2010 Annual Report
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.
Almond trees planted for this project are now in their third year of growth in fumigated and non-fumigated soils. Trees bloomed for a first time during this growth season and bloom strength was evaluated at full bloom. Blooming progressed similarly throughout the various treatments, but bloom strength differed. Blooming was more intense among trees planted in fumigated plots, regardless of whether trees were bare root/potted or with/without AM treatment. To date in the third year, trunk caliper measurements have been taken twice (752 and 832 days after planting on 1 March 2010 and 20 May 2010, respectively). While no trees have died in the test, several trees in non-fumigated plots appear weak and unhealthy. Five samples were collected from fumigated almond trees and the other from non-fumigated. Roots and surrounding soil were added to a potting mixture seeded with Sudangrass for detecting and isolating AM fungi. Spores were extracted from soils by wet sieving. Sudangrass roots cut in 1-cm segments were stained with trypan blue to detect AM colonization. Spores and stained roots were viewed under a Zeiss stero-microscope. DNA was extracted from spores and colonized roots using PowerSoil DNA isolation kit. Primers from AM fungal ribosomal genes were used for generating PCR fragments. TOPO TA cloning and DNA sequencing were also employed to aid in AM fungal identification. Several hundred clones are being sequenced to determine AM fungal species. Roots of Sudangrass from trap cultures were analyzed for AM fungal colonization in fumigated and non-fumigated soils. The data indicate that fumigation did reduce residual soil AM fungal population.
The ADODR monitored this project through site visits, emails and phone calls.
The goal of the specific cooperative agreement is to develop practical applications of arbuscular mycorrhizal fungi to reduce aflatoxin in almond, which contributes directly to Objective 2 of the in-house project.