VIRUS MIGHT BE CAUSE

Press, Volume CVI, Issue 31113, 16 July 1966, Page 9

VIRUS MIGHT BE CAUSE

TN these pages last week, reference was made to suspected nitrate poisoning in a herd of 150 dairy cattle grazing on oats in the ClarkvilleOhoka area. Dr. R. M. Allison, officer-in-charge of the Lincoln sub-station of the Plant Chemistry Division of the Department of Scientific and Industrial Research, has suggested this week that barley yellow dwarf virus might be responsible for high nitrate levels in the feed. An officer of the Plant Diseases Division of the Department of Scientific and Industrial Research who looked at a sample of the oats from the property said that they were infected with the virus. Dr. Allison said that in a glasshouse trial at Lincoln with Clintland 60 oats it had been shown that where plants were infected with the virus nitrate levels, as expressed in the form of potassium nitrate, became progressively higher as nutritional levels dropped and at very low nitrogen and phosphate levels the nitrate level was double that for healthy plants. This was a

level that might be considered toxic to livestock. Dr. Allison also referred to Australian work on the accumulation of nitrate in oats infected with barley yellow dwarf virus. This had also shown that the nitrate level of virus-infected plants was significantly higher than that of healthy plants and within the range considered to be toxic to ruminants. This was again the result of glasshouse investigations. It seemed, he said, that in oats the virus acted as a scavenger, upsetting the whole nitrogen metabolism of the plant. It was likely that it so affected the normal protein metabolism of the plant that nitrate instead of being used for protein synthesis accumulated in large amounts. In its effect on protein synthesis it might affect the synthesis of a group of enzymes which were responsible for converting nitrate into nitrite and then into ammonia, a form in which the plant was able to utilise it. In addition to this, he said, under low light intensities, as experienced at this time of the year, nitrate also tended to accumulate.