With “urban farming” now part of the vernacular, agriculture has spread beyond its rural roots: now New York City has its own farmer training project, San Francisco’s municipal code encourages urban “micro farms,” and Chicago has a vibrant commercial urban agriculture program. With concerns over climate change on the rise, the term “resilient” has joined “sustainable,” “organic,” and “diversified” in discussions of the type of agriculture we need to encourage. And many who are interested in agriculture and building healthy communities come from non-farming backgrounds with no hands-on experience. The new edition of Teaching Organic Farming & Gardening: Resources for Instructors, was developed with this growing audience and evolving agricultural framework in mind. Through lectures, demonstrations, and exercises that can be tailored for use in the field, the garden, or the classroom, it offers comprehensive lessons from the “core” curriculum taught annually through the CASFS Apprenticeship, with an emphasis on developing basic organic farming and gardening skills for small- and medium-scale organic mixed vegetable operations. It also recognizes agriculture’s social component and the increased interest in equity and justice in the food system, with new material on the social impacts of the current agricultural system and information on food justice activities. Other new features include narrative supplements that expand on the updated lecture outlines, along with new appendices, illustrations,plastic planter pot and resource listings. As with earlier editions, all of the written material is available free online, enhanced by Power point and video to accompany many of the units . 

We plan to continue updating and revising the curriculum and look forward to your feedback in helping us improve this resource.Resources for Instructorsrepresents nearly fifty years of experience teaching organic farming and gardening skills, soil sciences, and social issues in agriculture at the Apprenticeship in Ecological Horticulture at UC Santa Cruz. The 2003 and 2005 editions of the training manual provided the opportunity to share this experience with a broader audience. In developing this updated and expanded edition, editors Martha Brown and Jan Perez had the chance build on the vision and efforts of original editor and author Albie Miles, and to enhance the lectures, demonstrations, and hands-on exercises based on feedback and insights from many instructors, apprentices, and students. At the heart of this effort have been the dedicated teachers, researchers, farmers, and Apprenticeship graduates who wrote, revised, and reviewed the various units . These already busy people were asked to add even more work to their overflowing schedules, and we are grateful to them for the many hours they committed in bringing this project to fruition. Thanks go also to many other contributors: Jane Bolling of Jane Bolling Design created the cover and updated the layout. Science illustrators Jose Miguel Mayo and Catherine Genetti Reinhard created the original line art for Parts 1 and 2. Photographers Acknowledgments Abigail Huetter and Brandon Blackburn took many of the photos for the accompanying online Powerpoint presentations. Jessica Beckett Parr, Hillary Terashima, and Jim Clark created the online videos. Daniel Wu updated many of the resources. We thank Daniel Press, Executive Director of the Center for Agroecology & Sustainable Food Systems, for his support throughout this project. And a very special thank you to Amy Bolton for the many hours of skillful work and insights required to lay out and proof more than 700 pages of materials. The Center’s grant writer Ann Lindsey brought in the funding for the training manual revision effort and helped shape and guide it along the way.

This project would not have been possible without the generous funders who provided their support for the revised and expanded training manuals: Gaia Fund, the USDA Beginning Farmer and Rancher Development Program, Western Sustainable Agriculture Research and Education , the Joseph and Vera Long Foundation, and the Eucalyptus Foundation. Funding for the project’s initial development came from the True North Foundation, the Arkay Foundation, the Foundation for Sustainability and Innovation, the Organic Farming Research Foundation, Richard and Rhoda Goldman Fund, The Mary A. Crocker Trust, The Foxwhelp Group of the Tides Foundation, The Kellogg Foundation through the California Food and Fiber Futures Project, and John Kinder.Lettuce die back disease is widespread in commercially grown romaine and leaf-type lettuces. The disease is caused by two closely related soilborne viruses from the family Tombusviridae — Tomato bushy stunt virus and Lettuce necrotic stunt virus. Symptoms of lettuce die back include mottling and necrosis of older leaves, stunting, and plant death . The characteristic symptoms usually appear after the plant has reached 6 to 8 weeks of age and render the plant unmarketable. TBSV and LNSV are extremely persistent viruses and they are likely to survive in soil and water for long periods of time. The virus has no known vector and it seems to move through infested soil and water. While fungal vectors are not necessary for transmission, studies have yet to be conducted to determine if such vectors can facilitate or increase rates of virus transmission to lettuce. Previous studies have provided no evidence that either chemical treatment or rotation with non-host crops can effectively reduce, remove, or destroy the virus in infested soil. Since there are no known methods to prevent the disease in a lettuce crop grown in an infested field, genetic resistance remains the only option for disease control. Although susceptibility to die back is widespread in romaine and leaf lettuces, modern iceberg-type cultivars remain completely free of symptoms when grown in infested soil.

