Microbial Inoculants for Sustainable Forests

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<ul><li><p>This article was downloaded by: [University of Windsor]On: 24 November 2014, At: 08:24Publisher: Taylor &amp; FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,UK</p><p>Journal of Sustainable ForestryPublication details, including instructions forauthors and subscription information:http://www.tandfonline.com/loi/wjsf20</p><p>Microbial Inoculants forSustainable ForestsM. S. Reddy a , L. M. Funk a , D. C. Covert a , D. N.He a &amp; E. A. Pedersen aa Agrium Inc., AgBiologicals , Saskatoon,Saskatchewan, CanadaaPublished online: 17 Oct 2008.</p><p>To cite this article: M. S. Reddy , L. M. Funk , D. C. Covert , D. N. He &amp; E. A.Pedersen (1997) Microbial Inoculants for Sustainable Forests, Journal of SustainableForestry, 5:1-2, 293-306, DOI: 10.1300/J091v05n01_08</p><p>To link to this article: http://dx.doi.org/10.1300/J091v05n01_08</p><p>PLEASE SCROLL DOWN FOR ARTICLE</p><p>Taylor &amp; Francis makes every effort to ensure the accuracy of all theinformation (the Content) contained in the publications on our platform.However, Taylor &amp; Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness,or suitability for any purpose of the Content. Any opinions and viewsexpressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor &amp; Francis. The accuracy of theContent should not be relied upon and should be independently verified withprimary sources of information. 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Terms &amp; Conditions of access and use can be found athttp://www.tandfonline.com/page/terms-and-conditions</p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>ity o</p><p>f W</p><p>inds</p><p>or] </p><p>at 0</p><p>8:24</p><p> 24 </p><p>Nov</p><p>embe</p><p>r 20</p><p>14 </p><p>http://www.tandfonline.com/page/terms-and-conditions</p></li><li><p>Microbial Inoculants for Sustainable Forests </p><p>M. S. Reddy L. M. Funk </p><p>D. C. Covert D. N. He </p><p>E. A. Pedersen </p><p>ABSTRACT. Fungal root pathogens are widespread and may cause substantial seedling losses in conifer nurseries. Furthermore, poor seedling survival and growth on reforestation sites results in reduced forest regeneration. Use of microbial inoculants for disease control and plant growth promotion has become an important endeavour. A microbial culture collection of 500 strains was assessed for biologi- cal control of fungal root pathogens andlor plant growth promotion of conifer seedlings. Seven of these strains showed signiticant suppres- sive effects on various soil-borne fungal pathogens. On Douglas fir, two strains, RAL3 and 64-3, reduced disease caused by Fusarium by 7-42% in repeated growthroom assays. The same strains significant- ly increased healthy stand of white spruce seedlings inoculated with Fusarium and Pythium in a conifer nursery, and increased the surviv- al of bare-root white spruce seedlings planted on a reforestation site by 19-23%. Both strains also significantly increased new root and </p><p>M. S. Reddy, L. M. Funk, D. C. Covert, D. N. He and E., A. Pcdersen are affiliated with Agrium Inc., AgBiologicals, Saskatoon, Saskatchewan, Canada. </p><p>[Hawonh co-indexing entry note]: "Microbial lnoculants for Sustainable Forests." Reddy. M. S. el al. Co-published simultaneously in Journol o/'Suahinohle Formrn' (Food Products Press. an imprint of The Hewonh Prcss, Inc.) Vol. 5. No. 112. 1997. pp. 293-306; and: Surminohl~ Fowsrs: Glohol Clrol- Cnge.~ and Local Solurions (ed: 0. Thomas Bouman. and David G . Brand) Food Products Press. an imprint of The Hawonh Press. Inc.. 1997. pp. 293-306. Single or multiple copies of this article arr available for a fee from The Hewonh Document Delivery Sewice [I-800342-9678.9:00 a.m. - 5:00 p.m. (EST). E-mail address: getinro@hawonh.com]. </p><p>O 1997 by The Haworth Press, Inc. All rights reserved. 293 </p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>ity o</p><p>f W</p><p>inds</p><p>or] </p><p>at 0</p><p>8:24</p><p> 24 </p><p>Nov</p><p>embe</p><p>r 20</p><p>14 </p></li><li><p>294 Sustainable Forests: Global Challenges and Local Solutions </p><p>total plant dry weights. Strain RAL3 in commercial formulation maintained a viable population of about log 8-9 cfuiml for over a year whcn stored at 5C. Strain survival on seed varied with conifer species. No decreases in bacterial populations were observed on seeds of jack pine or Douglas fir after 37 to 44 days storage at S T , but decreases were observed on seeds of white spruce and Scots pine. This study has providcd candidate beneficial microbial inocu- lants which offer promise for development of commercial inoculants for the forestry industry. [Article copies available for a fee jiDm The Haworth Document Delivery Sewice: 1-800-342-9678. E-mail address: getinfo@ haworth.com] </p><p>INTRODUCTION </p><p>Forestry is an extremely important industry in many countries, including Canada (Reddy et al. 1993). With an increasing demand for forest products, foresters have turned toward more