CRISPR/Cas9-mediated tetra-allelic mutation of the 'Green Revolution' SEMIDWARF-1 (SD-1) gene confers lodging resistance in tef (Eragrostis tef).

Tef is a staple food and a valuable cash crop for millions of people in Ethiopia. Lodging is a major limitation to tef production, and for decades, the development of lodging resistant varieties proved difficult with conventional breeding approaches. We used CRISPR/Cas9 to introduce knockout mutations in the tef orthologue of the rice SEMIDWARF-1 (SD-1) gene to confer semidwarfism and ultimately lodging resistance. High frequency recovery of transgenic and SD-1 edited tef lines was achieved in two tef cultivars by Agrobacterium-mediated delivery into young leaf explants of gene editing reagents along with transformation and regeneration enhancing morphogenic genes, BABY BOOM (BBM) and WUSCHEL2 (WUS2). All of the 23 lines analyzed by next-generation sequencing had at least two or more alleles of SD-1 mutated. Of these, 83% had tetra-allelic frameshift mutations in the SD-1 gene in primary tef regenerants, which were inherited in subsequent generations. Phenotypic data generated on T1 and T2 generations revealed that the sd-1 lines have reduced culm and internode lengths with no reduction in either panicle or peduncle lengths. These characteristics are comparable with rice sd-1 plants. Measurements of lodging, in greenhouse-grown plants, showed that sd-1 lines have significantly higher resistance to lodging at the heading stage compared with the controls. This is the first demonstration of the feasibility of high frequency genetic transformation and CRISPR/Cas9-mediated genome editing in this highly valuable but neglected crop. The findings reported here highlight the potential of genome editing for the improvement of lodging resistance and other important traits in tef.

Development and characterization of GR2E Golden rice introgression lines.

Golden Rice with ß-carotene in the grain helps to address the problem of vitamin A deficiency. Prior to commercialize Golden Rice, several performance and regulatory checkpoints must be achieved. We report results of marker assisted backcross breeding of the GR2E trait into three popular rice varieties followed by a series of confined field tests of event GR2E introgression lines to assess their agronomic performance and carotenoid expression. Results from confined tests in the Philippines and Bangladesh have shown that GR2E introgression lines matched the performance of the recurrent parents for agronomic and yield performance, and the key components of grain quality. Moreover, no differences were observed in terms of pest and disease reaction. The best performing lines identified in each genetic background had significant amounts of carotenoids in the milled grains. These lines can supply 30-50% of the estimated average requirements of vitamin A.

Compositional Analysis of Genetically Engineered GR2E "Golden Rice" in Comparison to That of Conventional Rice.

Compositional analyses were performed on samples of rice grain, straw, and derived bran obtained from golden rice event GR2E and near-isogenic control PSBRc82 rice grown at four locations in the Philippines during 2015 and 2016. Grain samples were analyzed for key nutritional components, including proximates, fiber, polysaccharides, fatty acids, amino acids, minerals, vitamins, and antinutrients. Samples of straw and bran were analyzed for proximates and minerals. The only biologically meaningful difference between GR2E and control rice was in levels of ß-carotene and other provitamin A carotenoids in the grain. Except for ß-carotene and related carotenoids, the compositional parameters of GR2E rice were within the range of natural variability of those components in conventional rice varieties with a history of safe consumption. Mean provitamin A concentrations in milled rice of GR2E can contribute up to 89-113% and 57-99% of the estimated average requirement for vitamin A for preschool children in Bangladesh and the Philippines, respectively.

Easy and Efficient DNA Extraction from Woody Plants for the Detection of Phytoplasmas by Polymerase Chain Reaction.

A simple and efficient procedure for the extraction of high-quality DNA from phytoplasma-infected woody and herbaceous plants for polymerase chain reaction (PCR) detection is described. This procedure does not require phenol, chloroform, or alcohol for the precipitation of nucleic acids. Herbaceous and woody plant material are extracted in an identical manner with no additional purification or enrichment steps required. The method utilizes commercially available microspin-column matrices, and the extraction of total DNA can be achieved in less than 1 h. The method has been used to successfully purify phytoplasma DNA from whole leaves, leaf petioles and midribs, roots, and dormant wood from a diverse selection of plant material. The phytoplasmas detected by PCR include pear decline, western X-disease, peach yellow leaf roll, peach rosette, apple proliferation, Australian grapevine yellows, and Vaccinium witches'-broom.

Improved RNA Extraction from Woody Plants for the Detection of Viral Pathogens by Reverse Transcription-Polymerase Chain Reaction.

An efficient procedure for the extraction of high-quality RNA from woody plants without the use of phenol, organic solvents, or alcohol precipitation is described. The method employs commercially available spin-column matrices and mitigates the inhibitory effects of plant polysaccharides and polyphenolic compounds commonly observed on subsequent polymerase chain reaction amplification when conventional extraction methods are applied to woody plant species. The method described has been successfully used in the development of highly sensitive reverse transcription-polymerase chain reaction (RT-PCR) techniques for the detection of a number of viruses in their woody hosts. The viruses detected included apple stem grooving capillovirus (ASGV), apple stem pitting virus, Prunus necrotic ringspot ilarvirus (PNRSV), grapevine fanleaf and Arabis mosaic nepoviruses, and grapevine leafroll-associated closterovirus type 3. The method described was equally effective for the extraction of viral RNA from either budwood, leaves, or flower blossoms as determined by the equivalent RT-PCR detection of ASGV and PNRSV from these tissues. Detection of viral RNA in samples of total plant RNA prepared using this method was found to be as sensitive as was previously described for the immunocapture RT-PCR technique.