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Allanblackia seed germination protocols

Allanblackia seed germination protocols. Prepared by Lucy Mwaura For Allanblackia domestication workshop 23 rd to 27 th Oct 2006. Outline. AB seed physiology Conditions required for germination. Possible Allanblackia seed dormancy

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Allanblackia seed germination protocols

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  1. Allanblackia seed germination protocols Prepared by Lucy Mwaura For Allanblackia domestication workshop 23rd to 27th Oct 2006

  2. Outline • AB seed physiology • Conditions required for germination. • Possible Allanblackia seed dormancy • Seed germination treatments applied by partcipating countries • Treatment methods that have been use on a large scale • Lesson learnt

  3. Allanblackia seed physiology • Fruit/seed weight • Seed moisture • Storage • Dormancy • Germination

  4. Fruit/seed weight -A single seed weight ranged between 5-10grams when fresh -A kilo of fresh seeds had between 90-100 seeds -viable seeds per kilo?( not confirmed) -fruit weight ranged between 2.5-5.5kg

  5. Moisture content • Seed moisture -AB seed had moisture content of up to 40% when fresh. -Loss of seed moisture was found to be proportional to loss in viability (desiccation tolerance trial/biochemical test 2004 ) -The rate of moisture loss is high soon after extraction, and decreased with time of exposure to air.

  6. Storage trials • Storage - Extracted seeds can be stored at -20oC in airtight aluminum bags for at least one year without loss of moisture and viability. (desiccation tolerance test of 2004) . -Seeds remained viable with high moisture while still enclosed in the fruit buried, in moist soil/sand for three months.

  7. Conditions required for seed germination • In Tanzania and Kenya use of moist sand media has been used to pre-germinate seeds • The germination beds should remain moist during this period, however minimum watering is recommended to avoid water logging( seed would rot) • Seeds in nursery beds should be put under shade. (In Tanzania seeds are covered with dried banana leaves). • Temperatures should be between 25-30 degrees Celsius.

  8. AB possible seed dormancy • Dormancy-is the physiological state that prevents normal growth of most seeds when all the conditions are favorable. • Seed coat dormancy: gelatinous sticky substances found on seeds could contain chemical inhibitory compunds which make the seed coat impermeable to water and gases, this growth inhibitors must be leached out to allow germination (Forest Biology journal 2000). • Embryo dormancy: have growth-inhibitors present and lack growth promoters. -The embryo in enclosed in endocarp that contains high oil content, this could have chemical inhibitory compound that prevent germination -Abscisic acid contained in the embryo makes the seed dormant until certain native enzymes are triggered to permit breakdown of the hormones ( intensive work required here)

  9. Seed germination treatments applied and results obtained by specific countries • Cameroon. • Results from an experiment investigating the germination potential of Allanblackia seeds in a mixture of forest soil and sand (2:1) indicated that it took 18 months for A floribunda and 19 months for A gabonensis to reach 50% germination level. • 24 months after the trial was set an overall 86% of seeds germinated. Pretreatments experiments were developed to reduce the germination period • Preliminary results from pretreated seeds of AB (immersion in 90% gibberellic acid (GA3) for 72 hours indicate that a germination rate of 48.33 % can be obtained after 7 months (A. floribunda). • New experiment investigating the combined effects of GA3 concentration and duration of immersion on 4800 A. floribunda seeds subjected to 3 immersion durations and 4 GA3 concentrations in a factorial design; (experimental unit of 100 seeds) is being done in Cameroon.

  10. Seed germination trial in specific countries 2. Ghana • Out of 13 accessions sown at the nursery the overall germination was 0.02% as at June 2005. • Another 21 accessions were sown in the green house with three treatments, (with testa, without testa and soaking in water for 24 hrs) in early 2005, overall germination was 0.05% by February 2006. • ITSC also put 600,000 seeds on nursery beds of (A parviflora), only 0.1% of seedlings was transplanted into poly tubes.

  11. Treatments that have been used on a large scale ( best germination results so far )3Tanzania • Extracted seeds are sown on seed-beds • Burying the whole fruit in a hole and cover with forest debris and then transfer germinated seeds to the polyethylene tubes. • Collecting newly emerged seeds and raise in the polyethylene tubes( rat caches) • Extracted seeds are soaked in water while floater are discarded, the sinkers are removed and nicked on the distal end and later soaked in GA31000ppm( refer to note for GA3 preparation)

  12. Seed germination treatments from specific countries con’t 4. Kenya • Germination capacity -Seed germination capacity was low and slow -tap root emerged first within 3-5months -a fully developed seedling with two alternate leaves occurred after 7 months of sowing. -seeds that did not germinate after 5 months had an enlarged embryo and remained dormant -seed stained brilliant red indicating viable tissues with TTZ test.

  13. Pre-sowing methods • sowing without treatment - No seed treatment has been found effective to improve germination percentages. -First trial 2004 done without treatment (germination was 4%) • Sowing with treatment -seeds were stored for a month, soaked in water 24hrs, and dried for 2 days then cracked to open the seed coat( germination was 1%)

  14. Pre-sowing methods cont’ • Preparation and soaking in GA-3 and KNO3 -Gibberellic acid (GA-3) was dissolved in 1 ml ethyl-alcohol/water 250ppm, 500ppm,1000ppm( refer to notes) -Potassium nitrate(KNO3 ) 0.2%,0.5%,and 1%(ref: ISTA news bulletin No 130 Oct 2005) -Combined treatment (KNO30.2% and 250ppm) -one seedlot was not treated

  15. Treatments cont’ • Experimental set up -seeds were put in various treatment and soaked for 48hrs at room temperature. -Deep flower pots were filled with sterile sand at ¾ level, sown seeds were covered with a thin layer of sand. -similar set-up was put at the nursery same time.

  16. Germination progress. • Sowing -Dec 2005, seeds were sown 2 cm apart in containers, and incubated at 25ºC night and 30ºC day temperature, the sand was kept moist without logging. • Monitoring -Minimum watering with distilled water was done. -Daily monitoring and recording was continuously done.

  17. Germination chart

  18. Lesson learnt • We still have a big challenge ahead of us to find ways to improve seed germination. • Use of local knowledge practice in Tanzania is so far the best practice that improves seed germination. • More research needs to be done using KNO3 and GA-3 treatments. • Bioassay study will be important to find out whether hormones ratios found in seeds have any influence on physiological seed activities (germination? dormancy?). • We need to set-up seed propagators in central nurseries where environmental conditions can be controlled and temperatures monitored.

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