intensive management practices to increase productivity of forest lands. These methods include the breeding of forest trees with increased growth and superior wood characteristics, artificial regeneration using seedlings, control of competing vegetation, t h i ~ i n g stands to reduce competition between trees, fertilization to stimulate growth, and improved methods for harvesting and utilization of wood. Most of these practices are well understood and are used in modem forestry, Perhaps the most effective way of increasing productivity is the use of genetically improved material as planting stock. Unfor- tunately, this material is usually in short supply. </p><p>Over seven hundred million conifer seedlings are planted annual- ly in Canada, making silviculture an extremely important industry. It is imperative that seedling quality be at a high level to allow for successful reforestation of harvested land. Seedling losses occur in conifer nurseries as well as on reforestation sites. Fungal pathogens inciting seed and/or root diseases in nurseries include Fusariurn, Cylindrocarpon, Cylindrocladiunl and Pythium. Diseases caused by these pathogens may be important limiting factors in production of high quality seedlings in forest and conservation nurseries. All nurseries experience some losses to damping-off and root rot dis- eases, despite the best efforts at control. These losses may occur in several forms, the most obvious being dead and dying seedlings </p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>ity o</p><p>f W</p><p>inds</p><p>or] </p><p>at 0</p><p>8:24</p><p> 24 </p><p>Nov</p><p>embe</p><p>r 20</p><p>14 </p></li><li><p>Reddy et al. 295 </p><p>observed in nursery beds. The economic loss represented by this type of seedling mortality may vary with the age of the affected seedlings. Diseases may also damage seedlings, making them un- suitable for planting. Damaged seedlings are thrown away (culled) during lifting and packaging. Some diseased seedlings may escape culling or remain symptomless at the time of lifting. In these cases, pests are transported to field plantings, where they continue to cause economic losses by killing, stunting, or deforming trans- planted seedlings. </p><p>Chemical pesticides were initially formulated for effectiveness on many soil-borne pathogens. This broad spectrum efficacy often resulted in destruction of both beneficial and injurious organisms (Baker and Cook 1974). However, resistance to these chemicals can develop rapidly in pathogens. In recent years, problems with pesti- cide resistance, toxicity to non-target organisms, and environmental contamination have greatly reduced the desirability of chemical fungicides (Campbell 1989). Recent public and government in- volvement in banning chemicals used in agriculture and forestry will undoubtedly make the use of chemical fungicides difficult at best. Therefore, foresters and nursery managers need to examine all al- ternatives for controlling fungal diseases. One of the most accept- able approaches to disease control is the use of naturally occumng microbial inoculants to reduce or suppress the activity of hngal pathogens (Reddy 199 1). </p><p>Losses in forest productivity include poor seedling establishment and survival on reforestation sites due to factors other than disease. For example, root growth of transplanted seedlings is often limited, contributing to poor seedling health. Root system morphology is a major determinant of seedling success in the field. The goal of bare-root nursery managers is to produce high quality seedlings </p><p>' </p><p>which can tolerate lifting, handling, and planting processes, and not only survive but grow competitively in the field. This goal is a challenging one to attain. No two nurseries are alike and within- nursery variation in soil and microclimate may be as great as that among nurseries. Seedling grading has been controversial because no scientifically based procedure has been developed for identify- ing which seedlings in a nursery will be the most competitive in the field. The economic impact due to seedling losses on reforestation </p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>ity o</p><p>f W</p><p>inds</p><p>or] </p><p>at 0</p><p>8:24</p><p> 24 </p><p>Nov</p><p>embe</p><p>r 20</p><p>14 </p></li><li><p>296 Suslainable Forests: Global Challenges and Local Solulior~s </p><p>sites, regardless of the cause, is substantial since the approximate cost to plant a single seedling is $1.00. Many diverse groups of bacteria commonly inhabit nursery soil. Several species are antago- nistic toward common soil-borne pathogens (Reddy 1991; Reddy et al., 1991, 1992, 1993, 1994). In our program beneficial microor- ganisms specifically selected for forestry are being evaluated for: (I) Biological control of fungal root pathogens in conifer nurseries, (2) Enhancement of conifer seedling growth and survival on refor- estation sites. </p><p>The purpose of this report is to draw the attention of forest managers and researchers to the potential commercial value