寄主植物和接种物对丛枝菌根菌接种势的影响(英文)

在盆栽条件下研究了丛枝菌根菌(arbuscular mycorrhizal fungi,AMF)单孢、多孢和菌根根段接种物及其寄主植物烟草(Nicotiana tabacum L.)、苏丹草(Sorghum sudanense(Piper)Stapf)和三叶草(Trifoliumrepens L.)对AMF Glomus macrocarpum Tul ＆ Tul、Glomus mosseae(Nicol ＆ Gerd.)Gerdemann ＆ Trappe、Glomusversiforme(Karsten)Berch和Sclerocystis sinuosa Gerdemann ＆ Bakhi发育和接种势值(value of inoculum poten-tial,VIP)的影响。用50个孢子或0.5g菌根根段接种物处理的感染迟缓期为28d,大大短于单孢接种处理(64d);前者的VIP和根系感染百分率(percentage of root colonization,PRC)均高于后者。50个孢子和0.5g菌根根段接种物两处理之间仅在感染的早期阶段存在差异。0.5g菌根根段接种物(烟草上G.versiforme菌除外)接种处理的VIP大于其他两种接种物的处理;而50个孢子或0.5g菌根根段接种物处理的PRC直至接种后70d仍高于单孢接种处理。三叶草上AMF的VIP显著大于其他两种寄主植物上的VIP。G.mosseae、G.versiforme和S.sinuosa的VIP则大于G.macrocarpum的处理。这表明不同AMF菌种能产生不同接种势值的接种物。烟草则是用于单孢接种和接种物生产的良好寄主植物。     

宿主植物栽培密度对AM真菌生长发育的影响

温室盆栽条件下宿主植物高粱(SorghumvulgarePers.)的栽培密度对丛枝菌根(Arbuscularmycorrhizae,AM)真菌Glomusmosseae(Nicol.&Gerd.)Gerdemann&Trappe生长发育的影响试验结果表明:60株/盆密度处理的根外菌丝量及孢子数均高于其它处理。在一定栽培密度下(20~60株/盆),植株根系可溶性糖浓度与根外菌丝量呈显著负相关,与菌根侵染率呈显著正相关。植株根中磷浓度与根外菌丝量、根外菌丝量与孢子数均呈显著正相关。植株根中磷浓度与菌根侵染率呈显著负相关。结果说明:适当密植虽对植株生长有一定影响,但却促进了真菌的生长,此时菌根共生体有可能由互惠共生开始向偏利共生或弱寄生转化。密植作为一种调控手段,在菌剂生产中能获得较大数量的侵染根段、菌丝及孢子等繁殖体。     

BACTERIAL CANKER OF STONE-FRUITS: IV. INVESTIGATION OF A METHOD FOR MEASURING THE INOCULUM POTENTIAL OF CHERRY TREES

Pseudomonas mors-prunorum Wormald, the organism causing bacterial canker of stone-fruits, was present on healthy cherry leaves during the autumn in numbers sufficient to suggest that they were the main source of inoculum for the infection of stems and branches. Quantitative estimates of the pathogen could be obtained by shaking leaves in water and plating out the washings. This method was examined in detail as a possible means of comparing the inoculum potentials on different cherry varieties.
The numbers of the pathogen varied considerably between leaves and between branches, but not between trees of the same variety. It was estimated that a sample of 192 leaves, eight from each of twenty-four different branches would be adequate to show differences between varieties if sufficiently replicated in time. The accuracy of a twenty-four branch sample was tested by comparing parallel samples from two separate groups of trees of the same variety. There was a highly significant correlation between the numbers of bacteria obtained from the two series of samples. From the error variance in an analysis of variance, it was calculated that five successive samples would show a significant difference between two such groups of trees if one exceeded the other by 54%.
It was necessary to wash leaves for 4 hr. or more, depending on temperature, to recover all the bacteria from the leaf surfaces. At temperatures lower than 27° C. however, bacterial growth intervened before this stage was reached. At laboratory temperatures a period of 4 hr. washing was found to be most suitable for comparing varieties and gave 80–90% recovery of bacteria without errors due to growth.
A characteristic flora of non-parasitic bacteria was observed on cherry trees, coexisting with the pathogen on the leaf surfaces. The fungus Pullaria pullulans was also extremely abundant.     

THE ROLE OF UNICELLS IN THE POLYMORPHIC SCENEDESMUS ARMATUS (CHLOROPHYCEAE)1

The UTEX 2193 strain of Scenedesmus armatus (Chod.) Chod, when cultured in any of several media (whether natural or artificial, concentrated or dilute) produced a variety of colonial morphologies as well as a unicell population. Morphological expression was related to culture ape. When the initial cell density was just a feu1 hundred cells per mL. the culture first produced a unicell population, then spiny colonies, and as stationary phase was approached, spine-less colonies. Two classes of spiny colonies were detected. Type I colonies had elongate cells with the terminal cells shorter than median cells. Spines were longer than cell length. The wider, oval, grainy cells of Type II colonies were uniform m length. Spines were shorter and thicker than those on Type I colonies. Only Type I colonies produced unicells: the latter appeared as two morphs. The smaller unicell was obovoid with four delicate spines: the larger had ovate cells bearing four thicker spines. Control of unicell development in all media was achieved by carefully monitoring colony type and cell number used for the inoculum. A unicellular population developed in batch culture in defined media, both concentrated and dilute, when the initial cell density (either Type I or Type II colonies) was low (below 1000 cells-mL^?1), as well as in synchronous cultures. With higher initial cell densities, e.g. 2 × 10⁴ cells·mL^?1, the inoculum had to contain Type I colonies to produce unicells. Unicells were also produced in water from Agronomy Pond, where the strain originated. We discuss the role of unicell populations in the distribution of Scenedesmus.     

