VIEW ARTICLE

Sucrose in Virus Transmission. C. E. Yarwood, Department of Plant Pathology, University of California, Berkeley 94720; Phytopathology 61:1173-1176. Accepted for publication 4 May 1971. DOI: 10.1094/Phyto-61-1173.

Under most routine conditions tested, addition of sucrose to virus inoculum caused only slight or no increase in the mechanical transmission of the viruses of cucumber mosaic (CMV), citrange stunt (CSV), tomato spotted wilt (TSWV), tomato ringspot (TRSV), tobacco ringspot (ToRSV), tobacco mosaic (TMV), tobacco necrosis (TNV), and potato X (PXV), but caused significant increase in the transmission of all these viruses under certain conditions. The greatest increase (average, 55-fold; maximum, 467-fold) in virus transmission due to 5% sucrose (sucrose effect) was in the transmission of CMV from the inner leaves of old, systemically infected sugarbeets when 16% magnesium silicate was added to the inoculum after grinding, and when the young, inoculated cowpea leaves were dried slowly. The presence of Mg₂Si₃O₈ · 5H₂O or caffeine, absence of K₂HPO₄, use of cowpea as an indicator host, and slow drying were the most important variables for inducing a high sucrose effect. Other variables which increased the sucrose effect were: use of upper versus lower leaves of systemically infected cucumber or tobacco as inoculum; use of up to 20% Celite in the inoculum; aging of the inoculum suspension for 10 min to 1 hr; heating the indicator leaves 5-15 sec at 50 C before inoculation; and making inoculations in early morning during the winter months. The addition of sucrose or dextrose increased the longevity of TMV, TSWV, and CMV in liquid suspensions or as drying deposits on leaves.