Barley yellow dwarf virus: Effects on carbohydrate metabolism in oat (Avena sativa) during cold hardening

Abstract

Barley yellow dwarf virus (BYDV) causes significant losses in yield and in overwintering ability of winter cereals. Mechanisms which the physiology of plants is affected the virus are not clear. To see how carbohydrates in the crown of winter cereals were affected BYDV, fructan isomers of degree of polymerization (DP) 3-5, fructan DP > 6 and the simple sugars, glucose, fructose and sucrose, were measured before and during cold hardening in three oat (Arena sativa L.) cultivars, 'Wintok', 'Coast Black' and 'Fulghum'. On a fresh weight basis fructan DP > 6 decreased 50% in infected 'Wintok' and 'Coast Black' and 25% in 'Fulghum'. Two DP3, one DP4 and one DP5 isomer were significantly higher than non-infected controls. The percentages of simple sugars in infected crowns were significantly higher than controls in all three cultivars in every week except the first week of hardening. Crude enzyme extracts from BYDV infected plants incubated with sucrose suggested higher invertase and lower sucrose-sucrosyl transferase activity. When incubated with 1-kestose and neokestin, no significant difference was found in fructose fructosyl transferase or in bydrolase activity. The activity of unidentified enzymes catalyzing the synthesis of larger (DP > 5) fructan was altered BYDV. The decrease of carbohydrates in the crown induced indirectly BYDV may alter the plant's capacity to regenerate tillers in the spring. The ability of plants to prevent or tolerate carbohydrate fluctuations induced BYDV infection may be an important genetically regulated characteristic for developing virus-resistant cultivars.