Silicon Soil Amendments for Suppressing Powdery Mildew on Pumpkin

A greenhouse experiment was conducted with Cucurbita pepo L. “Howden” pumpkin to compare the effectiveness of various soil amendments for providing Si nutrition, improving soil fertility, and suppressing powdery mildew (Podosphaera xanthii). A sandy loam soil with an initial soil pH of 4.5 was left unamended or amended with various liming materials or silicon sources. Calcite limestone, dolomite limestone, wollastonite, CaMg silicate slag, and wood ash were similarly effective liming materials for neutralizing soil acidity, but Montanagrow™ and glacial rock flour were not shown to be effective liming materials. Powdery mildew disease incidence and severity was visually scored on the foliage. Disease development was inversely related to Si concentration in vine tissue. Wollastonite was the most effective amendment at increasing Si uptake and for suppressing powdery mildew disease and glacial rock flour was not effective

Evaluation of a New Harpin Product on Microbial Quality and Shelf Life of Minimally Processed Lettuce

The effect of pre-harvest application of Extend®, a newly developed second generation harpin product, on shelf life of fresh-cut lettuce was investigated. The lettuces were grown in locations A: Watsonville, CA; B: Cedarville, NJ; and C: Yuma, AZ, and treated five days before harvest at 30, 60 and 90 ppm (2,4 and 6 oz/acre in 50 gal/acre). Lettuce processed and bagged was stored at 34-37°F and evaluated for quality for 20 days. Lettuce from trial A treated with 60-90 ppm harpin consistently had a better overall quality and lower microbial population than the control. Results from trial B showed no differences among treatments. In trial C, microbial population was lower and visual quality higher in lettuce treated at 60 ppm than the control during early stages of storage. Overall results are mixed but it was revealed that a field application of harpin can improve quality of fresh-cut lettuce under conditions that need to be determined

Additional file 5: of Population structure, genetic diversity and downy mildew resistance among Ocimum species germplasm

Genotype data. Binary matrix of accessions (rows) and alleles (columns). (XLSX 186 kb

Additional file 1: of Population structure, genetic diversity and downy mildew resistance among Ocimum species germplasm

Description of 180-accession panel of Ocimum spp., cluster membership and response to downy mildew (Peronospora belbahrii) reported as disease severity. (PDF 115 kb

Additional file 2: of Population structure, genetic diversity and downy mildew resistance among Ocimum species germplasm

Primer sequences and melting temperatures (Tm) for the EST-SSRs used in this study. (PDF 52 kb

A first linkage map and downy mildew resistance QTL discovery for sweet basil (<i>Ocimum basilicum</i>) facilitated by double digestion restriction site associated DNA sequencing (ddRADseq)

<div><p>Limited understanding of sweet basil (<i>Ocimum basilicum</i> L.) genetics and genome structure has reduced efficiency of breeding strategies. This is evidenced by the rapid, worldwide dissemination of basil downy mildew (<i>Peronospora belbahrii</i>) in the absence of resistant cultivars. In an effort to improve available genetic resources, expressed sequence tag simple sequence repeat (EST-SSR) and single nucleotide polymorphism (SNP) markers were developed and used to genotype the MRI x SB22 F₂ mapping population, which segregates for response to downy mildew. SNP markers were generated from genomic sequences derived from double digestion restriction site associated DNA sequencing (ddRADseq). Disomic segregation was observed in both SNP and EST-SSR markers providing evidence of an <i>O</i>. <i>basilicum</i> allotetraploid genome structure and allowing for subsequent analysis of the mapping population as a diploid intercross. A dense linkage map was constructed using 42 EST-SSR and 1,847 SNP markers spanning 3,030.9 cM. Multiple quantitative trait loci (QTL) model (MQM) analysis identified three QTL that explained 37–55% of phenotypic variance associated with downy mildew response across three environments. A single major QTL, <i>dm11</i>.<i>1</i> explained 21–28% of phenotypic variance and demonstrated dominant gene action. Two minor QTL <i>dm9</i>.<i>1</i> and <i>dm14</i>.<i>1</i> explained 5–16% and 4–18% of phenotypic variance, respectively. Evidence is provided for an additive effect between the two minor QTL and the major QTL <i>dm11</i>.<i>1</i> increasing downy mildew susceptibility. Results indicate that ddRADseq-facilitated SNP and SSR marker genotyping is an effective approach for mapping the sweet basil genome.</p></div

Detection of major downy mildew resistance QTL <i>dm11</i>.<i>1</i> across three environments.

<p>LOD scores for genome-wide scan using square-root transformed phenotype data from three environments: NJSN14 (northern New Jersey; 2014), NJRA14 (southern New Jersey; 2014) and NJRA15 (southern New Jersey; 2015). Significant LOD thresholds (α = 0.05) were calculated by permutation tests with 1,000 iterations and are shown with red, dashed horizontal lines.</p