Studies On Germplasm Characteristics And Enhancement Of Four Lysimachia Landscape Species

The genus Lysimachia L. contains≈191 species from subtropical and temperate regions in the northern hemisphere, and more than 120 species are endemic to China. Up to now, more than 50 Lysimachia species were used as medicinal herbs or landscape plants. Approximately 30 Lysimachia cultivars, especially color-leaf cultivars, were traded in North America, East Asia and Europe. However, there are few species used as ornamental plants in China at prensent. Therefore, new cultivar selection has a broad prospect in the future. Twelve wild L. christinae （ES, W1, W2, W3, HS, BD and HL）, L congestiflora （ZY, ZJ and JH）, L. rubinervis （ZM） and L. pseudohenryi （ST） plants were collected from central China in recent years. In this research, the identification, evaluation and enhancement of these plants were studied, so as to make contribution to the new ornamental Lysimachia cultivars. The main results are as follows:1. Plants were identified by plant morphology, chromosome number and karyotype and ITS sequence of ribosome DNA. The color of leaves and flowers varied in these 12 plants, HL, HS and ST had green leaves and yellow flowers, while ES, W1, W2, W3, BD, JH, ZJ and ZM had purple-brown veins or red petal bases. ZY had purple-brown interveinal part, red-purple stem and yellow-green vein. Chromosome karyotype analysis showed that the karyotypes of L. christinae （ES, W1, W2, W3, HS and HL） were 2n=24=2m+2sm+4st+16t, the karyotypes of L. congestiflora （ZY, ZJ and JH） were 2n=24=2m+4sm+4st+14t, the karyotypes of L. rubinervis were 2n=24=4m+4sm+4st+12t. According to the ITS sequence （Genebank accession number: FJ529510-FJ529522） of ribosome DNA, plants of the same species clusterd together and with close relationship. The consistency of 7 L. christinae plants was 96.14%. The indentificaion result indicated that ES, W1, W2, W3, HS, BD and HL were geographic variations of L. christinae, ZJ and JH were geographic variations of L. congestiflora, while ZY might be wild mutation of L. congestiflora.2. The biology traits, ornamental features and garden application characteristics of Lysimachia plants were evaluated in the multi-year trial. The results indicated that plant development and flowering were related to photoperiod and irradiation. L. christinae, L. congestiflora and L. rubinervis were long-day plants. In ornamental features, the red purple on stems and leaves of ES, W1, W2, W3, ZJ, ZY and ZM were stable and obvious. The number of flower was very rich; flowering occurs in May and lasted for about 30 days. In addition, the yellow petals with red bases were very showly. Therefore, all the obove plants were color-leaf plants with pretty garden application prospects. For landscaping, ES, W1, W2, W3, ZJ, ZY and ZM were very adaptable in different light intensity. Meanwhile, the heat tolerance and drought tolerance of these plants were stronger than European cultivar-Lysimachia nummularia ’Aurea’ （JY）. The freezing tolerance degrade was W1, W3>W2>ES, ZJ, ZY, ZM, JY>BD. In addition, the wear tolerances of Lysimachia plants were stronger than Trifolium repens and Oxalis rubra. Moreover, they were easily propagated by division, cutting and stolon broadcasting, all the plants had vigorus creeping habit and were suitable for used as groundcover and potted plants. Furthermore, these Lysimachia plants exhibited no invasiveness and were free of major diseases. Therefore, these plants had great potential as ornamental groundcovers for urban landscaping in central China as well as other similar climatic regions.After identification and evaluation, ES, W1, W2 and W3 were studied out as new cultivars according to the International Code of Nomenclature for Cultivated Plants （ICNCP）, namely L. christinae ’Zixin’, L. christinae ’Zixin W1’, L. christinae ’Zixin W2’, L. christinae ’Zixin W3’; ZY and ZJ were studied out as new cultivars L. congestiflora ’Zidie’ and L. congestiflora ’Zimai’.3. Germplasm enhancement was developed by irradiation, polyploid induction and genetic transformation. It was shown that shoot tips and in vitro buds were the best explants for subculture after irradiation by ⁶⁰Co-γ. EF, a variant plant obtained from regeneration plants of ES in the present research, increased its area ratio of purple-brown vein by 21.5% than ES. On the polyploid induction of ES, the heightest mutation rate was achieved in the treatment of immersing the shoot tips in colchicine solution at 0.05-0.1% for 12 h. In this study, the sizes of stomata in polyploidy plants are higher 38.46% and 53.33% than diploid plants. The effective in vitro propogation and plant regeneration system of L. christinae, L. congestiflora, L. rubinervis and L. nummularia ’Aurea’ were developed using in vitro leaves and shoot tips. The results indicated that L. christinae developed the highest regeneration rate （100%） from shoot tips and leaf bases on the MS medium containing 3.0 mg/L BAP and 0.1 mg/LNAA, the numbers of shoots/explant were up to 14.34 for ES. For L. rubinervis, the highest shoot induction rate and number of shoots/explant were obtained from shoot tip （100%, 16.87-17.20） on the MS medium with 0.1 mg/LNAA and 3.0-5.0 mg/L BAP. L. nummularia ’Aurea’, however, showed the highest regeneration rate and number of shoots/explant （100%, 12.73） from leaf bases on MS medium supplemented with 1.0 mg/L BAP and 0.1 mg/L NAA. 100% of L. congestiflora stem segments （with nodes） developed cluster buds on the MS medium containing 3.0-5.0 mg/L BAP and mg/L NAA, while the leaves of L. congestiflora were not suitable as explats for plant regeneration. The roots in half macronutrient MS medium containing 0.1 mg l^-1 NAA were significantly greater than the roots in the other treatments. After acclimatization, transplanted plantlets grew normally in the same speed and flowered in the field. For the selection of genetic transformation system of ES, 250 mg l^-1 Cef could control the growth of Agrobacterium tumefaciens, 50 mg l^-1 Km was suitable for selection of the positive plants.