Improved technique for virus elimination in and production of certified planting materials of garlic (Allium sativum L.).

摘要

Elimination of diseases, particularly viruses, is an important concern in the production of planting materials of garlic. In the Philippines, cloves used for planting come from the previous crop or from imported bulbs which have not been certified as disease-free. These poor quality-planting materials result in very low average yield (2.78 t/ha) which is attributed to accumulated diseases through generations of asexual propagation. To solve this problem and to assist the Philippines and other garlic-producing countries in producing certified virus-free planting materials, we developed a technique using sequential shoot tip-meristem culture coupled with indexing. Results of virus-indexing using ELISA, PCR and electron microscopy, however, showed that not all plants were cleaned of the viruses. Hence, an improved technique was developed whereby all the plants were freed of the viruses. The technique consists of cold pretreatment (5 degrees C) of initial planting materials (bulbs) for 3-4 weeks coupled with thermotherapy (50 degrees C for 2 h) and sequential shoot tip-meristem culture followed by multiple shoot production and in vitro bulblet (G0) formation prior to transplanting. In vitro bulblets survived better than plantlets when transplanted to soil. Indexing was done using ELISA. This improved technique is now routinely used for production of certified virus-free garlic. Increase in bulb weight (up to 14x, i.e. from G0 to G2) was achieved when G0 bulblets were transplanted to potting media under greenhouse (3-4 weeks) then field condition to produce 1st generation (G1) bulbs, then planting the G1 bulbs in the field to produce 2nd generation (G2) bulbs, in which the normal size of bulbs was achieved from in vitro bulblets. Tissue-cultured materials had higher yield, in terms of the rate of increase in number bulbs produced per bulb planted, compared to conventionally propagated bulbs (1:4-8 vs 1:3-5)..