DRUM Community: Plant Science & Landscape Architecture

TRANSMISSION OF CYMBIDIUM MOSAIC VIRUS IN ONCIDIUM ORCHIDS BY PERIPLANETA AUSTRALASIAE

Sun, 01 Jan 2012 00:00:00 GMT

Title: TRANSMISSION OF CYMBIDIUM MOSAIC VIRUS IN ONCIDIUM ORCHIDS BY PERIPLANETA AUSTRALASIAE Authors: Allen, Carol Dianne Abstract: ABSTRACT Title of Thesis: TRANSMISSION OF CYMBIDIUM MOSAIC VIRUS IN ONCIDIUM ORCHIDS BY PERIPLANETA AUSTRALASIAE Carol Dianne Allen, Master of Science. 2012 Thesis Directed by: Gary Coleman, Ph.D. Department of Plant Science and Landscape Architecture Cymbidium mosaic virus is the most common disease in orchids infecting a large number of cultivated orchids found in all phases of the industry and around the world. Its transmission occurs through contact by contaminated cutting tools, human hands, or water. Although insects known to transmit plant viruses have been exposed to orchid viruses, none have been found to successfully transmit Cymbidium mosaic virus. Periplaneta australasiae, the Australian cockroach, is a common greenhouse pest that is known to feed on orchid plants. In controlled conditions Australian cockroaches were given inoculation access through feeding activity on known CymMV positive orchid plants and then allowed to feed on virus free plants. The virus free plants were isolated from subsequent insect exposure and after a period of time samples from the feeding damage sites were analyzed for the presence of virus RNA through nested and hemi-nested PCR techniques. A statistically significant number of samples were positive demonstrating that with high population numbers and long term exposure, virus transmission is possible.

Bacterial community diversity and variation in spray water sources and the tomato fruit surface

Thu, 21 Apr 2011 00:00:00 GMT

Title: Bacterial community diversity and variation in spray water sources and the tomato fruit surface Authors: Telias, Adriana; White, James R; Pahl, Donna M; Ottesen, Andrea R; Walsh, Christopher S Abstract: Background: Tomato (Solanum lycopersicum) consumption has been one of the most common causes of produceassociated salmonellosis in the United States. Contamination may originate from animal waste, insects, soil or water. Current guidelines for fresh tomato production recommend the use of potable water for applications coming in direct contact with the fruit, but due to high demand, water from other sources is frequently used. We sought to describe the overall bacterial diversity on the surface of tomato fruit and the effect of two different water sources (ground and surface water) when used for direct crop applications by generating a 454- pyrosequencing 16S rRNA dataset of these different environments. This study represents the first in depth characterization of bacterial communities in the tomato fruit surface and the water sources commonly used in commercial vegetable production. Results: The two water sources tested had a significantly different bacterial composition. Proteobacteria was predominant in groundwater samples, whereas in the significantly more diverse surface water, abundant phyla also included Firmicutes, Actinobacteria and Verrucomicrobia. The fruit surface bacterial communities on tomatoes sprayed with both water sources could not be differentiated using various statistical methods. Both fruit surface environments had a high representation of Gammaproteobacteria, and within this class the genera Pantoea and Enterobacter were the most abundant. Conclusions: Despite the major differences observed in the bacterial composition of ground and surface water, the season long use of these very different water sources did not have a significant impact on the bacterial composition of the tomato fruit surface. This study has provided the first next-generation sequencing database describing the bacterial communities living in the fruit surface of a tomato crop under two different spray water regimes, and therefore represents an important step forward towards the development of science-based metrics for Good Agricultural Practices.