THE ROLE OF ENDOMYCORRHIZAE IN REVEGETATION PRACTICES IN THE SEMI-ARID WEST. III. VERTICAL DISTRIBUTION OF VESICULAR-ARBUSCULAR (VA) MYCORRHIZA INOCULUM POTENTIAL

The changes in vesicular-arbuscular (VA) mycorrhiza inoculum potential (MIP) in soil profiles from a mid-elevation sage community were measured using a corn bioassay. The MIP was significantly reduced below 30 cm depth and approached zero at less than 1 m depth. The decrease in inoculum potential with depth in diluted soils did not always parallel changes in the nondiluted soil, indicating factors other than numbers of inoculum units also may be important in determining the extent of mycorrhiza formation. The relationship of these results to land disturbance and associated dilution of populations of VA mycorrhizal fungi and to defining topsoil is discussed.     

营养液强度对AM真菌生长发育的影响

研究了在贫营养基质中不同强度Hoagland营养液对丛枝菌根(Arbuscularmycorrhizae,M)真菌Glomus versiforme生长发育的影响.结果表明本试验条件下,菌根侵染率、菌丝量、孢子数间呈显著正相关.在施加5%～50%强度Hoagland营养液时,菌根真菌的生长与宿主植物高粱根中磷浓度、可溶性糖浓度密切相关,而与氮浓度无显著相关.由此认为在盆栽生产菌根菌剂时,基质中存在一个临界磷浓度,在这个临界浓度之下,菌根真菌的生长发育随磷浓度的提高而增长,超过该临界浓度则会随磷浓度的提高而下降.施用20%、50%强度Hoagland营养液对菌根真菌生长最为有利,其菌根侵染率、菌丝量、孢子数均高于其它处理,因此认为宿主植物-菌根真菌之间共生关系的基础是营养条件,基质中养分的高低会影响互惠共生关系的建立和发展.在高质量菌剂生产中,菌根共生体双方的生长发育完全可以由人工控制.施加营养液是一种有效的调控手段,有可能使共生平衡向有利于菌根真菌生长发育的方向倾斜,使真菌得到最大程度的生长.     

营养液强度对AM真菌生长发育的影响*

研究了在贫营养基质中不同强度Hoagland营养液对丛枝菌根(Arbuscular mycorrhizae, M)真菌Glomus versiforme生长发育的影响。结果表明:本试验条件下,菌根侵染率、菌丝量、孢子数间呈显著正相关。在施加5%~50%强度Hoagland营养液时, 菌根真菌的生长与宿主植物高粱根中磷浓度、可溶性糖浓度密切相关,而与氮浓度无显著相关。由此认为:在盆栽生产菌根菌剂时,基质中存在一个临界磷浓度,在这个临界浓度之下,菌根真菌的生长发育随磷浓度的提高而增长,超过该临界浓度则会随磷浓度的提高而下降。施用20%、50%强度Hoagland营养液对菌根真菌生长最为有利,其菌根侵染率、菌丝量、孢子数均高于其它处理,因此认为:宿主植物—菌根真菌之间共生关系的基础是营养条件,基质中养分的高低会影响互惠共生关系的建立和发展。在高质量菌剂生产中, 菌根共生体双方的生长发育完全可以由人工控制。施加营养液是一种有效的调控手段,有可能使共生平衡向有利于菌根真菌生长发育的方向倾斜,使真菌得到最大程度的生长。     

愈伤组织继代接种量、继代周期和年龄对软紫草原生质体脱壁的影响

本文的实验结果表明：软紫草愈伤组织脱壁所需的适宜酶浓度为：０．１％果胶酶十０．２５％纤维素酶;酶解处理的适宜时间与愈伤组织年龄有关：愈伤组织的适宜年龄随其继代周期、愈伤组织继代接种量而有变化。当接种量,１克／瓶,转代后７天进行原生质体分离：接种量３克／瓶,酶解材料则以培养５天愈伤组织为宜。继代周期１３天和１５天的比１５天和１５天的,适宜脱壁的愈伤组织当代培养天数要提前１天。     

BACTERIAL CANKER OF STONE-FRUITS III. INOCULUM CONCENTRATION AND TIME OF INOCULATION IN RELATION TO LEAF-SCAR INFECTION OF CHERRY

Leaf scars on the fruiting spurs of the cherry varieties Roundel (high resistance) and Napoleon (low resistance) were inoculated with Pseudomonas mors-prunorum on four separate occasions in the autumn, using, on each occasion, the same range of five different inoculum concentrations. The results, recorded the following year, showed that the percentage diseased spurs (disease incidence) and the severity of the disease symptoms (disease severity) both increased with inoculum concentration.
The median threshold concentration of inoculum (T. C. 50), defined as the concentration necessary to give 50% diseased spurs, varied with time of inoculation, but on all occasions was considerably higher for Roundel than for Napoleon.
In another experiment the leaf scars at the nodes of the current year's growth, inoculated at weekly intervals throughout the autumn, were found to be susceptible from the beginning of September to the latter part of October. During this period disease incidence varied considerably with time of inoculation. There was evidence that this variation was related to two factors which influenced the numbers of bacteria penetrating into leaf scars, namely, (1) the rate of evaporation of the infection drop, and (2) the rate of suction of inoculum into the vessels of the leaf traces.
The experiments provided evidence of a long infection period beginning early in the autumn. It is suggested, therefore, that the timing of bactericidal sprays in the autumn be advanced and that the present concept of 'protective' sprays in disease control be replaced by one based on the eradication of external sources of inoculum.