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					             CCN

Cereal cyst nematode, (Heterodera
avenae), a major pest of cereals in
      southeastern Australia
         CCN – Heterodera avenae
•   Stylet- bearing, tylenchid nematode
•   Dead female is a lemon-shaped cyst, full of eggs. The brown,tanned cyst is
    full of eggs.
•   Alive female is a white cyst
•   Eggs have diapause, hatching only after exposure to ~10 degrees C in autumn,
    but also need moisture to hatch and to move through soil
•   Conditions ideal for cereals also ideal for CCN!
•   Only ~80% of eggs hatch in a season – carry over effect
•   Males present
•   Juveniles attracted to root tips of hosts (grasses and cereals- alternative hosts)
•   Move to stele and initiate syncitea (cell walls dissolve to form multinucleate
    giant cells which act as transfer cells)
                         continued
•   Juveniles lose ability to move, become sedentary, sausage-like
•   When males become adult, worm-like again and recover movement
•   Move around seeking females (role of pheromones)
•   Fertilized females become white cysts

• One generation/year
• Root knots on plants produced in response to overproduction of auxins

• CCN occurs world-wide and probably evolved in West Asia
• Introduced into Australia which has only one race
 Fumigation(bright red strips) and fertilizer trial in the
Murray Mallee, photographed in IR, about 1970 (Rovira)
 Uninoculated (left) and inoculated intolerant showing the
root branching and depth restriction which follows invasion
   Root system grown in the absence of pathogenic and
saprophytic fungal invasion illustrating developing “white
           female” cysts containing nema eggs
Nemas released from the mature brown cyst
              (upper left) .
Adult nematodes
  Root system of paddock grown wheat plant
illustrating root rotting in the presence of other
 nematodes (probably Pratelenchus neglectus)
          and a range of fungi (Rathjen)
CCN control (Heterodera avenae)


       • Rotations

       • Chemicals

       • Resistant varieties

       • Education
Life cycle of CCN
The chart used to rate likely severity of CCN symptoms,
  used in recommendations for rotations and varieties
                         (Rovira)
Bioassay in summer and autumn months
  Field symptoms on Adelaide plains showing
effect of the „Hay cut‟ (either fallow or resistant
cereal variety in previous crop) compared to the
            heavily infested paddock.
Paddock symptoms in spring - CCN probably
         exacerbating N deficiency
Grain yields of samples relative to rating of severity of symptoms in
spring . Survey by A Rovira on 21 paddocks on the Adelaide plains
Survey by J Lewis. SA Dept of Agriculture of the prevalence of CCN in SA, 1989
           Chemical control
• Nemadi

• Insecticides
An early experimental control of CCN by chemicals,late 1970‟s, on the Adelaide plains,
                          (Rovira). Treatment plot on right
Another example of chemical control at Streaky Bay pre1980 (Rovira), with treated plot
                              on left of photograph.
Another example of chemical control, with untreated in centre of frame
                    Genetics
• Resistance, the nematode has almost no reproduction on
  the particular genotype. The host may however be
  severely damaged eg Avon variety of oats

• Tolerance, describes the host response with a tolerant
  variety showing little effect of the invasion even though
  the pest might be reproducing on the roots
Tolerant variety on right, intolerant on left (Rathjen)
Come of growing a resistant variety rather than a susceptible one in terms of nematode
                  population and grain yields (Dube and Fisher)
Breeding plots at Palmer showing segregation for tolerance. Individual plots are 4 rows
  4.2m in length, with a pathway,wheel tracks, between each bed of plots (Rathjen).
Variation in tolerance in oat lines. Paler varieties probably exhibiting Fe deficiency as
                          a result of rooting depth restrictions
Screening for resistance in controlled environment
     cabinet to enable out of season breeding
Effect of different varieties grown in 1975 (Festiguay, resistant , and Sabre, susceptible)
               on grain yields and nematode population in 1978). (Rovera)
Control strategy advocated to farmers as part of project 70 (Dube). The ‟70‟ derived
                from the estimated annual losses to the pest of $70m
Listing of the Tolerance and resistance of various cereal varieties in the early 1980‟s
 A summary of some of the features of the barley variety Galleon, released 1981, the
first major release of a resistant variety, with a resistance derived from the north coast
               of Egypt where barley is grown continuously in the wadis
Farmer‟s crop at Booleroo, where a CCN resistant variety had been grown in the left
side of the paddock and a susceptible in the centre when the farmer ran out of seed in
the previous cropping cycle. The earlier maturing section had about twice the yield
 Don Whiting at his variety trials. Don began his own variety trials in 1969 and the
results from these was responsible for the rapid uptake of Festiguay in the Wallaroo
                                        zone
                         The Festiguay story


• Festiguay was bred in northern NSW as a rust resistant variety
• It was brought to SA when two bags were brought back by visiting SA
  farmers
• Don entered it in his trials where it outyielded local wheats (later it
  was realised that this was a result of the severe CCN infestation on his
  farm as was the case on almost all the farms in the district)
• Its initial spread was enhanced by its resistance to stem rust in the 1973
  and 1974 epidemics and then by its yield results in Don‟s trials
• It formed about 60% of the deliveries in the Wallaroo Zone in 1980
  even though it was clearly lower yielding in the absence of CCN
               Major Resistant Varieties

• WHEAT – (Festiguay, post 1973), Molineux (1988), Frame (1992),
  Yitpi(1998).
• BARLEY – Galleon (1981), Barque (1997), Keel(1999), SloopSA
  (2002), all SA varieties since then have been resistant.
• OATS – Wallaroo and Marloo
                              Outcomes


• CCN damage is now vastly reduced from the estimated $70m, mostly
  as a result of growing resistant varieties.
• The better root systems are associated with the widespread adoption of
  nitrogenous fertilizers during the 1990‟s.
• Farmers are now concerned with „canopy management‟, ie too lush a
  canopy, rather the thin yellowish crops of the CCN era.
• Direct drilling has been adopted following the CCN control with the
  Victorian Mallee being the last to adopt the technique following
  widespread cultivation of the resistant wheats Frame and Yitpi.
• Land values in the area dominated by CCN have increased
  disporportionally.

				
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posted:7/6/2011
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