Rational Management of Didymella rabiei in Chickpea by Integration of Genotype Resistance and Postinfection Application of Fungicides

Abstract

Various aspects of the integration of genotype resistance and chemical control of Ascochyta blight (caused by Didymella rabiei) in chickpea were examined in field experiments from 1993 to 1999 and in greenhouse experiments. Four commercially available chickpea cultivars representing a range of resistance to D. rabiei were used. The efficacy of chemical control in a highly susceptible cultivar was significantly (P < 0.01) related to the conduciveness of the environment to the pathogen. Adequate disease suppression (>80% control) was achieved when weather supported mild epidemics, but insufficient control (<20%) was achieved when weather supported severe epidemics. The contribution of genotype resistance to disease suppression in a moderately susceptible cultivar varied from <10% when weather supported severe epidemics to approximately 60% when weather supported mild epidemics. Spraying a moderately resistant cultivar resulted in 95% control when weather supported mild epidemics, but only 65% control was achieved when weather supported severe epidemics. The existing level of resistance in a moderately resistant cultivar resulted in 70% control when weather supported severe epidemics; fungicides improved control efficacy significantly to >95%. Under mild epidemics, moderate resistance alone provided >95% control. The level of genotype resistance available in a highly resistant cultivar was sufficient to suppress the disease under all weather conditions, even without application of fungicides. The possibility of relying on postinfection rather than prophylactic application of fungicides was tested in the greenhouse and in four field experiments. Activity of the systemic fungicide tebuconazole was detected when the fungicide was applied up to 3 days postinfection, and application of tebuconazole or difenoconazole in the field as a postinfection treatment (i.e., after rain or overhead irrigation) suppressed the disease as effectively as preventive applications and required fewer sprays. In two experiments, the interaction between genotype resistance and chemical control at various amounts of irrigation applied via overhead sprinklers (as a simulation of rain) was tested. The results show that both the level of genotype resistance and the quantity of water should be taken into account in deciding whether to apply a postinfection spray.

Distribution of Mating Types and Diversity in Virulence of Didymella rabiei in Israel

“…These cultivars vary in their response to D. rabiei: 'Sfaradit' is highly susceptible; 'Ayala' is moderately susceptible; 'Hadas' is moderately resistant; and 'Bulgarit' is highly resistant (Shtienberg et al, 2000). Virulence tests were performed on detached leaves as described above.…”

“…Bulgarit (a highly resistant cultivar introduced to Israel from Bulgaria during the 1950s) or in cv-Hadas (a locally bred cultivar introduced in the late 1980s). These cultivars retain their resistance despite the repeated occurrence of severe epidemics in adjacent fields sown with susceptible cultivars., and despite the presence of the pathogen throughout all chickpea production areas in Israel (Shtienberg et al, 2000).…”

Ecological Genetic Divergence of the Fungal PathogenDidymella rabieion Sympatric Wild and DomesticatedCicerspp. (Chickpea)

“…Unlike other Ascochyta diseases of legumes and Septoria diseases of cereals, Ascochyta blight of chickpea may cause total yield loss under the appropriate environmental conditions (43). Autumn-sown chickpea is severely affected by Ascochyta blight because the crop growth period coincides with the rainy season and optimum environmental conditions for pathogen development and spread (3,56).…”

Survey of Chickpea (&lt;i&gt;Cicer arietinum&lt;/i&gt; L) Ascochyta Blight (&lt;i&gt;Ascochyta rabiei&lt;/i&gt; Pass.) Disease Status in Production Regions of Ethiopia

“…Any alteration in these factors would retard AB development. Rainfall and high relative humidity (> 95%) are critical for most epiphytotics, with temperature also playing an important role in development (Shtienberg et al, 2000). When the temperature is favourable and the moisture requirements of a pathogen on a susceptible host are fully met, an epidemic is likely to develop (Jhorar et al, 1998;Pande et al, 2005) which was observed during this survey.…”