向日葵细菌性茎腐病的研究Ⅰ.症状及病原菌鉴定

 本文首次报道了向日葵细菌性茎腐病在我国的发生。对分离到的20个菌株经形态学特性、培养性状、生理生化和血清学反应测定,确定引起我国东北地区向日葵细菌性茎腐病的病原细菌有三种,即Erwinia carotovora subsp.carotovora Dye,E.carotovora subsp.atroseptica Dye和Pseudomonas caryophylli (Burkholder) Starr and Burkholder。     

半湿润沙地凝结水的初步研究

本文通过一系列实地土壤凝结水（包括吸湿水）测定和实验，对所得的基本数据进行综合分析，提出土壤凝结水（包括吸湿水）的主要控制因素，是土壤的机械组成，尤以〈０．００１粘粒含量为主；土壤凝结水与气象条件密切相关，与０ｃｍ、５ｃｍ、１０ｃｍ地温和气温变化呈现相同周期，与相对湿度变化有相关关系。并说明林冠下沙地凝结水量变化比裸地凝结水量小。     

渭北旱塬农作物经济效益试验研究

通过两年试验，可以肯定，渭北旱塬的优势作物是红薯和花生。无论在干旱年或平水年均有较高经济效益。玉米的种植，在年降雨量不足４００ｍｍ、时不宜种植。近年因空害频繁，气候不佳，烤烟不宜提倡，棉花应该停止种植。中药材具有根大开发潜力。作物从土壤中吸水，平水年主要在１米以上；干旱年则在１米以下。其耗水规律随种类及处理而变化。     

Pectate lyases of Erwinia chrysanthemi: Pel E-like polypeptides and pelE homologous sequences in strains isolated from different plants

Pel E, one of the four major pectate lyases produced by Erwinia chrysanthemi (Echr) strain EC16, was purified to homogeneity and was found to have an apparent molecular weight of 47 500 and a pI of 10. Antibodies produced against this preparation inhibited Pel E activity, but did not affect Pel A, Pel B or Pel C activities. Immunotitration revealed that Pel E accounted for a major fraction of the total extracellular Pel activity ranging from 40–60% in culture and potato tuber tissue. Isoelectric focusing of the extracellular Pels produced by various Echr strains indicated that while the Pel profiles of strains isolated from various hosts were different, the profiles of strains isolated from the same host were very similar. A significant proportion (ranging from 39 to 74%) of the Pel activity of these strains was inhibited by the anti-Pel E antibodies. DNA hybridization under stringent conditions indicated the presence of pelE homologous sequences in the genomes of E. chrysanthemi strains. We conclude that a Pel E-like enzyme occurs in all E. chrysanthemi strains examined.     

Rhizobacteria with broad-spectrum antifungal activity*

Antifungal rhizobacteria were obtained from maize, barley and chicory using direct or indirect isolation procedures. Effective isolates were tested for broad-spectrum activity against a set of phytopathogenic fungi. Isolates with broad-spectrum activity were identified as Pseudomonas fluorescens, P. cepacia, Serratia liquefaciens, S. plymuthica and Bacillus sp. Broad-spectrum compounds produced by P. cepacia and Erwinia herbicola were characterized as pyrrolnitrin and herbicolin-like compounds respectively.     

Perspectives d'utilisation de Hansfordia pulvinata contre la cladosporiose de la tomate1

La cladosporiose demeure l'une des principales maladies des cultures de tomate en serre car la lutte chimique reste peu satisfaisante. Elle est parfois naturellement ralentie par l'installation spontanée d'un hyperparasite de Fulvia fulva (syn. Cladosporium fulvum), Hansfordia pulvinata, antagoniste actif de l'agent pathogène. L'élaboration d'une méthode de lutte biologique a été envisagée. Une production industrielle de ce biopesticide est en cours de mise au point. En serres de production, 80% ou plus des taches de cladosporiose sont recouvertes par l'hyperparasite. Cependant, l'efficacité du controle est limitée par l'incapacité de H. pulvinataà entrer en contact avec F. fulva lors de sa phase biotrophe ainsi que par la faible autodissémination de l'hyperparasite. Un apport de phoséthyl-Al (1.6 g l^-1) a amélioré l'efficacité de la méthode. Ce fongicide, compatible avec H. pulvinata, inhibe la germination des spores de F. fulva. Dans cette lutte intégrée, l'hyperparasite abaisse la pression d'inoculum du parasite et le fongicide limite les nouvelles contaminations. Au vu des premières expérimentations en serre, cette méthode pourrait etre préconisée en début d'attaque de cladosporiose et devrait réduire la fréquence des traitements, favorisant en cela une large lutte intégrée et l'emploi des auxiliaires.     

Biotypes of the citrus nematode (Tylenchulus semipenetrans Cobb) in Israel

Two biotypes of the citrus nematode, Tylenchulus semipenetrans Cobb, were identified among five populations occurring in different regions in Israel. These biotypes originated from Sour orange and Troyer citrange roots and differed in their ability to infestPoncirus trifoliata hybrids (particularly Troyer citrange). They appear to be close to two recognized biotypes known to be present in other countries and designated as the “Poncirus” and “Mediterranean” biotypes. The different infectivity of the two biotypes on Troyer citrange roots was maintained even after they were cultured for 6 months on Sour orange. Both biotypes readily reproduced on persimmon, but failed to infest olive and grapevine. Two newP. trifoliata x Poorman orange hybrids exhibited good resistance to both biotypes.     

Overwintering of the Japanese bayberry whitefly,parabemisia myricae,in Israel

The Japanese bayberry whitefly,Parabemisia myricae (Kuwana), was discovered in Israel on citrus and avocado trees in 1978. In order to clarify its mode of overwintering, observations and counts were carried out during the winters of 1979/80, 1982/83 and 1983/84, with the following findings. Larvae and adults were detected on citrus and avocado trees throughout the winter; only females were found. The oviposition rate ofP. myricae in winter was low, and rose steeply in spring. The density of larvae on the lower side of leaves was higher than on the upper side. Substantial numbers of larvae survived the winter on avocado trees. Emergence of adults became intensified at the end of February, reached a peak in early March, and ceased at the end of March or beginning of April.