Effects of temperature onPhytophthora porri in vitro,in planta,and in soil

Cardinal temperatures for mycelial growth ofPhytophthora porri on corn-meal agar were <5 (minimum), 15–20 (optimum) and just above 25 °C (maximum). The number of infections after zoospore inoculation of young leaf plants was relatively low at supra-optimal temperatures, but was not affected by sub-optimal temperatures. Even at 0 °C plants were infected. The incubation periods needed for symptom formation were 36–57 d at 0 °C, 13–18 d at 5 °C, and 4–11 d at > 11 °C, and were fitted to temperature between 0 and 24 °C with a hyperbolical model (1/p=0.00812^*T+0.0243). Oospore germination, reported for the first time forP. porri, was strongly reduced after 5 h at 45 °C, and totally absent after 5 h at 55 °C. Soil solarization for six weeks during an exceptionally warm period in May–June 1992 in The Netherlands raised the soil temperature at 5 cm depth for 17 h above 45 °C, but did not reduce the initial level of disease in August significantly.     

Viruses of pepper in plastic houses in Crete

During a survey of virus diseases affecting pepper grown in plastic houses in Crete, during 1984–1986, tomato mosaic virus (ToMV) and tobacco mosaic virus (TMV) were detected. The most common virus was TMV, being present in samples of alle pepper cultivars carrying the L₁ resistance gene, while ToMV was isolated only from susceptible pepper cultivars. According to responses ofCapsicum spp. the isolates from 640 samples checked were classified into three pathotypes: P₀, P_1.2 and P_1.2.3. Results of this study show that P_1.2 represents at present the major threat to the Cretan pepper industry.Samenvatting Bij een in de jaren 1984–1986 gehouden inventarisatie van virusziekten in paprika in plastic-foliekassen op Kreta werd zowel het tabaksmozaïekvirus (TMV) als het tomatemozaïekvirus (ToMV) aangetoond. TMV kwam zeer algemeen voor: het werd aangetroffen in alle monsters van de paprikarassen met het resistentiegen L₁. ToMV werd alleen geïsoleerd uit planten van vatbare paprikarassen. Volgens de waargenomen symptomen die de isolaten van 640 monsters opCapsicum spp. vertoonden, konden de isolaten in drie pathotypen, nl. P₁, P_1,2 en P_1,2,3, worden geklassificeerd. Uit het onderzoek is gebleken dat P_1,2 de belangrijkste bedreiging vormt voor de teelt van paprika op Kreta.     

Inheritance of virulence in Fusarium circinatum,the cause of pitch canker in pines

Wildtype strains of Fusarium circinatum, the causal agent of pitch canker, were crossed to obtain an F₁ generation. Progeny of this cross were tested for virulence by inoculating Pinus radiata seedlings, and were found to induce a wide range of lesion lengths. Two strains from the F₁ generation that induced long lesions (= high virulence) were used as parents to produce an F₂ generation, followed by a second round of selection for high virulence to obtain an F₃ generation. Mean lesion lengths were not significantly different between the three generations (P ≥ 0.196). A parallel set of crosses was performed to select for low virulence by using progeny in the F₁ and F₂ generations that induced short lesions as parents for F₂ and F₃ generations, respectively. In this case, both rounds of selection resulted in a significant reduction in mean lesion length, from 33.8 ± 0.8 mm in the F₁ generation, to 19.7 ± 0.7 and 12.9 ± 0.7 mm in the F₂ and F₃ generations, respectively. Thus it is apparent that F. circinatum retains the genetic capacity for avirulence to pines, which could reflect a lack of strong selection for virulence in nature. Progeny of a cross between high and low virulence parents manifested nearly continuous variation in lesion lengths, consistent with virulence being a quantitatively inherited trait. Based on this cross, broad‐sense heritability (H²) was determined to be 0.74, which suggests that virulence is under strong genetic control.     

