The overwintering ofExserohilum turcicum in Israel

Exserohilum turcicum (Pass.) Leonard and Suggs, the causal agent of northern leaf blight of corn, overwinters onSorghum halepense L. plants and on corn debris (dead leaves). Spqrulating lesions ofE. turcicum were observed on sorghum plants in the winter (February). Spores from these lesions were pathogenic to susceptible sweet corn plants cv. ‘Jubilee’. Infected sporulating leaves of corn were stored for 1 year at 20°C (40-60% relative humidity), at 5°C (60% relative humidity), or buried 5 cm underground. During the storage period, 32% and 22% of the spores formed chlamydospores, at 20° and 5°C, respectively. Leaves buried 5 cm underground were totally decomposed after 6 months. After 4 months, 25% of the spores in the buried leaves had formed chlamydospores. Spores with chlamydospores were pathogenic to corn plants. The viability of spores without chlamydospores stored at 20°, 5°C or buried underground was 0, 60 and 0%, respectively. In a parallel experiment infected leaves were stored under similar conditions and allowed to sporulate. No sporulation occurred on infected leaves buried in soil. Spores produced on infected leaves stored at 20° and 5°C were highly pathogenic to corn plants. In leaves treated with 0.1N glucose, chlamy dospore formation was significantly inhibited.     

Mating types ofExserohilum turcicum in Israel

Fifty-one single conidial isolates ofExserohilum turcicum were collected from seven locations in Israel and three in the USA and tested for mating type and aggressiveness. Sixteen isolates mated were mating type a; 29 were mating type A; and six failed to mate with either the A or the a mating type. Isolates differed significantly in their ability to cause lesions of different sizes, and in their ability to produce conidia on the susceptible corn hybrid Jubilee. They also differed in their rate of growth on lactose casein agar. No significant difference in lesion size or conidial production was noted between mating types. Conidial production and radial growth were significantly lower for isolates with no mating capacity as compared with conidial production of defined mating types. Pseudothecia were produced after 14–16 and 21 days when mating occurred onSorghum halepense straw or barley straw, respectively. The average number of pseudothecia produced on 10 cm² of straw was 17 and 8 forS. halepense and barley, respectively. Pseudothecia were not produced on corn straw.     

Pathogenic races of the melon-wilt Fusarium in Israel

Two races ofFusarium oxysporum f. sp.melonis were identified among 54 isolates of this pathogen, tested on three differential lines of melon. Of the two races, race 0 was the more prevalent, comprising 92.5% of the total number of isolates tested. Race 1 has been encountered so far in one growing area only. The identity of the local races is compared with those defined in France and in two areas of melon-growing in California.     

2004年陕西省小麦条锈菌生理小种监测结果

对2004年采自陕西省及甘肃省天水的287份小麦条锈病标样生理小种鉴定结果表明,出现频率居前4位的小种及致病类型是条中32号、水1、水6及水4,分别为33.44%、9.75%、9.40%、7.66%。与2002、2003年同期相比,条中31号频率逐年下降,水14频率略有下降,水7、水5频率有所上升,其他各小种(类型)频率相对较低。毒力频率分析表明,Yr9、Yr3 b.4 b、YrSu等抗性基因已经失效。     

Physiological races of Fusarium oxysporum f.sp. melonis in Tunisia

Fusarium wilt of melon, caused by Fusarium oxysporum f.sp. melonis (Fom), is an important disease; races of the pathogen were identified by inoculating differential standard host cultivars. A total of ten isolates that were obtained from 23 fields located in four different geographical regions were identified as pathogenic. Results indicate that all four known Fom races, namely, 0, 1, 2 and 1.2, were found in north and middle Tunisia. Race 1.2 was the most prevalent.     

Physiological races and soil population level of fusarium wilt of watermelon

Results of a comparative test oflocal isolates ofFusarium oxysporum f. sp.niveum with isolates from abroad indicate the existence of a highly virulent race of this fungus in Israel. All these isolates were found also pathogenic to resistant cultivars from the U.S.A. When inoculum density was tested, a one-hundredfold higher fungus population was required for extensive wilt of watermelon seedlings in freshly infested sterilized soil compared with the same soil kept dry for three months. In naturally infested soil, where almost 100% of the plants were infected toward the end of the season, the lowest count of the fungus population (400 propagules/g soil) was comparable to the inoculum density required for total wilt of watermelon seedlings in infested sterilized soil.     

