Infected Aphids Research Articles

Infectivity of aphids after several hours on tobacco infected with potato virus Y.

WATSON showed that fasted Myzus persicœ (Sulz.) were more than 60 per cent infective after 5 min. on tobacco infected with potato virus Y, but after 4 hr. on infected plants only about 10 per cent of the aphids were infective1. During investigations on the aphid transmission of potato virus Y, it was observed that, after several hours on tobacco, some aphids appeared to be feeding, others were just commencing to insert their stylets, and still others were wandering about the plant. The present communication reports which aphids transmit potato virus Y after a group has spent several hours on an infected plant.

Studies on the dwarf disease of milk vetch (Astragalus sinicus).

The present paper deals with the results of experiments on a dwarf disease of milk vetch (Astragalus sinicus L). The results obtained are summarized below:-I An infested plant discolors yellowish green to dull yellow and stunts as a whole and its leaflets become small and narrow. Margin of the leanet is often colored reddish purple. Later on, necrotic lesions develop often on Ieaflet, petiole and stem. Most of flower buds of the severe1y infested plant drop down before blossoming. Slightly infested Plants may bloom but the seeds do not ripe perfectly. In case of severely infested plants, the lower leaves dry up from the margin of leaflets and finally, the whole plant die prematurely.1. Causal agent of this disease was found to be a virus.2. 4 species of aphids i.e. Aphis laburni Kaltenbach, A. glycines Matsumnura, Macrosiphum Pelargoni Kaltenbach and Myzus persicae Sulzer were tested for transmissibility of the virus and only the first named species of aphid proved to be a vector.3. Aphis laburni became infective when it was fed on the diseased plant for 24 hours and the virulent aphid was able to transfer the virus to the healthy plant by feeding for more than 6 hours.4 The infective aphid was able to transfer the virus through its who1e life.5. The virus was not transferd to viviparous offsprings from the infective parent aphids.6. The writer failed to obtain successful transmission by mutilating with the diseased plant juice.7. The transmission of this virus through the seeds was not determined distinctly.8. This virus seems to be some what differerent from the red clover mosaic virus or common bean mosaic virus. With regard to its identification further investigation is needed.II this disease was found to be distributed in the prefectures, Yamagata, Fukushima, Niigata, Nagano and Ibaragi.

Aphid transmission of a mosaic virus and symptoms of other virus diseases ofPrimula obconica

Abstract does not appear. First page follows. Primula obconica is a popular, attractive, ornamental potting plant which has commonly been found to be infected with a mosaic disease in commercial greenhouses in San Francisco. The losses of infected seedling plants have ranged from 5 to 25 per cent. A study was undertaken on aphid transmission of the mosaic virus of Primula obconica. Tests were made both with species of aphids that breed on this host plant in the greenhouse, and with species that do not. Other aspects investigated include the efficiency in the transmission of the virus by single unfasted, infective aphids. A comparison was made of the transmission of the virus by lots of 20 unfasted, infective aphids with lots of 20 fasted aphids in short infection-feeding periods on a diseased plant. A comparison was made of the symptoms of P. obconica mosaic with those of common-cucumber, celery-calico, and western-cucumber-mosaic viruses. An attempt was made to experimentally infect P. obconica with the ordinary-tobacco-mosaic virus. Tests were made on the susceptibility of this species of Primula to the California-aster-yellows and spotted-wilt viruses. Review of Literature Tompkins and Middleton (1941)4 reviewed the literature on mosaic diseases of Primula species, and reported the experimental host range and properties of a mosaic virus of P. obconica. Since the publication of that paper, other references to virus diseases aifecting the genus have appeared in the literature. (Moore (1947)) lists a mosaic of Primula in his report on diseases of crops in England.

Transmission of radish-mosaic virus by aphids

does not appear. First page follows. Introduction A mosaic disease of the cultivated radish (Raphanus sativus) is common in the vegetable gardens of the San Francisco Bay districts. The disease also occurs on wild radish, which probably serves as a reservoir of the virus. (Tompkins (1939))4 reviewed the literature on mosaic diseases of Raphanus species. He also published the results of studies on host range and properties of the radish-mosaic virus. The virus was found to be readily transmitted by mechanical inoculation. Numerous unsuccessful attempts were made to transmit the virus by means of the cabbage aphid, Brevicoryne brassicae (L.), turnip or false cabbage aphid, Rhopalosiphum pseudobrassicae (Davis), and the green peach aphid, Myzus persicae (Sulzer). (Magistad (1938)) listed daikon (Raphanus sp.) mosaic in the Hawaiian Islands. (Parris (1940)) listed a mosaic on Raphanus sp. in Hawaii. (Dale (1948)) recorded the occurrence of a mosaic disease on three crucifers in Trinidad, British West Indies, one of which was an eastern variety of radish, known locally as moorei and which he suggested may be Raphanus sativus var. hortensis. He found by inoculation tests that the radish (R. sativus) varieties French Breakfast and Burpee’s Red Giant appear to be immune to the virus described in his paper. The virus was transmitted by Rhopalosiphum pseudobrassicae (Davis). The following is a report of a study undertaken on aphid transmission of the radish-mosaic virus described by (Tompkins (1939)). Tests were made with aphid species that breed on White Icicle radish under natural conditions and with species that have not been reared on this host plant. A comparison was made between transmission of the virus by unfasted infective aphids, and transmission by previously noninfective fasted aphids after short infection-feeding intervals. Other aspects investigated include a comparison of virus transmission, by lots of varying numbers of aphids, with mechanical inoculation; and the retention of the virus.

