Cotton Variety (COTVAR)
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COTVAR
is computer program that may be used to summarize cotton variety performance
data from state cotton variety tests conducted in five states (Arkansas,
Louisiana, Mississippi, Missouri, and Tennessee) in the Mississippi River
Delta region. Within each state
variety test, entries are evaluated at different sites and in different
experiments (also referred to as "tests") based upon maturity of
varieties (early or mid-maturity tests), years that the entry has been
evaluated (main or first-year tests), types of transgenic traits (e.g.
Roundup Ready Flex tests) or treatment of test (e.g. whether test is sprayed
with glyphosate). Specific varieties
entered in tests will typically differ among years (within a state), among
states (within a year), and among experiments within a state. Comparisons of data for different varieties
are only valid when the specific varieties are evaluated in the same
experiment.
Several terms throughout the program are linked to a glossary. Selecting one of these highlighted terms will create a popup screen which will display the definition of the term selected. The entire glossary of terms is also found at the bottom of this guide.
At different points throughout the program, additional information can be found on the output screens by allowing the mouse to hover over an item.
As the user makes choices, those choices will be displayed in a table at the top of the page during the course of the program.
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The COTVAR program contains two program links at the top of the page.
The first item,
COTVAR Cotton Variety Selection, will return the user to the beginning of the program at any time to run a new COTVAR situation.
The second menu item, COTVAR User Guide, opens this document in a new screen. To return to the program, close the screen.
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COTVAR Program Description
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Step 1. Select the Year
Varietial differences in fiber quality are relatively consistent over
years. If fiber data are not available for most current year, user may be able obtain fiber data from pervious
year. If data from multiple years are desired, user may return to step 1 and choose alternate year.
The three most recent years will be available in COTVAR.
Only one year at a time may be selected.
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Step 2. Select Variety Status
Users will be able to select from 3 categories of varieties: Commercially Available Varieties,
Experimental Lines, and Obsolete Varieties.
Experimental lines are often entered into variety tests before they
are commercially available. Sometimes these
new lines (along with standard varietal checks) are evaluated in
experiments (tests) separate from the main variety test. With rapid turnover of varieties, some varieties entered
in previous years may no longer be commercially available (i.e. obsolete).
Updates on variety status (e.g. an experimental line becomes an available or an available variety becomes obsolete)
and variety names (experimental to commercial name) will be made in COTVAR as
information becomes available.
Users can select one, two or all three selections for variety status.
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Step 3. Select Variety Type(s)
Users will be able to select from 3 type of varieties: Multiple trait types (insect resistance and herbicide tolerance),
Single trait types (either insect resistance or herbicide tolerance), or Conventional type (no transgenic traits added).
Insect resistance traits include Bt, Bt2, and Widestrike. Herbicide tolerance traits include Round-up
Ready, Flex, and Liberty Link. If user wishes to compare varieties from different types, each appropriate type should
be chosen.
Users can select one, two or all three variety types.
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Step 4. Select Location(s)
Users can quickly select from regions, or indiviual test sites can also be selected using these options:
All Sites, North Delta (includes MO, TN, northeast AR and northwest MS sites), South Delta (includes LA, central MS, southeast AR sites),
Hill Area (includes Mississippi sites), or Selected Test Sites - Ordered By State, then North to South within each State.
If selected test sites are chosen, a list of locations is displayed for Arkansas, Louisiana, Mississippi, Missouri, and Tennessee which have variety tests for the year selected.
Performance over several sites in previous years is a better predictor of the
relative performance of varieties at a specific site than relative performance
at that specific site in previous years. This is true because environment at one location varies greatly among
years. Varieties that perform well over a wide range of locations will likely also perform well over a wide range of
years. An exception may exist when comparing varieties that differ greatly in maturity since later maturing
varieties are not adapted to the northern Delta. Only varieties of similar maturity should
chosen if data from “all” locations or locations from different regions are to
be compared.
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Step 5. Select up to five (5) varieties
Varieties will now be displayed for the year, variety status, variety type(s) and location(s) selected. The number of sites for each applicable experiment is shown for each variety.
Varieties are listed from the most frequently to least frequently tested. Columns to the right indicate the number
of test sites by experiment within each state. Valid comparisons can only be made among varieties evaluated in the same experiments. If varieties of interest
are not evaluated in the same tests, they can be compared independently to a
variety that is common to the diffferent tests.
