Phytophthora tolerance in chickpea varieties

Paddock selection and management

Varieties displaying this symbol beside them are protected under the Plant Breeders Rights Act 1994.

 GRDC codes: DAN00143, DAN00176, DAQ00154

Authors

• Kevin Moore, NSWDPI, Tamworth, NSW
• Mal Ryley, DAFFQ, Toowoomba, QLD
• Kristy Hobson, NSWDPI, Tamworth, NSW
• Ted Knights, NSWDPI, Tamworth, NSW
• Steve Harden, NSWDPI, Tamworth, NSW
• Willy Martin, DAFFQ, Warwick, QLD
• Kris King, DAFFQ, Warwick, QLD
• Paul Nash, NSWDPI, Tamworth, NSW and
• Gail Chiplin, NSWDPI, Tamworth, NSW

Take home message

Minimise the risk of Phytophthora root rot, PRR in your 2014 chickpeas by:

• avoiding poorly drained paddocks
• avoiding paddocks with a history of lucerne, medics or chickpea PRR
• not growing PBA Boundary if you even suspect a PRR risk
• selecting the best variety suited to soil type, farming system and disease risk which, for PRR is Yorker>HatTrick>Jimbour>Kyabra>Boundary

Note: metalaxyl seed treatment is not recommended in any situation.

The 2013 northern NSW/southern QLD chickpea season

The 2013 chickpea season in northern NSW/southern QLD followed a wet January to March, below average post-sow rain in Jun/Jul and then well below average rain for the rest of the growing season (Dalby’s July rain was just above average).  Saturated soil in the early part of the chickpea season resulted in waterlogging and in certain paddocks Phytophthora root rot.  Mild winter conditions favoured rapid vegetative growth resulting in valuable soil moisture being used to grow high biomass crops.  From mid-late Aug to mid- Oct, average daily temperatures fluctuated above and below 15C and this stress caused flower and pod abortion; 2-3 days of severe frosts around 20 Aug killed flowers and pods on what were by now moisture stressed plants.  The much needed rain that started on 15 Sep, was too late and instead of encouraging crops to set new flowers and pods, had the opposite effect – most crops started shutting down by the end of Sep.  Across the region, diseases were of little concern.  Of 280 crops inspections, Ascochyta blight was found in only five and caused no yield loss.  Viruses appeared in late Sep - end Oct, but unlike 2012 caused only minor losses across the region.

Phytophthora root rot

Phytophthora medicaginis, the cause of phytophthora root rot (PRR) of chickpea is endemic and widespread in southern QLD and northern NSW, where it carries over from season to season on infected chickpea volunteers, lucerne, native medics and as resistant structures (oospores) in the soil.  The importance of alternative hosts in chickpea PRR was strikingly demonstrated at Moree in 2012.  The paddock had never grown chickpeas and had only had three crops (all wheat) after at least 30 years of Coolatai grass and native medic.  PRR was first diagnosed on 5 Jul 12 in a few groups of plants; but by mid-Aug, large areas had been killed and on 31 Aug, the entire crop was sprayed out.  In contrast, no PRR was found in the adjoining paddock which had a long history of cropping (and thus opportunities to control medics).

The importance of varietal susceptibility became obvious on the Darling Downs during the 2013 season.  The high yielding, Ascochyta resistant PBA Boundary was grown widely in the Dalby-Macalister-Warra-Jondaryan area.  Unfortunately, saturated soil conditions in the early part of the season showed up PBA Boundary’s susceptibility to Phytophthora, with lower parts of several paddocks killed. 

PRR (and waterlogging) are favoured by wetter than normal seasons, or by periods of soil saturation in normal seasons as happened in the early part of 2013.  Waterlogging can be confused with PRR, but differs in that (i) roots die from lack of oxygen whilst with PRR the Phytophthora organism consumes them; (ii) plants are most susceptible during flowering and early pod fill whereas PRR can affect plants of any age (iii) symptoms develop within 2 days of flooding compared to at least 7 days for PRR, (iv) roots are not rotted immediately after the waterlogging event and, (v) initially, plants are not easily pulled from the soil unlike those affected by PRR.

As there are no in-crop control measures for PRR or waterlogging, a critical management tool is avoidance of high risk paddocks (based on previous experience and paddock history). The other key tool for PRR is varietal selection.  Current commercial varieties differ in their resistance to P. medicaginis, with Yorker and PBA HatTrick have the best resistnce and are rated MR (Yorker slightly better than PBA HatTrick), Jimbour MS - MR, Flipper and Kyabra MS and PBA Boundary having the least resistance (S). PBA Boundary should not be grown in paddocks with a history of PRR, lucerne, medics or other hosts.  

A 2012 PRR trial at Warwick showed that hybrid breeding lines, generated by crossing chickpea with a wild Cicer species, have higher levels of resistance to P. medicaginis than the most resistant variety, Yorker (Table 1). Although the yields of the hybrids in the absence PRR in this trial were slightly lower than those of PBA HatTrick and PBA Boundary, their improved Phytophthora resistance will compensate for that lower yield in wet years. The results also confirm that PBA Boundary suffers a higher yield loss from PRR than PBA HatTrick. The trial was inoculated with P. medicaginis, and some plots were soil-drenched with a fungicide to stop root infection; yield loss calculations for each variety/line were based on the difference in yield between the fungicide-treated plots and untreated plots.

^A D lines are hybrid crosses between chickpea (C. arietinum) and a wild Cicer species

In 2013, a scaled down version of this trial was again conducted at the Hermitage Research Station, Warwick.  In this trial PRR was more severe than in the 2012 trial and differences among the varieties were not as great.  It is thought the milder winter conditions of the 2013 chickpea season kept soil temperatures above average and this favoured the disease.  Nevertheless, the improved resistance of hybrids over varieties was obvious and the ranking of the varieties remained similar to that of the 2012 trial.  Indeed, since we started these PRR yield loss trials in 2007, the ranking of varieties has been consistent with the cumulative survival data showing: Yorker>HatTrick>Jimbour>Kyabra>Boundary

What the 2013 trial clearly demonstrated was that even the current best varieties eg Yorker, can sustain serious yield loss under high Phytophthora pressure.  The trial also highlights the importance of assessing the PRR risk for a given paddock/season.

^AD lines are hybrid crosses between chickpea (C. arietinum) and a wild Cicer species

For detailed information on control of PRR in chickpea read Pulse Australia's Northern Pulse Bulletin article on Chickpea: Phytophthora Root Rot Management (PDF, 1.5MB)

Acknowledgements

Thanks to growers and agronomists for help with crop inspections and submitting specimens, to Woods Grains, Goondiwindi for planting material for trials and to chemical companies who provided products for research purposes and trial management.  Thanks to Steve Harden for trials designs and analyses and to Paul Nash, Gail Chiplin, Willy Martin and Kris King for technical support.

Contact details

Kevin Moore
NSW Department Primary Industries
Ph: 0488 251 8660488 251 866
Fx: 02 6763 1100
Email:  kevin.moore@dpi.nsw.gov.au