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Control of ascochyta blight in chickpeas using resistant varieties and foliar fungicides

Trevor Bretag1, Kevin Meredith1, Ted Knights2, Chris Pittock1 and Michael Materne1

1 Department of Natural Resources and Environment, (Victorian Institute for Dryland Agriculture), Private Bag 260, Horsham, VIC 3401, Australia.
www.nre.vic.gov.au chris.pittock@nre.vic.gov.au
2 Tamworth Centre for Crop Improvement, NSW Agriculture, RMB 944, Tamworth, NSW 2340, Australia
www.agric.nsw.gov.au ted.knights@agric.nsw.gov.au

Abstract

A field trial was established at Horsham to compare the grain yield of current commercial chickpea varieties and ascochyta resistant breeding lines, under three foliar fungicide spray regimes. Regular fungicide sprays (every 10-14 days) effectively controlled the disease in all varieties. The strategic application of four fungicide sprays (6 weeks after sowing, early flowering, mid flowering and late pod set) reduced yield losses in many varieties but did not prevent serious yield losses in the most susceptible varieties. The most resistant chickpea lines (Desis: ICCV 96836, FLIP 94-508C, Paidar-91; and Kabulis: S 95362, S 95342, FLIP 94-90C and FLIP 94-92C) yielded well without any fungicide sprays. Moderately resistant chickpea lines required at least four sprays to prevent significant yield losses and the most susceptible lines required fortnightly sprays to prevent complete crop loss. In the highly susceptible varieties (Lasseter and Bumper), fortnightly sprays did not completely control ascochyta blight.

Key Words

Chickpea, ascochyta blight, chemical control, disease resistance

Introduction

Ascochyta blight, caused by Ascochyta rabiei (Pass.) Labr., is a devastating foliar disease of chickpeas (Cicer arietinum L.) and most of the varieties currently grown in Australia are very susceptible to the disease. Some farmers have successfully controlled ascochyta blight by applying fungicide sprays every 2-3 weeks and have produced profitable chickpea crops. However, the risk of crop failure remains high. The use of resistant cultivars, as a major component of an integrated pest management strategy, appears to be the best long-term option for the control of this disease.

In 2001, a field trial was established at Horsham to compare the grain yield and ascochyta blight resistance of current commercial varieties and advanced breeding lines under three foliar fungicide spray regimes. The spray treatments allow the profitability of chickpea production to be explored for genotypes with differing resistances to ascochyta blight.

Materials and methods

Seven chickpea lines (from the International Center for Agricultural Research in Dry Areas, Syria and the International Crops Research Institute for the Semi Arid Tropics, India) and 8 Australian chickpea varieties were chosen for their differing ascochyta blight resistances. They were sown in experimental plots (5 m x 1.5 m) at Horsham on 22 June 2001. Seeding rates were adjusted according to seed size and percentage germination to obtain 50 plants/mē. Experimental design was a randomised split block with four replicates. Main plots were fungicide treatments and sub-plots were chickpea genotypes.

The three foliar spray regimes compared were: (1) Strategic - 4 sprays (23 Aug, 14 Sep, 12 Oct and 9 Nov), (2) Regular - 8 sprays at 14 day intervals (3 Aug, 17 Aug, 31 Aug, 14 Sep, 28 Sep, 12 Oct, 26 Oct and 9 Nov), and (3) Control - no fungicide applied. The fungicide used contained 500 g chlorothalonil per L of product, and was applied at a rate of 1.5 L/ha.

Plants from the unsprayed treatment (control) were assessed for ascochyta blight damage on 14 Dec, according to a 1-9 rating scale developed by Singh et al. (1). Plots were harvested at maturity on 9 Jan 2002 with a Hege plot harvester and grain yields were recorded.

Results

Table 2. Effect of foliar fungicides on the grain yield and gross margin of eight commercial chickpea varieties and seven chickpea lines grown at Horsham in 2001 in the presence of ascochyta blight

Name

RatingA

No fungicide

4 Sprays

8 Sprays

 

(1-9)

Yield
(t/ha)

GMB ($/ha)

Loss (%)C

Yield
(t/ha)

GMB ($/ha)

Loss (%)C

Yield
(t/ha)

GMB
($/ha)

Desis

                  

FLIP 94-508C

4

1.99

537

10

2.06

501

6

2.20

530

ICCV 96836

4

2.01

544

25

2.60

690

3

2.67

695

Howzat

6

1.60

400

41

2.52

662

7

2.72

712

Sona-4028

6

1.29

292

41

2.03

491

6

2.17

520

Tyson

7

0.96

176

65

1.80

410

35

2.75

723

Jimbour

8

0.21

-87

92

1.78

403

28

2.48

628

Sona

8

0.17

-101

93

1.31

239

44

2.35

583

Amethyst

8

0.06

-139

98

1.41

274

43

2.47

625

Lasseter

9

0.00

-160

100

0.05

-203

98

2.56

656

Kabulis

                  

FLIP 94-92C

3

2.29

1363

-2

2.39

1373

-7

2.24

1208

FLIP 94-90C

3

2.76

1692

4

2.84

1688

1

2.88

1656

S95342

4

2.30

1370

12

2.41

1387

7

2.60

1460

S95362

4

2.17

1279

24

2.56

1492

11

2.87

1649

Kaniva

8

0.20

-100

92

0.63

141

75

2.56

1432

Bumper

9

0.08

-184

96

0.29

-97

85

1.90

970

LSD (5%)

  

0.27

  

11

0.27

  

11

0.27

  

A Resistance to ascochyta blight: 1 = Very resistant; 9 = Very susceptible.
B Gross margin = [Grain yield (t/ha) x Grain Price ($/tonne) - Variable costs ($/ha)].
Based on a grain price of $350/t for desi and $700/t for kabuli lines. Desi costs of $160/ha + $15/ha/fungicide spray. Kabuli costs of $240/ha + $15/ha/fungicide spray.
C Comparison of yield with fortnightly sprayed treatment.

Discussion

Ascochyta blight significantly reduced the grain yield of all Australian chickpea varieties grown at Horsham in 2001. Applying fungicides every 14 days effectively controlled the disease in all but the most susceptible varieties, but added significantly to the cost of production. The strategic application of four fungicide sprays (8 weeks after sowing, first flowering, early pod and late pod set) reduced yield losses in moderately resistant and moderately susceptible varieties but did not prevent serious yield losses in susceptible or very susceptible varieties.

Three of the most resistant chickpea lines evaluated in this trial (desi: FLIP 94-508C and kabuli: FLIP 94-90C and FLIP 94-92C) yielded well without any fungicide sprays but may still require some fungicide sprays during podding in order to produce high quality grain. The best ascochyta blight resistant lines tested in this experiment were commercialised in June 2002 and should be widely available to chickpea growers from 2004. Howzat, a new variety with better resistance to ascochyta blight than current commercial varieties, will enable desi chickpeas to be grown profitably in most regions again. However, this variety will still require strategic sprays in order to prevent serious crop losses from the disease. In 2001, at Horsham the grain yield of Howzat was reduced by 41% where no fungicide was applied and by 7% following four strategic sprays.

Acknowledgments

The authors thank Dennis Ward, Tim Mellington and Bruce Holding for technical assistance. The Victorian Department of Natural Resources and Environment and the Grains Research and Development Corporation provided financial assistance.

References

(1) Singh, K.B., Hawtin, G.C., Nene, Y.L. and Reddy, M.V. (1981) Plant Disease 65: 586-587.

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