Study on the Establishment of a Rapid Propagation System for Succulent Plant Haworthia heidelbergensis

This study took the inflorescence and leaves of the succulent plant Haworthia heidelbergensis as explants, and explored the effects of different mediums with different hormone ratios on the rapid propagation of Haworthia heidelbergensis. The results showed that the optimal medium component for inflorescence callus induction was MS (Murashige and Skoog)+2.0 mg/L 6-BA+1.0 mg/L 2,4-D+0.2 mg/L NAA, the callus induction rate was 90%; the optimal medium component for leaf callus induction was MS+0.5 mg/L 6-BA+2.0 mg/L KT+0.3 mg/L NAA; the optimal medium for callus differentiation was MS+1.0 mg/L 6-BA+2.0 mg/L KT+0.3 mg/L NAA, the clump bud differentiation rate was 50%; the optimal medium for clump bud proliferation was MS+0.5 mg/L 6-BA+1.0 mg/L KT+0.05 mg/L NAA, the proliferation rate was 600%; the best medium for rooting was 1/2 MS+ 0.2 mg/L NAA+0.3 g/L AC. In conclusion, this study selected the explants and culture mediums, established an aseptic propagation system and provided a reference for the in vitro culture and rapid propagation of Haworthia heidelbergensis.

Genome-wide association studies of callus differentiation for the desert tree, Populus euphratica

Callus differentiation is a key developmental process in plant regeneration from cells. A better understanding of the genetic architecture of callus differentiation timing can help improve tissue transformation and the efficiency of artificial propagation. In this study, we investigated genotypic variation in callus differentiation capacity among 297 diverse P. euphratica trees sampled from a natural population. We employed a genome-wide association study (GWAS) of binary and growth-based parameters to identify loci and characterize the genetic architecture and genetic network underlying regulation of callus differentiation in P. euphratica. The results of this GWAS experiment suggested potential associations controlling whether the callus could differentiate and the process of callus differentiation. We identified multiple significant quantitative trait loci (QTLs), including the genes LOG1 and LOG7 and a locus containing WOX1. We reconstructed a genetic network that visualizes how each QTL interacts uniquely with other variants, and several core QTLs were detected that are involved in the degree of callus differentiation, providing potential targets for selection. This study represents one of the first to identify genetic variants affecting callus differentiation in a forest tree. Our results suggest that callus differentiation may be a typical qualitative-quantitative trait controlled by a major gene as well as polygenes across the genome of P. euphratica. This GWAS will help to design more complex and specific molecular tools for systematically manipulating organ regeneration.

PERFORMANCE OF SOMATIC EMBRYOGENESIS DEVELOPMENT UNDER DIFFERENT 2,4-D AND COCONUT WATER CONCENTRATION IN SUGARCANE VAR. BULULAWANG

Mass propagation technology through somatic embryogenesis has become an alternative for producing sugarcane seedlings rapidly.Application of proper plant growth regulator and concentration contribute to support somatic embryogenesis development. This study applied the combination of liquid and solid culture during proliferation stage to promote cell dispersion of embryogenic callus, rapid embryo somatic production, and improve regeneration potency of somatic embryo. Application of 2,4-D and coconut water during proliferation may expected as proper combination for accelerating somatic embryo development and regeneration.Development of somatic embryogenesis in sugarcane var. Bululawang during proliferation were described in this study. Embryogenic callusfrom induction media were transferred to proliferation media containing MS Basal + vitamin supplemented with sucrose different level of 2,4-D (1 mgl-1, 2 mgl-1, 3 mgl-1, 4 mgl-1 ) and coconut water (0% and 5%).Result showed that low concentration of 2,4-D induced optimum somatic embryogenesis development in proliferation and regeneration. Concentration of single 2,4-D 1 mgl-1 without coconut water induced rapid development of scutelar and coleoptilarduring proliferation and resulted in better shoot regeneration. In other way, 4 mgl-1 of 2,4-D concentration affected to inhibit scutelar and coloeptilar formed as the result of failure callus differentiation.

