Article pubs.acs.org/JAFC
Assessment of Peanut Quality and Compositional Characteristics among Transgenic Sclerotinia Blight-Resistant and Non-Transgenic Susceptible Cultivars Jiahuai Hu,† Darcy E. P. Telenko,† Patrick M. Phipps,† and Elizabeth A. Grabau*,‡ †
Tidewater Agricultural Research and Extension Center (TAREC), Virginia Polytechnic Institute and State University, 6321 Holland Road Suffolk, Virginia 23437, United States ‡ Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, 413 Price Hall, Blacksburg, Virginia 24061, United States ABSTRACT: This study presents the results of a comparison that includes an analysis of variance and a canonical discriminant analysis to determine compositional equivalence and similarity between transgenic, sclerotinia blight-resistant and nontransgenic, susceptible cultivars of peanut in 3 years of field trials. Three Virginia-type cultivars (NC 7, Wilson, and Perry) and their corresponding transgenic lines (N70, W73, and P39) with a barley oxalate oxidase gene were analyzed for differences in key mineral nutrients, fatty acid components, hay constituents, and grade characteristics. Results from both analyses demonstrated that transgenic lines were compositionally similar to their non-transgenic parent cultivar in all factors as well as market-grade characteristics and nutritional value. Transgenic lines expressing oxalate oxidase for resistance to sclerotinia blight were substantially equivalent to their non-transgenic parent cultivar in quality and compositional characteristics. KEYWORDS: Arachis hypogaea, Sclerotinia minor, oxalate oxidase, genetically modified organism (GMO), canonical discriminant analysis, substantial equivalence
■
INTRODUCTION Arachis hypogaea L. (peanut) is an important food crop worldwide for both commercial and subsistence production. Peanut is susceptible to many fungal and viral diseases. Sclerotinia blight, caused by the soilborne fungus Sclerotinia minor Jagger, is a major and economically important disease of peanut in the mid-Atlantic and southwestern regions of the United States.1,2 Yield losses can be significant and reach nearly 75% under favorable conditions for disease development.3 Because of a lack of natural resistance to Sclerotinia blight in commercial varieties, growers have relied on crop rotation and applications of the fungicide fluazinam (Omega 500, Syngenta Crop Protection) to mitigate the disease.4 Crop rotation is not highly effective because sclerotia, the overwintering structures of S. minor, can persist in the soil for several years. Chemical control can cost producers as much as $89 per hectare for a single application and require up to two or three applications in a season for adequate disease control.5 Currently, there is a pressing need for development of peanut lines with resistance to Sclerotinia blight and end the need for costly fungicide sprays for disease control. Transgenic lines provide a sustainable and profitable tool to combat the devastating disease. In Oklahoma, runner-type peanut cultivar Okrun has been transformed with a chitinase gene from rice or a β-1−3-glucanase from alfalfa.6,7 At Virginia Tech, a biotechnology approach to confer resistance to Sclerotinia blight of peanut resulted in transgenic Blight Blocker peanut lines with a barley oxalate oxidase gene expressing high levels of resistance.5,8 S. minor produces oxalic acid as a pathogenicity factor to predispose plant cells to infection.9,10 The oxalate oxidase transgene confers resistance © 2014 American Chemical Society
through the enzymatic activity of its protein product to degrade oxalic acid to carbon dioxide and hydrogen peroxide. Three Virginia-type peanut cultivars (NC 7, Wilson, and Perry) have been successfully modified with a barley oxalate oxidase gene to provide resistance to Sclerotinia blight.5,8 Six years of field demonstrations clearly indicated that transgenic Blight Blocker peanut lines possessed high levels of resistance to Sclerotinia blight and significantly improved yields and profitability under high levels of disease incidence.5 Prior to release, regulatory agencies require comprehensive characterization and thorough safety assessment of transgenic crops in field trials. Chemical compositions as well as agronomic and morphological characteristics have been key elements in the evaluation process. One component of the safety assessment is to compositionally compare transgenic lines to their corresponding near-isogenic counterparts. For decades, the U.S. Food and Drug Administration (FDA) and international agencies, such as the World Health Organization (WHO) and the Organization for Economic Cooperation and Development (OECD), routinely used the principle of substantial equivalence as a key starting point for the safety assessment of transgenic crops. Equivalence is defined as the lack of differences except those as a result of natural biological factors.11 The determination of substantial equivalence provides a basis for identifying similarities and differences between transgenic lines and their non-transgenic counterparts. Received: Revised: Accepted: Published: 7877
April 13, 2014 June 23, 2014 June 27, 2014 June 27, 2014 dx.doi.org/10.1021/jf5016297 | J. Agric. Food Chem. 2014, 62, 7877−7885
Journal of Agricultural and Food Chemistry
Article
Virginia-type peanuts.18 Extra-large kernels (ELK) were the percentage by weight of extra-large kernels that ride the 8.5 × 25.4 mm slotted screen; sound mature kernels (SMK) were the percentage by weight of kernels that ride the 6.0 × 25.4 mm slotted screen; sound splits (SS) were the percentage by weight of kernels that consist of undamaged split or broken kernels with size between 0.25 and 0.75 mm; total sound mature kernels (TSMK) were the sum of ELK, SMK, and SS; other kernels (OK, percentage by weight) were kernels from the shelled peanut that goes through the SMK screen; and damaged kernels (DK, percentage by weight) were kernels from the shelled peanut that are inedible because of decay, mold, insect damage, sprouting (>3.2 mm), discoloration or pitting darker than light yellow, freeze damaged, or skin discoloration ( F
1 2 3 4 5
0.9974 0.9455 0.7478 0.5495 0.4086
0.6745 0.2657 0.0399 0.0136 0.0063
0.6745 0.9401 0.9801 0.9937 1.0000
0.0012 0.0272 0.2563 0.5815 0.8330
13.86 7.50 3.11 1.80 1.24
