Low light intensity prediposes black spruce seedlings to infection by Botrytis cinerea

Zhang, P.G.; Sutton, J.C.; He, B.; Hopkin, A.A.

Low light intensity prediposes black spruce seedlings to infection by Botrytis cinerea

1995

Zhang, P.G. | Sutton, J.C. | He, B. | Hopkin, A.A.

Seedlings of black spruce [Picea mariana] were kept in low light intensities for 0-42 days and inoculated with Botrytis cinerea (10(6) conidia/mL). Infection was assessed indirectly by estimating sporulation incidence of the pathogen on 6-mm segments of the needles. Sporulation incidence in seedlings kept in light (400-700 nm) intensity of 0 and 7 micromoles.m(-2).s(-1) was 0.7% and 0.4% after 6 and 12 days of the preinoculation treatment, increased to maximum levels of 45.6% and 32.5%, after 21 and 27 days, and declined after 27 and 39 days, respectively. Sporulation incidence was zero in seedlings kept at 15 and 30 micromoles.m(-2).s(-1) for up to 24 and 39 days before inoculation, and less than or equal to 6.3% and less than or equal to 0.4% after 30 and 42 days, respectively. Botrytis cinerea sporulated on needles only when light intensity was sufficiently low that the chlorophyll content fell below 1.3-1.4 micrograms/6-mm segment. In studies in canopies of seedlings in greenhouses, sporulation incidence decreased as light intensity increased and reached zero when the mean intensity at noon on sunny days was near 10 micromoles.m(-2).s(-1). We conclude that light (400-700 nm wavelength) intensity of less than or equal to 10 micromoles.m(-2).s(-1) predisposed the needles to infection by B. cinerea.

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