Potential of South African Members of the Amaryllidaceae for New Crop Development J.G. Niederwieser, M. Terblanche and M.H. Spreeth ARC-Roodeplaat Private Bag X293 Pretoria 0001 South Africa. Tel: +27-12 841 9609 Fax: +27-12 8080353. Email: [email protected] and [email protected] Keywords: Cyrtanthus, flower bulb crop, genebank Abstract The results of a scoping study on the potential of the South African Amaryllidaceae for commercialisation are reported. An extensive project to collect as many as possible species of the family in the wild and from other collectors were undertaken. A total of 85 species of 13 genera were obtained, established and maintained in the genebank and observed for a number of years. Plants were evaluated according to appearance of flowers, flowering, vase life of flowers, size of bulbs, multiplication, ease of cultivation, etc. Intra- and inter genera crosses were made to determine the potential for breeding of improved varieties. Although many species of this family have spectacular flowers, characteristics such as the size of the flowering bulb, difficulty of cultivation, difficulty to induce flowering in cultivation, limited flower colours within a genus, multiplication rate and vase life present challenging problems with regard to commercialisation. Specific challenges and advantages for some of these genera are discussed briefly. We came to the conclusion that few genera have the potential for further development. Preliminary work on Cyrtanthus indicated that flowering needs to be studied in depth and work at the institute has been suspended until more information is available. INTRODUCTION The family Amaryllidaceae consists of 17 genera, with approximately 217 species indigenous to Southern Africa (Gibbs Russel, et al., 1985). Species of the family vary from small, for example Strumaria Jacq. Ex Willd., to large for example Brunsvigia Heist. Many species have spectacular flowers that are predominantly red or shades of pink. Some genera have yellow and orange flowers for example Clivia Lindl. and Cyrtanthus L.f. Nerine Herb. is a well known genus of the family and has been improved through breeding to one of the most popular flower bulbs. A project to evaluate the potential of the family for new crop development has been initiated in the late 1980’s (Coertze and Louw, 1990). The objectives of the project were to collect a comprehensive collection of species accessions from different climatic areas in the region and to make intra- and intergeneric crosses to develop new cut flowers and pot plants. Coertze and Louw (1990) reported that crosses between species of Cyrtanthus, Nerine and Crinum L. resulted in seedlings and that the Nerine hybrids were sterile. Hybrids were obtained from some inter genera crosses through ovule culture. This paper gives an overview of the results of the scoping study which included preliminary characterisation of the genebank accessions, intra and intergeneric crosses and evaluation of the hybrids, especially for the genus Cyrtanthus. Irregular flowering appeared to be the biggest challenge to overcome in this family. MATERIALS AND METHODS Species accessions were obtained from Botanic Gardens, collectors and some were Proc. 8th Int. Symp. on Flowerbulbs Eds. G. Littlejohn et al. 359 Acta Hort. 570, ISHS 2002 collected during field trips for which permits were obtained. The identity of plants was confirmed by the National Botanic Institute (Pretoria) where necessary. Plants were maintained in plastic pots in water-cooled green houses at Roodeplaat. Where possible, watering and soil type were similar to those of the natural habitats. The temperature in the green houses varied from approximately 1- 30 oC. Plants were transplanted when the pots became overcrowded as recommended by Du Plessis and Duncan (1989). Cyrtanthus bulbs were transplanted more regularly. Members of the family have four different growing patterns: Summer flowering types with a dormant stage in winter, winter and spring flowering types with a dormant summer, autumn flowering types with a dormant period in summer and evergreen types. This complicated maintenance of the collection as watering and transplanting for different species varied. Pollination was done in the green houses. In general, species that were available in sufficient numbers were used as maternal parent. Pollen of scarce species was collected, dried, stored at 4 oC and used for pollination when maternal parents flowered. Pollen viability was checked regularly through in vitro germination. Cyrtanthus seed were germinated in vitro and seed of other genera were sown as soon as they started to germinate. Pollen tube growth in inter genera crosses was studied by fluorescent microscopy to get a better understanding of the reasons for incompatibility between the genera used. Cyrtanthus hybrid seedlings were grown for four years and evaluation was done in years 2 – 4. Seedlings of inter genus crosses were maintained for a longer period. Hybrids were evaluated for propagation, flowering, appearance of the flowers, stem length and vase life of flowers. RESULTS AND DISCUSSION