Characterization of two races of the stem and bulb nematode (Ditylenchus dipsaci) in Israel

Two distinct races ofDitylenchus dipsaci in Israel were identified: one, which infects and damages onion and garlic, reproduces on pea, but does not infect phalaris grass; and a second, which infects and damages phalaris—and, probably, also ‘Saia’ oats—but fails to infect onion and garlic. A new ‘garlic’ race of the nematode does not appear to have been introduced into Israel together with the ‘Lavinia’ garlic cultivar, as previously speculated, but rather the introduced Lavinia clone is highly susceptible to the existing ‘onion and garlic’ race ofD. dipsaci.     

江西省辣椒疫霉生理小种构成及其对烯酰吗啉的敏感性分析

为了明确江西省辣椒疫霉对烯酰吗啉的抗药性风险,采用灌根法鉴定了108个江西辣椒疫霉菌株的生理小种,并采用菌丝生长速率法测定了江西省辣椒疫霉对烯酰吗啉的敏感性.结果表明,菌株LP20、LP38和LP48属于生理小种3,占测定菌株总数的2.8％,其余菌株属于生理小种2,占测定菌株总数的97.2％,为优势生理小种,且未发现生理小种1.烯酰吗啉抑制辣椒疫霉菌丝生长的EC50值范围为0.1149～0.2868 μg/mL,最不敏感菌株的EC50值为最敏感菌株的2.49倍.不同地区的菌株对烯酰吗啉的敏感性差异不大,崇义的菌株平均EC50值最低,为0.1367 μg/mL,分布范围为0.1213 ～0.1462 μg/mL;吉水的菌株平均EC50值最高,为0.2185 μg/mL,分布范围为0.1805 ～0.2835 μg/mL.     

2009—2010年黑龙江省主要瓜类作物白粉病菌生理小种鉴定

瓜类白粉病是一种世界性病害,其主要病原为单囊壳白粉菌Podosphaera xanthii和二孢白粉菌Golorinomyces cichoracearum [1].瓜类白粉病菌生理小种众多、演替分化快,其相关研究一直备受关注.我国曾对杭州[2]、北京[3]、三亚[4]、甘肃[5]、陕西关中地区[6]瓜类白粉病菌生理小种演替、分化进行研究,而黑龙江省尚无相关报道.为此,作者于2009-2010年对黑龙江省瓜类白粉病菌生理小种进行鉴定,以期为该省瓜类白粉病抗病育种及综合防治提供参考.     

Physiological races and vegetative compatibility groups within Fusarium oxysporum f.sp. gladioli

The pathogenicity and vegetative compatibility of mainly Dutch isolates ofFusarium oxysporum collected from diseased gladioli and other Iridaceae were investigated. Based on their pathogenicity to two differential gladiolus cultivars, the isolates could tentatively be divided into two races. All self-compatible isolates ofFusarium oxysporum f.sp.gladioli belonged to one of three distinct vegetative compatibility groups, VCG 0340, 0341 or 0342, and were incompatible with isolates that were not pathogenic to gladiolus. Isolates of one of the two races were restricted to one VCG while isolates of the other race were present in all three VCGs.     

Stage specificity of catalase isoform activity in Exserohilum turcicum

Exserohilum turcicum is the fungal agent that causes northern leaf blight disease in maize. Spores of E. turcicum can germinate in water containing up to 15 m M hydrogen peroxide. Initially the catalase isoform activities from E. turcicum cultured on artificial medium were analysed by polyacrylamide gel electrophoresis. Seven different catalase isoform activities were detected during a 72-hour time course from spore germination to young hyphal formation. During the time period studied the activity levels of each isoform varied independently. In two-week-oldE. turcicum mycelia, only the activities of catalase isoforms #2 and #3 were detected. During a compatible interaction on maize leaves, plant catalases were suppressed with E. turcicum isoform #3 being detected from 72 h after inoculation onwards. E. turcicum #2 was the predominant isoform detected in necrotic lesions. Salicylic acid was not found to effect fungal or maize catalase activities. E. turcicum isoform #3 activity was found to be strongly induced by hydrogen peroxide and by the herbicide 3-amino-1,2,4-triazole (AT), while the activity of all other isoforms was suppressed by AT.     

Physiological races and vegetative compatibility groups of butterhead lettuce isolates of Fusarium oxysporum f. sp. lactucae in Japan

Races were identified among butterhead lettuce isolates of Fusarium oxysporum f. sp. lactucae collected from three geographical areas of Hokkaido, Shizuoka, and Fukuoka in Japan by inoculation tests using Fujinagas race differential cultivars of lettuce (i.e., Patriot, Costa Rica No. 4, and Banchu Red Fire). Eighteen isolates from Shizuoka and Fukuoka were designated race 3, with two unknown vegetative compatibility groups (VCGs) that differed from Ogisos VCG 1 and 2. These two new VCGs were obtained from both Shizuoka and Fukuoka. On the other hand, three isolates from Hokkaido were classified as race 1 and identified as VCG 1, which represents a VCG of crisphead isolates from Nagano.     

