量为36L/min时,灭菌率为100%;在T10降低为11.58%、病原浓度为1.44×104conidia/ml、最大流速为35L/min时,灭菌率也在50%以上。     

种植密度对2个青稞品种抗倒伏及秸秆饲用特性的影响

种植密度是影响青稞抗倒伏和秸秆饲用特性的重要因子。以抗倒伏品种昆仑14号和倒伏品种门源亮蓝为试验材料,比较研究种植密度对这2个品种生长发育、抗倒伏特性和秸秆饲用特性的影响。结果表明,种植密度对2个品种的抗倒伏和秸秆饲用特性的影响存在差异。随着种植密度的增加,昆仑14号根长、根体积、根数和根干重先增后降,茎粗和壁厚依次下降;门源亮蓝根系和茎秆相关指标则随种植密度增大而下降。昆仑14号抗倒伏相关指标先增后降,但整个生育期未发生倒伏;门源亮蓝各指标均显著降低,诱发倒伏现象提前发生,致使倒伏率增大、倒伏程度加剧。昆仑14号茎秆中性洗涤纤维、酸性洗涤纤维、半纤维素、纤维素和木质素等化学成分含量随密度增加先增后降,门源亮蓝各成分含量呈下降趋势,相对饲喂价值随密度增加呈现增高的趋势。综合抗倒伏特性与秸秆饲用特性,昆仑14号最佳种植密度为375×104株hm^-2,门源亮蓝粮饲兼用时适宜密度为300×104～375×104株hm^-2。     

冬瓜枯萎病菌核糖体rDNA ITS区的克隆与序列分析

采用镰刀菌核糖体基因转录间隔区(ITS)通用引物,PCR扩增冬瓜枯萎病菌核糖体基因ITS区,并对产物进行克隆和序列分析;利用Mega 4.1软件对序列及GeneBank中以葫芦科为寄主的镰刀菌不同专化型ITS序列进行聚类。冬瓜枯萎病菌ITS全长1 063 bp,其中包括18S rDNA一部分序列,5.8S rDNA,ITS1和ITS2全部序列及28S rD-NA部分序列。聚类结果将15个菌株ITS序列划分为2个类群,类群I包括4个菌株,分别为2个西瓜枯萎病菌株和2个甜瓜枯萎病菌株;类群II包括11个菌株,其中冬瓜枯萎病菌株就在该类群中,其余为甜瓜枯萎病菌株5个、西瓜枯萎病菌株3个、黄瓜枯萎病菌株、丝瓜枯萎病菌株和葫芦枯萎病菌株各1个。     

Isolation of wheat mutants with increased resistance to powdery mildew from small induced variant populations

Small variant wheat populations created by induced mutagenesis (n = 69) or adventitious regeneration (n = 66) were intensively screened for an altered response (compared to the parent variety ‘Guardian’) to the causal pathogen of powdery mildew in wheat, Blumeria graminis f. sp. tritici. Intensive field screening following natural infection of replicated plots of wheat lines over two years revealed a total of 13 mutants exhibiting significantly greater resistance than ‘Guardian’: eight from induced mutagenesis (11.6%) of the M2 population and five from adventitious regeneration (7.6%). Complete resistance was identified in two lines, (one (M66) developed following induced mutagenesis, and the other (SC240) by adventitious regeneration). The complete resistance in the induced mutant was stable over two generations and was associated with a high frequency of leaf flecking, and consequently a low grain yield. Resistance in SC240 proved to be unstable; SC240 exhibited complete resistance to powdery mildew in the SC₂ and SC₃ generations, but only 20% of the SC₄ plants were completely resistant, while the remainder were indistinguishable in mildew response to ‘Guardian’. The mildew response of all the SC₅ generation of SC240 was not significantly different from ‘Guardian’. Yield analysis of the thirteen mutants with increased resistance in the presence of powdery mildew indicated that eleven exhibitedgrain yields at least as high as that of ‘Guardian’, while the mutant M19 exhibited a yield significantly higher than that of ‘Guardian’. This revised version was published online in July 2006 with corrections to the Cover Date.     

