Impact of climate change on foliar and soil borne pathogens of wheat in the Pacific Northwest region
Fusarium crown rot (FCR) caused by Fusarium pseudograminearum (Fp) and F. culmorum (Fc) and Rhizoctonia root rot caused by Rhizoctonia solani AG8 (Rs8) and R. oryzae (Ro), are major soil-borne fungal diseases responsible for economic losses in dryland wheat in the Pacific Northwest region of the US. This study focuses on exploring the finer details of soil moisture and temperature impacts on these four pathogens and, develop models for projecting their growth in response to these variables. Methods were developed using NaCl, KCl and polyethylene glycol to precisely define water potential (WP) treatments at different temperatures. On defined media and sterile wheat straw, the optimum temperature for the mycelial growth and dry weight gain for Fc and Rs8, and Fp and Ro was 20-25°C and 25-30°C, respectively. The optimum WP was -0.3 MPa for both Rhizoctonia spp. and -1 to -2 and -2 to -3 MPa for Fc and Fp, respectively. Macroconidia of Fusarium spp. were capable of germinating across all ranges of WP, even the driest. In soil, except for Fp, the other three pathogens had different optimal temperatures and WPs for their growth, as measured by DNA concentrations quantified by real-time PCR. The optimal temperature and WP for both Rhizoctonia spp. were 10-15°C and -2 MPa, respectively. Fc had a temperature optimum of 10-15°C with a preference for the driest WP ranges below -5.5 MPa. Fp was restricted to a narrow range of WP from -1.43 to -3.12 MPa. In a greenhouse study, the increase in Fp DNA in the infected wheat plants was strongly negatively correlated to the median values of WP in the whole column. FCR disease score in Fp inoculated columns was negatively correlated with the WP at depths where roots would be active. On the other hand, there was no significant difference of DNA and FCR disease score in Fc inoculated columns with the WP levels. Models were developed for projecting pathogen growth in defined nutrient media, soil, and infected plants based on the temperature and WP levels.
Iqbal Singh Aujla joined Dr. Timothy Paulitz's lab as a Ph.D student in the fall semester, 2012. He completed his research on 'The Influence, Interactions and Modeling of Water Potential and Temperature on the Growth of Soilborne Pathogens of Wheat' in 2017. He did his BS in 1998 and MS specializing in Plant Pathology in 2000 from Punjab Agricultural University (PAU), Ludhiana (India). He joined PAU services as Assistant Professor (Extension Plant Pathology) in 2001. During his stint of 7 years in extension, besides raising income of many vegetable growers several folds by practicing proper disease management practices, three farmers were also awarded with best farmer award by PAU working under his guidance. He also gave recommendation on fungicidal management of false smut of rice. Then in 2007, he was transferred to the post of Assistant Plant Pathologist in vegetable research. His research work focused on vegetables grown under protected environment. He has given recommendation on management of soil-borne pathogens (fungi and nematodes) through soil solarization and has also developed a complete package on cultivation of peppers in net houses and naturally ventilated poly houses, increasing yield of peppers by 100-250 percent.
Publications and Presentations:
Auijla, Iqbal S., and T. Paulitz. 2017. An Improved Method for Establishing Accurate Water Potential Levels at Different Temperatures in Growth Media. Frontiers in Microbiology. 8:1497. (doi: 10.3389/fmicb.2017.01497)