Chickpea is a valuable rotational crop choice on the prairies, especially given its high level of partial resistance to Aphanomyces root rot which is very problematic for pea and lentil production. Recent unexplained chickpea disease issues in Saskatchewan have led to questions about the importance and causes of root rot in chickpea. This study aimed to identify the most prevalent and virulent chickpea root rot pathogens in our production system, and to search for sources of root rot resistance among a diverse panel of chickpea germplasm, including wild chickpea accessions. As root rot resistance can be strongly mediated by dark pigmented seed coats, promising chickpea genotypes were also assessed with their seed coats removed.

Unlike pea and lentil, there is very little information about which root rot pathogens are predominant and virulent on chickpea in our production system. This question was addressed by conducting chickpea root rot surveys over two seasons, in which a diverse selection of 42 Saskatchewan chickpea fields were sampled in 2020 and 19 fields in the rural municipalities with the most severe root rot symptoms in 2021. Root samples were analyzed using end-point PCR to detect root pathogens previously cited in the literature from other locations, and by conducting pathogen isolation. PCR detection showed Fusarium redolens, F. solani and F. avenaceum to be the most prevalent pathogens in chickpea roots.

Pathogen isolation showed the prevalence of F. redolens, F. oxysporum, and F. avenaceum. The devastating chickpea wilt pathogen, F. oxysporum f. sp. ciceris was not detected. Two previously unreported chickpea pathogens, Verticillium dahliae and Berkeleyomyces sp., were detected in a small number of samples. Virulence testing of 19 root rot pathogen isolates in a series of controlled-environment experiments identified F. avenaceum and F. culmorum isolates with high virulence on chickpea. Berkeleyomyces sp. isolated from research plots and an isolate of V. dahliae obtained from a culture collection also showed the potential to cause severe root rot on chickpea.

Root rot resistance screening methods were successfully developed for chickpea, including protocols for seed coat removal that minimize negative impacts on seedling emergence. Suitable spore concentrations were carefully determined for a two-step inoculation protocol for F. avenaceum to ensure that chickpea genotypes can be effectively differentiated. This method includes incorporation of spores into potting mix and pipetting spore suspension at seedling bases 10 days after seeding. These methods were used to screen 186 diverse chickpea genotypes, 50 of which were also screened after the seed coats had been removed. An additional 21 wild chickpea accessions were screened with intact and removed seed coats. Several sources of promising root rot resistance not associated with seed coat characteristics were identified, including 19 C. arietinum and 2 C. reticulatum genotypes. These genotypes provide an excellent basis for breeding improved chickpea lines.

Extension Messages

• F. avenaceum is a prevalent root rot pathogen that can cause severe damage to chickpea, as well as pea and lentil
• Although detected less frequently in chickpea root samples from surveys, highly virulent isolates of culmorum were also identified.
• Two previously unreported chickpea pathogens with the ability to cause severe root rot of chickpea were detected during surveys. Berkeleyomyces, the cause of black root rot, was isolated from two research fields. Verticillium dahliae was detected by PCR, but not isolated from chickpea roots under the study conditions.
• Chickpea genotypes with resistance to root rot caused by F. avenaceum were identified in cultivated and wild germplasm, including resistance not mediated by the seed coat. These resistance sources provide an excellent basis for breeding improved chickpea lines.F