Pg. Zhang et al., PACLOBUTRAZOL PROTECTS BLACK SPRUCE SEEDLINGS AGAINST PREDISPOSITION TO GRAY MOLD INDUCED BY HIGH-TEMPERATURE AND DROUGHT, Canadian journal of forest research, 24(5), 1994, pp. 1033-1038
Effects of paclobutrazol on the ability of high temperature and drough
t to predispose black spruce (Picea mariana (Mill.) B.S.P.) seedlings
to infection and sporulation of Botrytis cinerea Pers.:Fr. were examin
ed. Paclobutrazol was applied as a soil drench at doses of 0, 20, and
40 mg/seedling pair on the first and third days of 2- and 4-week perio
ds before the seedlings were subjected to darkness at 35 and 45-degree
s-C, or to drought, for various periods and inoculated with the pathog
en. The paclobutrazol treatments markedly reduced sporulation incidenc
e and the number of spores produced by the pathogen on needles of seed
lings subjected to the environmental stresses for periods that margina
lly or moderately exceeded those needed for predisposition to B. ciner
ea. Sporulation in needles of paclobutrazol-treated seedlings increase
d substantially only when the stress treatments were relatively prolon
ged. The activity of paclobutrazol in suppressing effects of environme
ntal predisposition of the seedlings to infection and sporulation of B
. cinerea was considered to be mediated through stress protection as o
pposed to fungicidal action of the triazole.