Status of pesticide resistance in arthropod pests in Israel

A complex of events and factors, pertinent to a specific insect and insecticide, governs the development of resistance to insecticides. In Israel, resistance to conventional and novel insecticides occurred in insect pests such asBemisia tabaci andSpodoptera littoralis (that damage agricultural crops),Tribolium castaneum and other flour beetles (that contaminate stored products), andPediculus humanus spp., house flies and mosquitoes (that threaten public health). In the mid-1980s an insecticide resistance management (IRM) strategy was established for all cotton grown in Israel and is being adjusted on a yearly basis as needed. At present, insect pest management and IRM strategies are being developed and implemented area-wide for three regions in Israel: Bet She’an Valley, western Galilee, and western Negev. There are several research groups now working in Israel on various aspects of resistance including occurrence, mechanisms, and management practices. This paper offers a tentative review of the status of insecticide and acaricide resistance in pests in Israel.     

Frequency of Alternaria brassicicola in commercial cabbage seeds in Japan

Plug seedlings, widely used in cabbage cultivation in Japan, are often infected by seed-borne pathogens, especially the serious pathogen Alternaria brassicicola. Because information on seed infestation is scant in Japan, we investigated fungal infestation in commercial batches of cabbage seeds produced between 1984 and 2001. A total of 123 lots were divided into six groups by production period (1984–1989, 1994–1998, and 2001) and by use or nonuse of fungicide. One hundred seeds from each lot were incubated separately on agar at 25°C to isolate the predominant fungus. Alternaria brassicicola was isolated most frequently, 0%–94% of the seeds depending on seed lot or 6%–21% of the seeds grouped by production period and fungicide treatment. Thus, the pathogen was isolated even from seeds refrigerated for 17 years. Alternaria brassicicola accounted for 57%–95% of all isolated fungi by the group and was higher on older or fungicide-treated seeds. Seeds that were not treated with fungicide in lots grouped by production districts in western Japan were infested with A. brassicicola at a rate of over 12%, higher than that in the eastern region (<4%). Infestation was higher in the warmer areas of Japan. Eighty-five isolates, other than A. brassicicola, produced spots on cabbage cotyledons, although they were not isolated as frequently: less than 5% of seeds by group separated by production period and fungicide treatment. Most of these isolates were Alternaria alternata. This is the first report on the frequency of fungal infestation of commercial cabbage seeds in Japan.     

Solarization of soil in piles for the control of Meloidogyne incognita in olive nurseries in southern Spain

The potential of solarization to control Meloidogyne incognita in piles of soil used at olive nurseries in southern Spain was studied in 1999 and 2000. Kaolin and soil infested with free eggs and egg masses of the nematode in nylon bags were buried 20 and 40 cm deep inside conical piles of soil 80 cm high and with a base diameter of 1 m. Soil piles were solarized for 3 weeks in July and August. The effect of various periods of solarization was assessed by egg hatch bioassays in sterile water, and by infectivity to tomato plants. Maximum soil temperature at 20 cm depth in solarized piles was 47·4°C in 1999 and 48·2°C in 2000, compared with 32·9°C and 31·7°C in nonsolarized piles. Solarization reduced egg hatch by > 95% compared with nonsolarized samples, irrespective of type, burial depth and location of inocula in a soil pile. Egg hatch of egg mass-infested samples buried at 20 cm depth was higher than that of free eggs buried at the same depth. The differential effect associated with burial depth and type of inoculum was not found in solarized piles. In nonsolarized piles, hatch of free eggs from samples buried at 40 cm depth was higher than that from samples buried at 20 cm depth. Egg hatch in samples from solarized piles was lower than that from nonsolarized piles. A bioassay of tomato plants in 2000 confirmed the reduction in infectivity of free eggs buried in solarized soil piles. Under the conditions in southern Spain, solarization of 40 cm-high piles of soil for 3 weeks can therefore be used for the control of root-knot nematodes in potting soil for olive nursery production.     

会宁剖面MIS3阶段黄土元素地球化学特征及气候变化

在会宁剖面元素地球化学数据分析和气候替代指标分析的基础上，重建了会宁地区约20～70 ka的古气候特征和序列。研究表明：Ba、Rb、Sr、Ti、Fe₂O₃、SiO₂、Al₂O₃、MgO、K₂O等在剖面上都有随深度的减小含量随之增加的趋势；CaO、Na₂O等在剖面上有随深度的减小含量随之减小的趋势。MIS3气候略显温湿，可划分为3个阶段：早期(L₁S₁S₂)，55.5～45.9 ka，气候为弱温湿；中期(L₁S₁L₁)，45.9～27.3 ka，气候为干冷；晚期(L₁S₁S₁)，27.3～23.8 ka，气候为温湿；会宁剖面较明显地记录了5次Heinrich事件。     

