Genetic Markers and Horticultural Germplasm Management

This paper is adapted from the text of a seminar of the same title presented as part of the Workshop on Sustainability of Vegetable Breeders’ Genetic Resources, 26 July 1993, at the 90th Annual Meeting of the American Society for Horticultural Science. It represents the distillation of a more extensive treatment of genetic markers and germplasm management (Bretting and Widrlechner, 1995)

Genetic Markers and Plant Genetic Resource Management

Plant genetic resource (or simply germplasm) management comprises two phases. The first, germplasm conservation, includes acquisition, or securing germplasm in situ (by establishing reserves) or ex situ (by assembling collections through exchange or exploration). It also comprises maintenance: monitoring and protecting germplasm in reserves or storing it ex situ under controlled conditions, propagating it while preserving its original genetic profile with maximum fidelity, monitoring its viability and health in storage, and maintaining associated passport and other data. Germplasm conservation also involves characterization, assaying highly heritable morphological and molecular traits of germplasm, for taxonomic, genetic, quality assurance, and other management purposes

Phylogenetic Relationships among North American Popcorns and Their Evolutionary Links to Mexican and South American Popcorns

To determine genetic relationships among representative popcorns (Zea mays L.) of the New World, 56 maize populations from the USA and nine Latin American countries were characterized for 29 morphological traits, 18 isozyme loci, and 31 SSR loci. Cluster and principal component analyses were performed upon standardized morphological data and allelic frequencies from isozyme and SSR loci to elucidate relationships among populations within a geographical and historical context. Three groups of popcorn, with distinctive morphological characteristics and genetic profiles, were identified in the North American populations. The first group includes the North American Yellow Pearl Popcorns, which are currently the most important for U.S. commercial production. This group could be derived from introductions of the race Curagua from Chile into New England in the 19th Century. The second group includes the North American Pointed Rice Popcorns, which probably originated from the complex of traditional races of pointed popcorns from Latin America, such as Palomero Toluqueño, Confite Puntiagudo, Canguil, and Pisankalla, which diffused from the highlands of central Mexico into northern Mexico and then into southwestern USA. The third group includes the North American Early Popcorns, which show a marked influence of Northern Flint maize, from which they probably acquired the trait of early maturity. This third group also shows genetic influences of maize from northwestern Mexico and even from early European varieties of popcorn introduced late in the 19th Century. We propose that the three groups of North American popcorn identified in this study be recognized taxonomically as distinct races, and we provide characteristic traits as well as isozyme and SSR alleles to define the new races

Cucurbits (Cucurbitaceae; Cucumis spp., Cucurbita spp., Citrullus spp.)

The Cucurbitaceae is a remarkable plant family, deserving of attention because of its economic, aesthetic, cultural, medicinal, and botanical significance. In the Old and New Worlds, cucurbits have been associated with human nutrition and culture for more than 12,000 years (Brothwell and Brothwell 1969; Lira-Saade 1995). Thus, the Cucurbitaceae, along with the Brassicaceae and Asteraceae, can be considered families of extraordinary importance to humans, and they follow cereals and legumes in their economic significance to human economy (Whitaker and Davis 1962; Nayar and More 1998)

Germplasm Resources at the North Central Plant Introduction Station

History The introduction of potentially useful plant species into the United States dates back to the early 19th century when embassies were asked to collect and import these materials.A more organized effort was established when the Section of Seed and Plant Introduction was formed in 1898 within the USDA. No provisions were made, however, to store these materials adequately and much was lost (Wilson et al. 1985)

Screening Coriander Gene Pool for Special Uses

Coriander (Coriandrum sativum L.) is an aromatic member of the Apiaceae with a wide diversity of uses (Diederichsen 1996). Its rapid life cycle allows it to fit into different growing seasons, making it possible to grow the crop under a wide range of conditions. Three subspecies and 10 botanical varieties of coriander have been proposed at the infraspecific level (Diederichsen and Hammer 2003) based on phenotypic characteristics; however, molecular evidence does not support classifications based on phenotypic and/or biochemical characteristics (López 2006). The objectives of our study were to assess the phenotypic and biochemical characteristics of coriander germplasm collections that would make them suitable for different uses and to use amplified fragment length polymorphism (AFLP) (Vos et al. 1995) to clarify patterns of genetic diversity and its partitioning among these populations, by means of an analysis of molecular variance (AMOVA) (Excoffier et al. 1992)

NORTH AMERICAN CONTINENT - A NEW SOURCE OF WILD LACTUCA SPP. GERMPLASM VARIABILITY FOR FUTURE LETTUCE BREEDING

In the years 2002-2008, missions were undertaken in the USA and Canada to search for wild and weedy Lactuca species. Altogether, 16 states in the USA (Arizona, California, Colorado, Idaho, Iowa, Minnesota, Montana, Nevada, New York, North Carolina, Oregon, South Dakota, Utah, Washington, Wisconsin and Wyoming) and two provinces in Canada (Ontario and Quebec) were visited. In total, seven wild and weedy Lactuca spp. (L. serriola, L. saligna, L. virosa, L. canadensis, L. biennis, L. floridana, and L. ludoviciana), an interspecific hybrid (L. canadensis × L. ludoviciana), and an undetermined Lactuca species were observed and collected in 200 locations. In this paper, we present new data on the distribution and ecobiology of Lactuca naturally occurring in North America. Morphological assessment of L. serriola samples acquired from North America revealed considerable intraspecific phenotypic variation. Although L. serriola samples originating from various eco-geographical regions differed significantly in their genetic polymorphisms (based on AFLP markers), little variation was observed in their absolute DNA content.This is a proceeding from Acta Horticulturae 918 (2011): 475, doi: 10.17660/ActaHortic.2011.918.59.</p