Phytophthora in chickpea varieties - resistance rankings and yield loss

¹ NSWDPI, Tamworth, ² DAFFQ, Toowoomba, ³ DAFFQ, Warwick, ⁴USQ, Toowoomba

Take home message

• Even in a dry season, substantial yield losses from PRR can occur in susceptible varieties such as PBA Boundary
• do not grow PBA Boundary if you suspect a PRR risk
• avoid paddocks with a history of lucerne, medics or chickpea PRR
• there is no yield penalty in the absence of PRR associated with varieties with improved resistance to PRR

Varietal resistance to 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.  Although registered for use on chickpeas, metalaxyl seed treatment is expensive, does not provide season-long protection and is not recommended.  There are no in-crop control measures for PRR and reducing losses from the disease are based on avoiding risky paddocks and choosing the right variety.

Detailed information on control of PRR in chickpea is available on the Pulse Australia website.

Current commercial varieties differ in their resistance to P. medicaginis, with Yorker and PBA HatTrick having the best resistance and are rated MR (Yorker slightly better than PBA HatTrick), while Jimbour is MS - MR, Flipper and Kyabra are MS and PBA Boundary has the lowest resistance (S). PBA Boundary should not be grown in paddocks with a history of PRR, lucerne, medics or other known hosts such as sulla. 

From 2007 to 2014 PRR resistance trials at the DAFFQ Hermitage research Facility, Warwick QLD have evaluated a range of varieties and advanced PBA breeding lines.  Each year the trial is inoculated with P. medicaginis at planting.  There are two treatments, (i) seed treatment with thiram, thiabendazole and metalaxyl and regular soil drenches with metalaxyl and (ii) seed treatment with thiram + thiabendazole only with no soil drenches.  The first treatment has prevented infection by the PRR pathogen in all of these trials.  The difference in yield between the metalaxyl-treated plots and untreated plots are used to calculate the yield loss caused by PRR i.e. % loss = 100*(Average yield of metalaxyl-treated plots – Average yield of nil metalaxyl plots)/ Average yield of metalaxyl-treated plots.

Yields in metalaxyl-treated plots were relatively high for the 2014 season with the lowest yielding varieties (CICA1328, CICA1007, PBA Boundary) yielding close to 2.8 t/ha (Table 1).  The highest yielding variety, CICA0912, produced 3.2t/ha.

In 2014 the level of PRR in the trial was less than those of previous 2012 and 2013 seasons.  However, the 2014 trial again confirmed the Yorker>PBA HatTrick> PBA Boundary variety resistance ranking order (Table 1), which has been consistent across previous trials.

Results for this low disease pressure season showed that susceptible varieties still sustain substantial yield loss from PRR and that varieties with moderate resistance have reduced losses.  For example, although disease pressure was less than that of previous seasons PBA Boundary still had a very high yield loss of 74%.  These losses were approximately 10% lower than the previous two seasons (85% in the 2012 trial and 82% in the 2013 trial).  In contrast, Yorker which has moderate PPR resistance had a yield loss of 10% in 2014 but had respective losses of 35% and 66% in 2012 and 2013.

The 2014 trial again confirmed the superior PRR resistance of the PBA breeding line CICA1328 which is a cross between a chickpea (Cicer arietinum) line and a wild Cicer species.

CICA1211 was included in the trial for the first time in 2014.  Results were promising with a good yield where PRR was controlled (3 t/ha) and a yield loss from PRR of only 12%.

Table 1. Yields of commercial chickpea varieties and breeding lines protected from phytophthora root rot, and % yield losses from PRR in a 2014 trial at Warwick QLD.  (P Yield<0.05; LSD Yield = 0.80)

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

We believe that the lower yield losses recorded in the 2014 trial compared to the 2012 and 2013 trials were due to lower in-crop rainfall between July and November.  For the 2014 season at Warwick there were three months where the monthly total was ≤ 20mm (July 7mm, September 20mm and October 15mm). In the 2013 season when PRR was severe, there was only one month (August 9mm) when rainfall was ≤ 20mm.  In 2012 when PRR severity was between the 2013 and 2014 seasons, there were two months when rainfall was ≤ 20mm. In 2014 immediate post-sowing conditions were cooler than normal with 17 days in July having a minimum temperature ≤ 1°C.  The combination of low soil temperatures and low rainfall early in the season may have reduced the number of primary infections from the inoculum applied at sowing, and so reduced the capability of further disease development later in the season despite good rainfall in August (45mm).

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.  This research is made possible by the significant contributions of growers through both trial cooperation, field access and the support of the GRDC, the authors would like to thank them for their continued support.

Contact details

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