CONCLUDING REMARKS

Production of Lilium has dramatically increased since the First International Symposium was convened in Korea sixteen years ago.
Today, more than 2 billion bulbs are produced annually world-wide.
Bulb production is increasing in the Southern Hemisphere with Chile and New Zealand as the principal exporting countries for forcing from fall to early winter.
In this second symposium topics related to taxonomy and classification, bulb and flower production, physiology and bulb dormancy and flowering, nutrition, genetics (including genetic transformation) and breeding, physiology of flower scent, postharvest technologies and disease control were reported.
A few of the contributions that distinguish the advances made in lily research during the past several years include:

• Taxonomic revisions of sections in the genus Lilium are under ongoing review.
  Concepts based on the value of morphological traits related to bulb structure, cell shape and structure were presented.
  Further research should also include genetic relationships using molecular markers and genetic compatibility between and among different sections as additional revisions are made.
• Lily nutrition and growth control in soil and soilless culture were evaluated on growth and flowering as well as on bulb size and weight.
  Although this information was developed for local conditions, it may serve as a baseline for nutrition deficiency symptoms and nutritional requirements.
  This information may have wider applications to other sites of production and different geographical locations.
• A reduction in the fragrance in Oriental lilies was achieved through the identification of four principal chemical components responsible for scent.
  An inhibitor of the catalytic reaction producing the odor components was identified and the inhibitor uptake in cut lily stems reduced the undesirable scent.
• The application of transformation technologies to introduce desirable traits through gene transfer has not yet produced a commercially acceptable product with enhanced physiological traits.
  A protocol was, however, developed that resulted in transient GUS expression in callus, shoots and basal plate discs using Agrobacterium tumefaciens. This system will be used to introduce the rice chitinase gene to produce Lilium with enhanced fungal resistance.
• Molecular regulation of vernalization in lilies is important in affecting flowering time and flower quality.
  Understanding the process of gene regulation in vernalization will lead to a better understanding of factors that control dormancy and flowering.
  Subtraction libraries were generated and cDNA-AFLP analysis was applied to detect genes expressed differentially in cold vernalized and non-vernalized bulbs.
  Clones were analyzed for homology to known genes and those from subtraction libraries showed genes involved in dormancy.
• Approximately 80 species are classified in seven sections.
  Development of Asiatic hybrid lilies was followed by the Oriental hybrids and subsequently LA, LO, OT and OA hybrids crossing with members of different sections.
  The range of hybrids from these intersectional crosses will increase in the future.
  Depending on consumer preferences and national preferences, both large and small flowered selections will be developed.
  Characters that will be emphasized, in addition to flower color, will be new pollen-less and disease resistant cultivars.
  Six QTLs for Fusarium resistance were mapped on an Asiatic lily population.
  The major QTL for Fusarium resistance was confirmed in an LA population.
  The development of Fusarium resistant selections will be a major breakthrough in the development of disease resistant cultivars.
• Factors affecting the postharvest quality of cut flowers and flower bud abscission are complex.
  Petal wilting is apparently enhanced by low carbohydrate and not the result of ethylene.
  The effects of selected chemical treatments applied to foliage under controlled environment conditions showed a significant positive effect on stem height and diameter, flower size and color with a reduction in flower bud abortion and increased inflorescence longevity.
  Factors that influence these characteristics as well as lower leaf yellowing, should be further evaluated to improve market quality.
• LSV remains the most important virus in commercial culture.
  Although the virus is widespread, and certification standards in the EU allow up to 10% infection in commercially traded bulbs, RT-PCR is now available as the most sensitive method for virus detection of LSV, LMoV, LVX and CMV and can be utilized for certification where nuclear stocks are established.
  Methods of fungus disease control have remained essentially the same over many years with the use of fungicides in pre-plant treatments and postharvest.
  A new method of controlled hot water treatment of bulbs before and after harvest has, however, eliminated the use of formaldehyde in control of the nematode, Pratylenchus penetrans, and the bulb mite, Rhizoglyphus robini. Natural products have been evaluated for improved nematode control in the field with reduced use of fumigants.
  The use of chlorine dioxide in hot water treatments to control nematodes in harvested bulbs should be further evaluated.
  Improved weather forecasting based on predictive models has significantly reduced the amount fungicide used to control Botrytis elliptica in field grown lilies.
• Future research directions may include: (1) development of a more inclusive and comprehensive data base for lily classification based on both morphological and molecular genetics data; (2) application of new sequencing technologies for construction of a complete genetic map of lily and production of a set of molecular markers for a range of characters (QTLs) for biotic and abiotic resistances, flower keeping quality, forcing qualities, production, etc., to be used for indirect selection in breeding programs; (3) improving methods of genetic engineering resulting in selected breeding lines for disease and insect resistance and other desirable characteristics in commercial cultivars; (4) identification and manipulation of genes controlling dormancy and flowering with and improved understanding of the vernalization process; (5) selection of lilies with good fragrance and a reduction in the undesirable scent associated with some commercial cultivars; and (6) development of efficient and economical systems to produce bulbs that can be forced in developing countries.
• The Third International Symposium will be convened in the US in 2014 with a possible fourth symposium in China in 2018.

II International Symposium on the Genus Lilium

R.H. Lawson, M.S. Roh

https://doi.org/10.17660/ActaHortic.2011.900.50