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United States Department of Agriculture

Agricultural Research Service


Location: Floral and Nursery Plants Research

2011 Annual Report

1a. Objectives (from AD-416)
The primary objective of this work is to develop techniques and methods that will lead to sterile or highly infertile cultivars of invasive or potentially invasive nursery crops.

1b. Approach (from AD-416)
The general approach is to use use biotechnology or genetic engineering to create seedless plants or to develop methods that will lead to the creation of seedless plants. One area of study will be to test gene suppression using the AGAMOUS gene and dsRNA-RNAi. The AGAMOUS gene is a floral homeotic gene that, when suppressed or mutated, can result in flowers that have petals in place of pistils and stamens, and are therefore sterile. The second area of study will be to create transgenic plants using several different gene constructs that may induce male and/or female sterility.

3. Progress Report
The main goal of this work is to develop methods that will lead to sterile or highly infertile cultivars of invasive or potentially invasive woody nursery crops. As a model, transgenic sweetgum trees were produced and planted in the field four years ago. They continue to grow very well, showing similar or greater growth and fall color than the wild-type controls that were also propagated in vitro and transplanted at the same time. We are expecting that, with their obvious vigorous growth this year, they will flower in 2012. Tissue samples were collected from all of these transgenic trees in summer of 2010 and 2011 and methods for RNA extraction confirmed as effective for them. PCR primers for five control genes for qPCR were designed based on published sequences, and are currently being tested. Gene expression studies for most transgenic lines should be completed by end of summer 2011. Near the start of this project, we produced an RNAi construct directed against the AGAMOUS homolog in apple. The construct was sent to a cooperator, who produced transgenic Gala apples with it. He has reported the recovery of a number of sterile transgenic flowering trees with multiple whorls of petals, as expected for AG inhibition. He is now studying gene expression, morphology, and fertility for those lines. These results suggest that RNAi against AGAMOUS could be an effective means for producing sterile crabapples with showy flowers. We are collaborating with another scientist at Oregon State University on a problem analysis of approaches to reducing invasiveness using conventional biotech and transgenic methods. A complete draft is nearly ready for submission to a journal. Research activities conducted under this agreement were monitored by regular email communication, submission of reports by the cooperator, and by in-person communication at scientific and stakeholder meetings.

4. Accomplishments

Last Modified: 06/24/2017
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