Chickpeas in 2010: Viruses in 2009, Recommendations for 2010

Kevin Moore¹, Mark Schwinghamer¹, Gail Chiplin¹, Ted Knights¹, Kurt Lindbeck² and Safaa Kumari³

¹NSWI&I, Tamworth, ²NSWI&I, Wagga Wagga and ³ICARDA, Syria

Viruses that infect chickpea naturally have been identified in northern NSW (and Qld) since the early 1990s. There are at least fourteen species of virus plus a virus-like phytoplasma—more than for other pulses. All are spread by insect vectors, mostly aphids that have airborne life stages. The most common chickpea viruses can be divided into two groups: 1) viruses transmitted by aphids non-persistently, and 2) luteoviruses transmitted by aphids persistently Non-persistent transmission means the aphids can acquire and transmit the virus in seconds but the virus does not persist in the vector for more than a few hours. Persistent transmission means the aphids can retain the virus for many weeks but need at least 30mins to acquire and to transmit the virus. 

 

The virus situation in chickpeas is dynamic and changes from season to season, location to location and even from paddock to paddock on the same farm within a season. Clovers, medics, lucerne, weeds, and other pulses and broadleaf crops can host viruses that infect chickpea. It is thought that stress (moisture, herbicide, nutritional, other disease) and proximity to creeks and timber increase risk as these render the crop more attractive to the aphid vectors. 

 

Whilst we know something about which viruses can infect chickpea crops, we know little about their annual distribution, importance and epidemiology i.e. what factors favour virus epidemics and how do they develop. This is in part because local data on where the viruses come from (e.g. seed, volunteers, alternative hosts, air borne vectors) and on their vectors are lacking. In October 2009, a survey of northern NSW chickpea crops was conducted as a first step in capturing information about chickpea viruses.

Chickpea crops known from earlier inspections to have virus-like symptoms were sampled. Both virus symptomatic and random samples (symptomatic and asymptomatic) were taken from each chickpea paddock visited: Two operators collected around 100 random samples each at around 10 m between samples. One remained close (5 – 20 m) to the edge of the paddock, while the other sampled the centre. Two other operators collected samples showing virus-like symptoms. Number of symptomatic samples varied between paddocks (Table 1). All samples were blotted onto membranes that absorb sap – these were tested for virus groups and specific viruses using TBIA, Tissue Blot Immuno Assay. The specific ones are listed in Table 2.

 

Table 1: Type of symptomatic samples taken from 23 chickpea paddocks in northern NSW, 3 – 9 October 2009.

No	Location	Total samples	Reddening	Tip Wilting	Yellowing	Other symptoms
1	Inverell	50	12	17	14	7
2	Inverell	35	15	15	5
3	Warialda	20	12	6	2
4	Moree - Foxes Lane	44	21	22		1
5	Boggabilla	34		16	18
6	North Star	21	17	4
7	Croppa Creek	32	27	5
8	Bogamildi	34	22	11		1
9	Pallamallawa	34	31	3
10	Biniguy	53	26	27
11	Biniguy	33	10	23
12	Biniguy	27	24	3
13	Biniguy	31	21	10
14	Terry Hie	40	23	17
15	Gurley	29	22	7
16	Bald Hill	33	27	6
17	Wee Waa	37		8	25	4
18	Come-by-Chance	37	24	8	5
19	Coonamble	51	50			1
20	Armatree	39	19	20
21	Armatree	35	20	12		3
22	Warren	29	26	3
23	Mullaley	48		24	22	2
	Total	826	449	267	91	19

 

Table 2: Names and abbreviations of virus species tested for in samples taken from 23 chickpea paddocks in northern NSW, 3 – 9 October 2009.

Name	Abbrev.	Group	Vector and transmission in chickpea
Bean leaf roll virus	BLRV	Luteovirus	aphids, persistent
Beet western yellows virus	BWYV	Luteovirus	aphids, persistent
Soybean dwarf virus	SbDV	Luteovirus	aphids, persistent
Alfalfa mosaic virus	AMV	Alfamovirus	aphids, non-persistent (seed?)
Cucumber mosaic virus	CMV	Cucumovirus	aphids, non-persistent, seed
Bean yellow mosaic virus	BYMV	Potyvirus	aphids, non-persistent
Beet mosaic virus	BtMV	Potyvirus	aphids, non-persistent
Pea seed-borne mosaic virus	PSbMV	Potyvirus	aphids, non-persistent
Chickpea chlorotic dwarf virus	CpCDV	Mastrevirus	leafhoppers, persistent
Tomato spotted wilt virus	TSWV	Tospovirus	thrips, persistent

No samples were positive for TSWV, BtMV or BYMV and only two were positive for PSbMV. Table 3 summarises results for the general luteovirus test and the six specific tests for the symptomatic samples.   Most of the 826 symptomatic samples reacted with the general luteovirus antibody. However, 101 of the 456 luteovirus positives did not react to any of the four luteovirus specific antibodies.   Next to luteoviruses, AMV was the most prevalent virus in the symptomatic samples with 294 positives out of a total of 826 samples. There was no relationship between AMV and luteovirus infection.