SOME EFFECTS OF HOST NUTRITION ON THE SUSCEPTIBILITY OF PLANTS TO INFECTION BY CERTAIN VIRUSES

Fertilizer treatments that greatly influenced the growth of tobacco and potato plants in pots had little effect on the number that became infected with potato virus Y when the plants were colonized by equal numbers of infective aphids, though the number was slightly decreased by nitrogen and increased by phosphorus.The number of local lesions produced on leaves of tobacco and Nicotiana glutinosa by tomato aucuba mosaic and tobacco mosaic viruses was increased by additions of both nitrogen and phosphorus, provided that these also increased growth. The predominant effect of both nutrients in increasing susceptibility was indirect by increasing plant size, but over certain critical ranges both elements also increased the numbers of lesions produced per unit leaf area. Conditions of maximum susceptibility approximated closely to those producing optimal growth, and susceptibility, whether measured by lesions per half‐leaf or per unit area, was decreased by a deficiency or excess of either element. Sometimes the addition of nitrogen reduced susceptibility when still increasing plant growth.

Aphid transmission of cauliflower-mosaic virus

does not appear. First page follows. Summary ELEVEN SPECIES OF APHIDS that do not multiply on cauliflower plants in nature were demonstrated to be vectors of the cauliflower-mosaic virus, five of them being more efficient vectors than three aphid species that do breed on cauliflower. Of three aphid species that breed on cauliflower under natural conditions, the cabbage aphid, Brevicoryne brassicae (Linnaeus), was a more efficient vector of the virus (in single-insect tests) than the turnip or false cabbage aphid, Rhopalosiphum pseudobrassicae (Davis), and the green peach aphid, Myzus persicae (Sulzer). Natural infectivity of the cabbage aphid was demonstrated. None of twenty-one varieties of cauliflower experimentally infected with the virus by the cabbage and green peach aphids was resistant to the disease. Mechanical inoculation was more efficient than transmission by the cabbage, turnip, or green peach aphid. In tests with hourly transfers, most transmissions occurred within 2 hours after the aphids had fed on a mosaic-infected plant. Aphids acquired the virus in 15 to 25 minutes on a diseased plant (5 to 10 minutes actual feeding time) and transmitted it in feeding periods as short as 5 or 10 minutes. In tests with short feeding periods, most of the transmissions occurred during the first 10 minutes after transfer from the infected plant, but an occasional aphid transmitted the disease during the second or third 10-minute period. The cabbage and green peach aphids recovered the virus from inoculated cauliflower plants many days before the first symptom appeared. Mechanical inoculation of healthy cauliflower seedlings and annual stock plants with the centrifuged virus extract from crushed, infective cabbage aphids produced 18 per cent infection.

EVIDENCE AGAINST THE HYPOTHESIS THAT CERTAIN PLANT VIRUSES ARE TRANSMITTED MECHANICALLY BY APHIDES

In further experiments on the mode of transmission of persistent and non-persistent plant viruses by insects [R.A.M., xix, p. 230], starved individuals of Myzus persicae after feeding for two minutes on infected plants successfully transmitted Hyoscyamus 3, potato Y, and severe etch viruses, all non-persistent in the vector, from tobacco to a number (up to 10) of successive healthy plants. With all three viruses aphids often failed to infect some healthy plants in the middle of a series, but infected later plants. When infective aphids were fed on two successive healthy plants the number of second plants infected decreased with increasing feeding time on the first healthy plant, none being infected after one hour. Infective aphids allowed short feeding periods on a succession of healthy plants gave infections in a series of nine consecutive healthy plants, while others fed continuously on one healthy plant for a corresponding total period failed to infect any of the second plants. These results are held to contradict the opinion that the non-persistent viruses are transferred mechanically through the cleansing of contaminated stylets of the infective aphids when feeding on a healthy plant. The hypothesis is advanced that the mechanism of transmission is not fundamentally different between the persistent and non-persistent viruses, but while the latter are inactivated by a secretion produced by the aphids during feeding, the former are resistant to it. A close specific relationship between the non-persistent viruses and insects with a particular type of physiology is postulated.