Nj. Spence et al., THE EFFECT ON YIELD IN COURGETTE AND MARROW OF THE MILD STRAIN OF ZUCCHINI YELLOW MOSAIC-VIRUS USED FOR CROSS-PROTECTION, Annals of Applied Biology, 129(2), 1996, pp. 247-259
The effects on yield in courgette and marrow (Cucurbita pepo) crops re
sulting from inoculation with the mild strain of zucchini yellow mosai
c virus (ZYMV:WK), have been determined in polythene-house trials and
in three years of outdoor, commercial field trials. In polythene-house
trials ZYMV:WK inoculated plants were up to 10 days later in flowerin
g than uninoculated plants and their cumulative yields were between 5%
and 26% less than uninoculated plants depending on the cultivar. In m
ost field trials cumulative yields from inoculated plants were between
4% and 38% less than uninoculated plants depending on the site and cu
ltivar, but in one trial the yield was 7% higher from inoculated plant
s. In all experiments, courgette and marrow fruits harvested from ZYMV
:WK inoculated plants were symptomless and indistinguishable from frui
t harvested from uninoculated plants. The mild leaf symptoms induced b
y ZYMV:WK infection did not intensify to severe leaf symptoms and wher
e there were natural outbreaks of severe ZYMV infection, fruits from i
noculated plants remained symptomless whilst those from uninoculated p
lants were severely affected and unmarketable.