Host Preference of Mating Type in Pseudoperonospora cubensis, the Downy Mildew Causal Agent of Cucurbits.

The A2 mating type of Pseudoperonospora cubensis was first discovered in Israel in May 2010 on butternut gourd (Cucurbita moschata) (1). We monitored the occurrence of the A2 mating type of P. cubensis in isolates collected during May 2010 through September 2012 from downy mildew-infected cucurbit crops growing along the coastal plain of Israel. Mating type was determined by oospore production in melon leaf discs co-inoculated with sporangia of a test isolate mixed with sporangia of A1 or A2 tester isolates (2). The A1 and A2 tester isolates were maintained at 14°C (14 h light/day) by repeated inoculation of detached leaves of cucumber and pumpkin, respectively. The 29 isolates that were collected from cucumber (Cucumis sativum) were all A1. Of the 33 isolates collected from pumpkin (Cucurbita maxima), squash (C. pepo), or butternut gourd (C. moschata), 88% were A2 and 12% were A1. The host preference of mating type in P. cubensis was monitored at Bar-Ilan University farm during April to July 2012, among about 800 plants of eight cucurbit species (~100 plants per species) that were grown side-by-side in three adjacent net-houses (two 6 × 50 m and one 6 × 100 m) and exposed to natural infection. Downy mildew developed on cucumber, melon, pumpkin, squash, and butternut gourd, but not on watermelon, sponge gourd (Luffa cylindrica), or Momordica balsamina. Three-hundred and three isolates of P. cubensis were collected and tested for mating type: 123 from cucumber, 53 from melon, 30 from pumpkin, 48 from butternut gourd, and 41 from squash. The cucumber isolates expressed A1, A2, and A1A2 at a ratio of 94.3%, 3.3%, and 2.4%, respectively; the melon isolates 58.5%, 26.4%, and 15.1%; the pumpkin isolates 0%, 96.7%, and 3.3%; the butternut isolate 7.3%, 87.3%, and 5.5%; and the squash isolates 2.4%, 97.6%, and 0%, respectively. A1A2 isolates produce oospores when crossed with either A1 or A2 tester isolates. This is the first evidence suggesting a preference of A1 isolates to Cucumis spp. and of A2 isolates to Cucurbita spp. similar preference was recently observed among Chinese isolates of this pathogen (unpublished data). The mechanism(s) controlling this preference is not known. Classical genetics is currently employed to P. cubensis in order to understand if it derives from true linkage. The practical implication for downy mildew management is that growing cucumber/melon in close proximity to pumpkin/squash/butternut gourd should be avoided as it may enhance oospore production in nature. Oospores in soil were recently shown to serve as a primary source of downy mildew infection in cucumber (3). References: (1) Y. Cohen, A. E. Rubin, and M.Galperin. Plant Dis. 95:874, 2011; (2) Y. Cohen and A. E. Rubin. Eur. J. Plant Pathol. 132:577, 2012; (3) Y. J. Zhang et al. J. Phytopathol. 160:469, 2012.

First Report on the Occurrence of A2 Mating Type of the Cucurbit Downy Mildew Agent Pseudoperonospora cubensis in China.

