A mutation confers Monochoria vaginalis resistance to sulfonylureas that target acetolactate synthase

Acetolactate synthase (ALS) is the target enzyme for four distinct families of compounds: sulfonylureas (SUs), imidazolinones, triazolopyrimidine sulfonanilides, and pyrimidinyl oxybenzoates. We cloned and sequenced the fragments encoding ALS genes from biotypes of Monochoria vaginalis susceptible (S) and resistant (R) to SU-herbicides. The nucleotide sequences of the 39 bp Domain A region for R M. vaginalis biotype differed from that of the S biotype by a single nucleotide substitution at variable Pro codon of Domain A (CCT to TCT), predicting a Pro in the S but a Ser in the R biotype. No nucleotide differences between S and R M. vaginalis were observed in Domain D. We suggest that the amino acid substitution at Domain A region is responsible for resistance to SU-herbicides in M. vaginalis collected from Ushiku City, Ibaraki Prefecture, Japan.     

狐阴道加德纳氏菌病防治技术的研究

狐阴道加德纳氏菌病是一种新的人兽共患传染病 ,也是导致狐空怀与流产的重要病原之一。本文就其病原分离鉴定、流行病学、病原菌的血清型、血清学的特异诊断、病原菌对化学药物的敏感谱及疫苗的免疫预防研究进行了系统概述     

Effects of low-intensity pulsed ultrasound on wound healing in corneas of dogs following keratoplasty

The effects of low-intensity pulsed ultrasound on wound healing were evaluated at the graft-cornea transition in dogs following lamellar keratoplasty using tunica vaginalis preserved in 98% glycerin. Twenty-one dogs were subdivided into three groups of seven animals. The first group (W/US) received daily treatment of low-intensity pulsed ultrasound (20 mW/cm2) for 15 min for the first 10 days post surgery. The second group (N/US) was submitted to the same procedure but with the ultrasound apparatus turned off. The third group, the control (CO), underwent the surgical procedure only. The animals were clinically evaluated during the initial (1-15 days), intermediate (16-30 days) and late (31-120 days) postoperative period. The corneas were evaluated by light microscopy at 1, 3, 7, 15, 30, 60 and 120 days after surgery. Clinically, there were no differences which would promote an advantage to any of the treatments. Light microscopy, however, revealed more extensive vascularization and more advanced wound healing in the W/US group, as well as a tendency towards early graft incorporation. Based on the present results, low-intensity pulsed ultrasound shows advantages, especially in situations where trophic support is a mandatory condition, facilitating better graft incorporation and rapid recovery of stromal organization.     

Inhibitory and promotive allelopathy in rice (Oryza sativa L.)

Studies on allelopathic rice, which inhibits the germination and development of weeds such as barnyardgrass ( Echinochloa spp.) and ducksalad [ Heteranthera limosa (Sw.) Wild.], have been strongly conducted in the USA, the Philippines, Japan, Korea, and other countries since the 1980s. Weed-suppressing rice plants can compete with weeds for light and mineral nutrients by their rapid and thick growth characteristics, and probably also by their allelopathic effects. It was suggested that allelopathic properties were inherited from parents. Different screening methods for finding allelopathic rice simply and rapidly have been proposed. In contrast, stimulative allelopathy in rice, which promotes germination of the dormant and dormancy-awakened seeds of Monochoria vaginalis (Burm. f.) Kunth var. vaginalis , has been investigated by the authors since the 1990s. Rice seeds promoted the germination in the dark and in light under submerged conditions. Our experiments suggested that rice seeds, hulls, plants and straw contain stimulative substance(s) that promote seed germination of M. vaginalis .     

采用ASPCR技术检测抗药性雨久花ALS突变基因 碱基种类的探讨

等位基因特异性扩增(Allele-specific PCR简称:ASPCR)技术是一项快速、简便、低成本的检测等位基因单核苷酸多态性的新方法。作者针对雨久花感抗磺酰脲类生态型ALS基因编码区第592位碱基密码(ALS氨基酸第197位)特征,采用在引物3′末端设有胸腺嘧啶核苷酸(感性)或鸟嘌呤(抗性)核苷酸的2种引物,对延边稻田发生的雨久花感抗磺酰脲类生态型ALS基因编码区第592位进行了ASPCR。检测结果显示,当以引物3′末端设有胸腺嘧啶引物时,感性类型出现ASPCR扩增带,而抗性类型无带出现,反之抗性类型有带而感性类型无带,检测到延边稻田发生的抗磺酰脲类雨久花生态型的ALS 197位点的脯氨酸被组氨酸替代,证明了该方法的有效性和可靠性。     

