重病田和无病田棉花根组织中细菌群落结构的差异

为了研究黄萎病菌侵染条件下内生细菌群落结构多样性变化,以不同时期健康棉株和感染黄萎病菌(Verticillium dahliae)的棉株根部组织为材料,提取样品总DNA,扩增内生细菌16S r DNA的V3可变区,将扩增产物进行变性梯度凝胶电泳分析,并对21个优势条带进行切胶回收、克隆测序,构建系统发育树。结果表明:不同时期发病棉株和健康棉株样品可以聚成2大类,一是苗期和蕾期的根部样品,二是初花期和结铃期的根部样品;感染黄萎病棉株内生细菌种类多样性下降;BLAST比对结果发现21个克隆序列与Gen Bank数据库中已知16S r DNA基因序列同源性很高(99%~100%),绝大多数属于变形菌门(Proteobacteria),占总克隆序列的80.95%,其他不可培养细菌占19.05%。说明黄萎病菌的侵染能明显影响内生细菌群落结构多样性。     

Comparative effect of root-knot nematode on severity of verticillium and fusarium wilt in cotton

The effect of root-knot nematode (RKN) (Meloidogyne incognita) onVerticillium dahliae andFusarium oxysporum f.sp.vasinfectum in cotton (Gossypium hirsutum) was investigated. Two different inoculation methods were used, one in which inoculum was added to the soil, so that nematode and fungal inoculum were in close proximity; the other, inoculation into the stem, whereby the two inocula were spatially separated. Invasion of the roots by RKN enhanced disease severity, as measured by the height of vascular browning in the stem, following inoculation with either wilt pathogen. The effect of RKN on Fusarium wilt was more pronounced than that on Verticillium wilt. Nematode-enhanced infection byF. oxysporum is a well known effect but there are few reports of enhanced infection byVerticillium due to RKN. Relative resistance of a number of cotton cultivars to both wilt diseases, as measured by height of vascular browning, was similar to the known field performance of the cultivars. The use of vascular browning as an estimate of disease severity was therefore validated. http://www.phytoparasitica.org posting Feb. 3, 2003.     

Dry mycelium of<Emphasis Type="Italic">Penicillium chrysogenum</Emphasis> induces resistance against verticillium wilt and enhances growth of cotton plants

Dry mycelium (DM) ofPenicillium chrysogenum and its water extract (DME) were examined for their effects on induced resistance against Verticillium wilt and plant growth of cotton in the greenhouse. Soil application of 0.1–5% DM or 0.5–5% DME provided significant protection against the wilt, relative to the control. As neither DM nor DME inhibited mycelial growth ofVerticillium dahliae in vitro, it is suggested that the disease-controlling effects of DM or DME are attributed to induced resistance. DME (5%), as well as DME treated with chloroform or cold acetone, were as effective as 2% DM in reducing disease severity of Verticillium wilt, implying that the resistance-inducing substance(s) in DM are mostly water-soluble, with neither proteins nor lipids likely to be responsible for the induction of resistance. No significant difference in root colonization withV. dahliae was found between control-inoculated and 2% DM- or 5% DME-inoculated plants. However, colonization of hypocotyls and epicotyls was drastically suppressed by either 2% DM or 5% DME relative to the control. Treatments with 2% DM or 5% DME significantly increased ionically-bound peroxidase (POX) activity in roots, hypocotyls and the second leaf of cotton plants, with the hypocotyls expressing the highest increase. Soil application of DM or DME increased plant height, fresh and dry weight of inoculated and non-inoculated cotton plants, relative to their corresponding controls. It is concluded that DM may be used in cotton crops to promote plant growth and to induce resistance againstV. dahliae. POX might be associated with the defense against Verticillium wilt. http://www.phytoparasitica.org posting Jan. 9, 2002.     

