ON THE STEM AND BULB EELWORM (ANGUILLULINA DIPSACI KUHN) WITH SPECIAL REFERENCE TO ITS OCCURRENCE ON WEEDS OF ARABLE LAND

The importance of wild hosts of Anguillulina dipsaci Kühn as carriers of infection needs no emphasis. The occurrence of the eelworm in the weeds, cleavers ( Galium aparine ) and duckweed ( Stellaria media ) taken in crops of oats and field beans which were themselves suffering from stem eelworm disease, was recorded by Johnson (1936) and Johnson & Thompson (1937); Walton (1937) confirmed the occurrence of infested cleavers plants in eelworm-infested oats. Walton also stated that experiments indicated that seed oats failed to carry eelworm infection, and from circumstantial evidence similar to that recorded by Johnson (1936) stated that "infestations of oat crops which occur, even after the absence of the crop for more than six years, are in all probability attributable to weeds rather than to infested seed". The present writer failed to obtain living eelworms from oat seed from infested crops in Yorkshire. This paper summarizes the results of field observations and experiments accumulated mainly during the past three years.     

THE SUSCEPTIBILITY OF POTATO VARIETIES TO INFESTATION BY THE EELWORMS DITYLENCHUS DESTRUCTOR AND D. DIPSACI

Twenty-five varieties of potato in common commercial cultivation were found to be susceptible to tuber attack by potato-derived populations of Ditylenchus destructor under field and pot experimental conditions. Stunting and leaf deformation may also be caused by the eelworms but appear less consistently. A race of D. destructor from mushroom spawn had almost no effect on potatoes. Various races of D. dipsaci can reproduce in the shoot tissue of potato, sometimes causing damage. One population of this stem eelworm produced lesions on the tubers.     

INVESTIGATIONS ON RESISTANCE TO DISEASE AMONG SPECIES OF THE GENUS AVENA

Fifty-three samples representing species of the genus Arena were tested for resistance to infection by Ustilago avenae and U. kolleri following artificial inoculation. Among the diploid and tetraploid species tested, eleven out of thirty-seven samples of Arena strigosa subsp. strigosa showed complete resistance to all the cultures with which they were inoculated. Avena strigosa subsp. barbata (three samples), and Avena strigosa subsp. abyssinica (one sample), also proved to be resistant to all the available races.
Variation in morphological and physiological characteristics within species and samples (varieties?) of the lower chromosome groups of Avena were observed and its consequences in breeding and race identification discussed.
Race identification was carried out on the eight Ustilago cultures and the existence of at least six races established. The tester varieties used in the present study proved inadequate for the complete separation of the smut races.     

THE POTATO TUBER NEMATODE, DITYLENCHUS DESTRUCTOR THORNE, 1945; THE CAUSE OF EELWORM DISEASE IN BULBOUS IRIS

For about twenty-five years a fairly widespread disease of bulbous iris has been known, the cause of which has always been attributed to a biologic race of the stem eelworm Ditylenchus dipsaci (Kühn, 1857), Filipjev, 1936.
Thorne (1945) showed that the nematode causing rot in potato tubers is different from D. dipsaci and named it D. destructor. This nematode has since been reported from Mentha arvensis L. by Hurst (1948) and from Sonchus arvensis L. by Goodey & Goodey (1949).
Examination of nematodes from diseased iris bulbs showed them to possess rounded tail tips and six incisures on each lateral field; characters by which Ditylenchus destructor is distinguished from D. dipsaci.
Cross-inoculation experiments showed that the eelworm causing disease in potato tubers would invade and set up characteristic symptoms in iris bulbs and, in the opposite direction, the eelworm responsible for disease in iris bulbs would give rise to characteristic symptoms in potato tubers. Transfer was also effected from potato and iris to Mentha arvensis and from iris to Sonchus arvensis.
The history of the disease in bulbous iris is briefly reviewed and the biology of Ditylenchus destructor discussed and compared with that of D. dipsaci.
The conclusion that D. destructor is the nematode causing eelworm disease of bulbous iris has been reported earlier (Goodey, J. B. 1950).     

THE EFFECT OF REPEATED SPRAYING OF INSECTS ON THEIR RESISTANCE TO INSECTICIDES

The administration of carbon dioxide in sublethal concentrations or for sublethal periods of time gave rise to an increased resistance to its effect in a strain of Drosophila melanogaster susceptible to the toxic effects of this gas. The effect did not appear to be permanent.
The successive administration by spraying of sublethal concentrations of DDT and BHC did not increase the resistance of a strain of D. melunoguster to their effects, either in the insects sprayed or their progeny. Only when the dosages were such as to give a high death-rate did a significant increase of resistance of the progeny of the treated insects take place; the tendency was if anything to increase susceptibility, although the indications were not in favour of DDT acting as acumulative poison.
In a preliminan series of tests the topical application of D D T in sublethal doses to the adult insects resulted in a reduction in the amount or in the rate of egg laying.     

种子引发提高小麦抗渗透胁迫能力的效应

种子经渗透势－０．８ＭＰａ或－１．２ＭＰａＰＥＧ－６０００处理后,抗旱性不同小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．）“晋麦３３”和“８４Ｇ６”种子萌发率均有提高,种子电解质外渗率明显降低,种子萌发适应渗透胁迫能力提高,种子可溶蛋白质含量、ＰＡＬ和ＰＯＤ活性显著增加,“晋麦３３”种子ＣＡＴ活性增加,两品种幼苗ＰＡＬ、ＰＯＤ和ＣＡＴ活性也均有提高,但“８４Ｇ６”种子ＣＡＴ活性下降。     

老年获得性肺炎病原菌及耐药分析

目的：了解老年人获得性肺炎的病原菌及耐药趋势。方法：对本院1999年6月－2001年6月两年间老年性获得性肺炎患者的痰标本进行细菌学分离鉴定及耐药分析。结果：老年院内感染以G杆菌为主67．19％,其次是真菌22．08及G^ 球菌10．73％。G杆菌中以大肠埃希菌（29．12％）,非发酵菌（24．88％）和肺炎克雷伯菌（20．19％）为主,在大肠埃希菌和肺炎克雷伯菌中,产超广谱β－内酰酶株（ESBLS）占49．52％,真菌中以白色假丝酵母菌（68．57％）为主;G^ 球菌中以凝固酶阴性葡萄球菌为主（87．88％）,耐苯唑西林凝固酶阴性葡萄球菌（MRSCN）占63．64％。2000年6月－2001年6月所分离的细菌与上一年相比,真菌由15．43％增加到29．03％（P＜0．01）,G^＋细菌由6．17％增加到15．48％（P＜0．01）,G杆菌由78．4％下降到55．48％（P＜0．01）。所分离细菌除对亚胺培南,特治星（哌位西林／他唑巴坦）及万古霉素耐药率较低外,常用的抗生素显示较高的耐药率。结论：老年性获得性肺炎以G^- 杆菌为主,而真菌的感染也不容忽视;致病菌呈多重耐药趋势,其感染菌谱的变迁和多重耐药率的升高应该引起高度重视,合理应用抗生素应有法规制度。