THE RESISTANCE OF SLASH PINE TO BROWN SPOT NEEDLE BLIGHT

The resistance of slash pine to brown spot needle blight (Lecanosticta acicola) rose gradually as the age of slash pine increased.The needles became blight most frequently in the seedling stage. The resistance of seedlings could be improved by applying fertilizers and selecting vigorous seedlngs.The resistance of scion which were taken from hightly resistant, moderalely res-istant,and susceplible individual trees was identified by means of natural inoculation. The results indicated that the differential resistance of the individual trees to L. acicola was significant. This kind of resistanle was rather stable, but could be affected by the resestance of the stock.As for mechanisms of resistance, experiments showed that there was a relationship between the buffering capacity of the needle extracts and the numbers of spots on the needles of slash pine. The extracts from the susceptible plants promoted the sporulation of the pathosen more significanty than those from the hightly resistant ones.