Changes in the structure of Arabidopsis thaliana roots induced during development of males of the plant parasitic nematode Heterodera schachtii

Plant parasitic nematodes of the genus Heterodera show a high degree of sexual dimorphism, which is reflected by different nutritional demands and differences in the structure of the induced specific syncytial feeding site in the plant. The determination of the sex of the nematode Heterodera schachtii and other related species was repeatedly reported to be dependent on trophic factors, which are provided by the induced syncytia. The structural differences of syncytia induced by H. schachtii in roots of Arabidopsis thaliana were analysed at the anatomical and ultrastructural level. Syncytia of males were induced in the root pericycle. The developing syncytium then expanded into procambial or cambial cells of the vascular cylinder. Differentiated vascular elements were not included. The expansion of the syncytium triggered the proliferation of cambial and peridermal tissues, in a manner similar to secondary growth, and the formation of additional xylem and phloem elements. In comparison to syncytia associated with females, syncytia associated with males were less hypertrophied and were composed of more cells. Distinct cell wall openings were mostly found between the few strongly hypertrophied syncytial elements at the actual feeding site in the pericycle. The ultrastructure was very similar to female-associated syncytia but showed conspicuous differences in the structure and localization of cell wall ingrowths. These ingrowths were rare and weakly developed and occurred not only at the interface with xylem elements but also at the internal and external walls of the syncytia. After feeding had ceased at the end of the third developmental stage the syncytia degenerated.     

不同测试条件对燕麦孢囊线虫在小麦上产生孢囊数量的影响

小麦对燕麦孢囊线虫的抗性评价基于根系产生的孢囊数量,为优化小麦抗燕麦孢囊线虫鉴定技术,分别测试了土质类型、接种次数、接种密度、接种苗龄对燕麦孢囊线虫在根系形成孢囊数量的影响。结果表明:燕麦孢囊线虫在砂质粘壤土中产生的孢囊数量最高;对于温麦4号品种,分4次接种处理在小麦根部形成的孢囊数量显著高于分1、2、3次接种处理,但依据传统评价标准,各接种次数处理对其抗性鉴定结果相同,均为高感;每株接1 000头二龄幼虫能较好区分不同抗性程度品种的敏感程度。小麦播后3～6d接种在小麦根部形成的孢囊数量显著高于播种时及播后9～15d接种处理。综合上述结果建议在小麦抗孢囊线虫的鉴定中以采用砂质粘壤土、播后3～6d每株1次性接种1 000二龄幼虫为宜。     

陕西省小麦禾谷孢囊线虫病的新发生地区与田间侵染规律

【目的】明确陕西省渭北旱塬区和陕北地区小麦孢囊线虫病（cereal cyst nematode,CCN）发生状况及其田间侵染规律,为陕西省CCN的综合防控提供决策依据。【方法】在小麦孕穗期至灌浆期,采用五点法随机取样、芬萘维克漂浮法（Fenwick）分离孢囊、利用形态学方法鉴定孢囊线虫种类;定点定期取样,利用次氯酸钠-酸性品红法对根系染色,显微镜检查根内线虫虫态与数量。【结果】陕西省渭北旱塬区和陕北地区等24个县（市）小麦的禾谷孢囊线虫病的致病线虫种类为禾谷孢囊线虫（Heterodera avenae Wollenweber）。麟游县的平均孢囊量最高,为32.0个/100 g土,永寿县的平均孢囊量最低,为5.5个/100 g土。调查的陕北地区县市没有发现CCN。冬小麦秋播后,土壤中CCN孢囊孵化后的2龄幼虫（J2）即可侵入根系内。翌年小麦返青,J2幼虫开始侵染,高峰期为3月下旬至4月上旬,4月中旬开始出现3龄幼虫（J3）,4月下旬J3开始膨大,5月初在小麦根表可见白色孢囊。【结论】麟游县、永寿县、礼泉县和武功县为CCN 新发生地区;CCN在陕西省存在秋播后与返青后2个侵染阶段,1年发生1个世代。     

二硫氰基甲烷与灭菌唑和吡虫啉的联合使用对小麦孢囊线虫的防治

在田间自然情况下测试2种主要成分为二硫氰基甲烷的新型种衣剂及其与常规种衣剂灭菌唑和吡虫啉的联合使用对小麦孢囊线虫的防治效果。播种前用种衣剂对小麦种子分别进行包衣处理。分别调查播种前、抽穗期和收获后土壤中的孢囊数量及单孢囊卵量的变化,同时对小麦抽穗期的株高和收获时的千粒重等进行测定。结果表明:测试种衣剂对小麦进行包衣处理后均对该处理小区的孢囊及单孢囊卵量有抑制作用,其中甘农Ⅲ号种衣剂单独使用和甘农Ⅲ号种衣剂+灭菌唑(0.5∶0.5)联合使用处理小区的单孢囊卵量减退率最高,防效分别达到37.59%和32.86%,实际增产率分别达到16.09%和26.40%;甘农Ⅲ号种衣剂+灭菌唑(0.5∶0.5)联合使用和甘农Ⅲ号种衣剂单独使用2个处理,对抽穗期白雌虫的抑制率最高,分别为72.27%和70.29%,对孢囊的防效分别达到51.61%和50.74%;甘农Ⅲ号种衣剂+灭菌唑(0.5∶0.5)联合种衣剂、甘农Ⅲ号种衣剂+吡虫啉(0.5∶0.5)联合种衣剂2个处理的小区增产效果显著高于其他处理,理论增产率分别达到40.35%和44.39%。甘农Ⅲ号种衣剂+灭菌唑(0.5∶0.5)联合种衣剂可有效防控小麦孢囊线虫病害,不仅降低了农药的使用量,同时也显著提高了小麦产量,适于在生产上推广应用。     