User may select up to five varieties for comparison.
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Step 6. Display Lint Yield Averages
Step 6 displays the mean lint yield and fiber quality for selected cotton varieties and experiments. Varieties selected are shown in the first column, and averages displayed are lint yield lb/a,
, Lint fraction %, Quality score, Fiber length in., Micronaire, Length Unif. %, and Fiber strength g/tex. The final row in the table displays the Total Number of experiments (at all sites selected). A link to a printer-friendly page is provided for this screen.
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Step 7. Yields for Selected Varieties and Test Sites
Step 7 displays the yields (% of experiment means) for selected varieties and test sites and the data is sorted according to experiment mean. Information displayed includes location (city, state),
site code, soil type, irrigation status of the experiment, varieties selected, and experiment mean (lb/A).
A particular site may be listed more than once because of multiple experiments at that site. To see the experiment name, place the mouse over the line in the table and the experiment name will appear with addtional details about the location. A link to a printer-friendly page is provided for this screen.
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Step 8. Display Additional Parameters
Additional information for selected varieties includes plant height (inches), percentage of open bolls, seed index, lint index, seed per acre, and leaf pubescence. The mean of the experiments for each of these parameters is shown, as well as the number of sites.
By placing the mouse over the data in the "Number of Sites" column, users can see the actual site numbers. A link to a printer-friendly page is provided for this screen.
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For additional program information, contact:
Fred Bourland
Director/Professor, Cotton Breeding |
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Becky Bridges
Extension Computer Specialist |
| Northeast Research and Extension Center, P. O. Box 48 |
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P.O. Box 391 |
| Keiser, AR 72351 |
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Little Rock, AR 72203 |
(870) 526-2199
fbourland@uaex.edu |
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(501) 671-2192
bbridges@uaex.edu |
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Special acknowledgement is given to Chalmers H. Davis, Jr., former Extension Computer Specialist, for initial program development.
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| Glossary |
| Conventional Cotton Variety: A cotton variety that does not possess transgenes. The first commercial transgenic cotton varieties were the BXN varieties (resistant to Butril herbicide), which were first tested in state variety test in 1996. With the advent of Roundup Ready and Bt genes, transgenic varieties soon became dominant. |
| Fiber and Seed Sampling: Fiber and seed traits are obtained by ginning hand-picked boll samples from at least two replications of cotton variety tests or by ginning machine harvested yield (or a grab sample) from each plot. After ginning, seed and lint samples are removed for determination seed and fiber traits. Fiber properties (fiber length, length uniformity, micronaire, and strength) are determined using high volume instrumentation (HVI) classification. Boll samples are usually ginned on small laboratory gins without lint cleaners to determine true lint percentage. Reliable measurements of fiber color and trash cannot be obtained from these samples. Grab and whole plot samples are typically ginned on modified commercial gin with seedcotton cleaning and one-stage of lint cleaning. |
| Fiber Length: HVI determines the mean length (average length of all fibers) and the upper half mean (mean length of longest one-half of the fibers) in a sample. Fiber length is reported as the upper half mean (UHM). UHM (expressed in inches) multiplied by 32 is equal to staple length (expressed in 32nd's of an inch). Fiber lengths obtained from small laboratory gins tend to slightly longer than those from commercial gins due to less harsh ginning and the absence of lint cleaners. However valid comparisons of fiber length among varieties can be determined from samples processed on small gins. Standard pricing of cotton lint uses a fiber length base of 1.25 inches. |
| Fiber length uniformity (UI): HVI calculates UI as the ratio of the mean fiber length to upper half mean (expressed as a percentage). Without lint cleaners, UI values tend to be exaggerated in samples processed on small laboratory gins. Standard pricing of cotton uses a UI base of . |