It appears that the resistance observed in iceberg cultivars was originally introduced into the iceberg gene pool from the cultivar Imperial around 70 years ago. If true, this suggests that the resistance is effective and highly durable despite extensive cultivation of iceberg cultivars. Through use of molecular marker technology, the single dominant gene , which is responsible for the die back resistance in iceberg lettuce, has been mapped to chromosomal linkage group 2. Position of the gene was inferred with AFLP and RAPD markers in a population originating from a cross between the resistant cultivar Salinas and the susceptible cultivar Iceberg . Another die back resistance gene was discovered in the primitive romaine-like accession PI491224. Analysis of resistance in offspring originating from a cross between the two resistant genotypes indicates that the resistance locus in PI491224 is either allelic or linked to Tvr1. Because of the increased interest in non-iceberg types of lettuce,30 litre plant pots introgressing Tvr1 into romaine, leaf, and other susceptible types is of high priority for the lettuce industry. However, the breeding process is slow and labor intensive due to a need for extensive field-based testing. Application of marker-assisted selection can reduce the need for field screening and accelerate development of die back resistant material. To pinpoint the location of the Tvr1 gene and develop markers for marker-assisted selection, we employed acombination of classical linkage and association mapping techniques. The association mapping approach is based on the extent of linkage disequilibrium observed in a set of accessions that are not closely related. In contrast to linkage mapping, association mapping is a method that detects relationships between phenotypic variation and genetic polymorphism in existing germplasm, without development of mapping populations. This method incorporates the effects of recombination occurring in many past generations into a single analysis and is thus complementary to linkage analysis. Association mapping has been successfully applied in mapping resistance genes in several diploid and polyploid plant species . The main drawback of association mapping is the possibility of false-positive results due to an unrecognized population structure. When the trait of interest is more prevalent in one sub-population than others, the trait will be associated with any marker allele that is in high frequency in that sub-population . Our previous analysis of population structure with molecular markers revealed that cultivated lettuce is divided into several well-defined sub-populations that correspond approximately to different horticultural types. Consequently, traits that are strongly correlated with lettuce types display many false-positive results when population structure is ignored. However, these spurious associations disappear when estimates of population structure are included in the statistical model. Therefore, the best approach for avoiding spurious associations in lettuce association studies is to assess relatedness of accessions with molecular markers and to include this information into the statistical model. In the present study we mapped the Tvr1 gene using a combination of linkage and association mapping.

High resolution DNA melting curve analysis was used to assess polymorphism in mapping populations and to detect haplotypes associated with the disease resistance. The potential for marker-assisted selection was then validated in the genetic backgrounds present in most common horticultural types of lettuce. Finally, we used SNP markers to assess intra- and inter-locus linkage disequilibrium in the Tvr1 region.Recombinant-inbred lines were derived from a cross between an F1 of cv. Valmaine × cv. Salinas 88 and cv. Salinas. Both Salinas and Salinas 88 are iceberg type lettuces resistant to die back whose appearance and performance is the same, except for reaction to Lettuce mosaic virus . Two hundred and fifty three F8 RILs were screened for resistance to die back in multiple trials and 192 of these RILs were randomly selected for genotyping with molecular markers.A set of 68 cultivars, plant introductions , and breeding lines representing all predominant types of cultivated lettuce was used for association mapping. The set includes 8 Batavia types, 5 butter head types, 5 iceberg types, 5 Latin types, 9 leaf types, 31 romaine types, and 5 stem types.The lettuce accessions were selected from material used in breeding programs, ancestors frequently observed in pedigrees, and newly developed breeding lines. For each horticultural type both die back resistant and susceptible accessions were selected, with the exception of iceberg lettuce, where only resistant cultivars were available, and the Latin type, where only susceptible cultivars were available.Die back resistance data were obtained from field observations as previously described. Susceptibility was evaluated by seeding lettuce directly in the field in Salinas, CA, from which TBSV and LNSV had previously been isolated from plants exhibiting characteristic die back symptoms. The experiment was comprised of two complete blocks, with ~30 plants per genotype per block. Plants were seeded in two rows on 1 m wide beds and were thinned to obtain spacing of 30 cm between plants. Standard commercial practices were used for irrigation, fertilization, and pest control. Plants were checked weekly for disease symptoms in order to discriminate between plants dying due to die back and those due to unrelated causes.Accessions with < 5% of symptomatic plants were considered to be resistant. To minimize the possibility of inaccurate scoring, all accessions were tested in at least three independent field trials. If results from all three trials were consistent, the material was not tested further. In the case of inconsistent results, material was retested in another two independent trials,after which all accessions were classified into one of the two groups. The resistance and susceptibility classification was subsequently used in statistical analyses.Primer pairs were designed for each marker from EST sequence with the PRIMER 3 software. The selection of ESTs from the CGPDB database was based on their position in the genome – only ESTs previously mapped to the linkage group 2 were considered for development of markers. Due to the presence of introns in genomic DNA, primers for several markers had to be designed more than once to obtain an amplicon for the given marker. The polymerase chain reaction was performed in a 20 μl volume containing 10 ng of genomic DNA as a template, 200 μmol/L of each dNTP, 1× Standard Taq PCR buffer with 1.5 mmol/L MgCl2, 1.2 U Taq polymerase , and forward and reverse primers at a concentration of 0.25 μmol/L each. The reaction conditions were as follows: 95° for 2 min, followed by 35 cycles of 95° for 30 s, annealing temperature for 30 s, and 72° for 30 s, with final extension of 72° for 5 min. Amplification was performed in an MJ Research Tetrad Thermal Cycler . The PCR products were analyzed on gels composed of 0.7% agarose and 1.15% Synergel run with 0.5× TBE buffer. PCR samples were stained prior to electrophoresis with 1× GelRed . Alternatively, the PCR products were separated using an HDA-GT12 DNA analyzer and scored by Biocalculator software . If sequencing was needed, PCR products were first treated with Exonuclease I and subsequently with Antarctic Phosphatase .