1a. Objectives (from AD-416)
1. Assess the rooting behavior of apple as affected by different resource inputs (e.g. mineral fertilizer, compost, seed meal) and determine the relative contribution of soil biology and input to root development. 2. Examine the effect of fertility management programs on the dynamics of nematode and protozoan communities in the apple rhizosphere through application of T-RFLP and real-time quantitative PCR analysis. 3. Key genes steering microbial nitrogen cycling in the apple rhizosphere will be quantified under different resource input programs and linked to efficiency of use in the orchard ecosystem. 4. Determine the effect of altered soil biology on fruit quality characteristics including ripening; coloring; and long term storage quality.
1b. Approach (from AD-416)
Rooting behavior of apple in response to soil amendments and the contribution of native biology to these amendments will be assessed initially in greenhouse experiments. Short-term studies will employ apple seedlings and longer-term studies will utilize M9 rootstock as the plant material in these experiments. Initial trials will examine the effect of soil treatments on growth and architecture of apple seedling root systems when established in native and pasteurized soil systems. Seedlings will be grown in native and pasteurized soils with or without application of soil amendments. Overall seedling biomass will be determined after eight weeks growth in the respective soils. Root architecture will be assessed using winrhizo software analysis. It is generally assumed that organic matter based fertilizers will enhance soil fauna populations, but only a marginal number of materials (typically manure-based) have been examined). We possess preliminary data indicating that certain organic fertilizers will negatively impact soil fauna communities, including free living nematodes. Developing strategies to augment rather than suppress these populations will contribute positively to tree productivity both directly and indirectly. We will utilize real-time quantitative PCR and T-RFLP analysis to assess the effect of fertility management programs on quantitative and qualitative aspects of nematode and protozoan communities resident to apple orchard soils. Sustainable management of fertility inputs should seek to obtain a highly efficient turnover of minerals, with particular emphasis on minimizing nitrogen losses due to leaching of nitrogen and losses of gaseous N products. Previous studies have commonly ignored the fact that nitrogen turnover is the result of a network of closely interlinked processes. Therefore, we will investigate the effects of different fertility amendments on multiple transformation events within the nitrogen cycle in orchard soils and the specific microbial populations associated with these processes. Specifically, we will utilize real-time PCR to monitor expression of key genes steering microbial nitrogen cycling in the apple rhizosphere under different resource input programs and link expression patters to efficiency of nitrogen use in the orchard ecosystem. Fertility inputs significantly influence fruit quality through its effect on fruit ripening and capacity to retain desired eating characteristics under long-term storage. We will assess the impact of different fertility management practices on quality of fruit under long-term controlled atmosphere storage conditions. Documents Trust with Washington tree Fruit Research Commission. Log 40939.
3. Progress Report
Although funds were committed to this project by the Washington Tree Fruit Research Commission in February 2010, administratively funds still have not been made available to the PI. As such, there is no progress to be reported.