小麦叶锈菌寄生生理的研究

感染叶锈菌(Puccinia triticina)的小麦病叶段經消毒后在无光条件下飼以充足养分能产生大量夏孢子堆;并在培养后40—50天仍能继續形成新鲜孢子堆,部分菌絲从叶段切面生出。經三苯基四唑化氯染色,质壁分离测定及切片鏡检观察証明寄主細胞在培养中存活的时限为10天左右。这些資料说明小麦锈菌具有一定腐生能力,作者对“绝对寄生性”的概念以及过敏反应的生物学基础作了評論。不同碳源中葡萄糖、果糖、蔗糖及甘油对叶段上孢子堆的形成都有极明显的促进作用;氮源以蛋白腖为佳,无机氮亦可代替。培养过程中夏孢子堆有时变黑而死亡,試驗証明这是由于酚类物质經多元酚酶作用而氧化,产生对菌具有更強毒性的醌类物质,最后形成黑色素。这一过程可以被还原性的抗坏血酸抑制。叶段上所产生夏孢子在合成培养基上能形成白色小菌落,对碳氮源的要求大体与叶段培养相同。飼标記葡萄糖(G_1~(14)及G_(1～6)~(14)标記)后测定証实锈菌及病組織葡萄糖酵解的HMP趋势較強,健組織则EMP趋势較強。病組織有机酸含G~(14)的量显著高于健組織;病健組織間叶綠素、醣及氨基酸中G~(14)的含量則无差异。抗、感病品种間醣的含量似无明显差异,酚的绝对含量与抗病性无相关,但抗病品种受病后酚类物质增加,感病品种則相反。感病組織中去氫酶活性及抗坏血酸含量則較抗病組織为高。对抗锈机制的理論也作了討論。

STUDIES ON THE PHYSIOLOGY OF RUST PARASITISM WITH SPECIAL REFERENCE TO PUCCINIA TRITICINA

Surface sterilized wheat leaf segments infected with rusts (chiefly P. triticina) were found to be capable of producing large amounts of uredospores in complete darkness when sufficient nutrients were furnished. Sporulation continued for 40-50 days in culture and finally some rust mycelia were found to extend from within the leaf segments on to surrounding media. It was proved through TTC staining, plasmolysis test and microscopic examination that host tissues remained alive only for about 10 days. These observations verified that wheat rusts were able to grow and sporulate on dead host tissues. A critical discussion on modern concept of obligate parasitism as well as the biological basis of hypersensitive reaction was presented. Among different carbon sources, glucose, sucrose, fructose, and glycerin markedly enhanced sporulation on leaf segments so cultured; peptone was proved to be the best nitrogen source although inorganic nitrogen could also be utilized. Some leaf segments produced black uredo pustules with dead spores. This was proved to be due to the fact that phenolic compounds were oxidized through the action of polyphenoloxidase and more toxic quinone compounds were accumulated, and finally black pigments were produced. The oxidation of phenolic compounds could be inhibited by the addition of ascorbic acid to the media, and blackening of spores was successfully checked. Uredospores produced on leaf segments were transfered aseptically to different synthetic media and on some of them limited white colonies developed. The nutrient requirements for growth were essentially the same as those for leaf segment cultures. In respiration experiments with labeled glucose, a strong HMP tendency was observed in germinating uredospores as well as diseased tissues while healthy tissues exhibited a rather strong EMP tendency. More C¹⁴ was recovered in organic acid moiety of diseased tissues. No appreciable differences of C¹⁴ recoverage between healthy and diseased tissues in chlorophyll, sugar and amino acid moieties were found. It appears that there were no correlations between sugar or phenol contents and rust resistance among different wheat varieties. However, phenol contents of resistant varieties were invariably higher in the inoculated plants than in the controls, while a reversed situation was observed in susceptible varieties. Susceptible tissues contained more ascorbic acid with higher dehydrogenase activity than resistant, tissues. These facts were discussed on the basis of current hypothesis of rust resistance.