Dr. Timothy Paulitz

Research Plant Pathologist – USDA-ARS Wheat Health, Genetics and Quality Research Unit; Pullman, Washington 

Date: Tuesday, 22 September; 10-11 am,  SARDI Auditorium

Title: Eight Years in the Roots of Wheat: Long- Term Selection of Microbial Communities Driven by the Plant and Soil Water

Abstract: In this seminar, I will summarize a 50 year journey of our research group in understanding the mechanisms of disease suppression and present advances. The USDA-ARS unit in Pullman was originally called the Root Disease and Biological Control Research Unit, led by R. James Cook starting in the late 1970s.  This group did pioneering work on take- all suppressive soils and elucidating the molecular, genetics and biochemical mechanisms of suppressive Pseudomonas spp. that produced antifungal metabolites phenazine and phloroglucinol. But over the last 20 years, we have gained a greater insight into the ecology of these bacteria in the dryland Pacific Northwest. This led to a long-term trial at Lind, WA, a low rainfall wheat-fallow zone, where we monitored the microbiome of wheat roots for 8 years in dryland and irrigated plots.  We sampled multiple times in the season and looked at the bacterial microbiome with 16S amplicon sequencing in the bulk soil, rhizosphere and root.  We found that the abundance of individual bacteria were modulated by soil moisture, plant growth stage & length of wheat monoculture. Taxa exhibited seasonal dynamics and periodicity, and population trends were reproducible across multiple years. Over the 8-year study, certain genera became more prevalent in the root under irrigated or dryland conditions. One discovery was the prevalence of actinobacteria in the root.  Over three years, we isolated a collection of over 1,000 actinobacteria.  The collection was dominated by Streptomyces, Kribbella, Amycolatopis and Promicromonospora. We did genomic sequencing and functional analysis of a subset, and many showed antifungal activity and growth promotion.  We are presently looking at the ability of selected strains to protect wheat and alfalfa against water stress.

Bio: In this seminar, I will summarize a 50 year journey of our research group in understanding the mechanisms of disease suppression and present advances. The USDA-ARS unit in Pullman was originally called the Root Disease and Biological Control Research Unit, led by R. James Cook starting in the late 1970s.  This group did pioneering work on take- all suppressive soils and elucidating the molecular, genetics and biochemical mechanisms of suppressive Pseudomonas spp. that produced antifungal metabolites phenazine and phloroglucinol. But over the last 20 years, we have gained a greater insight into the ecology of these bacteria in the dryland Pacific Northwest. This led to a long-term trial at Lind, WA, a low rainfall wheat-fallow zone, where we monitored the microbiome of wheat roots for 8 years in dryland and irrigated plots.  We sampled multiple times in the season and looked at the bacterial microbiome with 16S amplicon sequencing in the bulk soil, rhizosphere and root.  We found that the abundance of individual bacteria were modulated by soil moisture, plant growth stage & length of wheat monoculture. Taxa exhibited seasonal dynamics and periodicity, and population trends were reproducible across multiple years. Over the 8-year study, certain genera became more prevalent in the root under irrigated or dryland conditions. One discovery was the prevalence of actinobacteria in the root.  Over three years, we isolated a collection of over 1,000 actinobacteria.  The collection was dominated by Streptomyces, Kribbella, Amycolatopis and Promicromonospora. We did genomic sequencing and functional analysis of a subset, and many showed antifungal activity and growth promotion.  We are presently looking at the ability of selected strains to protect wheat and alfalfa against water stress.