大豆抗感SCN基因的一个RAPD标记

对组合ＲＮｇ（抗）× ７７０５（感）的Ｐ１、Ｐ２、Ｆ１、Ｆ２、ＢＣ１Ｆ１和ＢＣ１Ｆ２分离群体进行抗病性鉴定,遗传分析的结果表明,大豆对ＳＣＮ１号小种的抗性由４对相互独立的主基因、包括一对显性基因和三对重叠的隐性基因决定。用 ＢＳＡ法筛选在五个 ＢＣ１Ｆ２分离家系内具有多态性的 ＲＡＰＤ标记,发现 ＲＡＰＤ标记 ＯＰＡ０１９１２００在亲本间及 ＢＣ１Ｆ２分离群体内具有多态性,只能在感亲、 ＢＣ１Ｆ２家系 １１和 ４３的感病单株中扩增出来,表明和这两个家系独有的感病基因有关。     

燕麦胞囊线虫(Heterodera avenae Woll.)孵化特性研究

在室内离体条件下研究了低温预处理、植物根分泌物（包括寄主和非寄主）、溶液的ｐＨ值以及干燥等条件对燕麦胞囊线虫孵化的影响．结果表明：处于滞育期的胞囊经５℃低温预处理４周后，再置适宜的孵化温度（１５℃）即有幼虫孵出，低温处理的时间越长，孵化量越大；过低温度预处理（－１０℃）后，其孵化量明显低于５℃的处理．根分泌物既不能打破燕麦胞囊线虫的滞育，对处于孵化期胞囊内幼虫的孵出也无明显的刺激作用．在供试条件下，保湿液ｐＨ６时的孵化量最大，ｐＨ１２对幼虫的孵出有明显的抑制作用．干燥不利于幼虫孵化．     

中国小黑豆对大豆胞囊线虫3号生理小种的抗性遗传研究

用大豆胞囊线虫（Ｈｅｔｅｒｏｄｅｒａｇｌｙｃｉｎｅｓ）３号生理小种接种抗病品种小粒黑豆、连毛会黑豆、磨石黑豆与感病品种铁丰２４号、铁丰１８号、开育１０号杂交组合，根据Ｆ２代分析结果，小粒黑豆在铁丰２４号背景下表现出有两对抗病基因，在开育１０号的背景下由４对显性抗病基因控制对３号小种的抗性，磨石黑豆在铁丰２４号背景下有两对隐性抗病基因，铁丰１８号×连毛会黑豆组合Ｆ２代分离表现为三对基因的互补作用。     

Genetic and molecular characterization of resistance to Heterodera glycines race isolates 1, 3, and 5 in Peking

Soybean cyst nematode (SCN), Heterodera glycines Ichinohe, has caused severe damage to soybean [Glycine max (L.) Merr.] worldwide since its discovery in 1954. ‘Peking’ is one of the most important sources in breeding SCN resistant soybean cultivars because it is resistant to Races 1, 3, and 5. Genetic information on SCN Races 1, 3, and 5 from Peking is essential to efficiently develop resistant soybean cultivars. Resistance to Race 3 in Peking was found to be controlled by three genes, but little is known on the inheritance of resistance to Races 1 and 5, and whether alleles conditioning resistance to Races 1 and 5 belong to the same linkage group and are allelic to genes giving resistance to Race 3. To determine the genetic bases of resistance to SCN Races 1, 3, and 5, Peking was crossed to the susceptible line ‘Essex’ to generate F₁ hybrids. The F₂ population and F _2:3 families were advanced from the F₁ and evaluated for resistance to SCN Race isolates 1, 3, and 5. Resistance to H. glycines Race isolates 1, 3, and 5 in Peking was found to be conditioned by three genes, one dominant and two recessive (Rhg, rhg, rhg). Peking may share similar sets of resistance loci between Races 1 and 3, but not between Races 3 and 5, or between Races 1 and 5. This revised version was published online in July 2006 with corrections to the Cover Date.     

Genetic resistance to cereal cyst nematode Heterodera avenae Woll. in wild oat Avena sterilis I. 376

Summary Three dominant genes A, B and C are involved in the resistance of Avena sterilis I. 376 to Heterodera avenae. When associated, genes A and B are responsible for the high level of resistance in I. 376. In the absence of the first two genes, gene C confers intermediate resistance characterized by the presence of a limited number of cysts on the roots. Only the completely recessive genotype allows the nematode to develop normally.     

Two microsatellite markers flanking a dominant gene for resistance to soybean cust nematode race 3

The purpose of this work was to identifymicrosatellite markers linked to a gene forresistance to Heterodera glycinesIchinohe (Soybean Cyst Nematode – SCN) insoybean cultivar Hartwig. ABC₁F₂ mapping population derivedfrom a cross between Hartwig (resistant)and the Brazilian soybean line Y23(susceptible) was used. About 200microsatellite or simple sequence repeat(SSR) primer pairs were tested in a bulkedsegregant analysis (BSA). Those thatshowed clear polymorphisms were amplifiedin the BC₁F₂ population, whichhad been previously inoculated andevaluated for resistance/susceptibility toSCN Race 3. Three SSR markers linked toSCN resistance were detected in thepopulation. Two of them, Satt 038 and Satt163, flanking a dominant resistant gene(d/a = –0.90), explained 37% of thephenotypic variance. This gene was mappedat the edge of molecular linkage group G. Broad and narrow sense heritabilities wereestimated to be 50.54% and 37.73%,respectively. A selection efficiency of91.18% was obtained with the simultaneoususe of the two markers. The identified SSRmarkers will be useful tools for assistingthe selection of homozygous genotypes andfor expediting the introgression of the SCNresistance locus from cv. Hartwig tosoybean elite cultivars.