番茄抗叶霉病基因Cf19的抗性特点及遗传连锁分析

番茄抗叶霉病基因Cf19的抗性范围基本涵盖了中国目前分化出的所有叶霉菌生理小种,且抗性显著;台盼蓝染色结果显示该基因介导的抗性应答中出现明显的超敏反应,强度介于Cf4和Cf9基因之间;遗传连锁分析说明该基因的遗传特性符合单基因显性遗传规律;通过进一步SSR和AFLP分子标记连锁分析,共找到6个与Cf19基因连锁的分子标记,并将该基因初步定位于番茄1号染色体短臂区域。     

昆虫对双酰胺类杀虫剂抗性机制研究进展

双酰胺类杀虫剂是以昆虫鱼尼丁受体为作用靶标的新型杀虫剂,由于其作用机制独特,对多种鳞翅目害虫具有良好的防治效果而得到广泛应用。但已经有多种害虫的田间种群对该类药剂产生了抗性,甚至导致田间防治失败。本文在综述昆虫对双酰胺类杀虫剂抗性现状的基础上,重点总结了抗性机制方面的最新研究进展,并对今后的研究方向进行了展望,以期为进一步深入研究双酰胺类杀虫剂的抗性机制提供借鉴。     

CmRT1, a Ty3-gypsy-like retrotransposon in Castanea mollissima,is associated with a short-catkin mutation

Summary

Retrotransposons are major components of the genomes of most eukaryotic organisms and have resulted in the introduction of desirable traits in many crops, including fruit trees. Here, we describe a Ty3-gypsy-like retrotransposon associated with a short-catkin mutant in Chinese chestnut (Castanea mollissima), resulting in catkins that are < 20% the length of normal staminate catkins. A partial sequence of the retrotransposon, named CmRT1, detected by amplified fragment length polymorphism (AFLP) analysis, and its complete sequence were determined from the genome of Chinese chestnut (Castanea mollissima) using improved Tail-PCR. CmRT1 was 10,067 bp in length and shared high homology in its predicted amino acid sequence and motifs with other Ty3/gypsy-like retrotransposons. The 5’ long terminal repeat (LTR) of CmRT1 contained a TATA box and several cis-elements that were predicted to be important for processes involving abscisic acid, gibberellic acid, and auxins and in stress-mediated responses. Further characterisation of the transposition event that led to the short-catkin phenotype was performed using two pairs of primers that aligned with the flanking region of the LTRs. The expected PCR bands were observed only in genomic DNA from plants that showed the mutation. Finally, cloning and real-time qPCR analysis of an NADP-dependent alkenal double-bond reductase (CmADBR) target gene that was adjacent to CmRT1, revealed that CmADBR expression was significantly down-regulated in the short-catkin mutant. Taken together, these results suggest that the CmRT1 retrotransposon is responsible for the short-catkin phenotype.     

Polymorphism of 14α-demethylase Gene (CYP51) in the Cereal Eyespot Fungi Tapesia acuformis and Tapesia yallundae

Cereal eyespot fungi Tapesia acuformis and Tapesia yallundae are closely related species which show different behaviours upon treatment with sterol 14-demethylase inhibitors (DMIs). T. acuformis is naturally resistant to DMIs belonging to the triazole family and susceptible to the imidazole ones, whilst T. yallundae is sensitive to both inhibitors. Cloning of the target enzyme gene, CYP51, from the two species revealed an important polymorphism between them. Further sequencing of CYP51 from sixteen T. acuformis and eleven T. yallundae strains with different phenotypes with regards to resistance to DMIs confirmed that at least eleven variations are species related. Among them, a conserved phenylalanine residue at position 180, found both in T. yallundae and in all known CYP51 proteins from filamentous fungi and yeast, was replaced in T. acuformis by a leucine. Therefore, a leucine at 180 could be possibly involved in natural resistance of T. acuformis to triazoles. Other mutations were observed in some resistant strains, sometimes simultaneously, but in contrast to what was reported for other filamentous fungi, where a mutation at the 136 position of the CYP51 gene product seemed to correlate with resistance to DMIs, we did not find a clear relationship between a given mutation and a particular phenotype. This result suggests that resistance to DMIs could have a polygenic nature in Tapesia. We took advantage of species-related variations to develop a PCR-based assay allowing rapid and easy discrimination between field strains of the two species.     

