E. R. Morgan

In vitro propagation of Gentiana cerina and Gentiana corymbifera

Abstract The micropropagation of Gentiana cerina and G. corymbifera was investigated. Cultures were initiated from axillary shoots or seed. Seeds of G. corymbifera germinated on a Murashige & Skoog (MS) medium containing 100 mg/litre gibberellic acid (GA3) with 54% of the seed germinating within 70 days. In the absence of GA3 germination did not exceed 5%. Both species proliferated shoots on MS medium supplemented with 6‐benzylaminopurine (BAP). For G. cerina there was no significant difference in proliferation rates for BAP concentrations between 0.05 and 0.5 mg/litre. In contrast G. corymbifera gave highest multiplication rates on 0.2 mg/litre BAP. Addition of 1 mg/litre GA3 to the medium gave improved proliferation compared to treatments in which GA3 was absent. The best treatment for G. cerina resulted in a shoot multiplication rate in excess of 7‐fold after 50 days whereas for G. corymbifera this increase was more than 3‐fold. Root initiation occurred on MS medium supplemented with indole‐3‐butyric a...

Opportunities for synthetic plant chimeral breeding: Past and future

Many plant periclinal chimeras are selected by horticulturalists due to their distinctive, valuable phenotypes, and because they are relatively stable. Most of these have arisen by induced or spontaneous mutation. Interspecific chimeras have been accidentally produced from graft unions of plants from a wide range of families. Early last century Winkler developed a technique to produce interspecific chimeras from graft unions (graft chimeras). More recently in vitro techniques have been developed to synthesize interspecific and intervarietal chimeras. However, these techniques have only been successful for species in the families Solanaceae and Cruciferae, and rarely assessed on plants in other families. Research is required to improve these techniques or develop new approaches so that the efficiency of chimeral shoot production is improved and the techniques are applicable to plants in a wide range of families. The unique characteristics of interspecific or intervarietal chimeras show the potential of chimeral breeding to produce new cultivars. If chimeral breeding techniques were improved, they could become a standard breeding approach for some horticultural crops.

Interspecific hybridisation betweenLimonium perigrinum Bergius andLimonium purpuratum L.

SummaryInterspecific hybrids betweenLimonium perigrinum andL. purpuratum were obtained usingL. perigrinum as the female parent. No hybrids were produced by the reciprocal cross. Twelve- to 15-day-old embryos were rescued and cultured within their embryo sacs on modified B5 or KM medium. After two to three days the embryos were excised from their embryo sacs and re-plated on to fresh medium. When the embryo-derived plantlets had attained a length of 1 cm they were transferred to a modified MS medium containing BA and NAA for shoot proliferation. Plantlets were transferred to modified MS medium supplemented with IBA for 24 hours for root initiation then to a modified growth-regulator-free MS medium for root growth. After a further 28 days the plantlets were transferred to soil-less medium for acclimatisation. The hybrid characteristics of one of the 15 embryo-derived plants were determined by flow cytometry and by examination of morphological features. The mean DNA contents of 2C nuclei fromL. perigrinum, the hybrid andL. purpuratum were 13.98 pg, 16.81 pg and 19.37 pg, respectively. Mitotic and meiotic chromosome counts fromL. perigrinum andL. purpuratum showed that both parents and their hybrids had identical chromosome numbers (2n=24), and that the species were closely related. Morphological analyses of leaves and flowers showed that the hybrids displayed a number of features intermediate between both parents.

Characterization of carotenoid pigments and their biosynthesis in two yellow flowered lines of Sandersonia aurantiaca (Hook)

AbstractThe basis of the novel cream/yellow flower color found in two Sandersonia aurantiaca lines was examined as part of a project to develop new colors for this cut flower crop in New Zealand. The original color, bright orange, is due to the accumulation of the carotenoid pigments zeaxanthin and β-cryptoxanthin. The cream/yellow lines have much lower levels of total carotenoid pigments (17% and 21%) in their tepal tissue compared to the wild type progenitor. Microscopic analysis of epidermal cells showed alteration in the pigment cluster bodies of tepal tissue of the cream/yellow lines compared to the orange wild type. HPLC analysis of the pigments showed that one cream/yellow line (Y-H) produced the same pigment profile as the wild type (zeaxanthin and β-cryptoxanthin). In comparison, the other cream/yellow line (Y-S) produced the carotenoid profile normally found in green vegetative tissue (β-carotene and lutein). Analysis of carotenoid biosynthetic gene expression in Sandersonia indicated that the cream/yellow Y-H line showed expression patterns similar to the wild type, and gene expression in the Y-S line is decreased relative to the wild type and the Y-H line.

Wide crosses in the Colchicaceae: Sandersonia aurantiaca (Hook.) × Littonia modesta (Hook.)