of in- corporating microbials as seed or root inoculants to increase pro- ductivity in intensive forestry programs. Selection of these bacteria was based upon availability, ease of manipulation, wide geographic and host range, and demonstrated benefits to a wide variety of host trees. </p><p>MATERIALS AND METHODS </p><p>Seed and seedlings used for experimentation purposes were ob- tained from commercial nursery suppliers and industry seed or- chards. The best quality seed and seedlings, both genetically and physically, were selected. </p><p>Biological Control </p><p>Approximately 500 microbial strains isolated from conifer seed- ling rhizospheres, mycelial baits, and disease escape plants, and beneficial strains from other plantlpathogen systems were screened for suppression of Fusarium and Pythium diseases on Douglas fir and white spruce seedlings. Conifer seed was soaked in bacterial cell suspension in liquid proprietary formulation (log 3-5 cfulseed). Seed was then planted in Magenta GA7 jars containing peather- miculite planting mix fertilized with a liquid nursery solution to 79% moisture (planting mix pH 5.2). The planting mix surface was inoculated with conidia of F: oxysporutn in 1.0 mL spots under seeds (log 5 cWmL). Seeds were covered with granite grit and jars </p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>ity o</p><p>f W</p><p>inds</p><p>or] </p><p>at 0</p><p>8:24</p><p> 24 </p><p>Nov</p><p>embe</p><p>r 20</p><p>14 </p></li><li><p>Reddy el al. 297 </p><p>were capped with lids, randomized and incubated in a growth room for 4 weeks under an 18 hr photoperiod using a moderate heat stress (28-30C) to enhance disease development (8 seedsljar, 8 jarsttreat- ment; Fusarium control treatment utilized 24 jars). A similar ex- periment was conducted in a commercial nursery at Prince Albert, Saskatchewan. At the nursery, treatments were replicated 10 times and were arranged in a randomized complete block design. Percent- age germination and healthy stand were assessed during the experi- ment. All strains which resulted in a reduction in disease were tested two to four times. The data were analyzed using ANOVA and Fisher's protected LSD test. </p><p>Plant Growth Promotion Reforestation Trials </p><p>Select bacterial strains Burkholderia cepacia strain RAL3 and Pseudomonasfluorescens strain 64-3 were tested for enhancement of seedling growth and survival on field sites in British Columbia, Alberta, and Saskatchewan. The roots of container or bare-root white spruce seedlings were soaked in a bacterial suspension in liquid formulation (log 7 cfidmL) for 15 to 30 min and planted in reforestation field trials in a randomized complete block design. Control seedlings received no bacteria. There were 10 replicates with 20 seedlings per treatment. Experimental plots were flagged in each comer with surveyors' flags, and wooden stakes were labelled with plot numbers and placed at the centre-front of each plot to allow identification during planting and assessment. Seedling sur- vival, height (from ground line to the tip of the terminal bud), and root collar diameter were assessed at 4 and 15 months after plant- ing. Dry weight (biomass production) of above ground parts (fo- liage, stem, and branches) of the seedlings and new roots were also measured. The results were analyzed using ANOVA and Fisher's protected LSD test. </p><p>Shelf-Life of Bacteria in Formulation and on Conifer Seed </p><p>The shelf-life of strains RAL3 and 64-3 were evaluated in propri- etary commercial liquid formulation. The inoculum was produced in lab-scale fermenters and stored in commercial packages at 5"C </p><p>Dow</p><p>nloa</p><p>ded </p><p>by [</p><p>Uni</p><p>vers</p><p>ity o</p><p>f W</p><p>inds</p><p>or] </p><p>at 0</p><p>8:24</p><p> 24 </p><p>Nov</p><p>embe</p><p>r 20</p><p>14 </p></li><li><p>298 Stltrainable Forests: Global Challenges and Local Solutions </p><p>and 20C (room temperature). Shelf-life was assessed using stan- dard serial dilution plate technique onto replicated Pseudomonas Agar F plates at zero time and at 2 month intervals for one year. Plates were incubated for 48 h at 30C, colonies were counted, and the data were converted to colony forming units (cfu)/mL. </p><p>The shelf-life of strains RAL3 and 64-3 were also assessed on seed of white spruce, Douglas fir, jack pine, and Scots pine. Seeds were treated with rifampicin (ria marked strains as a seed soak (0.3 mL/g seed) and stored at 5C. There were 3 replications per treat- ment. Seeds were sampled to determine survival of the bacteria at various times up to 52 days after treatment. The sampling procedure was the same as described above. Shelf-life data were converted to </p><p>RESULTS </p><p>The locations of experimental sites are shown in Table 1. Some of the microbial inoculants included in greenhouse bioassays, com- mercial nurseries, and on reforestation sites are shown in Table 2. For the sake of brevity, only results for two bacterial strains RAL3 and 64-3...</p></li></ul>

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