玉米大斑病菌人工接种方法研究

 The efficient and accurate method of inoculating Exserohilum turcicum on maize is most important for studying the corn leaf blight. In this study, four approaches including spore suspension spraying, inoculation with grinding infected maize leaves, inoculation liquid inoculum into the leaf whorl and inoculation with inoculated sorghum seeds were compared with natural induction in fields during different growth stages of maize in the greenhouse and field. The results showed that disease incidence of all varieties tested were up to 100% by inoculating with inoculated sorghum seeds during the booting stage (11 to 12 leaf stages). This method will not only guarantee the enough pathogen inocula but also be easy to use, and could be an effective way for disease resistance identification in field and greenhouse.      

神农架玉米大斑病暴发原因及防治对策

神农架地处鄂西北山区,气温偏凉而且多雨,年降水量900~1 000mm.玉米是神农架主要粮食作物,常年种植玉米3 333hm2以上.玉米大斑病是玉米生产上常见的病害之一,由于历来发病较轻,因此没有引起足够重视,近几年来玉米大斑病发生趋重,2008年全区8个乡镇玉米大斑病普遍发生,局部暴发成灾,此病已成为影响神农架林区玉米高产的一个突出问题.     

Some new races ofPuccinia striiformis

In the Netherlands in 1961 three new field races were found ofPuccinia striiformis, the causal fungus of yellow rust on wheat. Two of these, viz. the Falco race and the Opal race, together with the already known Etoile de Choisy race, constitute the so-called Nord-group of races, which is now clearly distinguished from the so-called Rubis-group. Most dangerous and interesting is the third of the new races. This so-called Cleo race proved to be the first to break both resistance to the Nord-group and resistance to the Rubis-group. On wheat seedlings in the greenhouse all three new races behaved like green-house race W(ageningen) 8=B(raunschweig) 55.Samenvatting Er zijn van de schimmelPuccinia striiformis Westend., de veroorzaker van de gele roest van tarwe, in Nederland in 1961 drie nieuwe veldfysio's gevonden. Dit zijn het Falco-fysio, het Opal-fysio en het Cleo-fysio. De eerste twee bleken met het reeds bekende Etoile de Choisy-fysio een groep te vormen, de z.g. Nord-groep, die zich duidelijk onderscheidt van de reeds beter bekende Rubis-groep van fysio's. Eerstgenoemde groep kenmerkt zich o.a. door de aantasting van het tarweras Nord, de laatstgenoemde door de aantasting van Rubis (zie tabel 1). Het belangrijkst en het gevaarlijkst is het Cleo-fysio. Dit bleek voor zover bekend het eerste en enige fysio te zijn dat zowel de resistentie tegen de Rubis-groep als die tegen de Nord-groep doorbreekt. Het heeft zodoende een zeer breed aantastingsspectrum. Van de tarwerassen die voorkomen in de 39ste Nederlandse Rassenlijst voor Landbouwgewassen (1964) zijn de volgende negen rassen vatbaar voor het Cleo-fysio met een aantastingsgraad van 6 tot 9 (Internationale Schaal): Cleo, Cappelle Desprez, Heine's VII, Hector, Stella, Sambo, Mado, Wodan en Jufy I. Bovendien bleek het Cleo-fysio in vergelijking met de andere veldfysio's goed te overwinteren en in 1964 reeds op vele plaatsen in Nederland aanwezig te zijn. Het Cleo-fysio maakt het des te noodzakelijker bij de selectie op resistentie tegen gele roest te werken op een brede genetische basis. Bij toetsing op tarwekiemplanten in de kas gedroegen de drie nieuwe fysio's zich alle als het kasfysio W(ageningen) 8 =B(raunschweig) 55 (zie tabel 2).     

