Isolation, culture and regeneration of avocado (Persea americana Mill.) protoplasts

A method for the production and expedient screening of CRISPR/Cas9-mediated non-transgenic mutant plants

Developing CRISPR/Cas9-mediated non-transgenic mutants in asexually propagated perennial crop plants is challenging but highly desirable. Here, we report a highly useful method using an Agrobacterium-mediated transient CRISPR/Cas9 gene expression system to create non-transgenic mutant plants without the need for sexual segregation. We have also developed a rapid, cost-effective, and high-throughput mutant screening protocol based on Illumina sequencing followed by high-resolution melting (HRM) analysis. Using tetraploid tobacco as a model species and the phytoene desaturase (PDS) gene as a target, we successfully created and expediently identified mutant plants, which were verified as tetra-allelic mutants. We produced pds mutant shoots at a rate of 47.5% from tobacco leaf explants, without the use of antibiotic selection. Among these pds plants, 17.2% were confirmed to be non-transgenic, for an overall non-transgenic mutation rate of 8.2%. Our method is reliable and effective in creating non-transgenic mutant plants without the need to segregate out transgenes through sexual reproduction. This method should be applicable to many economically important, heterozygous, perennial crop species that are more difficult to regenerate.

Regeneration of viable oil palm plants from protoplasts by optimizing media components, growth regulators and cultivation procedures

Oil palm protoplasts are suitable as a starting material for the production of oil palm plants with new traits using approaches such as somatic hybridization, but attempts to regenerate viable plants from protoplasts have failed thus far. Here we demonstrate, for the first time, the regeneration of viable plants from protoplasts isolated from cell suspension cultures. We achieved a protoplast yield of 1.14×10(6) per gram fresh weight with a viability of 82% by incubating the callus in a digestion solution comprising 2% cellulase, 1% pectinase, 0.5% cellulase onuzuka R10, 0.1% pectolyase Y23, 3% KCl, 0.5% CaCl2 and 3.6% mannitol. The regeneration of protoplasts into viable plants required media optimization, the inclusion of plant growth regulators and the correct culture technique. Microcalli derived from protoplasts were obtained by establishing agarose bead cultures using Y3A medium supplemented with 10μM naphthalene acetic acid, 2μM 2,4-dichlorophenoxyacetic acid, 2μM indole-3-butyric acid, 2μM gibberellic acid and 2μM 2-γ-dimethylallylaminopurine. Small plantlets were regenerated from microcalli by somatic embryogenesis after successive subculturing steps in medium with limiting amounts of growth regulators supplemented with 200mg/l ascorbic acid.

Aspectos da propagação de Persea willdenovii Kosterm. (Lauraceae)

Resumo Persea willdenovii é uma espécie arbórea cuja ocorrência foi registrada desde o estado de Minas Gerais até o Rio Grande do Sul, principalmente nas formações de altitude. P. willdenovii encontra-se ameaçada de extinção no Rio Grande do Sul, principalmente devido ao amplo emprego fitoterápico. Para identificar e caracterizar aspectos relevantes na produção de mudas de P. willdenovii, foi conduzida uma série de experimentos, visando à propagação através de sementes e de partes vegetativas. Nos experimentos visando à propagação sexuada, a emergência ocorreu após um período mínimo de 34 dias. Também foi observada associação da germinação a um período de declínio da temperatura ambiente. Nos experimentos visando à propagação vegetativa, P. willdenovii apresentou limitações, principalmente a restrição do potencial morfogênico aos tecidos juvenis, a presença de contaminação de origem endógena e o alto índice de oxidação dos tecidos. A propagação vegetativa foi viabilizada a partir de tecidos de plântulas germinadas in vitro. Assim, foi possível registrar a resposta da espécie às estratégias mais comuns de propagação, identificar os problemas a serem resolvidos para viabilizar a multiplicação, além de gerar 300 novas plantas a partir de duas matrizes.