Optimal conditions for the use of cDNA probes to measure the concentration of barley yellow dwarf virus in barley (Hordeum vulgare).

Experiments which optimise the conditions for the measurement of the relative concentration of BYDV in barley (Hordeum vulgare) tissues using cDNA probes are described herein. These studies have shown that both the pH of the buffer and the ratio of buffer to tissue used to homogenise plant material greatly affects the amount of cDNA probe which hybridises to leaf extracts immobilised on nitrocellulose. These studies also showed that the measurement of this virus was greatly facilitated by using a dot-blot apparatus which allows samples contact with a piece of nitrocellulose 10 mm in diameter rather than a 3 mm (approx) diameter piece of nitrocellulose as is the case with most commercial dot-blot apparatuses. Further experiments using this technique showed that there was a large difference in the rate of replication of the PAV, BYDV serotype between BYDV-resistant and BYDV-susceptible cultivars of barley. These data suggest that a BYDV-resistant cultivar can easily be distinguished from a BYDV-susceptible one if the BYDV content of leaves is measured between 7 and 14 days after inoculation.