Genetic Diversity of Ascochyta rabiei in Canada

Abstract

Assessment of variability of Ascochyta rabiei (teleomorph: Didymella rabiei) was based on virulence tests of 40 isolates and on random amplified polymorphic DNA (RAPD) analysis of 39 isolates from Canada. In addition, isolates of A. rabiei from other countries were assessed in the virulence (18 isolates) and RAPD (20 isolates) analyses. Seven isolates of A. lentis (teleo-morph: Didymella lentis) and two of A. pinodes (teleomorph: Mycosphaerella pinodes) also were included in the RAPD analysis. Significant line-isolate interactions in the virulence tests indicated that certain isolates were virulent only on certain lines. Canadian isolates were grouped into 14 pathotypes using eight chickpea differentials. These groupings also encompassed 17 of the 18 isolates from other countries. RAPD analysis of all 68 isolates using 8 primers produced 112 fragments, of which 96% were polymorphic. Similarities among A. rabiei isolates from Canada ranged from 20 to 100%. In the RAPD dendrogram, all five A. rabiei isolates from Australia, three of six from Syria, three of five from the United States, and one of two from India clustered within the major groups of Canadian isolates. There was a weak association between RAPD and pathotype groups. A. rabiei was 45% similar to A. lentis and only 14% similar to A. pinodes. The levels of DNA variability and virulence among isolates show that the population of A. rabiei in Canada is highly diverse.

Improved sources of resistance to ascochyta blight in chickpea

“…The results of this experiment differed from those of Chongo et al (2004), who found lower levels of AB on leaves than on stems. However, the rating scale used by Chongo et al (2004) was different from the one used in the present experiment.…”

“…It was previously reported that AB symptoms are initiated later on stems than leaves, due to the thicker cell walls of stems (Ilarslan and Dolar 2002). The results of this experiment differed from those of Chongo et al (2004), who found lower levels of AB on leaves than on stems. However, the rating scale used by Chongo et al (2004) was different from the one used in the present experiment.…”

“…Planting resistant cultivars is an important tool to manage AB and maintain sustainability of production. The disease reaction of current chickpea cultivars in western Canada ranges from partially resistant to highly susceptible, and no cultivar is totally resistant (Chongo et al 2004). Airborne ascospores play an important role in the dispersal of the pathogen and make disease control difficult (Armstrong et al 2001).…”

Genetic and Pathogenic Variability of Ascochyta rabiei Isolates from Pakistan and Syria as Detected by Universal Rice Primers

“…The isolates were also characterized using 3 SSR markers [8] and 10 Universal rice primers (URP) that are repeat motifs obtained from Korean weedy rice and have been utilized in diverse genome like animals, plants and microbes [9]. Previous studies were based on RAPD and SSR markers for the assessment of genetic diversity of AR isolates [3,5,6,[10][11][12][13]. Only SSR markers were reported by Imtiaz et al (2011) to differentiate pathotype III and IV from Syria.…”

Sensitivity of field populations of Ascochyta rabiei to chlorothalonil, mancozeb and pyraclostrobin fungicides and effect of strobilurin fungicides on the progress of ascochyta blight of chickpea

“…The pathogen population is genetically diverse (Chongo et al 2004), reproduces sexually and produces wind-borne ascospores (Armstrong et al 2001), and repeated applications of fungicides are required for disease management each year. Also, resistance to strobilurin fungicides was reported from baseline studies of unexposed populations of A. rabiei (Gossen and Anderson 2004).…”