东北水稻白叶枯病菌生理小种及水稻品种对9号小种的抗性

对东北地区水稻白叶枯病菌生理小种群体的构成及分布,以及水稻品种对白叶枯病菌9号小种的抗性进行了研究。结果表明,东北地区水稻白叶枯病菌生理小种群体由6个小种,即Race 1、Race 2、Race 3、Race 6、Race 8和Race 9构成。小种Race 1、Race 2和Race 9在东北三省吉林、辽宁和黑龙江都有分布,小种Race 3和Race 8只存在黑龙江省,Race 6只存在辽宁省。在30个水稻品种中,对9号生理小种表现抗病的有13个,出现频率为43.3%;中抗7个,频率23.3%;中感6个,频率20.0%;感病4个,频率13.3%。本研究为在东北粳稻地区挖掘白叶枯病的抗源,以及利用抗病品种控制白叶枯病危害提供依据。     

玉米大斑病的流行原因与综合治理措施

1990～2004年,玉米大斑病在忻州滹沱河流域的6个县(市、区)有4年大流行。其中2004年发病面积9万hm2,因病害减产约49500t。根据多年系统观察,发现病害的发生与流行和作物茬口、品种抗病性、气象条件、耕作管理等密切相关。控制该病害,必须在选育抗病品种的同时,大力推广秋深耕、轮作倒茬、增施农家肥、做好病情测报、适时喷药控制田间中心病株等综合治理措施。     

A histological assessment of the infection strategy of Exserohilum turcicum in maize

Northern leaf blight is a lethal foliar disease of maize caused by the fungus Exserohilum turcicum. The aim of this study was to elucidate the infection strategy of the fungus in maize leaves using modern microscopy techniques and to understand better the hemibiotrophic lifestyle of E. turcicum. Leaf samples were collected from inoculated B73 maize plants at 1, 4, 9, 11, 14 and 18 days post-inoculation (dpi). Samples were prepared according to standard microscopy procedures and analysed using light microscopy as well as scanning (SEM) and transmission electron microscopy (TEM). Microscopic observations were preceded by macroscopic observations for each time point. The fungus penetrated the leaf epidermal cells at 1 dpi and the disease was characterized by chlorotic leaf flecks. At 4 dpi the chlorotic flecks enlarged to form spots, and at 9 dpi hyphae were seen in the epidermal cells surrounding the infection site. At 11 dpi lesions started to form on the leaves and SEM revealed the presence of hyphae in the vascular bundles. At 14 dpi the xylem was almost completely blocked by hyphal growth. Hyphae spread into the adjacent bundle sheath cells causing cellular damage, characterized by plasmolysis, at 18 dpi and conidiophores formed through the stomata. Morphologically, lesions started to enlarge and coalesce leading to wilting of leaves. This study provides an updated, detailed view of the infection strategy of E. turcicum in maize and supports previous findings that E. turcicum follows a hemibiotrophic lifestyle.     

Genetic differentiation in populations of Exserohilum turcicum from maize and sorghum in South Africa

Exserohilum turcicum is the causal agent of northern leaf blight, a devastating foliar disease of maize and sorghum. Specificity of E. turcicum to either maize or sorghum has been observed previously, but molecular evidence supporting host specialization is lacking. The aim of this study was to compare the genetic structure of E. turcicum isolates collected from adjacent maize and sorghum fields in Delmas and Greytown in South Africa. In addition, the mode of reproduction of this pathogen was investigated. Isolates from maize (N = 62) and sorghum (N = 64) were screened with 12 microsatellite markers as well as a multiplex mating type PCR assay. No shared haplotypes were observed between isolates from different hosts, although shared haplotypes were detected between isolates from maize from Delmas and Greytown. Population structure and principal coordinate analyses revealed genetic differentiation between E. turcicum isolates from maize and sorghum. Analysis of molecular variance indicated higher among‐population variation when comparing populations from different hosts, than comparing populations from different locations. Lack of shared haplotypes, high proportion of private alleles, greater among‐population variance between hosts than locations and significant pairwise population differentiation indicates genetic separation between isolates from maize and sorghum. The high haplotypic diversity in combination with unequal mating type ratios and significant linkage equilibrium indicates that both sexual and asexual reproduction contributes to the population genetic structure of E. turcicum in South Africa.     

以色列的现代化农业

以色列位于中东地区，北部与黎巴嫩接壤，东北部与叙利亚、东部与约旦、西南部与埃及为邻，西濒地中海。国土面积约27 800 km2，呈狭长形，长约470 km，而东西最宽处约135 km。山脉和平原，沃土和沙漠经常只相隔几分钟的路程。以色列境内，既有温带气候，也有热带气候，阳光充足，只有两个差别显著的季节，即从11月至来年3月的多雨冬季和延续7个月的干旱夏季，荒漠几乎占全国土地面积的一半。以色列的农业是一部长期同不利条件进行艰苦斗争和最大限度地利用珍贵水资源和可耕地的成功史，也是充分利用先进科学技术进行农业生产的发展史。节水灌溉，沙漠农业，高科技农业等方面的成果使以色列的农业生产位居世界前列，现代化农业也为以色列创造了巨大的社会和经济效益。