THE CONTROL OF POTATO VIRUS DISEASES BY INSECTICIDES

Replicated trials were carried out in the years 1950, 1951, 1953 and 1954 to see if the spread of leaf-roll virus and virus Y in potato crops could be reduced by applying insecticides. The crops were disease-free, except for small numbers of deliberately introduced infected plants, and were sprayed at intervals of 10 or 14 days, according to the stage of growth of the plants, with a tractor-mounted spraying machine at 1OO gal./acre/application. Disease spread was estimated by growing tubers taken from the five plants on either side of each infector. DDT emulsion, DDT suspension, endrin, schradan, mipafox, malathion, parathion and Systox prevented the spread of leaf-roll virus and decreased the spread of virus Y, although DDT emulsion was the only insecticide used in all the trials. Dieldrin and toxaphene were ineffective. When virus control was successful, aphid control (estimated by counting apterae in the crops) was good.     

THE USE OF SOIL INSECTICIDES TO CONTROL POTATO APHIDS AND VIRUS DISEASES

A replicated trial was done to find whether the insecticides Thimet and Rogor applied in the soil affected the spread of aphid-transmitted viruses from infected to healthy plants with potato crops. The insecticides were applied at planting as activated carbon formulations at rates equal in cost to three sprays with DDT emulsion at 2 lb. DDT per acre. The infected plants were removed (rogued) in late June.
Thimet applied along the furrows with the fertilizer, and Rogor applied in individual doses beneath each tuber, kept the plants free from aphids from a week after the plants emerged until early August. Thimet in individual doses was less effective but greatly decreased the aphid infestation. All treatments prevented or greatly decreased the spread of leaf-roll virus, but they only slightly decreased the spread of virus Y. No treatment damaged the plants or depressed yields significantly.
Tubers harvested from the plots treated with insecticides contained only very small quantities of the insecticides, but shoots from them, when infested with adult Myzus persicae (Sulz.), carried fewer aphids a week after infestation than did shoots from control tubers. Shoots of tubers from treated plots also grew more slowly than those from the controls.
The aphicidal efficiency of Thimet applied as individual doses separated from the tubers by distances of up to 6 in., decreased as the distance increased, but the effect of distance became less as time passed.
Reasons for the differences in the behaviour of the insecticides are discussed, and the possibilities that the method offers to control virus diseases. The application of insecticides to soil promises to be a useful way of controlling the spread of viruses, provided the harvested crop is free from toxic residues.     

THE INFLUENCE OF PLANTING DATE AND MANURING ON THE INCIDENCE OF VIRUS DISEASES IN POTATO CROPS

Field experiments with Majestic potatoes were made over six years at Rothamsted to test the effects of varying date of planting and manuring on the yield of tubers and the incidence of the aphid-transmitted leaf roll and Y (rugose mosaic) viruses. Yield was increased by early planting, and by all the manures, especially dung. Early planting also usually increased the incidence of virus disease. Different manures had different effects on disease incidence; the average results from all comparisons showed the largest increase in incidence of both viruses from the use of dung; sulphate of ammonia increased the incidence of leaf roll, and muriate of potash that of rugose mosaic. Counts in two years showed that aphid populations were highest on the earlier planted potatoes, and were increased by dung, sulphate of ammonia and superphosphate, but were reduced by muriate of potash.     

马铃薯Y病毒外壳蛋白基因在转基因马铃薯中的表达

ＰＶＹ是马铃薯Ｙ病毒组的典型成员,主要感染马铃薯、番茄、辣椒和烟草等。近年来,利用植物基因工程手段获得了不少抗病毒转基因工程植物,为培育抗病毒作物新品种提供了新途径［１］。病毒外壳蛋白基因导入并使之在植物中表达可获得抗相应病毒的转基因植物,已在烟草、番茄、马铃薯、苜蓿、黄瓜和番木瓜等植物中获得成功［１～３］。本室已成功地对在我国流行的ＰＶＹＮ株系外壳蛋白基因进行了克隆及序列测定［４］,在此基础上,我们构建了植物表达中间载体,通过土壤农杆菌介导的叶盘法转化马铃薯,获得了大量转基因植株。分子检测证明…