Effect of chickpea ascochyta on yield of current varieties and advanced breeding lines

Take home message

Under medium to high disease pressure, Ascochyta can be successfully and economically managed on susceptible varieties such as Kyabra and Jimbour.

However, Ascochyta management is easier and more cost effective on varieties with improved resistance eg PBA HatTrick, PBA Boundary

The Ascochyta resistance of the advanced breeding lines CICA0912 and CICA1007 has been improved to the point that in a typical average rainfall to dry season neither will require fungicide sprays.

Background

Ascochyta first caused widespread damage to chickpea crops in eastern Australia in 1998. At the time, all Australian chickpea varieties were susceptible (some highly so) to the pathogen (Phoma rabiei formerly known as Ascochyta rabiei). Following the 1998 epidemic, efforts to develop chickpea varieties with resistance to Ascochyta were increased, aided by considerable support from GRDC. Fortunately Ted Knights, who led the National breeding program had already started incorporating Ascochyta resistance into desi chickpea types suited to the GRDC Northern Region. Howzat, released in 2002, had better resistance than Amethyst but it wasn’t until 2005 when Flipper and Yorker were released that substantial gains in resistance were available to the chickpea industry. These were followed by PBA HatTrick in 2009 and PBA Boundary in 2011. Since 1999, Ascochyta management trials have been conducted at the Tamworth Agricultural Institute to determine yield losses caused by Ascochyta in current varieties and advanced breeding lines. We report here on the 2014 trial.

2014 Tamworth Ascochyta management trial, VMP14

VMP14 sought to match Ascochyta management to a variety’s Ascochyta rating. The trial was sown into standing cereal stubble on 15 May 2014 using disc openers on 40cm row spacing in plots 4m wide by 10m long. Each plot was separated from its neighbour on all sides by a 2m x 10m buffer of Genesis™425 (rated R to Ascochyta). There were ten genotypes and four replicates. On 15 Jul, when most genotypes were at the 6-7 node stage, the trial was inoculated with a cocktail of twenty isolates of the Ascochyta pathogen collected from commercial chickpea crops from 2009 onwards at a rate of 233,000 spores per mL in 100L/ha water. Five and a half hrs elapsed before the rain started and whilst Ascochyta did develop, not all unprotected plants were infected and those that were had a limited numbers of lesions. On 16 Aug, when plants had 13-15 nodes, the trial was re-inoculated during a rainfall event with the same isolate cocktail that also included a highly aggressive isolate collected from PBA HatTrick at Yallaroi on 24 July (not included in the 15 Jul inoculation) containing 833,000 condia/mL. It rained for 3.5 days and this time, every unprotected plant had multiple Ascochyta infections. From re-inoculation to desiccation (6 Nov), the trial received 94mm rain in 16 rain days (8 days >1.0mm) compared with the 120 year average for the same period of 141mm and 20 rain days (15 days >1.0mm).

Table 1 lists the ten genotypes and their current ratings to Ascochyta and Phytophthora (S = Susceptible, MS = Moderately Susceptible, R = Resistant, MR = Moderately Resistant).

Table 1. Chickpea varieties and advanced breeding lines used in the Tamworth VMP14 trial and their current ratings for Ascochyta and Phytophthora

There were three fungicide treatments: a low disease scenario with regular applications of 1.0L/ha chlorothalonil (720g/L active) (5 applications were made), a high disease scenario with Nil sprays and a VMP treatment with low and off-label rates of chlorothalonil. Data for the VMP treatment are not presented here but we describe the strategies for each genotype as these reflect their Ascochyta rating. The first VMP spray for Jimbour, Kyabra and CICA1211 was applied before the first inoculation. The first VMP spray for PBA Monarch and Genesis™ Kalkee was applied on 14 Aug after two infection events, when the Jimbour, Kyabra and CICA1211 were getting their 2^nd spray. The first VMP spray for PBA Boundary, PBA HatTrick, Genesis™ 425 and CICA0912 was applied on 12 Sep after four infection events, when Jimbour, Kyabra and CICA1211 were getting their 4^th spray. Conditions were not consistently favourable for Ascochyta and plants grew away from the disease between rain events. Nevertheless, unprotected (Nil) Kyabra plots were severely affected by Ascochyta and had no yield; unprotected Jimbour yielded only 22% of protected Jimbour.