| Micronaire: Micronaire is an indirect measure of coarseness of fibers, as determined by measuring airflow through a specific weight of lint. As fiber coarseness increases, fewer fibers (less fiber surface area) are required to obtain the specific weight of lint. Less surface area permits more airflow, and thus registers a higher micronaire value. Cotton may be penalized for high micronaire (mature but coarse fibers) or low micronaire (immature fibers). |
| Fiber strength: Fiber strength is the force required to break a bundle of fibers clamped between two jaws. The bundle is measured in units of 'tex' (1 tex is the weight in grams of 1000 meters of fiber) |
| Leaf Pubescence: Hairiness of leaves is visually rated on a scale of 1 (smooth leaf) to 7 (very hairy) using system described by Bourland et al. (2003). Full-sized leaves, about 5-6 nodes from plant apex, are normally rated. |
| Open bolls: Open bolls percentage is a visual measure of maturity taken Immediately before or after first application of defoliants. Typically, open bolls percentages are estimated from the front and back of each plot (all replications), then averaged for each plot. |
| Lint Index: Lint index (weight of lint on 100 seed) was determined from boll sample data by dividing lint weight from ginned sample by the number of seed per sample (estimated using average seed weight) then multiplying by 100. |
| Lint Percentage: Lint percentage (or lint fraction) is the proportion of lint in a harvested sample of seedcotton (lint and seed prior to ginning). Most variety tests report a true lint percent, as determined by ginning hand-cleaned (no burs) seedcotton sample without the aid of a lint cleaner. Gin turnout refers to the proportion of lint obtained from a seedcotton sample that is ginned with the aid of a seedcotton cleaner and one or more lint cleaners. |
| Lint Yield: In most cotton variety tests, seedcotton produced in 2-row plots (40 to 50 foot long) is machine harvested. Seedcotton yield per plot is converted to seedcotton yield per acre then multiplied by average lint percentage (specific for each variety and test location) to estimate lint yield per acre. Varieties are typically replicated three to six times in an experiment. |
| Plant Height: Plant height measurements are normally collected from each variety prior to harvest. One method of determining average plant heights for varieties is to measure the distance from the soil surface to the terminal of one averaged sized plant in each of the two rows, the average of the two measurements for a plot mean. |
| Qscore: A fiber quality index established by COTVAR. Qscore is calculated by assigning differential weights on standardized values of fiber length, micronaire, length uniformity, and strength. The differential weights are based on priorities global market demands as perceived by cotton fiber technology experts. Higher fiber quality is indicated by higher Qscores. |
| Seed Index: Seed index is the weight (in grams) of 100 seed. To avoid time and expense of delinting seed, seed index based on fuzzy seed weights may be reported in variety test data. |
| Seed per Acre: An estimate of number of seed produced per acre can be determined by multiplying seedcotton yield (lb/a converted to g/a) times average seed percentage (the percentage of seed weight to seedcotton weight in ginned sample, averaged by entry and location over reps), then divided by average seed weight (average seed index by entry over reps divided by 100). |
| Transgenic cotton variety: A cotton variety that possesses gene(s) from non-cotton sources. The first commercial transgenic cotton varieties were the BXN varieties which were resistant to bromoxynil (Butril®) herbicide. BXN varieties were first tested in state variety tests in 1996. |
| Round-up Ready cotton variety: A transgenic cotton variety that possesses the Round-up Ready gene, which permits application of glyphosate (Round-up®) over the top of the plants on 4-leaf or younger cotton. |
| Round-up Ready Flex cotton variety: A transgenic cotton variety that possesses the Round-up Ready Flex gene, which permits application of glyphosate (Round-up®) over the top of plants on 12 leaf or younger plants. |
| Bt cotton variety: A transgenic cotton variety that possesses the gene for the Cry1Ac protein, which provides good control of tobacco budworm but is weak on other lepidopterous insects. |
| Bt2 cotton variety: A transgenic cotton variety that possesses the genes for the Cry1Ac and the Cry2Ab2 proteins. These genes provide good control of all lepidopterous insects except cutworms. |
| Liberty Link: A transgenic cotton variety that possess the Liberty Link gene, which permits application of glufosinate (Ignite®) over the top of plants for weed control. |
| Stacked gene variety: A transgenic variety that possesses more than one transgenic trait. |
| Reference 1: Bourland, F.M., N.R. Benson, and W.C. Robertson. 2000. Inherent biases in the Arkansas cotton variety testing program. pp. 547-549. In Proc. Beltwide Cotton Prod. Res. Conf., San Antonio, TX. 4-8 Jan. 2000. National Cotton Council, Memphis, TN. |
