Inactivation of cucumber mosaic virus in cultured tissues of <i>Nicotiana rustica</i> by diurnal alternating periods of high and low temperature

Abstract

SUMMARY Cucumber mosaic virus (CMV) was inactivated in infected tissue cultures of Nicotiana rustica after periods of alternating high (32–40 o C) and low (22 C C) temperature. An increase in the incubation period at high temperatures resulted in greater virus inactivation but more rapid deterioration of the tissue cultures. Optimal programmes for virus inactivation and culture survival were 40 o C (8 h) +22 o C (16 h) per day for 12 or 18 days, 40 o C (16 h) + 22 o C (8 h) per day for 12 days or 36 o C (20 h) + 22 o C (4 h) per day for 12 days. Diurnal treatment periods of variable length and different high temperatures were related by using a concept of hour‐degrees above a base temperature. Taking this base temperature as 25 o C a linear relation was found between the logarithm of virus infectivity and the number of hour degrees.