Encyclopedia Of Plant

[Vikki Nagindas]

TheEncyclopedia of Plant Viruses and Viroids provides an up-to-date information on the viruses and viroids infecting all types of cultivated and weed plants at global level; and is unique among plant virology texts as it is organized alphabetically by the genus name of the host plant infected. It allows the reader to readily determine all of the different viruses currently reported naturally infecting the plant genus and species. Information is provided for each virus and viroids on common synonyms, current taxonomic status, geographical distribution, symptoms induced, other known hosts, means of transmission and properties of both the virus particles and the genome. Where ever the same virus is known to infect multiple hosts, host-specific information, biological properties and genome characters are presented under each host affected. The index can be utilized to identify other crops infected by the same virus, showing which other crops might be at risk of infection in the event of introduction of a virus that has not previously reported in an area, or which might serve as potential virus reservoirs for infection of more sensitive or economically important crops than the host in which it is initially identified.

The taxonomy and nomenclature of the viruses and viroids are followed based on the current guidelines of the 10th ICTV Report, covering up to 2018 and also about many new viruses and viroids that have been reported but not yet recognized as species by ICTV, have been included in this Encyclopedia. The uniqueness of this Encyclopedia is that all the known viruses and viroids affecting more than 1010 plant species at global level are described and the plant species are arranged in alphabetical order of the scientific name of the plant along the relevant information on 1518 viruses and viroids and is the ready-reckoner of the global plant species and their viruses and viroids for students, scientists, teachers of Plant Pathology& Virology; and also for the crop protection professionals, agricultural policymakers, seed companies and quarantine agencies.

Dr. K. Subramanya Sastry is currently retired and has last worked as Principal Scientist (ICAR), National Research Centre for Sorghum, Rajendranagar, Hyderabad from 1991 to 1998. His areas of interest are teaching and research in plant Virology, pathology, Microbiology. He has total 27 years of extension experience in Indian council of Agricultural Research and 5 years of teaching experience in Department of Botany, S.V. University, Tirupati. He has published total of 5 books and 83 research papers. Published three books on plant virology from Springer during 2012-14.

Dr. John Hammond is currently working as Research Plant Pathologist, United States Department of Agriculture, Agricultural Research Service, Floral and Nursery Plants Research Unit, Beltsville. His major areas of research are viruses affecting ornamental crops, with emphasis on potyvirus, potexvirus and carlavirus detection, differentiation, and methods of introducing resistance, use of transgenic plants to examine virus resistance and infectious viral clones to determine factors affecting host range, symptom induction, and systemic movement, and development of microarrays for plant virus detection and identification.

Dr. Simon W. Scott has recently retired from Clemson University as a Professor Emeritus in Plant Pathology. His major areas of research were viruses and virus-like agents affecting woody deciduous species with an emphasis on those viruses that affect the dominant fruit crop in SouthCarolina (peaches). He has established a program to index large blocks of peach trees in the southeastern USA prior to propagation as part of the USDA/APHIS National Clean Plant Network. In addition he has produced extensive sequence data for a number of Ilarviruses allowing long-standing taxonomic anomalies to be corrected.

Dr. Robert William Briddon has worked as Principle Investigator in Agricultural Biotechnology Division, National Institute of Biotechnology and Genetic Engineering (funded by United States Department of Agriculture (USDA) through the International Centre for Agricultural Research in the Dry Areas (ICARDA, Islamabad Office). His research area is in study of vector transmission of plant infecting viruses. Particularly the interactions involved between virus and insect vector of circulatively and propagatively transmitted viruses and the evolution thereof. He has total 135 publications in ISI Web of knowledge. He is also a member of British Society for Plant Pathology, European Whitefly Study Network and International Committee on Taxonomy of Viruses.