| Reference 2: Bourland, F.M., J.M. Hornbeck, A.B. McFall, and S.D. Calhoun. 2003. A rating system for leaf pubescence of cotton [Online]. J. Cotton Sci. 7:8-15. Available at http://www.cotton.org/journal/2003-07/2/8.cfm |
| Commercially available varieties: Varieties that are currently being maintained for sale in seed company's inventories. Updates on variety status (e.g. an experimental line becomes an available or an available variety becomes obsolete) and variety names (experimental to commercial name) will be made in COTVAR as information becomes available. |
| Experimental lines: Experimental lines are often entered into variety tests before they are commercially available. Sometimes these new lines (along with standard variety checks) are evaluated in experiments (tests) separate from the main variety test. Updates on variety status (e.g. an experimental line becomes an available or an available variety becomes obsolete) and variety names (experimental to commercial name) will be made in COTVAR as information becomes available. |
| Obsolete lines: With rapid turnover of varieties, some varieties entered in previous years may no longer be commercially available (i.e. obsolete). Updates on variety status (e.g. an experimental line becomes an available or an available variety becomes obsolete) and variety names (experimental to commercial name) will be made in COTVAR as information becomes available. |
| Multiple trait types: Cotton varieties that possess multiple (or stacked) transgenic traits, which infer an insect resistant trait (Bt, Bt2, or Widestrike) and a herbicide tolerant trial (Round-up Ready, Flex, or Liberty Link). |
| Single trait types: Cotton varieties that possess one transgenic trait, which infers either an insect resistant trait (e.g. Bt, Bt2, Widestrike) or a herbicide tolerant trial (e.g. Round-up Ready, Flex, Liberty Link). |
| Test site: Performance over several sites is a better predictor of the relative performance of varieties at a specific site than relative performance at that specific site in the previous year. This is true because environment at one location varies greatly among years. Varieties that perform well over a wide range of locations will likely also perform well over a wide range of years. An exception may exist when comparing varieties that differ greatly in maturity since later maturing varieties are not adapted to the northern Delta. Only varieties of similar maturity should chosen if data from 'all' locations or locations from different regions are to be compared. |
| Fiber Quality: Fiber and seed traits are typically obtained by ginning hand-picked boll samples from at least two replications of cotton variety tests or by ginning machine harvested yield (or a grab sample) from each plot. After ginning, seed and lint samples are removed for determination seed and fiber traits. Fiber properties (fiber length, length uniformity, micronaire, and strength) are determined using high volume instrumentation (HVI) classification. Boll samples are usually ginned on small laboratory gins without lint cleaners to determine true lint percentage. Reliable measurements of fiber color and trash cannot be obtained from these samples. Grab and whole plot samples are typically ginned on modified commercial gin with seedcotton cleaning and one-stage of lint cleaning. |
| Experiment Mean: Mean yield of all varieties evaluated in an experiment at specified test site within specified year. |
| Experiment: Multiple experiments may be conducted at a test site within a year. Entries in experiments may be distinguished by maturity (e.g. early or mid-maturity experiments), previous evaluation status (e.g. main or new entry experiments), or by treatment of test (e.g. Round-up used in RR experiment). Valid comparisons can only be made among varieties evaluated in the same experiments. If varieties of interest are not evaluated in the same experiment, they may be compared indirectly by comparison to a common check variety. |
| % dirty flowers, tpb: A measure of resistance to tarnished plant bug (TPB). TPB is sucking insect that can cause injury to anthers of a developing flower. When the flower open, the damage is detected by darkening of the anthers (dirty flower). Response of varieties to TPB can be evaluated by determining the percentage of white flowers having discolored anthers. |
| Bract trichome density: A direct measure of the hairiness of bracts that is determined by counting the number of trichomes (hairs) on the margins of bracts using methods described by Bourland and Hornbeck (2007). |
| Reference 3: Bourland, F.M. and J.M. Hornbeck. 2007. Variation in marginal bract trichomes on Upland cotton. J. Cotton Sci. 11:242-251. Available at http://www.cotton.org/jounal/2007/11/4/242.cfm |
| Fiber density: An estimate of density (number per square mm) of fibers on seed coat surface. |
| Widestrike: A transgenic cotton variety that possesses the genes for the Cry1Ac and the Cry1F proteins. These genes provide good control of all lepidopterous insects except cutworms. |