Frequency of Avirulence Alleles in Field Populations of Leptosphaeria maculans in Europe

This paper describes the first large-scale Europe-wide survey of avirulence alleles and races of Leptosphaeria maculans. Isolates were collected from the spring rape cultivar Drakkar, with no known genes for resistance against L. maculans, at six experimental sites across the main oilseed rape growing regions of Europe, including the UK, Germany, Sweden and Poland. Additionally in Poland isolates were collected from cv. Darmor, which has resistance gene, Rlm9. In total, 603 isolates were collected during autumn in 2002 (287 isolates from Germany and the UK) and 2003 (316 isolates from Poland and Sweden). The identity of alleles at eight avirulence loci was determined for these isolates. No isolates had the virulence allele avrLm6 and three virulence alleles (avrLm2, avrLm3 and avrLm9) were present in all isolates. The isolates were polymorphic for AvrLm1, AvrLm4, AvrLm5 and AvrLm7 alleles, with virulence alleles at AvrLm1 and AvrLm4 loci and avirulence alleles at AvrLm7 and AvrLm5 loci predominant in populations. Virulent avrLm7 isolates were found at only one site in Sweden. Approximately 90% of all isolates belonged to one of two races (combinations of avirulence alleles), Av5-6-7 (77% of isolates) or Av6-7 (12%). Eight races were identified, with four races at frequencies less than 1%. The study suggested that Rlm6 and Rlm7 are still effective sources of resistance against L. maculans in oilseed rape in Europe. The results are comparable to those of a similar survey done in France in autumn 2000 and 2001.     

Effectiveness of native parasitoids of Myzus persicae in greenhouse environments in India

Myzus persicae (Sulzer) is an economically important agricultural pest with over 500 known host plants in the world. The present study recorded the major parasitoids found parasitizing M. persicae on sweet pepper (Capsicum annuum [L.]) crops in greenhouses in Himachal Pradesh, India. Three species of hymenopteran parasitoids were reared from M. persicae from this source: Aphelinus asychis Walker (Aphelinidae), Aphidius matricariae Haliday (Braconidae), and Aphidius ervi (Haliday) (Braconidae), with parasitism rates per sample date ranging from 2.3–38.6%, 4.8–58.2%, and 2.9–28.4%, respectively, during 2011–2012. This is the first report of parasitoids associated with M. persicae in greenhouse environments in India. The present findings suggest that the management of M. persicae could be possible with the addition of augmentative releases of these parasitoids, which should help reduce pesticide use in Indian vegetable production greenhouses.     

Genotyping of acetylcholinesterase in insects

To investigate the genotyping criteria for the insect acetylcholinesterase gene (ace), we cloned two types of ace genes in domestic (Bombyx mori) and wild silkworm (Bombyxmandarina) through RT-PCR. The cloned genes were named Bm-ace1, Bm-ace2, Bmm-ace1 and Bmm-ace2, respectively. The ORFs of Bm-ace1 and Bmm-ace1 contained 2025 base pairs, encoding 683 amino acid residues (AA’s). The predicted protein has a molecular weight (MW) of 76.955 kDa and an isoelectric point (pI) of 6.36. The Bm-ace2 and Bm-ace2 genes contained 1917 bp nucleotides, encoding 638 AA’s. The predicted protein has a MW of 71.675 kDa and a pI of 5.49. Both ace1 and ace2 contain signature domains of acetylcholinesterases. Homology analysis of 18 NCBI downloaded insect AChEs peptide sequences and the 4 AChEs deducted in this study revealed that type 1 and type 2 insect AChEs had significant differences. Type 2 sequence is more conserved than type 1. Near the active centers of both types of AChEs, 48 strictly conserved AA’s (336-384) are present, and homology of these two peptide fragments was only 54.16%. Meanwhile, at AA positions 280-297, type 1 and type 2 AChEs both have conserved sequences with the similarity of the two being 52.94%. In type 2 AChEs, a uniquely conserved peptide sequence is found at positions 226-239 (QHLRVRHHQDKPL). We propose to use the above mentioned three conserved regions as criteria for insect acetylcholinesterases gene genotyping. This will benefit the genotyping of other acetylcholinesterase genes and the study of their functions.