BLIGHT IN POTATOES

Press, Volume XCV, Issue 28268, 4 May 1957, Page 9

BLIGHT IN POTATOES

Experiments At Lincoln VIRUS CONTROL METHODS

For the first time at the Crop Research Division of the Department of Scientific and Industrial Research at Lincoln, a method has been developed to cure potato plants of several viruses.

Plants of Aucklander Short Top have been produce.d free of the viruses A, S and Y. They are still infected by virus X, but one stock of the potato which is being built up by the station is infected by only a very mild strain of the virus so that its effect on yield should be slight. Discussing this development this week Mr C. M. Driver, senior plant breeder at the Crop Research Division, said that they had been looking for a way of eliminating virus infection for some time. Thought had been given to methods of pasteurising infected cells by finding the temperature at which a virus was killed while the plant was able to live on. More 'recently a -new approach had been considered. Formerly, the virus had been regarded as being static, but now it was thought it went through processes of building-up and breaking-down. So, if the process of building-up was interrupted while the break-ing-down process was allowed to continue it was felt progress might be made in eliminating a virus. Heat Treatment Heat treatment had been successful. Tips of sprout about a quarter of an inch long were grown in nutrient agar in a testtube so that roots were formed. The plants were then transferred to an incubator where they were grown for three or four weeks at temperatures of between 95 and 100 degrees Fahrenheit. The tips were then again cut off the sprouts and again rooted in the nutrient agar. It was found in subsequent tests that some of these shoots were quite free from certain of the viruses. In conjunction with the Department of Agriculture, the division has sorted out a line of Aucklander Short Top free of virus Y and that stock is now being increased so that it will soon be available for distribution. It will, however, be a few years before stock of the variety free of the three viruses is available. The division is also continuing its work on the development of hybrids resistant to blight. Blight is not so serious a disease in Canterbury because when it is most prevalent the seasons tend to be wet and yields are heavier, but in Southland and the Manawatu it can cause serious losses. At first, the problem of blight was thought to be a simple one. On the one hand there was the fungus and, on the other, varieties of potatoes immune from the disease. New Races Imported blight-resistant varieties and hybrids at first retained their immunity but towards the end of their third season of growth, blight appeared on all but a few. A net* race of blight had arisen and subsequent experience has shown that as in Europe and America new blight races regularly arise from the common race to attack previously immune varieties. Under these circumstances, can any permanent progress be made in breeding for blight resistance? Mr Driver says: “I think we can progress, for although new blight races arise which attack our new hybrids, some hybrids are but lightly attacked. In areas where blight is not severe, the resistance is sufficient to carry them through the attack with little damage, while even in areas of severe infection, some reduction in spraying is possible. “At Lincoln, hybrids are being bred for immunity to as many specific races of blight as possible, and others for a general resistance to all races. With a final combination of the two systems of breeding into one hybrid, we hope to produce varieties which are virtually immune in all but the very worst blight areas.” In the course of this work, blight resistant material has been brought in from Holland, Scotland and the United States and the division has just received permission to import more material from Dr. J. S. Niederhauser, potato specialist on the Rockefeller Institute of Agricultural Science, Mexico City. Mexico is regarded as the home of blight resistant varieties.