The complete sequences of the mitochondrial genomes of the oomycetes of Phytophthora ramorum and P. sojae were determined during the course of their complete nuclear genome sequencing (Tyler, et al. 2006). Both are circular, with sizes of 39,314 bp for P. ramorum and 42,975 bp for P. sojae. Each contains a total of 37 identifiable protein-encoding genes, 25 or 26 tRNAs (P. sojae and P. ramorum, respectively) specifying 19 amino acids, and a variable number of ORFs (7 for P. ramorum and 12 for P. sojae) which are potentially additional functional genes. Non-coding regions comprise approximately 11.5 percent and 18.4 percent of the genomes of P. ramorum and P. sojae, respectively. Relative to P. sojae, there is an inverted repeat of 1,150 bp in P. ramorum that includes an unassigned unique ORF, a tRNA gene, and adjacent non-coding sequences, but otherwise the gene order in both species is identical. Comparisons of these genomes with published sequences of the P. infestans mitochondrial genome reveals a number of similarities, but the gene order in P. infestans differs in two adjacent locations due to inversions. Sequence alignments of the three genomes indicated sequence conservation ranging from 75 to 85 percent and that specific regions were more variable than others.

The recent phase-out of the soil fumigant methyl bromide (MB) due to its impact on stratospheric ozone pre-sents a huge challenge to strawberry nursery producers. We evaluated the effectiveness of alternative fumigants on soil pests and plant productivity, as well as production costs in California strawberry nurseries. Our trials followed nursery stock through low- and high-elevation phases of runner-plant propagation and a complete cycle of fruit production in coastal fields. Plant yields from the nurseries and fruit yields from Oxnard and Watsonville indicated that nursery plots treated with iodomethane plus chloropicrin, with 1,3-dichloropropene followed by dazomet, and with chloropicrin followed by dazomet produced runner-plant yields that were similar to methyl bromide plus chloropicrin. However, our economic analysis suggests that nursery profitability may nonetheless suffer from the loss of methyl bromide.

A 5-year project to facilitate the adoption of strawberry production systems that do not use methyl bromide initially focused on fumigant alternatives and resulted in increased use of barrier films that reduce fumigant emissions. The focus shifted in year 3 to evaluating and demonstrating nonfumigant alternatives: soilless production, biofumigation, anaerobic soil disinfestation (ASD) and disinfestation with steam. In the 2010–2011 strawberry production season, fruit yields on substrates were comparable to fruit yields using conventional methods. Anaerobic soil disinfestation and steam disinfestation also resulted in fruit yields that were comparable to those produced using conventionally fumigated soils. Additional work is in progress to evaluate their efficacy in larger-scale production systems in different strawberry production districts in California.