 

Table 3: Number of symptomatic samples from 23 chickpea paddocks in northern NSW reacting to six virus specific antibodies and one non-specific antibody (Luteo).

		Total		No of samples reacting positive										No reaction
No	Location			Luteo	BWYV	BLRV	SbDV	CpCDV	AMV	CMV
1	Inverell	50		9		1	5	1	27	1			14
2	Inverell	35		7	1	1	5		12	2			16
3	Warialda	20		11		4	3		4				4
4	Foxes lane	44		39	11	5	11		1	6			3
5	Boggabilla	34		17	9	3	6	1	13	1			4
6	North Star	21		18	2	5	8						3
7	Croppa Creek	32		16	14	1			16				2
8	Bogamildi	34		16	6	2	4		15				10
9	Pallamallawa	34		23	14	3	7		12				3
10	Biniguy	53		36	8	9	10		10				7
11	Biniguy	33		21	5	6	4	1	4				7
12	Biniguy	27		14	3	5	4		13	1
13	Biniguy	31		18	1	3	12		13				1
14	Terry Hie	40		34	7	6	19		9	3
15	Gurley	29		21	4	3	11		5				2
16	Bald Hill	33		30	3		14		1				2
17	Wee Waa	37		27	5	4	19	1	1				9
18	Come-by-Chance	37		29	15	11	5		13				2
19	Coonamble	51		46	32	19	5		4				3
20	Armatree	39		4	2		2	1	36
21	Armatree	35		7	3	3	2		24				4
22	Warren	29		8	4	4			20				5
23	Mullaley	48		5	4	4			41				2
Total		826		456	153	102	156	5	294	14			103

There was no relation between any symptom classes and infection by a specific virus. 

Of all the crops sampled, in only two was the incidence of virus considered to be high enough to impact on yield, and that was estimated at less than 10-15%. Results of the random samples are still being analysed but they suggest: The incidence of TBIA positive plants ranged from 2 to 30%, including a 4% infection of asymptomatic plants from one crop. The edges of crops had a higher incidence of positives than the centres. Luteoviruses were more prevalent in western part of the survey area and were of a lower incidence in the Dubbo/Parkes and Liverpool Plains districts. In those districts AMV was the dominant virus.

For a detailed account of controlling chickpea viruses visit:

Virus problems in chickpea are distinct in several respects from those in other pulses. This means that control strategies need to be decided on separately.   Currently the best strategies to manage chickpea viruses are agronomic ones:

 

Retain standing stubble – this deters migrant aphids from landing. If possible use Precision Agriculture technology to plant between the stubble rows. This results in a uniform canopy which makes the crop less attractive to aphids.

 

Plant on time and at the optimal seeding rate – these result in early canopy closure which reduces aphid attraction to plants next to bare soil

 

Control in-crop, fence-line and fallow weeds – this removes in-crop and nearby sources of vectors and virus.

 

Avoid planting adjacent to lucerne stands weeds – lucerne is a perennial host on which legume aphids and viruses, especially AMV and BLRV survive and increase.

 

The Desi variety Gully has partial but useful resistance to luteoviruses, AMV and CMV. However, Gully is highly susceptible to Ascochyta (more so than Jimbour , Kyabra ) and will require diligent foliar disease management.

 

Seed treatment with insecticides e.g. imidacloprid are not effective for non-persistently transmitted viruses but may be effective for luteoviruses. Unfortunately, local data supporting seed treatment is lacking.

 

Foliar applications of insecticides do not work for any chickpea virus.

·         Viruses were present in every 2009 crop sampled with infection ranging from 2 to 30%; however yield losses were small

·         The main viruses in symptomatic samples were AMV and luteoviruses (BWYV, CpCSV, BLRV and SbDV)

·         Reduce losses from chickpea viruses by retaining cereal stubble, establishing a uniform closed canopy and controlling weeds

·         At this stage, seed and foliar insecticides are not recommended for chickpea viruses

 

Consult http://www.pulseaus.com.au/pdf/Virus%20Contol%20in%20Chickpea%20PA%202009%2010.pdf

Thanks to Joop van Leur for his contributions to the Virus survey and for collating much of the data, and to the growers and agronomists who helped with the survey.

Kevin Moore,

NSW Department Industry & Investment

Tamworth Agricultural Institute,

4 Marsden Park Rd,

Calala, NSW, 2340

Tel: 02 6763 1133,

Mob: 0488 251 866,

Fax: 02 6763 1222,

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