Peach enation, a new virus disease of peach was discovered on the variety Shinsei. The infected trees showed many small enations on the undersurface of leaves as well as shortening of internodes. A mechanically transmissible virus was isolated from the diseased peach trees to Chenopodium quinoa. This virus was transmitted from C. quinoa to C. amaranticolor, C. album, Vinea rosea, Gomphrena globosa, Celosia cristata, Tetragonia expansa, Zinnia elegans, Raphanus sativus, Crotalaria spectabilis, Phaseolus angularis, Vigna sesquipedalis, Sesamum indicum, Torenia fournieri, Nicotiana glutinosa, N. megalosiphon, N. tabacum, Petunia hybrida and Physalis floridana. The virus could be retransmitted from C. quinoa to peach seedlings by inarch grafting, and the affected seedlings showed the same symptoms as those of the original diseased trees. The virus was spherical and approximately 33nm in diameter. In crude sap of infected C. quinoa, the thermal inactivation point was 50-60C, 10 minutes, dilution end point was 10-4-10-5 and longevity was 30-40 days. The virus was neither transmitted by Myzus persicae nor by Aphis gossypii and no evidence of soil borne was obtained. The titer of the antisera prepared from the infected C. quinoa was 1, 280. This antiserum did not react with arabis mosaic virus, cherry leaf roll virus and strawberry latent ringspot virus and also the antisera of raspberry ringspot virus, arabis mosaic virus and tomato black ring virus did not react with this virus. These results indicated that this virus is a new one not yet being reported. It was named peach enation virus.
To elucidate the microbial succession in plant tissue rotted by Phytophthora, the association of bacteria with the surface of the hyphae of Phytophthora capsici on agar medium was studied by the opposition culture method using 16 species of bacteria, including cucumber-B1, which was isolated from the cucumber rotted by P. capsici. Among the 3 agar media used, the bacterial association with P. capsici occurred rapidly at 28-32C and pH 6.6 on oatmeal agar medium, which was favorable for the pathogen. Of the bacteria tested, cucumber-B1 was associated markedly with the hyphae 24-48hrs after the opposition culture, as well as was Erwinia carotovora and other several motile bacteria. The associated bacteria, cucumber-B1, were always found on the surface of the hyphae except at the growing point (or apical area), and the association was better in high concentration agar medium (2%) than in lower (1.0-1.5%). The taxis of bacteria to the hyphae of P. capsici in the bacterial suspension was studied. The taxis of E. carotovora E. aroideae, and cucumber-B1 occurred remarkably on oatmeal agar medium; Sarcina lutea showed no taxis on agar medium. Bacterial taxis to the sterilized hyphae and glass fiber was not observed. From this result, it is suggested that the association of bacteria with P. capsici could be established not only by an attachment or adherence by chance but also by an interrelationship between the bacteria and P. capsici, that is, the attractive phenomena due to exduation from the hyphae of the pathogen.
Phytophthora capsici caused a soft rot of cucumber fruits and produced a number of pectic enzymes in the macerated tissues. Both cell-free extracts of macerated tissues and fungus culture fluids effectively macerated potato tuber and cucumber fruit sections at pH optima of 6.2 and 7.0, respectively. P. capsici produced two enzymes in culture which preferentially degraded pectic acid (pH optima of 5.0 and 6.2) and four which attacked pectin (pH optima of 3.5, 5.5, 6.5, and above 7.0). The activity for pectin above pH7 appeared due endo-pectin methyl-trans-eliminase (endo-PMTE) bassed on the thio-barbituric acid test. The culture filtrates also contained one exo-type activity for pectic acid with a pH optimum at 5.5, but almost no pectin methylesterase and cellulase (Cx) activities. The extracts from infected cucumber fruit, however, showed only one endo-pectolytic activity for pectic acid with a pH optimum at 6.2 and two endo-type activities for pectin with pH optima at 6.5 and above 7.0. The latter activity appeared due to endo-PMTE activity. The data show that P. capsici produces an endo-polygalacturonase and an endo-PMTE which could be responsible for soft rot development in rot development in cucumber fruit.
Young colonies of the barley powdery mildew fungus growing on barley leaves were rubbed off with water-drenched absorbent cotton and then the leaves were inoculated secondarily with the powdery mildew fungi collected from wheat and Agropyron ciliare Franch, var. minus Ohwi and 49 powdery mildew fungi from dicotyledons. The haustoria of the barley powdery mildew fungus, torn off from the hyphae and remaining in the barley epidermal cells, survive for many days. Out of the 51 fungi, 45 grew close to the colonies of the barley fungus on the barley leaves and 30 produced conidia, though the hyphal growth and conidial formation were different in their degree according to the fungi. The powdery mildew fungi from wheat, Agropyron, cucumber, Physalis alkekengi L. var. francheti Hort. form. bunyardii Makino, etc. grew nearly as well as on their respective proper host plants at least for the first several days after inoculation. Some dicotyledonous species, such as Plantago asiatica L., Lycium chinense Mill., Euonymus japonicus Thunb., etc., were also proved to be susceptible to some secondarily inoculated fungi. For example, the powdery mildew fungi from cucumber, buckwheat and barley produced conidia on Lycium, but neither the cucumber fungus nor barley fungus grew at all on buckwheat.