Pseudoperonospora cubensis is a foliar pathogen of cucurbits. In cucumber, it produces chlorotic, angular lesions with dark sporangia on their under-surface. The distribution of pathotypes and mating types of P. cubensis were investigated in seven provinces in China. Twenty-nine isolates were obtained from Guangdong, Anhui, Hubei, Sichuan, Shandong, Beijing, and Harbin, one to six isolates from each province. They were collected from cucumber during summer 2011, except those from Harbin, which were collected from cucumber in summer 2012. Isolates were tested for pathogenicity and mating type. Pathogenicity was tested by inoculation of detached leaves of: cucumber (Cucumis sativum cvs. Bet-Alpha, SMR18), melon (Cucumis melo reticulatus cv. Ananas-Yokneam), pumpkin (Cucurbita maxima cv. Tripoli), squash (Cucurbita pepo, cv. Beruti), butternut gourd (Cucurbita moschata cv. Waltham), watermelon (Citrullus lanatus, cv. Malali), and sponge gourd (Luffa cylindrica, cultivar unknown). Mating type was determined by oospore production in melon leaf discs inoculated with mixed sporangia of a test isolate and A1 or A2 tester isolates, as recently described (2). The results showed that 22 isolates belonged to pathotype 3, sporulating on cucumber and melon; five isolates belonged to pathotype 6, sporulating on cucumber, melon, pumpkin, squash, and butternut gourd; one isolate belonged to pathotype 5, sporulating on the above five species and watermelon (1), and one isolate was capable of sporulating on the mentioned five species and sponge gourd, herein called pathotype 7. Of the 29 isolates tested, 22 belonged to the A1 mating type, six to the A2 mating type, and one did not produce oospores with either testers. Of the six A2 isolates, two originated from Sichuan, one from Beijing, and three from Harbin. All 22 isolates belonging to pathotype 3 were A1, whereas the other six isolates (four pathotype 6, one pathotype 5, and one pathotype 7) were A2. Crosses made between Chinese isolates belonging to opposite mating types resulted in the formation of abundant oospores in detached melon or cucumber leaves. The results prove that the A2 mating type of P. cubensis occurs in China. This explains the abundant occurrence of oospores of P. cubensis in nature in China (4). The data corroborate with Runge et al. (3), who suggested that the recent changes in the population structure of P. cubensis around the world resulted from the migration of a new genotype of P. cubensis from the Far East to Europe and the U.S.A. In Israel, a new pathotype attacking both Cucumis and Cucurbita appeared in 2002 (1), and A2 mating type first appeared in 2010 (2). References: (1) Y. Cohen et al. Phytoparasitica 31:458, 2003. (2) Y. Cohen and A. E. Rubin. Eur. J. Plant Pathol. 132:577, 2012. (3) F. Runge et al. Eur. J. Plant Pathol. 129:135, 2011. (4) Y. J. Zhang et al. J. Phytopathol. 160:469, 2012.

First Report of the Occurrence and Resistance to Mefenoxam of Peronospora belbahrii, Causal Agent of Downy Mildew of Basil (Ocimum basilicum) in Israel.

Downy mildew in basil was first reported from Uganda in 1933 (4). In 2004, it was reported from Italy (3) and, thereafter, from other countries around the world. In Israel, the disease was first observed in November 2011 in two greenhouses located in the northern part of the Jordan Valley. Within a month, second and third outbreaks of the disease occurred simultaneously near the southwest and southeast borders of Israel, 250 km from the initial disease outbreak. By the summer of 2012, the disease had appeared throughout the country, causing major economic damage. The causal agent, identified as Peronospora belbahrii (see below), produced chlorotic lesions on leaf blades with sporangia developing on the lower leaf surfaces. Lesions gradually turn necrotic, and infected leaves abscised. Sporangia were dark purple, oval, 30.4 ± 2.9 µm long × 21.4 ± 1.7 µm wide. Sporangiophores emerged from stomatal openings in a saturated atmosphere, were hyaline, 400 to 600 µm long, dichotomously branched, with three to five branches per sporangiophore, and bore a single sporangium on each branchlet tip. Oospores, seldom seen, were brown, round, and 46.2 ± 2.8 µm in diameter. Sporangia germinated directly, each producing a single germ tube that penetrated the periclinal wall of epidermal cells. PCR assays using sporangia and infected leaves as the template, and specific BAZ primers (1), produced a 134-bp band typical of P. belbahrii (1,2). Twenty isolates, collected from 12 locations in Israel from December 2011 to September 2012, were all sensitive to mefenoxam as the isolates did not cause symptoms on 15-leaf, potted basil plants (cv. Peri, Volcani Center, Israel) that were sprayed with 10 µg mefenoxam/ml (Ridomil Gold 48%, Syngenta, Basel, Switzerland) prior to inoculation. However, one isolate collected in early October 2012 from a severely infected plant in a greenhouse at Rehov in Bet-Shaan Valley, in which the plants had been treated with mefenoxam, was resistant to mefenoxan, showing abundant sporulation on leaves of potted basil plants that had been sprayed with 1,000 µg of mefenoxam/ml prior to inoculation. To our knowledge, this is the first report of the occurrence of downy mildew in basil in Israel. This is also the first global report of resistance to mefenoxam in P. belbahrii. References: (1) L. Belbahri et al. Mycol. Res. 109:1276, 2005. (2) R. Djalali et al. Mycol. Progress 11:961, 2012. (3) A. Garibaldi et al., Plant Dis. 89:683, 2004. (4) C. G. Hansford. Rev. Appl. Mycol. 12:421, 1933.

