Seed Processing

CALCULATE PERCENTAGE GERMINATION COUNT NO. OF SEEDS GERMINATED Have 30 seeds or more germinated? Does viability meet standard? PROGRAMME FOR REGENERATION Have more than 64 seeds germinated? REPEAT TEST WITH SECOND GROUP OF 40 SEEDS Have more than 75 seeds germinated? KEEP IN STORE PROGRAMME FOR REGENERATION REPEAT TEST WITH 3RD GROUP OF 40 SEEDS KEEP IN STORE ENTER THE DATA INTO THE FILES Flowchart 8.1. Viability monitoring. YES NO YES NO NO YES YES NO NO YES YES 106 Handbooks for Genebanks No. 8 Table 8.2. Threshold germination percentages for regeneration of accessions. Initial germination Regenerate if percentage germination after monitoring is below 100 85 99 84 98 83 97 82 96 82 95 81 94 80 93 79 92 78 91 77 ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

90 77 89 76 88 75 87 74 86 73 85 72 The number of seeds required for each replicate may vary, but it is recommended to use at least 40 seeds per replicate. 1. Conduct the germination test according to the methods described in Chapter 5 using (for example) 40 seeds 2. Count the number of seeds germinated after the prescribed period of testing. 3. Compare the results with the number germinated in Table 8.3, paying attention to the line with the value of 40 in the first column (number of seeds tested). • If the number of seeds germinated is 29 or less, the accession requires regeneration. • If the number of seeds germinated is more than 29, then the test must be repeated with another sample of 40 seeds exactly as described above. Table 8.1. Suggested interval for ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

monitoring germination of active or base collections in oily and non-oily seeds. Present level of germination (%) Monitoring interval (years) Active collection (4–5ºC) Base collection (-20ºC) Non-oily seeds Oily seeds Non-oily seeds Oily seeds 95 3 5 8 12 1 3 5 8 5 10 15 20 2 5 8 12 107 Manual of Seed Handling Table 8.3. Sequential germination test plan for 85% regeneration standard when testing seeds for germination in groups of 40.† Number of seeds tested Regenerate if the number of seeds germinated is less than or equal to Repeat test if number of germinated seeds is in the range of Store if number of seeds germinated is more than or equal to 40 29 30–40 - 80 64 65–75 76 120 100 101–110 111 160 135 136–145 146 200 170 171–180 181 240 205 206–215 216 280 240 241–250 251 320 275 276–285 286 360 310 311–320 321 400 340 - 341 † When 400 seeds have been tested, the test ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

can be terminated because enough tests have been conducted for an informed decision to be made. It is important to use the same number of seeds when repeating the test so that the different samples can be treated as replicates. 4. Count the number of seeds germinated in the second test and add this number to the result of the first test. 5. Compare the results of the test with the number germinated in Table 8.3, following the line with the value equal to the total number of seeds used for all tests (80 seeds) in the first column (number of seeds tested). • If the number of seeds germinated is 64 or less, the accession must be regenerated. • If the number germinated is above 75, the accession can be continued in storage. • If the number germinated is between 65 and 75, the accession must be tested again with another sample of 40 seeds and the results compared with the ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

value equal to the total number of seeds used in all tests (120 seeds) in Table 8.3. 6. Continue the test in this way until a decision can be made regarding regeneration or continued storage, or until the test is repeated ten times. For more information on test plans for other group sizes (20, 25, 50 or 100 seeds) and regeneration standards between 65% and 80%, refer to Ellis et al. (1985). The sequential test is only necessary when seed numbers are limited. Small-seeded crops like finger millet 108 Handbooks for Genebanks No. 8 normally have adequate numbers of seeds to use the fixed sample size method. Monitoring seed quantity Seed quantity can be monitored by checking the inventory data file. This is best achieved through a computer-based genebank documentation system. 1. Record the weight of the seeds initially transferred to the genebank. 2. Record all ( Seed Processing, Seed Cleaning, Stone separator, Combo Cleaner, Grading Machine, Gravity Separator  )

subsequent seed withdrawals for distribution, regeneration and germination-testing. 3. Update documentation of seed stocks immediately, adjusting the total after all seed withdrawals. 4. Prepare a list of accessions where the number of seeds in storage has fallen below the critical level (usually the number required for at least three regenerations). Germplasm accessions identified with low viability or inadequate quantity during the course of monitoring should be regenerated as soon as possible using the method described in the following section.