Apple skin patterning is associated with differential expression of MYB10

Fri, 20 May 2011 00:00:00 GMT

Title: Apple skin patterning is associated with differential expression of MYB10 Authors: Telias, Adriana; Lin-Wang, Kui; Stevenson, David E; Cooney, Janine M; Hellens, Roger P; Allan, Andrew C; Hoover, Emily E; Bradeen, James M Abstract: Background: Some apple (Malus × domestica Borkh.) varieties have attractive striping patterns, a quality attribute that is important for determining apple fruit market acceptance. Most apple cultivars (e.g. ‘Royal Gala’) produce fruit with a defined fruit pigment pattern, but in the case of ‘Honeycrisp’ apple, trees can produce fruits of two different kinds: striped and blushed. The causes of this phenomenon are unknown. Results: Here we show that striped areas of ‘Honeycrisp’ and ‘Royal Gala’ are due to sectorial increases in anthocyanin concentration. Transcript levels of the major biosynthetic genes and MYB10, a transcription factor that upregulates apple anthocyanin production, correlated with increased anthocyanin concentration in stripes. However, nucleotide changes in the promoter and coding sequence of MYB10 do not correlate with skin pattern in ‘Honeycrisp’ and other cultivars differing in peel pigmentation patterns. A survey of methylation levels throughout the coding region of MYB10 and a 2.5 Kb region 5’ of the ATG translation start site indicated that an area 900 bp long, starting 1400 bp upstream of the translation start site, is highly methylated. Cytosine methylation was present in all three contexts, with higher methylation levels observed for CHH and CHG (where H is A, C or T) than for CG. Comparisons of methylation levels of the MYB10 promoter in ‘Honeycrisp’ red and green stripes indicated that they correlate with peel phenotypes, with an enrichment of methylation observed in green stripes. Conclusions: Differences in anthocyanin levels between red and green stripes can be explained by differential transcript accumulation of MYB10. Different levels of MYB10 transcript in red versus green stripes are inversely associated with methylation levels in the promoter region. Although observed methylation differences are modest, trends are consistent across years and differences are statistically significant. Methylation may be associated with the presence of a TRIM retrotransposon within the promoter region, but the presence of the TRIM element alone cannot explain the phenotypic variability observed in ‘Honeycrisp’. We suggest that methylation in the MYB10 promoter is more variable in ‘Honeycrisp’ than in ‘Royal Gala’, leading to more variable color patterns in the peel of this cultivar.

Evaluation of qPCR reference genes in two genotypes of Populus for use in photoperiod and low-temperature studies

Mon, 23 Jul 2012 00:00:00 GMT

Title: Evaluation of qPCR reference genes in two genotypes of Populus for use in photoperiod and low-temperature studies Authors: Pettengill, Emily A; Parmentier-Line, Cecile; Coleman, Gary D Abstract: Background: Quantitative PCR (qPCR) is a widely used technique for gene expression analysis. A common normalization method for accurate qPCR data analysis involves stable reference genes to determine relative gene expression. Despite extensive research in the forest tree species Populus, there is not a resource for reference genes that meet the Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) standards for qPCR techniques and analysis. Since Populus is a woody perennial species, studies of seasonal changes in gene expression are important towards advancing knowledge of this important developmental and physiological trait. The objective of this study was to evaluate reference gene expression stability in various tissues and growth conditions in two important Populus genotypes (P. trichocarpa “Nisqually 1” and P. tremula x P. alba 717 1-B4) following MIQE guidelines. Results: We evaluated gene expression stability in shoot tips, young leaves, mature leaves and bark tissues from P. trichocarpa and P. tremula. x P. alba grown under long-day (LD), short-day (SD) or SD plus low-temperatures conditions. Gene expression data were analyzed for stable reference genes among 18S rRNA, ACT2, CDC2, CYC063, TIP4-like, UBQ7, PT1 and ANT using two software packages, geNorm PLUS and BestKeeper. GeNorm PLUS ranked TIP4-like and PT1 among the most stable genes in most genotype/tissue combinations while BestKeeper ranked CDC2 and ACT2 among the most stable genes. Conclusions: This is the first comprehensive evaluation of reference genes in two important Populus genotypes and the only study in Populus that meets MIQE standards. Both analysis programs identified stable reference genes in both genotypes and all tissues grown under different photoperiods. This set of reference genes was found to be suitable for either genotype considered here and may potentially be suitable for other Populus species and genotypes. These results provide a valuable resource for the Populus research community.