Formation and Infectivity of Oospores of Pseudoperonospora cubensis, the Causal Agent of Downy Mildew in Cucurbits.

The oomycete Pseudoperonospora cubensis attacks members of the Cucurbitaceae, causing severe foliage damage especially to cucumber and melon. Recently, new pathotypes of this oomycete appeared in Israel (2) and Italy (1) and highly aggressive isolates appeared in the United States (3). Since oospores of P. cubensis were rarely seen and sexual propagation by oospores was never reported (4), it is assumed that it propagates clonally by sporangia. Here we report on sexual reproduction of P. cubensis under controlled conditions in the laboratory. We found that field isolates belonging to the old pathotype 3 or to the new pathotype 6 (2) inoculated singly onto detached leaves of cucurbits in growth chambers at 15 or 20°C produced no oospores, even after prolonged incubation periods. However, when sporangia of some paired field isolates were mixed together at a 1:1 ratio, similarly inoculated onto detached leaves, and incubated at 15 or 20°C, numerous oospores (up to ~300/cm2) were formed in the mesophyll within 6 to 11 days, depending on the isolates pair, the host inoculated, and temperature. Oospores were also formed at 12.5°C but not at 25°C. Oospores developed in intact plants when kept at 15 or 20°C under a humidity-saturated atmosphere during disease development. Oospores were round, light brown to brown with an average diameter of ~40 µm. Oospores were produced in Cucumis sativum (cvs. Nadiojni and Dalila) and Cucumis melo (cvs. Ananas-Yokneam and Ein-Dor) but not in Cucurbita pepo (cv. Arlika, Beiruti), C. moschata (cv. Dalorit), or C. maxima (cv. Tripoli). To verify that oospores are infective, cucumber or melon leaves containing oospores were homogenized in water. The homogenate was twice brought to dryness at 25 to 30°C in petri dishes to differentially kill the vegetative structures of the pathogen (sporangia, cystospores, zoospores, and mycelia), resuspended in water, and inoculated onto detached leaves of various cucurbits in growth chambers at 15 or 20°C. Downy mildew lesions carrying sporangia appeared within 7 to 20 days in leaves of Cucumis sativum, Cucumis melo, and C. moschata but not in C. pepo or C. maxima. The recombinant origin of the F1 offspring isolates was confirmed by mefenoxam sensitivity tests, random amplified polymorphic DNA, and simple sequence repeat analyses. F1 progeny isolates of some crosses lost pathogenicity to C. moschata or C. maxima, toward which one of their parents was pathogenic, while others gained pathogenicity to Luffa cylindrica or Citrullus lanatus toward which neither parent was pathogenic. Data confirmed that isolates of P. cubensis can mate to produce oospores, especially under constant humidity conditions; such oospores are infective to cucurbits and F1 progeny isolates show altered sensitivity to fungicides or altered host range relative to their parents. To our knowledge, this is the first report of oospore formation by P. cubensis in the laboratory and on their pathogenicity to cucurbits. Reasons for the parallel appearance of new pathotypes of P. cubensis in Israel in 2002 (2) and Italy in 2003 (1) and the reemergence of highly aggressive isolates of the pathogen in the United States in 2004 (3) are not known. They may be related to oospore production and sexual recombination in P. cubensis. References: (1) C. Cappelli et al. Plant Dis. 87:449, 2003. (2) Y. Cohen et al. Phytoparasitica 31:458, 2003. (3) G. J. Holmes et al. Am. Veg. Grower. February, 14-15, 2006. (4) A. Lebeda and Y. Cohen. Eur. J. Plant Pathol.129:157, 2011.

Mesosiderite clasts with the most extreme positive europium anomalies among solar system rocks.

Pigeonite-plagioclase gabbros that occur as clasts in mesosiderites (brecciated stony-iron meteorites) show extreme fractionations of the rare-earth elements (REEs) with larger positive europium anomalies than any previously known for igneous rocks from the Earth, moon, or meteorite parent bodies and greater depletions of light REEs relative to heavy REEs than known for comparable cumulate gabbros. The REE pattern for merrillite in one of these clasts is depleted in light REEs and has a large positive europium anomaly as a result of metamorphic equilibration with the silicates. The extreme REE ratios exhibited by the mesosiderite clasts demonstrate that multistage igneous processes must have occurred on some asteroids in the early solar system. Melting of the crust by large-scale impacts or electrical induction from an early T-Tauri-phase sun may be responsible for these processes.