从土壤中分离棉枯萎病菌(Fusarium oxysporum f.sp.vasinfetum (Atk) Synder & Hansen)选择性培养基研究

本文介绍一种用于分离检测土壤中棉枯萎病菌的选择性培养基—植选2号。其成分为:KH_2PO_41g,MgSO_4·7H_2O 0.5g,K_2S_2O_50.2g,KCl0.6g,NH_4NO_3 0.5g,蛋白胨5g,山梨糖10g,蔗糖5g,琼脂20g,蒸馏水1000ml,PCNB 620mg,Oxgall1g,硫酸链霉素300mg,盐酸金霉素75mg。根据棉枯萎病在此培养基上的形态特征,能较容易地识别和检测该病菌。     

短短芽孢杆菌JK-2(Brevibacillus brevis)胞外物质抗香蕉枯萎病菌的稳定性

研究温度、光照、紫外辐射、蛋白酶K、pH对生防菌短短芽孢杆菌(Brevibacillus brevis)JK-2胞外物质抗香蕉枯萎病菌稳定性的影响,为香蕉枯萎病生防菌剂的研制提供理论依据。在30℃,170r/min的条件下,恒温振荡培养36h采样制备生防菌短短芽孢杆菌(Brevibacillus brevis)JK-2胞外物质,以香蕉枯萎病菌为指示菌,对胞外物质的抑菌特性进行研究。结果表明:该胞外物质具有一定的热稳定性,60~80℃温育1h保持88.5%以上活性,在100℃放置1h后无抑菌活性;在酸性pH3.0~5.0和碱性pH9.0~11.0条件下,抑菌活性保持在77.2%以上,对光照、蛋白酶K、紫外照射均不敏感。其抑菌作用的最适温度为30℃,最适pH为7.0。     

Evaluation of seedling and adult plant resistance to stem rust in European wheat cultivars

A total of 105 European wheat cultivars were assessed for seedling and adult plant resistance (APR) to stem rust using an array of Australian isolates of Puccinia graminis f. sp. tritici. Twenty-seven cultivars were susceptible at both seedling and adult plant growth stages. Twelve catalogued seedling stem rust resistance genes (Sr7b, Sr8a, Sr8b, Sr9b, Sr9g, Sr11, Sr15, Sr17, Sr29, Sr31, Sr36 and Sr38) were detected in the remaining cultivars, and 13 cultivars carried additional seedling resistance genes that could not be postulated with the isolates used. Low levels of APR to stem rust were found in the cultivars Artaban, Forno, Mec, Mercia, Pandas and Vlada. Although the genetic identity of this APR was not determined, it was clear that the only designated stem rust APR gene Sr2 was not present in any of the cultivars tested based on the absence of the linked traits seedling chlorosis and pseudo black chaff. One of these cultivars, Forno, is believed to carry the leaf rust APR gene Lr34, previously reported to be associated with improved resistance to stem rust. A detailed genetic characterisation of the APRs in these cultivars will be needed to understand their modes of inheritance and relationships with catalogued stem rust resistance genes. Such knowledge may help in developing cultivars with effective gene combinations that confer higher levels of protection.     

Fusarium wilt of chickpea: physiological specialization, genetics of resistance and resistance gene tagging

Chickpea wilt caused by Fusarium oxysporum f. sp. ciceris is one of the major yield limiting factors in chickpea. The disease causes 10–90% yield losses annually in chickpea. Eight physiological races of the pathogen (0, 1A, 1B/C, 2, 3, 4, 5 and 6) are reported so far whereas additional races are suspected from India. The distribution pattern of these races in different parts of the world indicates regional specificity for their occurrence leading to the perception that F. oxysporum f. sp. ciceris evolved independently in different regions. Pathogen isolates also exhibit differences in disease symptoms. Races 0 and 1B/C cause yellowing syndrome whereas 1A, 2, 3, 4, 5 and 6 lead to wilting syndrome. Genetics of resistance to two races (1B/C and 6) is yet to be determined, however, for other races resistance is governed either by monogenes or oligogenes. The individual genes of oligogenic resistance mechanism delay onset of disease symptoms, a phenomenon called as late wilting. Slow wilting, i.e., slow development of disease after onset of disease symptoms also occurs in reaction to pathogen; however, its genetics are not known. Mapping of wilt resistance genes in chickpea is difficult because of minimal polymorphism; however, it has been facilitated to great extent by the development of sequence tagged microsatellite site (STMS) markers that have revealed significant interspecific and intraspecific polymorphism. Markers linked to six genes governing resistance to six races (0, 1A, 2, 3, 4 and 5) of the pathogen have been identified and their position on chickpea linkage maps elucidated. These genes lie in two separate clusters on two different chickpea linkage groups. While the gene for resistance to race 0 is situated on LG 5 of Winter et al. (Theoretical and Applied Genetics 101:1155–1163, 2000) those governing resistance to races 1A, 2, 3, 4 and 5 spanned a region of 8.2 cM on LG 2. The cluster of five resistance genes was further subdivided into two sub clusters of 2.8 cM and 2.0 cM, respectively. Map-based cloning can be used to isolate the six genes mapped so far; however, the region containing these genes needs additional markers to facilitate their isolation. Cloning of wilt resistance genes is desirable to study their evolution, mechanisms of resistance and their exploitation in wilt resistance breeding and wilt management.