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2004 Artemisia tridentata Referee Application of AOSA and ISTA pure seed definitions and the subsequent effects on viability, pure live seed, and pure seed units per gram for 2 lots of Artemisia tridentata. To compare ISTA and AOSA definitions for Artemisia pure seed. To assess consistency of Artemisia pure seed determination among labs. To assess consistency of Artemisia PLS determination among labs. Seed units of Artemisia are achenes. Floral structures may or may not be attached. In the seed trade, lots of Artemisia tridentata often have very low purity with a wide range of achene size and condition. Purity methods vary among labs, causing frustration and confusion for those trying to compare results. The main point of disagreement is the application of the pure seed definition. This referee was conducted to compare the application of ISTA and AOSA pure seed definitions and their subsequent effects on viability, pure live seed, and pure seed units per gram. Materials and Methods:
Two lots of Artemisia tridentata seed were obtained and divided by the Wyoming Seed Laboratory. Two 1/3 purity weights (0.25g.) were prepared for each lot. It was hoped that smaller sample sizes would increase participation. Ransom Seed Laboratory assigned and mailed the samples. NCGRP compiled and evaluated the data. Twelve analysts completed sample 1. 14 analysts completed sample 2. SAS, PROC GLM procedure used to analyze data. Pure seed definitions: AOSA a. Immature or shriveled seed units, and seed units that are cracked or otherwise damaged. b. Insect-damaged seeds, provided that the damage is entirely internal, or that the opening in the seed coat is not sufficiently large to allow the size of the remaining mass of tissue to be readily determined. c. Seeds that have started to germinate d. Seed units with nematode galls, fungus bodies (i.e. ergot, smut, etc.) and spongy or corky caryopses, which are entirely enclosed within the seed unit. Refer to sections 2.10 a (1) and c (1). Artemisia PSU 27: Intact achene whether or not a seed is present. Piece of broken achene larger than one-half of the original size, unless no seed is present. Seed, with or without pericarp/seed coat. Piece of broken seed, with or without pericarp/seed coat, larger than one-half the original size. ISTA 3.2.1.1. The following structures (even if immature, undersized, shriveled, diseased or germinated, providing they can be definitely identified as of that species) unless transformed into visible fungal sclerotia (see 3.5.2.A.5.B. for exceptions when the uniform blowing method is used), smut balls or nematode galls: 1. Intact seed units (= commonly found dispersal units i.e. achenes and similar fruits, schizocarps, florets etc) as defined for each genus or species in the Pure Seed Definitions in the current Annexe 3.2.1.A. … 2. Pieces of seed units larger than one-half their original size. Annexe 3 Artemisia PSD 1: Achene, unless it is obvious that no seed is present. Piece of achene larger than one-half the original size, unless it is obvious that no seed is present. Seed with the pericarp/testa partially or entirely removed. Piece of seed larger than one-half the original size, with the pericarp/testa partially or entirely removed. Results: Using a 5% probability of error, statistically significant differences between ISTA and AOSA results were only found in PSU results for sample 2. AOSA and ISTA results were not significantly different for any other test on these two samples. Using a 10% probability of error, statistically significant differences between ISTA and AOSA results were found for sample1 viability and PSU results. In sample 2, differences were significant between ISTA and AOSA for purity, viability, and PSU/gram results. No statistically significant differences between AOSA and ISTA methods were observed for PLS results for either sample. It is possible that insufficient sample sizes were tested to examine this issue adequately. However, larger sample sizes would likely reduce participation. It is unclear whether the wording for ISTA pure seed would improve consistency of pure seed determination. 2004 Artemisia referee answers to questions: All respondents: 20C, 21 days, TB 11 respondents mentioned light, (4 respondents: 8 hrs, 1 respondent: 11 hrs, 1 respondent: 16 hrs.) Separation techniques: · screens, microscope, bottom light · sieves and hand · I used the general blower to make the hand separation a little easier. Did not use any kind of blowing point. Used diaphanoscope some with ISTA samples only. · Screening (size 0.686) first then hand separation with microscope · Over Hoffman sieve cups (range 3-7) lost less than blower, BW, sieve cups, Blower, hand separation · Hand separation only, stereoscope · Hand separation using magnifying light, then scoping to check · Hand separation with 7x eye lens · Hand separation · Blower, hand separation · Hand separation only under a dissecting microscope · Hand separation using a dissecting microscope Acknowledgements: Julie Laufmann (NCGRP) and Mark West (USDA/ARS Northern Plains Area Office) assisted with statistical analysis. Thanks very much to all the participants. Your time and effort was greatly appreciated. Annette Miller, USDA/ARS NCGRP, 1111 South Mason St., Fort Collins, CO 80521-4500 970 495 3240, almiller@lamar.colostate.edu
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Artemisia photo referee 2004 Photos
taken and results compiled by Annette Miller.
31-33
respondents (not everyone responded for every photo) Respondents were asked to classify each photo numbered above as Pure or Inert according to the AOSA definition and then again according to the ISTA definition. AOSA a. Immature or shriveled seed units, and seed units that are cracked or otherwise damaged. b. Insect-damaged seeds, provided that the damage is entirely internal, or that the opening in the seed coat is not sufficiently large to allow the size of the remaining mass of tissue to be readily determined. c. Seeds that have started to germinate d. Seed units with nematode galls, fungus bodies (i.e. ergot, smut, etc.) and spongy or corky caryopses, which are entirely enclosed within the seed unit. Refer to sections 2.10 a (1) and c (1). Artemisia PSU 27: Intact achene whether or not a seed is present. Piece of broken achene larger than one-half of the original size, unless no seed is present. Seed, with or without pericarp/seed coat. Piece of broken seed, with or without pericarp/seed coat, larger than one-half the original size. ___________________________________________________________________________________ ISTA Pure seed definition: 3.2.1.1. The following structures (even if immature, undersized, shriveled, diseased or germinated, providing they can be definitely identified as of that species) unless transformed into visible fungal sclerotia (see 3.5.2.A.5.B. for exceptions when the uniform blowing method is used), smut balls or nematode galls: 1. Intact seed units (= commonly found dispersal units i.e. achenes and similar fruits, schizocarps, florets etc) as defined for each genus or species in the Pure Seed Definitions in the current Annexe 3.2.1.A. … 2. Pieces of seed units larger than one-half their original size. Annexe 3 Artemisia PSD 1: Achene, unless it is obvious that no seed is present. Piece of achene larger than one-half the original size, unless it is obvious that no seed is present. Seed with the pericarp/testa partially or entirely removed. Piece of seed larger than one-half the original size, with the pericarp/testa partially or entirely removed. Higher
agreement was achieved more often using the AOSA definition than the ISTA
definition. Green and yellow boxes are full agreement. Orange boxes indicate reduced agreement.
Some possible reasons for the results: 1. The nature of a photo referee. One answer sheet had the following comment: "Difficult to evaluate under ISTA rules since you can't determine if a seed is present or not when looking at a photo." The photo quality could have contributed to the evaluation difficulty. It's difficult or impossible to see translucence in these photos. 2. AOSA instructions leave less room for questionable judgements. The intention of the wording is clearer. 3. People are less familiar with the intention of the ISTA wording than they are with the AOSA definition. Or, they may not have sufficient training to make a judgement that matches the intention of the wording for this pure seed unit (More of a problem with ISTA than AOSA). One analyst told me on the phone that he did not think there was any difference between the two definitions. |