In spite of treating all planting seed with metalaxyl (and thiram), Phytophthora root rot, PRR developed following 39mm rain on 18-20 Aug and 18mm on 25-26 Sep. By harvest, PRR had become quite severe in some areas of the trial; accordingly, %PRR infection was used as a covariate in the yield analyses The covariate adjusted yields for label rate and nil fungicide treatments only are summarised in Table 2, covariate adjusted yields were also used to calculate gross margins.

Key yield findings of VMP14 were:

1. Under moderate to high disease pressure, Ascochyta can be successfully managed on susceptible and MR varieties with registered rates of chlorothalonil
2. Under these moderate to high disease pressure conditions the Ascochyta resistance of two R and R/MR PBA breeding lines (CICA912, CICA1007) was robust and chlorothalonil application did not significantly improve yield

Findings for susceptible varieties:

• all susceptible varieties had significant improvements in yield with chlorothalonil for Ascochyta management
• Well managed Kyabra yielded 2.4t/ha with a GM of $669/ha compared to zero yield and a GM of minus $377/ha where the disease was not controlled
• The desi line, CICA1211 was perhaps the surprise of the trial, as although yield losses were significant the unsprayed CICA1211 yielded 86% of sprayed treatment. CICA1211 was rated Susceptible to Ascochyta in PBA Chickpea screening nurseries under very high disease pressure. In this drier than average season CICA1211 certainly handled Ascochyta much better than the other two S rated entries, Jimbour and Kyabra

Findings for MR and R/MR varieties:

• The Ascochyta resistance of PBA HatTrick was promising at 76% of the sprayed PBA HatTrick, although yield losses were significant. Treatment effects for PBA HatTrick resulted in a significantly lower unsprayed GM value of $492/ha in comparison to value of $630/ha for the sprayed treatment
• Unsprayed PBA Boundary, yielded 88% of the well managed PBA Boundary with GM of $637/ha
• The recently released kabuli, PBA Monarch, also performed well, with the unsprayed yielding 74% of the sprayed
• The potential desi release, CICA0912, performed exceptionally well with no significant difference (P<0.001) in yield between five sprays of chlorothalonil fungicide (2183 kg/ha) and no sprays (2132 kg/ha)
• There was also no significant difference (P<0.001) in yield of the desi line CICA1007 between five (2340 kg/ha) and no sprays (2343 kg/ha)

Further information

Further information on chickpea disease management can be found at the Pulse Australia website www.pulseaus.com.au and in the NSW DPI 2015 Winter Crop Variety Sowing Guide eg:

• Chickpea Ascochyta Blight Management pdf
• 2011 Chickpea Disease Management Considerations pdf
• Chickpea Botrytis Grey Mould Management pdf
• Chickpea Integrated Disease Management pdf
• Chickpea Phytophthor Root Rot Management pdf
• Virus Contol in Chickpea pdf
• Pulse Seed treatments & Foliar Fungicides pdf

Acknowledgements

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 most gratefully thank them and the GRDC. We also thank agronomists for help with the crop inspections and submitting specimens, Dr Mal Ryley, USQ for scientific discussion and advice, Gordon Cumming, Pulse Australia for industry liaison and chemical companies who provide products for research purposes and trial management.

Contact details

Kevin Moore
Department of Primary Industries, Tamworth, NSW
Ph: 02 6763 1133
Mb: 0488 251 866
Fx: 02 6763 1100
Email: kevin.moore@dpi.nsw.gov.au