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White Blister on Broccoli

Sep 3

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9/3/2013 11:24 AM  RssIcon

  

White Blister (White Rust) on Broccoli - Albugo candida (Ac)

White rust is common on Brassica oleracea (broccoli, Brussels sprouts and cabbage) but also mustards, radish, horseradish and weeds from the Brassica family. In Australia the greatest commercial problem occurs with broccoli.

The age at which the plant is infected determines the degree of economic loss. When infection occurs in seedlings, the plants are likely to die but the direct effect of infections later in the crop is generally not as severe. The difference in broccoli is that when lesions occur on fully developed heads, significant economic yield loss can result.

Symptoms can occur on different stages of development, affecting cotyledons, true leaves and florets (heads). On cotyledons, the effect is curling and necrosis, but on true leaves white blister can be seen on the under sides of the leaves.

Albugo candida is a pathogen belonging to the class Oomycetes. Currently only one species is recognised as affecting broccoli. Biotypes are defined as being pathogenic on most genotypes of the host species. Biotypes important on broccoli are shown below:

AcBr
(race 7)

AcBn
(race 8)

AcBo

AcBj
(race 2)

AcBc

AcRs
(race 1)

R/s

R/s

S/?

R/s

R/s

R


Letters after Ac refer to host of the Brassica spp.

  • Brassica rapa (Br) 
  • Brassica nigra (Bn) 
  • Brassica oleracea (Bo) 
  • Brassica juncea (Bj)
  • Brassica carinata (Bc)
  • Brassica sativus (Rs)
  • R/s = most host genotypes are resistant, some are susceptible
  • S/? = susceptible and uncertain due to limiting testing
  • R = resistant

    Note: Brassica napus (Rapeseed; Canola) as host species, do not have a known biotype

    Control measures include the use of fungicides and sanitation practices (crop rotation and weed control). Resistance has been identified in a number of brassica crops and is generally race specific. Resistance to isolates of a Brassica oleracea biotype has been identified, but no cultivars of this species in general production are resistant.

    Whilst there is no genetic resistance to White Blister in broccoli varieties at this stage, Lefroy Valley runs an intensive screening programme in an area where White Blister is very common. Only those varieties which show the least infection over a series of trials are advanced into Lefroy Valley’s commercial broccoli range.




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