To elucidate the relation between the staining with dyes and the starch accumulation in the surrounding region of the spots in rice leaves infected by Cochliobolus miyabeanus, degree of staining in every region of diseased leaves was observed. Necrotic lesions are slightly stained with some dyes, but mesophyll tissues of veneneous regions were not stained with most of the dyes used. Surrounding region of diseased lesions were stained somewhat weaker with basic dyes than the healthy parts of diseased leaves in the early stage of spot enlargement (up to the second day after inoculation), but this difference disappeared in the later stage (after the third day). Acidic dyes stained this region normally in all stage of spot enlargement, and acid fuchsin was exceptional, not only in veneneous region but also in surrounding of it, as it stained the surrounding deeper than the healthy parts. From these facts, ion charge of the surrounding region is considered to be positive especially in the early stage of spot enlargement. At 24 hours after inoculation, the region with abnormally high starch accumulation (St), region stained with acid fuchsin (Af), region which was not stained with basic fuchsin or light green (bf or lg respectively) showed the relation Af>>St>bf=lg. It seems that in this stage, there is no close relation between areas of abnormal staining and abnormal starch distribution in diseased leaves.
It was found that TMV inactivated by UV-radiation ray interfered with TMV infection in several kinds of plants when active and inactivated viruses were simultaneously inoculated on these plants. The degree of interference differed with plant species inoculated. The maximum inhibition was induced in Datura stramonium, and the minimum in Nicotiana glutinosa plants. The inhibitory action of the UV-irradiated virus was slightly affected by adjusting the hydrogen-ion concentration of the mixture of active and inactivated viruses at pH 5.2 as it was compared with that at pH 7.0. The infectivity of virus in the mixture was recovered by dilution. Although the virus protein interfered with the establishment of TMV in tobacco plants, the UV-irradiated RNA had no inhibitory action. The juices extracted from the leaves of several Solanaceous plants inoculated with the inactivated TMV had no inhibitory effect against TMV infection when they were mixed with TMV and inoculated on test plants.
The juices extracted from several species of plants which are susceptible to TMV, inhibited TMV infection when TMV and the juice were simultaneously inoculated on test plants. Among them, the juice from Chenopodium album plants showed a remarkable inhibition of TMV infection in N. glutinosa, but not in the original plant. The infectivity of the virus in the mixture of TMV and juice was partially recovered by dilution with distilled water. The inhibitory agent contained in C. album plants was stable to heat at 60°C for 10 minutes, and to incubation in 90% ethanol, in acid solution above pH 3, and in alkaline solution below pH 10 for 2 days. However, the inhibitor was thermolabile at 80°C and 100°C for 10 minutes, nondialyzable, and rendered inactive by adsorption with activated carbon, by incubation in highly acid or alkaline solutions, and by dilution 10-4 of the juice with distilled water. The inhibitor was tentatively precipitated by 50% and 90% ethanol, and by 50% saturated ammonium sulfate, An acquired resistance to the virus infection was not found to be induced by a previous application of the inhibitor in the leaves of N. glutinosa or French bean plants when these leaves or the extracts were examined for the inhibition.
This study was conducted at Furusato Hop Research Laboratory, Nagano Prefecture, by using Variety Shinshuwase grown in the field of this Laboratory. Three types of symptoms which were reported by Ware (1926) and Salmon & Ware (1927), i.e., basal, terminal, and lateral spikes, appear after the shoots began to elongate in late April to early May. Anatomical studies on the distribution of mycelium in each type of spikes revealed that almost all basal spikes and Type A of lateral ones carried mycelia in pith, whereas most of terminal ones and Type B of lateral ones contained mycelia in cortex. In basal spikes, mycelia grew upward within the pith as the shoot elongated and then shifted to the cortex. Thus they produced sporangia on the surface of stem and, also on the lower surface of leaves. The sporangia caused secondary infection and resulted in the formation of terminal and lateral spikes. Sometimes the combination of primary and secondary infections become in the origin of terminal and secondary spikes. Leaf infection was caused by both sporangia formed on these spikes and oospores survived in the debris. The optimun temperature for the germination of sporangia and oospores lies between 18 and 21°C. Fresh sporangia germinated within an hour. The oospores produced in the preceding year retained the ability to germinate, and the low temperature during their survival favored their longevity. Sporangia were produced in 4 to 5 days after zoospores were inoculated on the lower surface of leaves. In cones, bracts and bracteoles were most easily infected, causing a conspicuous decrease of resin content. Straps and rootstocks were successfully infected with the inoculation in late September and caused a considerable percentage of basal spikes in the following spring. Autumn foliar spray of Bordeaux mixture for consecutive four years decreased the percentage of basal spikes year by year. The present author emphasized the importance of wintered mycelium in rootstocks as the source of primary infection and the necessity to prevent the late infection.
From a pathophysiological point of view, following characters possessed by the broad bean (Vicia faba L.) appeared to show interrelationship with the effects of spotting of the leaves: a. the numbers of leaves and blossoms of a plant vary individually within its life period, but its period of blooming is limited between middle of April and early May; b. the plant must overwinter during its early stages of growth to produce fruit; and c. in early spring, numerous branches grow from the base of the stem. These branches and stem are capable of bearing fruits. Differentiation of the first flower bud occurs at this time. Experiments were performed to produce artificial spots on the leaves of the broad bean plant by applying aqueous solution of KC103 at its various growth stages. Results obtained were as follows: 1. When the seedling of a broad bean plant was spotted at the time when the nutrients were being supplied from the endosperm, the yield of seed was greater than half of that of the untreated plant. When the nutrients from the endosperm became limited, the yield of seed was further reduced. When the nutrients of the endosperm were depleted and its carbohydrate assimilation was very faint, the yield of seed was markedly reduced. 2. When the broad bean plant was spotted immediately before overwintering, its growth was disturbed considerably, and resulted in no yield of seed. 3. When the bean plant was spotted during the winter, the damage was slight, and the yield was 80-105% of the unspotted control. 4. When the bean plant was spotted early in spring at the time of differentiation of the first flower bud, about 50% yield was obtained. 5. When the bean plant was spotted during April and May at the time of flowering, there was no yield of seed.
Since some years, an outbreak of brown rot has been noticed in fruit trees in northeastern Japan. Apothecia of this brown rot fungus were collected, probably for the first time in Japan, by Tetsuo Kudo in 1963 from mummified cherries in an orchard in Akita Prefecture. The fungus has the following morphological characteristics: sporodochia grey; conidia hyaline or light-colored, lemon-shaped or ellipsoidal, 10-20×6-12μ, with no disjunctors; microconidia hyaline, spherical, about 3μ in diameter; apothecia Pecan Brown (Ridgway), funnel-shaped, 5-15mm in diameter, with stipes of 15-50mm in length; asci cylindric-clavate, 130-210×7.5-12μ, 8-spored; ascospores hyaline or slightly colored, ovoid to elongate-ellipsoidal, unicellular with rounded ends, 9.5-18×6.8μ. When cherry fruits are inoculated with this fungus, there occur typical symptoms of brown rot, with abundant conidia. On potato dextrose agar media the fungus spreads rapidly, forming uniform colonies with abundant conidia. The conidia germinate readily in 0.1% dextrose solution, and hyphal anastomoses commonly occur beween developing hyphae. The grey sporodochia, large apothecia, and abundant conidial production distinguish this fungus from both Monilinia fructigena and M. laxa. On the other hand, these and other characteristics of this fungus agree with those of Monilinia fructicola (Winter) Honey, and so the authors have identified this fungus with M. fructicola. This same species has also been isolated from plums, apricots, peaches, and pears in this area.