Application of post-harvest treatments to extend storability of pedunculate acorns (Quercus robur) without loss of viability or germinability.

Pedunculate oak acorns are difficult to store for longer than several months without significant crop losses due to desiccation, fermentation, fungal infection and premature germination. Desiccation below the critical threshold (circa. 38%), resulted in rapid decreases in germination of stored acorns regardless of treatment. However, two approaches indicated potential areas for further research and development.

1. Coating acorns entirely with bees- or microcrystalline-wax reduced desiccation during storage and maintained viability for up to 36-weeks. These coatings, however, hampered subsequent germination. This could be overcome by partially removing the wax at the apex of acorns (difficult when handling large quantities of seed) or developing thinner/weaker coatings.
2. Storing acorns in polyester bags maintained high moisture content for 60-weeks. Critically, germination remained constant between 47-52% from 24-to 60 weeks storage. It is possible that germination could be close to the target 70% if the fungal infection that caused 16-18% losses in this treatment was controlled more effectively during storage.

Aims and Objectives:

(i)    Project aim(s):

To extend storability of recalcitrant acorns for 18 months without significant loss of seed quality and thereby overcome the supply and demand problems for seed traders/nursery managers, resulting from irregular fruiting in pedunculate oak.

(ii)  Project objectives:

1.  To conduct a short review/desk study on current knowledge of acorn storage.

2.  To use two approaches to extend shelf-life of acorns:

a.  wax coatings/anti-transpirants to reduce water loss;

b.  permeable/barrier packaging to reduce respiration of acorns.

3.  To determine which treatments are effective by tracking changes in seed quality using a range of seed tests.

a.  to track water loss by measuring moisture content.

b.  to detect changes in seed fill (shrinkage) by taking x-rays.

c.   to detect membrane damage by measuring electrolyte leakage. d.  to determine loss of viability/germinability of acorns.

4.  To determine the seedling performance/vigour of treated acorns under nursery conditions.

5.  To communicate research to stakeholders through different media including technical articles, peer- reviewed articles and workshops/presentations.