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Phase 3 (2007 Deadline)
Biotechnological Approaches to the Control of Ascochyta Blight of Chickpea
Weidong Chen, Washington State University (WSU), Pullman
S. Sarwar Alam, Nuclear Institute for Agriculture and Biology (NIAB), Faisalabad
Pakistani Funding (MoST): $67,000
US Funding (USAID): $127,219
Project Dates on US Side: March 1, 2008 - September 30, 2011
Project Overview
Chickpea (Cicer arietinum L.) ranks first among legume crops in Pakistan and is an important source of dietary protein for many people in Pakistan. However, average yields for chickpea are quite low due to susceptibility to various stresses, both biotic (Ascochyta blight, Fusarium wilt, and insect pests) and abiotic (drought and cold). Among the stresses affecting chickpea productivity, Ascochyta blight caused by Ascochyta rabiei is one of the most important. This devastating disease is difficult to control, and chemical, cultural, and biocontrol treatments cannot effectively manage it. The overall research goal of this project was to advance control measures of Ascochyta blight of chickpea through understanding genetics of host resistance and pathogenic mechanisms of the pathogen. The project had four specific objectives: (1) to identify the resistant germplasm and study the genetics of resistance to Ascochyta blight of chickpea, (2) to map and tag the chromosomal regions involved using molecular markers for developing marker-assisted selection, (3) to determine relationship between phytotoxin production and virulence of the chickpea pathogen Ascochyta rabiei, and (4) to prove the roles of toxin production in causing the disease by generating non-pathogenic mutants via insertional mutagenesis and using complementation tests.
This cooperative research built upon the combined previous expertise of Dr. Alam and Dr. Chen, and the research tasks being undertaken by the Pakistani and US scientists were truly complementary. The research in Pakistan was focused on host resistance genes, while the research in the United States addressed mechanisms of pathogen activity. In summary, these researchers are working to gain a mechanistic understanding of the chickpea-Ascochyta rabiei pathosystem. Their results should not only facilitate management practices regarding this important disease in Pakistan and elsewhere, but also should advance basic understanding of host-pathogen interactions and improve the quality and capacity of education and research at the Nuclear Institute for Agriculture and Biology (NIAB) in Pakistan.
Major Results
- Provided a female Pakistani PhD student with six months of training at Washington State University in modern plant pathology and molecular techniques
- Determined the contemporary distribution of mating types of the fungal pathogen Ascochyta rabiei of chickpea in Pakistan
- Discovered new virulent forms of the wilt pathogen Fusarium oxysporum f. sp. ciceris of chickpea in Pakistan
- Identified new sources of resistance to Fusarium wilt of chickpea for Pakistani chickpea breeding programs
- Established long-term research cooperation on chickpea research between Pakistani and U.S. researchers
Quarterly Update
Much of the work on this project had already been completed as of May 2011, thanks to ongoing communications between the researchers involved and an extended training visit completed by Ms. Hina Ali of NIAB to WSU from December 2009 through May 2010. A no-cost extension was issued on the US side through September 30, 2011, to allow time for additional experiments and preparation of results for publication. The goal for 2011 was to complete genotyping and phenotyping isolates of Ascochyta rabiei collected from Pakistan and to relate virulence of the isolates to the pathotypes; however, the main challenge is that the Pakistani principal investigator never received his funding for this project from the Ministry of Science and Technology, so he had to do his best to complete the tasks using existing resources.
Progress Report Summaries
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2010 Show summary || Hide summary
In 2010, a collection of 32 isolates of Ascochyta rabiei from six geographical regions of Pakistan was compared with a U.S. population for frequency of mating types and for genetic variation using microsatellite marker loci. The results revealed that Pathotype II (virulent on Spanish White and Dwelley) and Pathotype III (virulent on all three differentials) are prevalent in Pakistan. The prevalence of the highly virulent isolates in Pakistan presents challenges in identifying resistance sources for chickpea breeding programs for managing chickpea Ascochyta blight in Pakistan.
2009 Show summary || Hide summary
Dr. Alam made a brief visit to the United States June 28-July 2, 2009, during which he participated in the Second International Ascochyta Workshop at Washington State University (WSU). At the workshop, he and Dr. Chen presented a total of four abstracts on work related to the project. Meanwhile, during the spring and summer 2009 growing season the research teams in both countries continued collecting isolates of Ascochyta rabiei, evaluating the isolates for pathogenicity and capacity for toxin production, investigating chickpea mutants and progenies of crosses for reaction to Ascochyta blight, and measuring toxin production in insertional mutants. Strains of Ascochyta rabiei and Fusarium oxysporum f.sp. ciceris were isolated from diseased chickpea plants in various regions of Pakistan and shipped under USDA-APHIS permits to Dr. Chen in the United States for molecular testing and phenotyping. Ms. Hina Ali, a junior researcher involved in the project at NIAB, arrived at WSU for six months of training beginning December 4, 2009. Her stay in Pullman was not only useful with regard to the project objectives but also helped her complete work required for her PhD dissertation. In addition to her research at WSU, she also had the opportunity to participate in the International Plant and Animal Genome Conference in San Diego, California, in January 2010. During the subsequent months, she was involved in several research activities on the project, including continued characterization of chickpea genotypes for resistance to Aschochyta blight and Fusarium wilt, identification of races of Fusarium isolates obtained from Pakistan, and characterization of isolates of Ascochyta rabiei for genetic diversity, pathogenic variation, and toxin production. On May 28, 2010, Ms. Ali returned to NIAB, where she is now applying her skills to the institute’s efforts to produce a resistant chickpea variety that can be cultivated by Pakistani farmers. She reports that her training at WSU and her interactions with Dr. Chen and his colleagues have also spurred new avenues of her research related to both biotic and abiotic stresses in chickpea.
2008 Show summary || Hide summary
During the first year of their project beginning in 2008, the researchers collected more than 100 isolates of the pathogen Ascochyta rabiei in several chickpea growing regions in the United States, and more than 50 of the isolates were tested for virulence. Most of the isolates exhibited Pathotype II phenotype showing severe pathogenicity on both cultivars tested. Dr. Alam and his team also attempted to collected isolates in Pakistan, but the disease was not epidemic in the 2008 growing season so no isolates were collected. Collection efforts continued in the next growing season. Mutant chickpea phenotypes were also produced through radiation so that they could be screened for reactions to pathogen infection, including infections by Ascochyta rabiei. In addition, more than 50 genotypes of chickpea germplasm were screened for resistance to Ascochyta rabiei, and three (PI 559361, PI 559363 and W6 22589) showed significantly higher levels of resistance to both pathotypes of Ascochyta rabiei. Several chickpea genotypes were also found to be highly resistant to Pathotype I of the pathogen. Genetic crosses between susceptible and resistant chickpea genotypes were made, and the resulting progeny plants were cultivated in the greenhouse for further genetic testing.
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