Pengaruh TDZ terhadap induksi embrio somatik sagu (Metroxylon sagu Rottb.) pada tiga metode kultur berbeda (Effect of TDZ on the somatic embryo induction of sago palm (Metroxylon sagu Rottb.) in three different culture methods)

A right combination of cytokinin is able to support the process of callus differentiation to somatic embryo formation in plant somatic embryogenesis. Liquid culture application could increase the efficiency of in vitro culture process on plants. This research aimed to determine the best concentration of TDZ combined with kinetin for callus differentiation to somatic embryo of sago palm on three culture methods. Plant material used was embryogenic callus derived from tips meristem culture from sucker of Alitir sago palm. Callus was cultured on modified MS media added with: 0.0, 0.1, 0.5 and 1.0 mg/L TDZ combined with 0.5 mg/L kinetin for 12 weeks with subcultures every 6 weeks. Three culture methods used were suspension, temporary immersion system (TIS), and solid media. There were 12 treatments with 4 replicates. The results showed that the highest number of somatic embryos was achieved on TIS culture with 1.0 mg/L TDZ and 0.5 mg/L kinetin in 6 weeks (167.3 embryos/flask) and 12 weeks (389.2 embryos/flask) with its fresh weight of 18.4 g and 29.1 g, respectively. The highset survival rate in final culture (12 weeks) was achieved on TIS culture with 1.0 mg/L TDZ and 0.5 mg/L kinetin (100%). The shortest time for somatic embryos expression was achieved on TIS culture with 1.0 mg/L TDZ and 0.5 mg/L kinetin in two weeks after culture. Histological analysis of early-stage somatic embryos showed the presence of dense and compact cellular arrangements which formed growth spot axis for shoot or SAM (shoot apical meristem) and root or RAM (root apical meristem) that connected each other. [Key words: culture method, embryogenic callus, Metroxylon sagu Rottb., kinetin, sago palm, TDZ] AbstrakAplikasi kombinasi sitokinin yang tepat dapat mendorong proses diferensiasi kalus membentuk embrio somatik pada proses embriogenesis somatik tanaman. Penggunaan metode kultur cair dapat meningkatkan efisiensi proses kultur in vitro tanaman. Penelitian ini bertujuan untuk menentukan konsentrasi TDZ terbaik dikombinasikan dengan kinetin dalam proses diferensiasi kalus membentuk embrio somatik tanaman sagu pada tiga metode kultur. Bahan tanam penelitian berupa kalus embriogenik tanaman sagu asal kultur meristem pucuk dari anakan sagu jenis Alitir. Kalus dikulturkan pada media modifikasi dengan penambahan TDZ dengan konsentrasi 0,1; 0,5; dan 1,0 mg/L dikombinasikan dengan kinetin 0,5 mg/L selama 12 minggu yang disubkultur pada umur 6 minggu. Metode kultur yang digunakan terdiri atas tiga macam yaitu: kultur suspensi, sistem perendaman sesaat (SPS) dan media padat. Perlakuan terdiri atas 12 kombinasi perlakuan dengan empat ulangan. Hasil penelitian menunjukkan bahwa rerata jumlah embrio somatik tertinggi dicapai pada perlakuan metode kultur SPS dengan TDZ 1,0 mg/L baik pada umur kultur 6 minggu (167,3 buah) maupun umur 12 minggu (389,2 buah). Rerata bobot segar tertinggi juga diperoleh pada perlakuan metode kultur SPS dengan TDZ 1,0 mg/L pada umur kultur 6 minggu (18,4 g) dan 12 minggu (29,1 g). Rerata daya hidup kultur akhir (12 minggu) tertinggi sebesar 100% diperoleh pada perlakuan SPS. Induksi embrio somatik tercepat yakni setelah dua minggu diperoleh pada metode kultur SPS dengan TDZ 1,0 mg/L dikombinasikan dengan kinetin 0,5 mg/L. Analisis histologi embrio somatik stadium awal menunjukkan adanya susunan sel yang rapat dan kompak yang menyusun semacam poros atau berkas titik tumbuh tunas atau SAM (shoot apical meristem) maupun akar atau RAM (root apical mersitem) yang saling terhubung.[Kata kunci: kalus embriogenik, metode kultur, kinetin, TDZ, sagu, Metroxylon sagu]