Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2006
Publication Date: 6/28/2006
Citation: Chen, W., Mcphee, K.E., Muehlbauer, F.J. 2006. Seed treatment with systemic fungicide prevents foliar infection of chickpea by ascochyta rabiei. Meeting Abstract.
Technical Abstract: BACKGROUND and OBJECTIVES Management of Ascochyta blight of chickpea is mainly through planting resistant cultivars and judicious application of fungicides. In the Pacific Northwest of the United States, fungicides are usually applied early in the growing season when the ascospores are released and environmental conditions are conducive to disease development. If an effective seed treatment were available to protect seedlings from early infection by Ascochyta rabiei, it could postpone or even avoid the need for foliar fungicide application under certain conditions. The objective of this research is to identify seed treatment fungicides with systemic activity and prevent foliar infection by A. rabiei. MATERIALS and METHODS Seeds of the susceptible cultivar ‘Spanish White’ were treated before planting with the following chemicals: (1) Base mix (Crusier, Sodium molybdenum, and Colorant pink) as control; (2) Base mix + Apron; (3) Base mix+Apron+Mertect; (4) Base mix+Apron+Mertect+Maxim; (5) Base mix + Apron + Mertect + Protégé; (6) Base mix+Captan+Allegiance+Kodiak; and (7) Base mix + Allegiance + Topsin + Trilex. Treated seeds were air-dried and planted in a greenhouse. Two weeks after planting, plants were inoculated with conidia of A. rabiei isolates AR19 and AR628 at three inoculum concentrations (103, 104 and 105 spores/ml) using the mini-dome technique. Disease severity was evaluated two weeks after inoculation using the 1-to-9 rating scale. RESULTS Disease severity ratings for the control treatment (Base mix) when inoculated with isolate AR19 at the three inoculum concentrations were 4, 5.8 and 7.5, respectively, and when inoculated with isolate AR628 at the three inoculum concentrations ratings were 2.0, 4.7, and 6.8, respectively. Treatment with Protégé (#5) resulted in disease severity ratings significantly lower that that of the control at inoculum concentrations 104 and 105 spores/ml for both isolates (3.3, and 5.3 for isolate AR19 and 3.0 and 5.4 for isolate AR628, respectively). Treatment with Maxim (#4) produced disease severity ratings significantly lower than the control at inoculum concentration of 104 spores/ml for both isolates (3.7 for isolate AR19 and 3.2 for isolate AR628). The remaining treatments (#2, #3, #6 and #7) did not show any difference from the control. Regression analyses of disease severity over inoculum concentration showed that the slope of treatment Protégé (#5) was significantly lower that that of the control treatment. CONCLUSIONS Fungicide Protégé (a.i. azoxystrobin) showed promise as a seed treatment to protect chickpea from foliar infection by A. rabiei. This chemical could become an important component of integrated management of Ascochyta blight of chickpea. Further research is needed to determine the duration of the seed treatment to prevent foliar infection.