ON FORMS OF THE HOP (HUMULUS LUPULUS L.) RESISTANT TO MILDEW (SPHAEROTHECA HUMULI (DC.) BURR.); III.

SUMMARY.
1. Certain seedlings of the wild hop when grown in the greenhouse are persistently immune to the attacks of the mildew Sphaerotheca Humuli. This immunity has been shown by the same individual seedling for three consecutive years. Under the same cultural conditions other seedlings of the same parentage prove to be very susceptible.
2. Certain seedlings (Group 2) which are immune when grown in the greenhouse are also immune when grown in the open. These seedlings have retained this immunity after four years' residence in a hop-garden under normal conditions of cultivation and manuring.
3. Certain seedlings (Group 3) which are immune when grown in the greenhouse are susceptible when grown in the hop-garden; in some cases the susceptibility shown is of the highest grade.
4. "Cuts" taken from the seedlings of Group 3 in the same year in which the seedling proved to be susceptible in the hop-garden are immune in the greenhouse under cultural conditions in which "cuts" taken from other susceptible seedlings in the hop-garden are very susceptible.
5. Certain seedlings (Group 4) are semi-immune to the attacks of the mildew.
6. One seedling (of American ancestry) grown in the greenhouse was immune throughout the season in 1916 and very susceptible in 1917.     

DEVELOPMENT OF POWDERY MILDEW (ERYSIPHE POLYGONI) ON SUSCEPTIBLE AND RESISTANT RACES OF OENOTHERA BIENNIS

Races of Oenothera biennis (evening primrose) resistant and susceptible to Erysiphe polygoni (a powdery mildew fungus) were artificially inoculated with E. polygoni and the time course and mode of disease development recorded. This study was the initial stage in investigating the host's resistance mechanism(s). On leaves of susceptible and resistant races, spores germinated within 5 hr, appressoria were formed in 8-12 hr, and penetration had been effected and haustoria initiated by 20 hr. There was no further development on resistant plants. On susceptible hosts, secondary penetration occurred by 26 hr after inoculation, secondary haustoria were formed, and sporulating colonies were seen in 4 days. It was concluded that the fungus is unable to establish a feeding relationship with the epidermal cells of resistant Oe. biennis, marking the period between 20 and 26 hr after inoculation as the time frame for the manifestation of the resistance mechanism(s).     

A STUDY OF THE EFFECT OF MILDEW INFECTION ON THE REACTION OF WHEAT VARIETIES TO BROWN RUST

The effect of the presence of Erysiphe graminis tritici on the reactions of each of five wheats, Malakoff, Democrat, Mediterranean, Hussar and Webster, to Puccinia triticina was studied. Under normal environmental conditions, mildew increased the susceptibility to rust of Malakoff and Democrat, though not, except in isolated instances, that of Mediterranean or Hussar. High light intensities enhanced the effect of mildew on the reaction of Democrat to P. triticina. The susceptibility of Webster to rust was unaffected or decreased by the presence of mildew.
In all varieties there was a decided tendency for rust and mildew to develop on different parts of the leaf, and when a leaf was heavily mildewed the development of P. triticina was sometimes almost entirely inhibited. The reason for this is obscure, since spores of P. triticina and E. g. tritici germinate well in each others presence, and cytological studies revealed several cases of the presence of both mildew and rust haustoria in a single living host cell. Anatomical investigations also showed that the effect of mildew on rust infection was confined to rust pustules within 1 mm. of mildew colonies.
The results obtained are in accordance with Gassner's theory that susceptibility to rust is due to the presence of certain specific proteins in the host leaf.     

葫芦茶化学成分的研究(Ⅰ)

从葫芦茶[Desmodium triquetrum(L.)DC.]中分离得到三个结晶性化合物,经化学及光谱分析鉴定为木栓酮(Ⅰ),表木栓醇(Ⅱ)、豆甾醇(Ⅲ)。上述三个成分在葫芦茶中均系首次分离得到。     

氨基寡糖素对黄瓜白粉病菌侵染的抑制作用*

用透射电子显微镜,研究了寡聚糖类药剂中科6号(2%氨基寡糖素)处理黄瓜Cucumis sativus 植株叶片后对白粉病菌Sphaerotheca fuliginea侵染的抑制作用。超微结构观察表明,病菌发育受到明显抑制,表现为白粉菌菌丝细胞质凝聚,细胞器解体和细胞组织崩解;吸器内的原生质电子致密度加深,吸器畸形,吸器壁增厚,细胞器解体,最终吸器坏死。     

THE EFFECT OF DATE OF SOWING ON THE INCIDENCE OF POWDERY MILDEW ON SPRING-SOWN CEREALS

Delaying the date of sowing of spring-sown barley in 1953 and wheat in 1954 from February to April increased the incidence of powdery mildew, Erysiphe graminis DC., from May onwards. Before then, conditions did not favour the rapid spread of mildew.
From mid-June, infected barley produced necrotic lesions. These developed sooner on the early- than on the late-sown crops, and on the lower than upper leaves. Perithecia were first seen on 29 June. They were abundant on the wheat by 20 July.
Mildew reduced the yield of barley sown on 30 March and 28 April 1955 by 8 cwt./acre. The percentage loss was greater in the late- than in the early-sown crops. The number of ears per metre of row, the weight of 100 ears and the 1000-grain weights were reduced. Altering the seed rate from 1 ½ to 2½ bushels/acre did not affect the incidence, or the effect, of mildew on grain yield.     

东北地区菊属植物叶表面结构的研究

本文利用光镜和扫描电镜研究了中国东北菊尼（Ｄｅｎｄｒａｎｔｈｅｍａ）９种和变种（野菊;葫芦岛野菊;楔叶菊;小红菊;甘菊;甘菊甘野菊;紫花野菊;细叶菊和小山菊）的叶表面特征。这些类群在表皮细胞,气孔复体和毛状体方面等存在着一些差异。依据这些特征讨论了一些类群的关系并尝试性地依据这些特征编制了这些类群检索表。     

棉铃虫AChE不同分子型对抑制剂的敏感度及其与抗药性的关系(英文)

在分离到的棉铃虫AChE五种不同的分子型中 ,2 .1s和 8.7sAChE抗性品系对毒扁豆碱的敏感度明显低于敏感品系 ,成虫头部I50 值分别相差 1 86.3和 84.8倍 ,幼虫I50 值分别相差 1 0 1 0 倍和 1 0 5 倍。幼虫 5.3sAChE对毒扁豆碱的敏感度抗性品系和敏感品系相差达 1 2 3倍 ,而成虫则没有差异。研究结果表明 2 .1s、5.3s和 8.7sAChE敏感度降低可能是造成棉铃虫对有机磷和氨基甲酸酯类杀虫药剂产生抗性的主要原因