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MicroRNAs (miRNAs) are small non-coding RNA molecules that function as diverse endogenous gene regulators at the post-transcriptional level. In the past two decades, as research effort on miRNA identification, function and evolution has soared, so has the demand for miRNA databases. However, the current plant miRNA databases suffer from several typical drawbacks, including a lack of entries for many important species, uneven annotation standards across different species, abundant questionable entries, and limited annotation. To address these issues, we developed a knowledge-based database called Plant miRNA Encyclopedia (PmiREN, ), which was based on uniform processing of sequenced small RNA libraries using miRDeep-P2, followed by manual curation using newly updated plant miRNA identification criteria, and comprehensive annotation. PmiREN currently contains 16,422 high confidence novel miRNA loci in 88 plant species and 3,966 retrieved from miRBase. For every miRNA entry, information on precursor sequence, precursor secondary structure, expression pattern, clusters and synteny in the genome, potential targets supported by Parallel Analysis of RNA Ends (PARE) sequencing, and references is attached whenever possible. PmiREN is hierarchically accessible and has eight built-in search engines. We believe PmiREN is useful for plant miRNA cataloguing and data mining, therefore a resource for data-driven miRNA research in plants.

Canola is often called a flexible or plastic crop because individual plants can adjust the number and size of branches and pods they produce in response to available moisture, light and nutrients. Therefore, canola naturally compensates for variations in plant population over relatively wide ranges with very little effect on final yield1,2.

At plant densities of 70-100 plants per square metre (approximately seven to 10 plants per square foot), canola plants normally produce three to five secondary branches (in addition to the main stem). At low densities of 20-30 plants per square metre, canola plants can produce up to four times the number of branches that stands of 70-100 plants per square metre produce3.

As the canopy becomes more dense (plant population increases), each plant produces less dry weight, thinner stems, fewer branches and fewer seeds per plant due to increased competition from adjacent plants. However, fewer seeds per plant are offset by a higher number of plants, resulting in similar seed yield per unit area compared with lower plant populations. This is why canola can produce similar yields across plant populations ranging from 50 to 200 plants per square metre (approximately five to 20 plants per square foot).

In a canopy with more than 200 plants per square metre (approximately 20 plants per square foot), stems are very thin and pods are concentrated at the top of the plants. These stands are more likely to lodge, which can create a better microenvironment for diseases (such as sclerotinia) to flourish, and can make harvest more challenging. Severe lodging during bolting or early flowering stages may also directly impede the efficient uptake of moisture and nutrients through stem crimping, leading to lower yields.

When overall plant populations are lower than the ideal, stand uniformity becomes more important for overall yield potential. An Agriculture and Agri-Food CanadaAgriculture and Agri-Food Canada is a department of the Government of Canada. More study conducted in the Brown soil zone at Swift Current, Saskatchewan found that uniform canola populations at or below 40 plants per square metre (approximately four plants per square foot) were more likely to produce higher yields than non-uniform stands. The same study also found that when moisture is limited, stands with fewer than 40 plants per square metre (approximately four plants per square foot) yielded much lower than dense, more uniform stands5.

Moderate to high plant densities can improve crop competitiveness against early season weed growth because the canopy closes faster with more plants. With low plant populations, canola crops are slower to cover the ground and provide less competition to weeds in the early growth stages. Prolonged exposure to bare soil also increases evaporation of soil moisture.

Moderate to high plant densities in early growth stages can also reduce the yield impact of damage due to insects, disease, frost and hail, because the stand can afford some plant mortality and still maintain its yield potential. Low plant densities can produce viable crops, but the management of thin stands is more challenging, due to more variable maturity and lower tolerance for additional plant losses.

Since canola plants in low population density situations grow larger and branch more, they tend to mature later. Secondary branches account for up to 80 per cent of the yield for canola crops with 20 plants per square metre (approximately two plants per square foot)1,2.

The plants will also have a wider range of maturity, creating yield and quality losses simply due to inability to time applications that align with all the plants and harvest limitations. In these situations (with low plant populations and a wide maturity window) pods on the main stem may be dry with completely mature seeds while pods on secondary branches may still be green with watery seeds inside. Top pods may also start to shell out before pods on side branches are ready to swath, causing yield losses to occur no matter when a grower decides to swath this crop.

Extra branching in very thin stands (20 plants per square metre) can delay seed maturity up to 21 days depending on environmental conditions3.

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