Patent Abstract:
the invention disclosed relates to a naturally occurring fungus , valdensinia heterodoxa , and to its culture , formulation and delivery systems , as well as its use as a biocontrol agent for salal .

Detailed Description:
[ 0024 ] valdensinia heterodoxa ( pfc 3027 ) having all of the identifying characteristics of idac deposit accession no . ida 180402 was isolated from salal leaf tissues in biologically pure form , by surface sterilizing small pieces of infected tissue , plating them onto potato dextrose agar ( pda ) or malt extract agar ( mea ) and incubating in the dark at 20 ° c . emerging colonies were subcultured onto pda plates , and then transferred to pda slants for long - term storage at 5 ° c . cultures of v . heterodoxa ( pfc 3027 ) were initiated by placing small ( v . heterodoxa ) mycelium pieces from potato dextrose agar ( pda ) slants maintained at 4 ° c . on salal pda ( spda ; pda amended with 40 g fresh , blended salal leaf and stem material / l dh 2 o ). fungal cultures were grown at 19 / 13 ° c . ( day / night ) with a 12 h day photoperiod ( 180 - 200 μem − 2 s − 1 ). eight days after inoculation , mycelial plugs of 5 - mm diameter were transferred onto weak oatmeal agar ( woa ; 15 g oatmeal agar and 12 g agar / l dh 2 o ) and incubated at the desired conditions , depending on the experiment . effect of temperature on growth , sporulation , and conidia discharge of valdensinia heterodoxa growth chambers were programmed at 11 / 6 , 14 / 9 , 17 / 12 , and 20 / 15 ° c ., respectively , with a 12 h day − 1 photoperiod ( 180 - 200 μem − 2 s − 1 ). fungal cultures of v . heterodoxa were initiated on spda and transferred onto woa as described above . at 3 , 6 , and 9 days post - inoculation ( dpi ), mycelial radial growth ( colony diameter ), total number of conidia , and number of discharged conidia adhering to the lid of the petri dish were determined . for each temperature treatment , five replicates were used and the experiment was performed twice . data were subjected to a one - way analysis of variance ( anova ). in case of failed normality or equal variance tests , a kruskal - wallis one - way anova on ranks was used instead . differences between treatment means were evaluated by a student - newman - keuls multiple comparison procedure ( p = 0 . 05 ). throughout the experiment , mycelial radial growth was greatest at the higher temperature regimes of 17 / 12 and 20 / 15 ° c . and was strongly inhibited at 11 / 6 ° c . similarly , total sporulation was improved at higher temperatures . however , conidia discharge displayed a clear optimum at 17 / 12 ° c . and declined substantially at both temperatures above and below this regime . differences in sporulation were observed as early as 3 dpi but more pronounced towards later evaluation dates . the results of both trials are summarized in table 1 . three photoperiod conditions including continuous light , alternating light / dark ( 12 h day − 1 photoperiod ), and continuous darkness were investigated . cultures of v . heterodoxa were initiated on spda and transferred onto woa as described above . fungal cultures were grown in a single chamber programmed at 17 / 12 ° c . with 24 h day − 1 light ( 180 μem − 2 s − 1 ). the treatment of continuous darkness was achieved by wrapping the petri dishes in aluminium foil . petri dishes assigned to alternating light conditions were unwrapped daily at the start of the higher temperature cycle . evaluation of mycelial growth , sporulation , and conidia discharge was performed as described above . for each photoperiod treatment , five replicates were used and the experiment was performed twice . data were analyzed as for the previous experiment . radial mycelial growth was moderately slower and total sporulation and conidia discharge were strongly inhibited by continuous darkness . although all evaluated parameters were improved by a continuous light treatment , differences between and continuous and alternating light were not always significant ( table 2 ). as in the temperature experiment , differences were observed as early as 3 dpi . sporulation data at later dates were highly variable for any of the light treatments . results of both trials are summarized in table 2 . starter cultures of v . heterodoxa on spda were initiated as described above . erlenmeyer flasks containing 250 ml of liquid weak oatmeal medium ( wom ; 20 g blended rolled oats / l dh 2 o ) were inoculated with 10 mycelial plugs from the starter cultures . flasks were placed on a shaker ( 125 rpm ) at 19 / 13 ° c . with a 12 h day − 1 photoperiod ( 180 - 200 μem − 2 s − 1 ). after 7 days , resulting mycelium was harvested on double - layered cheesecloth and blended in a waring blender for 20 sec at high speed . five ml of wet mycelium was added to erlenmeyer flasks containing autoclaved salal leaf pieces ( 7 g litter + 5 ml dh 2 o ). the fungal inoculum was incubated as described above and flasks were shaken daily . after 14 days , the colonized leaf material was air - dried for 2 days in a fume hood . salal seedlings were grown outside in 8 cm pots containing peat - vermiculite - sand ( 1 : 1 : 1 ) and a low rate of slow release fertilizer . plants of similar size were selected and transferred into a growth chamber at the original conditions . fungal inoculum was applied below salal leaves . for potted salal plants , usually several leaves protrude farther than the pot rim , hence , a structure was built beyond the rim to ensure that all leaves could be reached by discharging conidia . plastic sheets ( coroplast ) were cut into 14 × 14 cm pieces with a 6 × 6 cm hole in the centre . to provide a rougher surface for the leaf pieces to be placed onto , cheesecloth was cut into the same outside dimensions as the coroplast with a ¾ slit in the centre . both coroplast and cheesecloth were carefully placed around the plant and fixed with a pin . for each plant , 3 g of dried leaf pieces were applied onto the cheesecloth and watered with dh 2 o from a spraying bottle . uninoculated leaf pieces served as the control treatment . for each treatment , five replicate plants were used . pots were then transferred to a dew chamber ( 100 % relative humidity , 20 ± 1 ° c .) for 24 h ; and subsequently covered with clear plastic bags and the ends tucked under the base of the pots . after the dew treatment , pots were moved back to the original growth chamber . plastic bags were removed daily for a few minutes to ensure proper aeration . leaf damage was evaluated 14 dpi , based on the percentage of necrotic leaf area . data were analyzed using a kruskal - wallis one - way analysis of variance on ranks followed by a student - newman - keuls multiple comparison procedure in order to evaluate differences between treatment means ( p = 0 . 05 ). first disease symptoms on salal plants developed 4 dpi and necroses expanded quickly over the next days , whereas no symptoms were observed on the control plants ( figure ). older leaves with thicker cuticle became infected as well , but necroses did not expand as fast compared with young leaves . the origin of the necrosis was easily identified by the discharged conidium still attached to the leaf surface in the centre of the necrosis . some leaves with their upper surface facing down , developed disease symptoms as well . as the stomata of salal are only found on the lower leaf surface , it is assumed that conidia of v . heterodoxa are able to penetrate their host directly . in trial 1 and trial 2 , plants exposed to the fungal inoculum developed on average 33 and 39 % leaf damage , respectively . the observed leaf damage in this study is rather low compared with a spray application of other potential bioherbicides in which plants are usually completely covered with fungal propagules . although most necroses developed rapidly , many leaves were not infected until the end of the experiment . on those leaves , very few conidia were found , due to either insufficient sporulation and / or loss of discharged conidia . the findings of this research confirm the potential of v . heterodoxa to be used as a biological control agent for salal , and in particular , the use of colonized leaf pieces as an inoculum source and delivery technique . d &# 39 ; 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