EFFECT OF SEED INFESTATION AND FLOWER BUD INOCULATION ON SYSTEMIC INFECTION OF TURNIP RAPE BY ALBUGO CANDIDA

Abstract

Oospores of (Albugo candida race 7 mixed with seeds of turnip rape (Brassica campestris L. ’Torch’) prior to sowing resulted in a significant increase over the control in both locally (foliar) and systemically-infected plants in field plots, demonstrating the potential importance of seed infestation in initiating the disease. In growth room studies, inoculation of flower buds with zoospores resulted in a 10-fold increase, over cotyledon and leaf inoculations, in the number of stagheads on turnip rape. Over 55% of the flower-bud-inoculated plants produced stagheads. Results suggest that flower bud infection is probably a major source of systemic infection of individual branches. Stagheads may also result from systemic infection beginning at the seedling stage.