Intergeneric hybrids were obtained between Sandersonia aurantiaca and Littonia modesta using ovule culture. The embryos were rescued by culturing 14 to 30 day old ovules. The ovules were cultured on modified KM medium for varying lengths of time until they germinated. After germination the embryo-derived-plantlets were transferred to modified growth regulator-free MS medium on which they developed tubers and became quiescent. The quiescent tubers could be successfully transferred to soil. The hybrid nature of both the putative Sandersonia × Littonia and the Littonia × Sandersonia hybrids was indicated by flow cytometry that showed the hybrid plants had a DNA content midway between that of the two parents. Mitotic and meiotic chromosome counts from S. aurantiaca, L. modesta and the hybrids gave chromosome numbers of (2n=) 24, 22 and 23 respectively. Morphological analyses of the leaves and flowers showed that the hybrids displayed features that were intermediate between both parents. Hybrids were male and female sterile. No morphological differences were observed between the two hybrids.

Display life of Gentiana flowers is cultivar specific and influenced by sucrose, gibberellin, fluoride, and postharvest storage

Abstract Gentiana are developing into a significant New Zealand export cut flower crop. The current investigation was undertaken to describe the postharvest characteristics of the cultivars grown in New Zealand, thereby establishing a baseline for selection of new cultivars with superior postharvest performance. Three cultivars were used in the current postharvest investigation, G. triflora ’Nasu No‐Hakuryo’ (a white flowered cultivar), and two blue flowered cultivars, G. triflora ’Late Blue’ and G. triflora ’ Ashiro No‐Ake’. The postharvest quality of these Gentiana cut flowers is influenced by a number of factors including harvest maturity, pulsing solutions, cultivar, fluoride, and postharvest storage. In particular, pulsing solutions that contain sucrose (2–5%) or gibberellic acid (GA3, 10 μM) extended the vase life of ‘Late Blue’ and enhanced the quality (blue coloration of apical buds) of ‘Ashiro No‐Ake’, but did not improve the postharvest quality of ‘Nasu No‐Hakuryo’. The effectiveness of these solutions is reduced when stems are not subjected to extended periods of postharvest storage, or when stems are harvested at an advanced stage of maturity.

Use of in ovulo embryo culture to produce interspecific hybrids between Gentiana triflora and Gentiana lutea

Abstract Gentiana is increasingly being exploited as a cut flower crop but its colour range in commercial varieties is limited despite a wide range of colours being present in the genus. The aim of this work was to produce interspecific hybrids between G. triflora and G. lutea with the ultimate aim being to produce yellow‐flowered cultivars. Six to 8‐day‐old embryos were rescued from the G. triflora parent and cultured within their ovules on modified B5 medium. Following embryo germination, plantlets were transferred to modified Murashige & Skoog (MS) medium for further growth and proliferation. Shoots were then transferred to growth‐regulator free, modified MS medium for root initiation before transfer to the greenhouse. However, plants died within a few months of transfer to the greenhouse. The hybrid nature of the embryo‐derived plants was indicated first by flow cytometry, then confirmed by chromosome counts and examination of morphological features. Mitotic chromosome counts of one of the G. triflora × G. lutea hybrid plants gave a chromosome number 2n = 33.

Biosynthesis of the sesquiterpene hodgsonox from the New Zealand liverwort Lepidolaena hodgsoniae

The incorporation of [1-13C] labelled glucose into hodgsonox, a sesquiterpene epoxide with a unique, doubly allylic ether functionality has been studied in axenic cultures of the liverwort Lepidolaena hodgsoniae. Quantitative 13C NMR spectroscopic analysis showed that the isoprene units are derived exclusively from the methylerythritol phosphate pathway.

Production of tetraploid Gentiana triflora var. japonica ‘Royal Blue’ plants

Abstract The aim of this work was to test a protocol for producing tetraploid plants of Gentiana. Tetraploid plants were produced by growing in vitro cultures of Gentiana triflora var. japonica ‘Royal Blue’ in the presence of oryzalin for 4 weeks. A population of plants was regenerated from these in vitro cultures and transferred to the greenhouse. The treated plants were screened for higher ploidy level on the basis of leaf thickness and further confirmation of polyploidy was provided by measuring guard cell lengths. The tetraploid nature of one plant with larger than normal guard cells was confirmed by flow cytometry and chromosome counts. The mean nuclear DNA contents of 2C and 4C nuclei were 9.26 pg and 17.77 pg DNA, respectively. Mitotic chromosome counts from diploid and tetraploid plants were 2n=26 and 2n=52 respectively.

Shoot regeneration from leaf discs of Limonium perigrinum using thidiazuron

Abstract Shoots were regenerated from 12‐mm diameter leaf discs derived from greenhouse plants of Limonium perigrinum (Bergius), with either zeatin or thidiazuron (TDZ), the latter producing five times the number of shoots. After 8 weeks exposure to a modified Murashige and Skoog basal medium (BM) supplemented with 3.0 mg/litre TDZ, an average of 13 shoots/disc formed, 90% of which were ≤ 1 mm long. There was no significant difference in the total number of shoots formed at 1.0–5.0 mg/litre TDZ, however at lower rates (1.0–2.0 mg/litre) a greater proportion of longer shoots (> 1 mm) developed. Shoots regenerated after 8 weeks from leaf discs exposed to BM with TDZ for from 2 h to 6 weeks before being transferred to growth‐regulator‐free medium. A mean of 4.8 shoots/disc formed from the shortest TDZ pulse period, with the majority being longer than 1 mm. Serial sections of discs pulsed with TDZ medium showed many suppressed shoot initials within the new tissue originating from the cut edge of the discs.