1a. Objectives (from AD-416)
1) Determine if there is value in adding arbuscular mycorrhizal (AM) fungi inoculum, particularly at planting. 2) Determine if pre-plant fumigation impacts the extent and nature of AM fungal populations in the soil and is this of consequence? 3) Characterize the AM fungi populations present on field grown nursery stock vs. potted plants at the time of planting and the resulting tree performance.
1b. Approach (from AD-416)
Nonpareil almond trees on Nemaguard rootstock will be planted in Spring 2008 at USDA Parlier. Plot strips will be fumigated in the fall of 2007 and non-fumigated plot strips will be used as comparison. An assessment of the extent and nature of AM fungi populations present in the soil/residual roots after fumigation but before planting. At time of planting and before any inoculation, there will be an assessment of the extent and nature of AM present on tree roots. Tree performance data to be collected will include: 1. Trunk circumference: initial and final yearly. 2. Annual pruning weights; Nutrient status-characterize nutritional deficiencies if and when symptoms arise. 3. At end of trial: Whole tree top weight, trunk diameter, etc. Annual assessments will be made of the extent and nature of AM fungal populations on tree roots.
3. Progress Report
Aflatoxin contamination is associated with water stress, insect wounding or natural cracking in peanuts, corn, cotton and tree-nuts. Aflatoxin levels are shown to be much higher in commodities when the crops are under water stress. Application of arbuscular mycorrhizal fungal inoculum to almond orchard is likely a feasible way to lessen water stress before harvest. The fungus colonizes the root and grows out into the soil. Hyphae net work, the part of the fungus that's in the soil acts as an extension of the root system. Evidence also suggests the symbiosis provides protection of the plant against pathogens as well as modifies soil microbial population. A field trial was initiated in early 2008 to examine the effects of Arbuscular Mycorrhizal (AM) fungi on almond tree growth. The trial was planted on 7 February 2008 at the San Joaquin Valley Agricultural Sciences Center. Trees used in the study were either traditional bare root (1/2” caliper) Nonpareil/Nemaguard or 3/8” caliper ‘potted’ Nonpareil/Nemaguard trees. Three AM treatments were imposed on the bare root trees (control, field cultured AM and commercial cultured AM) and potted trees were utilized as either controls, or field cultured AM (five total tree treatments).Trunk caliper was measured during the 2008 growing season to provide an indication of relative tree growth. Performance evaluation will be continued for at least two years. DNA was extracted from spores and colonized roots by CTAB method. Primers from different region of AM fungal ribosomal genes were designed for identification AM fungal species. Glomus Mosseae, Glomus 3, Gigasproa rosea, Glomus intraradices were present in the soil and in colonized roots. Methods used, as ADODR, for interacting with collaborators and stakeholders involved two meetings. At these meetings, discussions were held on research results, progress and future direction.