For the purpose of obtaining efficient and uniform inoculations in the screening test of anti-plant-viral substances, airbrush-inoculation technique was examined by using the combination of TMV and Nicotiana tabacum var. Xanthi. The optimum conditions were: 1) 4kg/cm2 gauge pressure of the air compressor, 2) 20cm distance of airbrush nozzle to leaf surface, 3) 0.5 seconds exposure period under airbrush of the inoculum, 4) 1% by weight of 400-500 mesh carborundum in the inoculum, and 5) 0.88μg TMV in 1ml of the inoculum. These conditions are also suitable for the inoculation of TMV to 4cm-tall seedlings of Lycopersicon esculentum. Aabomycin A, blasticidin S, bihoromycin and sodium arginate were tested for their anti-viral activities using this inoculation technique. Among these, the emulsion of aabomycin A was the most effective for the inhibition of symptom development. The efficiency of this inoculation technique is much higher than that of the rubbing method.
This paper reports the results of further investigations of the transmission and retention of inoculativity of potato leaf-roll virus (PLRV) in the green peach aphid, Myzus persicae (Sulz.). The frequency of virus transmission, the length of the latent period, and the retention period of inoculativity of the virus in the injected aphids were dependen ton the virus concentration of inocula. Virus recovery from viruliferous aphid extracts was influenced by the length of the acquisition feeding period of the aphids used as sources of inoculum. However, irrespective of the length of the acquisition feeding period, the virus concentration in the aphids tended gradually to decrease after leaving the source plant. The virus was recovered from the guts and blood, but not from the salivary glands of aphids given a 4-day acquisition feeding period on infected plants. Virus recovery from the aphid blood was also dependent on the length of the acquisition feeding period of aphids used as sources of inoculum. PLRV was detected in the blood of aphids up to 2 days after injection with a massive dose of the virus solution using aphid extracts as the inoculum. The results of virus recovery with the blood of the injected aphids were the same as for those following an acquisition feeding period. Attempts to maintain the virus inoculativity in serial passage using extracts or blood of viruliferous aphids were unsuccessful.
Studies on pectolytic enzymes secreted by Pseudomonas marginalis were conducted to elucidate a specific dissolution of pectic substances in infected host cell walls. Two isolates of pathogenic bacteria, N-6122 and N-6301, secreted pectic acid trans-eliminase (PATE), when grown on pectin-asparagine medium. Pectin esterase (PE) activity was extremely weak in culture filtrates. As for N-6301, the dialyzed filtrate also had a strong pectin trans-eliminase (PTE) activity, which reacts specifically to methylated pectin. In addition, weak polygalacturonase (PG) activity was found in this preparation. In the case of N-6122, these enzyme activities were not detected. From these results, it is concluded that polyuronide-chain spliting enzyme system in N-6122 obviously differs from N-6301. PATE and PTE showed maximum reaction velocity at pH8.3 in Sørensen borate buffer systems, when pectin was used as a substrate. PATE activity was remarkably accelerated by addition of 10-3M CaCl2, and completely inhibited by 10-4M EDTA, using sodium-polypectate as a substrate. PTE activity was not apparently affected by these chemical compounds. Dialyzed culture filtrate of N-6122, mainly containing PATE, showed typical action to degradate plant tissues. When maceration activity was measured by per cent loss in dry weight of radish, the preparation indicated an ability to decrease about 12% of sliced tissues, after incubation at 30C for 8 hours. The physical properties of tissuemacerating agent in dialyzed filtrate were similar to those of PATE. They responded in the same way to pH and temperature, viz, inactivation by lower or higher pH value and heating. From these reasons, it can be said that the tissue degradation in this preparation is, in part, attributable to an action of PATE, although the enzyme has not been purified to homogeneous state. In culture filtrates obtained from two saprophytic isolates of Ps. fluorescens, only a trace of trans-eliminase activity was detected. From these results, it is proposed that pathogenic pseudomonads are able to secrete pectolytic enzyme(s), causing degradation of plant tissues, but saprophytes have a little or no ability to produce them in this culture medium.
Rough colony type mutant was obtained from an isolate, S 6914-1 of Pseudomonas mori. The cells of the mutant grew as long filaments, being 200μm in length. No difference was observed in the mutant and the wild type on main physiological characteristics, pathogenicity, agglutination reaction and lysotype. The isolate, S 6914-1 differed from the other on properties, such as non-motility, non-flagellated, and chemical characteristics on hydrolyzation of arbutin.