High Resolution Melting Analysis as a Rapid and Highly Sensitive Method for Cichorium Plasmotype Characterization

Somatic hybridization in Cichorium species has already been extensively investigated. Hybrid or cybrid characterization requires an effective plasmotype screening method. We evaluated high resolution melting (HRM) analysis for the detection of specific mitochondrial (mt) and chloroplast (cp) markers to distinguish two industrial chicory (Cichorium intybus var. sativum) plasmotypes from five wild type chicory (C. intybus) and two endive (C. endivia) plasmotypes. Three mt (coxII-2, cob-1, and cob-2) and three cp HRM markers (trnL-trnF, trnL-trnF-2, and ndhF-1) were successfully developed. Two markers (coxII-2 and trnL-trnF) were additionally able to discriminate heterozygous plasmotypes containing at least 25 % of one parental plasmotype. Moreover, the technique was successfully used to characterize the cytoplasms of 50 simple sequence repeats (SSR) confirmed somatic hybrids of C. intybus var. sativum ‘VL52’ and C. endivia var. crispum ‘Wallone Despa’. HRM enables a rapid (less than 2 h) and efficient high-throughput scanning of multiple fragments due to the 384-well plates and is cost efficient because of its small reaction volume of 10 μl. This is the first report on the use of HRM analysis on Cichorium species. The technique is a fast and simple alternative for laborious and costly sequencing in plasmotyping regenerants obtained after somatic fusion.     

Effect of enzyme concentrations on protoplast isolation and protoplast culture of <Emphasis Type="Italic">Spathiphyllum</Emphasis> and <Emphasis Type="Italic">Anthurium</Emphasis>

Vital protoplasts from Spathiphyllum wallisii ‘Alain’ and Anthurium scherzerianum ‘238’ were isolated from both somatic embryos and leaves. The highest yields were obtained when 1.5% cellulase, 0.5% macerase and 0.5% driselase were used for Spathiphyllum wallisii leaves and 0.5% cellulase, 0.3% macerase and 0.5% driselase for Anthurium scherzerianum embryos. About 1 × 10⁶ protoplasts g⁻¹ and 1 × 10⁵ protoplasts g⁻¹ could be isolated from leaves and embryos, respectively. For protoplast fusion Spathiphyllum wallisii ‘Alain’ and Anthurium scherzerianum ‘238’ were mixed in a 1:1 ratio in a fusion solution containing 1 mM CaCl₂·2H₂O, 1 mM MES and 0.5 M mannitol. Fusion was performed by protoplast alignment under 500 V cm⁻¹ alternating current for 60 s and subsequent generation of two pulses of 4500 V cm⁻¹ direct current during 50 μs. Development until colony stage was achieved using agarose beads for protoplast culture.     

Application of embryo rescue after interspecific crosses in the genus Rhododendron

Interspecific hybridization between evergreen pot azalea (Tsutsusi) cultivars and genotypes of other Rhododendron subgenera or sections (Rhododendron, Hymenanthes, Pentanthera, Vireya) is significantly hampered by many prezygotic and postzygotic barriers. The objective of our work was to overcome spontaneous abortion and lack of endosperm formation and to increase germination rates by establishing an embryo rescue protocol. The optimal germination medium for immature Rhododendron seeds was a basal medium supplemented with 145 μM GA₃. This medium induced germination of fertilized ovules after several sexual combinations of subgenera. Its use was clearly more efficient than in vivo sowing. The direction of the cross significantly influenced the occurrence of abortion, germination and albinism. The obtained seedlings were multiplied on Woody Plant Medium + 4.5 μM 2iP, and rooted afterwards. Finally, about 9% of the germinated ovules resulted in vigorously growing seedlings that were successfully acclimatized.     

Temperature-dependent development of the broad mite Polyphagotarsonemus latus (Acari: Tarsonemidae) on Rhododendron simsii

The broad mite, Polyphagotarsonemus latus (Banks), is one of the major pests causing severe economic damage in Rhododendron simsii Planch hybrid production in Belgium. In order to optimize biological control programs and to parameterize warning programs, we studied the effect of environmental temperature on the development of P. latus on R. simsii leaves. In combination with a photoperiod of 16:8 h (L:D) and a relative humidity of 80 ± 5 %, six constant temperatures (15, 17, 20, 25, 30 and 33 ± 1 °C), were studied. Total developmental times of 13.3, 10.5, 6.6, 4.2, 3.5 and 4.0 days were measured, respective to each of the aforementioned temperatures. Development of females took significantly longer than that of males at 15, 17, 20 and 30 °C. Survival rates observed between 17 and 30 °C varied between 43.5 and 96.9 %. Lower survival rates were found at 15 and 33 °C, i.e. 31.8 and 23.6 %, respectively. The lower, optimal and upper developmental threshold (t _min , t _opt and t _max , respectively) and thermal constant (K) of the pest were estimated for each life stage by a linear and two non-linear models. Based on measurements of total development of P. latus thermal thresholds of 10.0, 30.1 and 36.0 °C were calculated for t _min , t _opt and t _max , respectively. The number of degree-days needed to complete immature development when feeding on R. simsii was 66.7.     

Development of an optimal culture system for callogenesis of <Emphasis Type="Italic">Chrysanthemum indicum</Emphasis> protoplasts

This study is a comparison of four methods to induce calli formation in a protoplast culture of Chrysanthemum indicum. Culture in liquid medium (17.6 calli/10⁵ protoplasts) was preferable to culture in solid agarose beads, although the efficiency of the latter could be improved by layering them on glass beads (12.5 vs. 0.83 calli/10⁵ protoplasts). Culture of protoplasts on moistened filter paper was unsuccessful. In the liquid media, microcalli and calli were induced efficiently and easily after 6 weeks. These effects may be explained by reduced toxicity due to cell breakdown and improved aeration.