Functional characteristics of the lung in chronic uremia treated by renal dialysis therapy.

Ventilatory studies and arterial blood gas analyses were performed in 29 patients with chronic renal failure undergoing renal dialysis therapy (RDT). Twenty-three of the 29 had nearly normal pulmonary function, and the accumulation of body water between dialyses did not influence pulmonary function significantly. A trend was observed towards overinflation and air trapping in the presence of normal airway resistance, indicating narrowing of the small airways. Repeated studies over a 16-month period suggest that these patients develop neither chronic obstructive airway disease nor restrictive ventilatory impairment. Six patients had a restrictive ventilatory impairment with a trend to overdistension and air trapping as in the "normal" patients. This was observed both early and late in the course of RDT and appeared to be irreversible but not progressive. These patients had suffered from uremic pleuropericarditis and either had serous effusions or residual adhesions.

The treatment of asthma in adults using sodium cromoglycate pressurized aerosol: a double-blind controlled trial.

Sodium cromoglycate formulated as a pressurized aerosol (2 mg 4-times daily) and placebo were compared in 31 adult asthmatic patients in a double-blind crossover trial lasting 12 weeks. Sodium cromoglycate was superior to placebo in improving breathlessness at rest (p less than 0.001), breathlessness on exertion (p less than 0.05) and the quality of sleep (p less than 0.001), and also in improving the morning peak expiratory flow rate value (p less than 0.05). Both the patients' (p less than 0.05) and the clinicians' (p less than 0.01) treatment opinions, and their treatment preferences (p less than 0.05), favoured sodium cromoglycate. Moreover, usage of bronchodilators (theophylline and aerosol beta-stimulants combined) declined significantly (p less than 0.001) during sodium cromoglycate treatment compared to placebo. No side-effects were reported. The results of this study show that sodium cromoglycate delivered by pressurized aerosol was significantly superior to placebo, not only in improving asthmatic symptoms, but also in reducing the amount of concomitant bronchodilator therapy required.

Effects of nasal occlusion on respiration in sleep. Evidence of inheritability of sleep apnea proneness.

An influence of complete mechanical obstruction of the nasal passages was investigated in 6 apneic-free sons of fullblown sleep apnea patients and in 4 age-matched normal young adults without a familial history of sleep apnea. Nasal obstruction caused a significant increase in the number of sleep apneas in the sons of the sleep apnea patients as compared with controls. The results support the suggestion that sleep apnea syndrome may be caused by an exacerbation of an inherited respiratory instability in sleep resulting from increased airway resistance.

[Pulmonary alveolar proteinosis].

Pulmonary alveolar proteinosis is a rare disease of unknown etiology characterized by alveoli filled with PAS-positive material high in protein and lipid. A 30-year-old man was referred because of respiratory failure. 2 years previously exertional dyspnea and productive cough appeared and gradually worsened. A year later he sought medical advice but defaulted on follow-up. After further deterioration he returned for treatment. On examination he had tachypnea and cyanosis. Diffuse crackles were audible in both lungs. X-ray revealed diffuse bilateral airspace consolidation. Arterial blood gases on air showed PaO2 41 mm Hg, PaCO2 35 mm Hg, and pH 7.46. There was a restrictive pattern on pulmonary function testing. Fiberoptic bronchoscopy with broncho-alveolar lavage and transbronchial biopsy established the diagnosis of pulmonary alveolar proteinosis. Whole lung lavage lead to gradual improvement over the next few weeks. However, chest X-ray, arterial blood gases and pulmonary function tests failed to revert completely to normal. Such severe manifestations and such an aggressive course as in this case might have been prevented had the diagnosis been made and treatment instituted earlier in the course of the disease.

[A respiratory health questionnaire for occupational screening].

A Hebrew pulmonary health questionnaire was designed for occupational screening, based on the American Thoracic Society questionnaire but adjusted to conditions in Israel. It was designed for assisted completion using a computer, but can easily be modified to become self-administered. We propose that it be used here as the standard, occupational, pulmonary health questionnaire and as the basis for a standard, general purpose, respiratory health questionnaire.