Читать книгу Dry Beans and Pulses Production, Processing, and Nutrition - Группа авторов - Страница 33
INTRODUCTION
ОглавлениеCommon bean (Phaseolus vulgaris L.) includes a wide array of edible dry bean seed types that differ in size, shape, and color and are known collectively as dry beans; and the many horticultural pod types that also vary in color, size, shape, and flavor known collectively as snap, or garden, or green beans. The major focus of this chapter will be on dry bean breeding, but many of the characteristics discussed are common to both horticultural types. Common bean is a self‐pollinated diploid crop (2n = 2x = 22) with a small genome size of approximately 587 million base pairs distributed along 11 chromosomes (Schmutz et al. 2014). The breeding systems used to improve the crop and the genetic structure of the varieties released to farmers is dependent on the pollination system and flower structure. Varieties are highly inbred homozygous pure lines that maintain their genetic integrity and stability for generations. Bean varieties do not ‘run out’ or change due to genetic drift, but perceived changes due to inadvertent seed mixtures that go undetected, low levels of outcrossing in the field, and the accumulation of seed borne bacterial, fungal and/or viral pathogens can occur. More subtle changes may result in differential performance from changes in climate or from the emergence of new pathogen strains to which the variety is not adapted or lacks resistance. Since beans are an inbreeding species, with no effective mechanism to transfer pollen, hybrid bean varieties are not a viable option at this time.
The first dry bean breeding program in the US was established at Michigan State University (formerly Michigan State College) in the early 1900s (MSU 2009). This was followed by the establishment of a breeding program at the University of Idaho in 1925 (Singh et al. 2007). The most recent bean‐breeding program was established at North Dakota State University in the early 1980s. Currently, there are four public bean‐breeding programs at major land grant Universities, four USDA‐ARS programs that focus on bean genetics and pathology and four private companies actively working on bean breeding. The reader is referred to a few reviews where different aspects of bean breeding are summarized (Kelly 2004, 2018; Miklas et al. 2006; Singh et al. 2007; Beaver and Osorno 2009; Singh and Schwartz 2010; Kelly and Bornowski 2018; Beaver et al. 2020).