General Species of 13 genera of the Amaryllidaceae have been obtained: Amaryllis (1 species), Ammocharis (1), Boophane Herb. (4), Brunsvigia (6), Clivia Lindl. (3), Crinum L. (11), Cyrtanthus L.f. (38), Gethyllis L. (3), Haemanthus L., (6), Hessea Herb. (1), Nerine Herb. (7), Scadoxus (3) and Strumaria Jacq. Ex Willd. (1). The majority of the genera are used by traditional healers in Southern Africa and have been included in the traditional medicinal plant nursery at the institute. Ten inter genus crosses resulted in viable seedlings (Table 1). Hybrids of only one cross flowered (C. mooreii x A. belladona) and the flowers were similar to that of C. mooreii. ). Fluorescence microscopy showed that pollen tube growth typically associated with incompatible combinations in most inter genera crosses. In general, the Amaryllidaceae have large bulbs and some of them come into flower only after 6-7 years. The irregular flowering was identified as an important constrain for commercialisation and breeding. Methods for in vitro propagation were published for Cyrtanthus (Niederwieser and Kleynhans, 1997), Amaryllis (De Bruyn, et al., 1992) and Crinum (Slabbert, et al., 1993 & 1995). Attempts to propagate Clivia in vitro were not successful. Gethyllis and Scadoxus were multiplied in vitro using double scale explants. Plants of a number of species were made available to the public through plant sales at the National Botanic Institute (Pretoria) and nurseries. Following an evaluation of the results of the program in 1992, we decided to abandon further inter genera crosses in the Amaryllidaceae and to continue with a scoping study on Cyrtanthus. Cyrtanthus Genebank A number of 38 species of the approximately 50 described species (Reed and Dyer, 1984) have been obtained and are being maintained in the Roodeplaat genebank. The aim was to obtain accessions from 7 different localities for each species, unless they occur in very restricted areas, for example C. eucallus. A number of endangered species were included in the genebank. C junodii, that was described in 1906 and not seen for 88 years was thought to be extinct. However, it was found during a collection trip to the 360 Drakensberg near Ofcalaco to collect C. thorncroftii. Following identification, the plant was multiplied in vitro and specimens given to the NBI and other collectors. A number of scarce species or ecotypes were propagated through tissue culture, namely C. clavatus, C. staadensis, C. bicolor, C. flanaganii, C. smithiae, C. spirallis, C. tuckii, C. huttonii, and C. junodii. Cyrtanthus species occur naturally in a variety of habitats ranging from the peaks of the Drakensberg (2500- 3000m) (C. erubescence and C. flanaganii), to coastal flats (C. loddigesianus and C. fergusoniae) to the grassy hills of the high veld (C. tuckii and C. contractus) and escarpment (C. junodii and C. thorncroftii). The soil types of the natural habitats vary from sandy to loam and clay. Also, the growing season vary from winter growing, to summer growing and evergreen. We assumed therefor that the conditions in the genebank (especially the temperature, watering and soil type) were not optimal for a number of species and probably had an effect on flowering and propagation of a number of species in the genebank. Flowering in Cyrtanthus Some species, especially C. brachyscyphus, C. mackenii, C. macowanii and C. staadensis flowered regularly and during specific times of the year. Cyrtanthus elatus is an evergreen species that flowered sporadically throughout the year, but more in the early summer. C. contractus and C. tuckii flower in their natural habitats for a short period in early spring. The plants did not flower regularly under the conditions at Roodeplaat. C. flanaganii and C. erubescence (both growing at high altitudes, 2500 - 3000 m, in the Drakensberg) did not flower at Roodeplaat in seven years. It is possible that the optimal average temperature was too high for these species. Flower initiation and flowering of C. elatus and C. mackenii was described by Slabbert (1997a & 1997b). These species were chosen because they have different growing patterns and plants were available in sufficient numbers. Flower initiation in C. elatus took place throughout the year and up to four inflorescences at different stages of development were observed within a bulb. Bulbs were treated at 10 & 17 oC, but the treatments did not result in increased flowering. In C. mackenii two inflorescences were initiated in the early summer. The primary inflorescence reached anthesis during the following mid winter and the secondary one towards late winter. Flower manipulation of C. mackenii was possible by subjecting the plants to a treatment of 10 C for 3, 6 and 9 weeks after new inflorescences have been initiated in early summer (Slabbert, 1997b). Research needs to be expanded with species such as C. contractus and winter growing species such as C. loddigesianus, as well as promising hybrids. It appears at this stage, that breeding should be aimed at hybrids with seasonal flower initiation as it seems to be difficult to manipulate evergreen plants.