Characterizing Compost Teas for Biofertilization Research

Primary author: Adel Almesmari
Faculty sponsor: Lynne Carpenter-Boggs

Primary college/unit: Agricultural, Human and Natural Resource Sciences
Campus: Pullman

Abstract:

Compost teas (CT) have gained attention as possible alternatives or supplements to synthetic fertilizers and pesticides used in agriculture. CTs are becoming increasingly popular, and several studies have shown that CTs can provide nutrients to plants, increase soil and foliar microbial diversity, stimulate crop systemic disease resistance, and build soil structure. However, CTs are poorly studied and controlled, and vary widely in composition. For both research and practical purposes, there is need to standardize recipes for CTs with repeatable microbial and chemical characteristics. This experiment was conducted to determine the effects of compost type, recipe (additives and aeration), and brewing time on characteristics of CTs. Eight CTs were prepared by using four recipes (A, B, C, and D) with two types of compost (WSU bedding compost [Wb] and vermicompost [Ver]) or control (no compost). Each solution was characterized after 1, 3, 6, and 10 days of brewing time. CT characteristics were highly affected by the recipes and time of brewing, and minimally affected by type of compost. Recipes A and B supported high microbial populations and more soluble nutrients compared to recipes C and D. This was true with both types of compost and the controls with no compost. Microbial populations were smallest at day 1 and greatest at day 3. The study shows that CT characteristics can be well managed by recipe and brewing time. This work has potential to affect all future work on CT by describing standardized recipes and procedures for CTs with particular desired characteristics.

The hijacking of barley wall associated kinases by a fungal pathogen, Bipolaris sorokiniana to cause spot blotch disease

Primary author: Gazala Ameen
Co-author(s): Shyam Solanki; Thomas Drader; Lauren Bittara-Sager
Brian Steffenson; Chrysafis Vogiatzis; Robert Brueggeman
Faculty sponsor: Robert S. Brueggeman

Primary college/unit: Agricultural, Human and Natural Resource Sciences
Campus: Pullman

Abstract:
Plants have cell membrane bound immunity receptors that sense the pathogen attack and triggers the signalling to initiate defense responses which mostly result in localized programmed cell death (PCD). This PCD mediated resistance subdues biotrophic pathogens, which survive on living cells but can be hijacked by necrotrophic pathogens, that acquire nutrients from and colonize the resulting dead host cells to further plant diseases. We report that a necrotrophic pathogen Bipolaris sorokiniana, hijacks two barley wall associated kinase (WAK) cell-membrane bound receptors, Sbs1&2, underlying the previously reported rcs5 disease resistance locus on barley chromosome 7H to intentionally trigger the plant immune responses to cause PCD and ultimately causes spot blotch disease. Post-transcriptional gene silencing of Sbs1&2 genes in the susceptible barley lines Steptoe and Harrington resulted in spot blotch resistance, thus, proving that these two WAKs function as susceptibility genes. The expression analysis of Sbs1&2 showed nearly undetectable expression in resistant and susceptible lines prior to pathogen challenge, however, upregulation of both genes specifically occurred in susceptible lines post inoculation. Allele analysis of Sbs1&2 from eight resistant and two susceptible barley lines identified sequence polymorphisms associated with disease phenotypes in the promoter regions indicating that differential transcriptional regulation by virulent isolates contribute to WAK mediated susceptibility. Virulent isolate apoplastic wash fluids induced Sbs1 suggesting regulation by an apoplastic-secreted effector. Thus, the Sbs1&2 genes underlying the rcs5 QTL are the first susceptibility/resistance genes identified that confer resistance against spot blotch, a disease that threatens barley and wheat production worldwide.