A Greenhouse Test for Screening Sugar Beet (Beta Vulgaris) for Resistance to Rhizoctonia Solani

Rhizoctonia solani Kühn is a serious plant pathogenic fungus, causing various types of damage to sugar beet (Beta vulgaris L.). In Europe, the disease is spreading and becoming a threat for the growing of this crop. Plant resistance seems to be the most practical and economical way to control the disease. Experiments were carried out to optimise a greenhouse procedure to screen plants of sugar beet for resistance to R. solani. In the first experiment, two susceptible accessions were evaluated for root and leaf symptoms, after being grown in seven different soil mixtures and inoculated with R. solani. The fungus infected all plants. It was concluded that leaf symptoms were not reliable for the rating of disease severity. Statistically significant differences between the soil mixtures were observed, and there were no significant differences between the two accessions. The two soil mixtures, showing the most severe disease symptoms, were selected for a second experiment, including both resistant and susceptible accessions. As in the first experiment, root symptoms were recorded using a 1–7 scale, and a significant expression of resistance was observed. The average severity of the disease in the greenhouse experiment generally was comparable with the infection in field experiments, and the ranking of the accessions was the same in the two types of experiments. It was concluded that evaluation procedures in the greenhouse could be used as a rapid assay to screen sugar beet plants for resistance to R. solani.     

南方水稻区域试验品种对水稻白叶枯病抗性调查

1983-2007年,对南方稻区水稻区域试验品种、组合的白叶枯病抗性进行了研究。结果表明,在1 805个参试品种、组合中,78个表现抗白叶枯病,抗病品种频率为4.3%;其中,常规水稻74个,占抗病品种的94.9%。在1 219个籼型杂交水稻中,抗病的组合3个,中抗的76个,抗病和中抗组合频率分别为0.2%和6.2%。不同类型和不同生态型水稻的抗病品种频率差异显著,晚粳>早籼>中籼>晚籼;常规水稻>杂交水稻。籼型杂交水稻中抗病组合频率为:杂交晚稻>杂交早稻>杂交中稻。1990-2004年,17个抗或中抗白叶枯病的优良水稻新品种、组合通过国家审定。     

不同向日葵品种对黄萎病的抗性*

采用浸根接种法鉴定不同向日葵种质资源对黄萎病的抗性差异。结果表明：40份供试向日葵品种依据抗性划分标准共分为3类,其中中抗品种有5份如：‘118’、‘新葵杂5号’等;低抗品种有8份如‘767’、‘KJ003’等;其余27份供试材料均呈现感病;没有鉴定出免疫和高抗的向日葵品种。     

硅对盐胁迫下葡萄幼苗生理效应的影响

以酿酒葡萄"赤霞殊"(Cabernet Sauvignon,CS)1年生扦插苗为试材,采用营养液水培系统,研究了根施外源硅(K2SiO3·9H2O,Si)对盐(50 mmol/L NaCl)胁迫下赤霞珠葡萄幼苗叶片生理生化特性的影响.结果表明:盐胁迫处理下,葡萄幼苗叶片超氧阴离子(O2-')产生速率加快,过氧化氢(H2O2)、丙二醛(MDA)含量和相对膜透性增加;超氧化物歧化酶(SOD),过氧化物酶(POD)和过氧化氢酶(CAT)活性增强;组织含水量降低;施用2.0mmol/L Si明显抑制了O2-、H2O2和MDA的积累,增加了组织含水量,并进一步提高了抗氧化酶SOD和POD的活性.说明外源Si可通过提高盐胁迫下葡萄幼苗体内的抗氧化酶活性,从而降低活性氧(ROS)水平,一定程度上减轻盐胁迫对植株所造成的细胞膜脂过氧化伤害,增强其耐盐性.