鸭舌草生物学特性及治理对策

对稻田恶性杂草鸭舌草的植物学和生物学特性及其对水稻产量的影响等进行了室内外系统研究。结果表明 ,鸭舌草分布广泛 ,有较长的生理休眠期 ;种子在 1cm土层内萌发最好 ,在 2～ 4cm土层内则出苗极少 ;土壤饱和水分条件有利于种子萌发 ;生长发育的最适温度为 2 0～ 2 5℃ ,土壤水分饱和或薄水条件下生长最好 ,肥料充足则生长迅速 ;鸭舌草在直播稻田、抛栽稻田和移栽稻田均有明显的出草高峰 ;1m2 定植鸭舌草 80株 ,稻、草共生 4 0d水稻减产 14 0 % ,全生育期稻、草共生 ,水稻减产达 19 5 % ;鸭舌草与水稻竞争的临界密度为 1m2 6 0株 ,水稻减产达10 0 %以上。生产中宜采取水旱轮作、减少追肥、科学治虫、保护天敌、促进水稻早生快发 ,并以群体优势控草、稻田养鸭 ,以及应用除草剂乙苄或苯噻酰苄等综合措施来治理鸭舌草     

Mechanism of the rice hull‐induced germination of Monochoria vaginalis seeds in darkness

The seeds of Monochoria vaginalis require light to germinate. However, they are able to germinate in darkness in the presence of rice hulls. The mechanism of this phenomenon was investigated in this study, in which only the unsterilized seeds of Monochoria were induced to germinate by the presence of a rice hull extract. The rice hull extract was able to be replaced by either a mixture of amino acids and phosphate or a yeast extract. The culture media in which germination was observed always showed turbidity, indicating the propagation of bacteria, which were identified as Bacillus sp., Pedobacter sp., Pantoea sp. and Sphingomonas sp. Treatment with the individual bacterial species or combinations of these bacteria induced Monochoria seed germination when added to the media containing the rice hull extract. It was concluded that the rice hull extract accelerates the propagation of bacteria, which in turn digest the seed coat of Monochoria, facilitating its germination.     

Genetic diversity of sulfonylurea-resistant and -susceptible Monochoria vaginalis populations in Japan

Monochoria vaginalis is one of the most serious weeds of rice fields in Asia. The species is predominantly selfing. To reveal the potential for multiple mutational events, outcrossing and gene flow in the sulfonylurea‐resistant (SU‐R) M. vaginalis populations, we investigated (i) if each SU‐R population was a single SU‐R biotype or a mixture of several SU‐R biotypes using restriction analysis or direct sequencing of acetolacatate synthase (ALS) genes and (ii) genetic diversity of SU‐R and ‐susceptible (S) populations using amplified fragment length polymorphism (AFLP) analysis. Nineteen or 20 individuals were sampled from four SU‐R and five SU‐S populations respectively. Amino acid substitutions conferring resistance in the SU‐R populations were Pro₁₉₇Ser in the ALS1 or ALS3, or Asp₃₇₆Glu in the ALS1 and each SU‐R population was composed of a single SU‐R biotype. In cluster analysis each SU‐R individual formed a cluster, whereas the individuals from a SU‐S population belonged to different clusters. Some SU‐R populations showed polymorphic AFLP loci. The results indicated that these SU‐R biotypes emerged from a single mutational event and any gene flow of SU‐R genes from adjacent populations did not occur. A low level of outcrossing and recombinations of SU‐R genes occurred within some SU‐R populations of M. vaginalis.     

Inheritance of sulfonylurea resistance in Monochoria vaginalis

The inheritance of sulfonylurea (SU) resistance in Monochoria vaginalis was investigated based on the bensulfuron‐methyl response phenotypes of F₁ plants between SU‐resistant (R) and ‐susceptible (S) and segregation analysis in F₂ progenies. Differences of SU resistance between SU‐R biotypes and F₁ plants at the recommended field dose were also investigated by comparing shoot dry weight. All F₁ plants survived the treatment with 25 g a.i. ha^?1 bensulfuron‐methyl, one‐third of the recommended field dose, and showed similar responses to SU‐R plants. Conversely, all F₁ plants died or showed extreme necrosis at 225 g a.i. ha^?1, three times the recommended field dose, as SU‐S plants. F₂ plants were classified as either R or S phenotype. Segregation for resistance to bensulfuron‐methyl in F₂ families did not differ from the expected 3:1 (R:S) ratio at 25 g a.i. ha^?1. At 225 g a.i. ha^?1, the F₂ families segregated in a 1:3 (R:S) ratio. These results suggest that SU resistance in M. vaginalis is controlled by a single nuclear allele with resistance being dominant at low dose and susceptibility dominant at high dose. Moreover, F₁ plants died or were extremely injured after application of bensulfuron‐methyl at the recommended field dose, although SU‐R biotypes grew normally.