嫁接对茄子生长发育和黄萎病抗性的影响

利用茄属野生种粘毛茄作砧木，六叶茄为接穗进行嫁接，探讨嫁接对茄子抗黄萎病能力及生长发育的影响。经接种鉴定，嫁接苗比六叶茄自根苗（ＣＫ）病情指数下降５５．４，春大棚生产试验中，嫁接苗未发现病株，表明嫁接能显著提高茄子对黄萎病的抗性；砧木与接穗之间有较强的亲和性，嫁接苗成活率３年平均达８９．６％，且嫁接苗根系极其发达，根体积超过对照１倍以上，明显促进了地上部各器官的生长，果实产量显著提高，１９９５、１９９６年嫁接苗茄子产量分别比对照增产３５．１％和２６．８％。     

Note: Extrapolating the use of an entomopathogenic nematode and fungus as control agents forFrankliniella occidentalis toThrips palmi

Little is known regarding non-chemical control measures againstThrips palmi Karny. Since entomopathogenic fungi and nematodes have been found to be active against thrips species such asFrankliniella occidentalis Pergande, comparative bioassays were conducted to determine the extent to which they also show activity againstT. palmi. Significant mortality of the larvae of the species was recorded following treatment withLecanicillium muscarium (Petch) Zare and Gams, and addition of the wetting agent Agral enhanced pathogenicity toT. palmi. T. palmi pupae were not affected byS. feltiae. The potential for use of these agents againstT. palmi in the field is discussed in the light of these results. http://www.phytoparasitica.org posting Aug. 28, 2005.     

棉花黄萎病菌落叶型菌系研究

通过对我国棉花黄萎病菌 V_B 与已知的美国落叶型黄萎病菌 T_9以及我国非落叶型黄萎病菌 V_6、V_10进行对照比较研究,所得结果表明,菌系 V_B 为强致病力,病株落叶成光杆,在6个抗感不同的棉花寄主上致病,平均病情指数达54.6;对不同温度反应显示偏耐高温,适宜生长温度为20～30℃,最佳温度25℃;在 PDA 培养基上菌落白色,微菌核不明显,呈束状膨胀菌丝团等生理特性方面,均和美国落叶型黄萎菌 T_9表现趋于一致,而与非落叶型黄萎菌系差异明显。从而证实江苏常熟徐市的棉花黄萎菌系 V_B 是落叶型的病原菌。为综合防治提供科学依据。     

北方植棉区棉花黄萎病菌生理分化类型研究

通过对采自北方植棉区落叶和非落叶病株的５１个棉花黄萎病菌系致病力分化测定结果，确定我国北方植棉区存在落叶类强致病力菌系；混合类中度致病力菌系及非落叶类弱致病力菌系的３个致病类型，并分别占测试菌的４１．５１％、３５．８５％和２２．６４％，其中９个强致病菌系致害棉苗出现落叶程度与对照菌的落叶程度相当或略重，表明河北、山东、河南植棉区重病田有落叶型黄萎菌系。病菌培养性状研究，得出３个培养型，即黑色菌落型、灰白色菌落型与白色菌落型。明确了黄萎病菌生长最佳温度为２５℃，这一结果同田间黄萎病大发生要求的温度一致。     

棉花抗黄萎病种质资源的选育与鉴定

棉花黄萎病是目前棉花高产、稳产的主要障碍,近年来我国棉花黄萎病不断蔓延,危害逐年加重,其主要原因之一就是生产上缺乏抗黄萎病品种。河北省农科院棉花研究所在枯黄萎病混生病圃连续多年的定向选择,培育出的冀616和冀171等,是棉花抗黄萎病育种的优良种质材料。     

棉花黄萎病抗病性鉴定新方法探讨

测试了12个具有不同抗性的棉花品种根冠细胞对棉花黄萎病毒素的敏感性,以孢子悬浮液苗期接种和毒素醮根为对照.试验结果表明,供试品种的根冠细胞死亡率与苗期接种病指和幼苗萎蔫指数均呈正相关,相关系数分别为0.719与0.816,试验证明,利用离体根冠细胞对毒素的敏感差异鉴定品种抗性,操作简便,结果可靠,适于大批量鉴定.     

陆地棉抗黄萎病QTL的定位

以棉花抗黄萎病品系苏抗045和感黄萎病品系苏研116为亲本构建了一个含有237个F2单株的作图群体。利用中等致病力黄萎病菌株BP2对P1、P2、F1、F2∶3家系群体进行纸钵撕底菌液醮根鉴定黄萎病抗性,计算各世代的相对病指。用2 400对SSR引物进行筛选,获得78个SSR多态性标记位点,进一步利用Join Map作图软件,构建了一张陆陆杂种遗传连锁图,包含41个标记、15个连锁群,总长为359.90 c M,覆盖棉花总基因组约7.2%。利用复合区间作图法分析,在NAU2970~MUSS138区间内检测到1个抗黄萎病QTL,可解释的表型变异为9.69%。