ABSTRACT
Genetic variation is the foundation of all plant breeding programmes. As a species, Sorghum bicolor (L) Moench contains an incredible amount of diversity, and much good work has been done in collecting and characterizing this vast germplasm (Dahlberg and Madera-Torres, 1997; Morris et al., 2013; Cuevas and Prom, 2013; Cuevas et al., 2015). The task of the breeder is to effectively incorporate these diverse sources of genes into their crop improvement programmes, in order to develop cultivars with higher yields, greater stress tolerance or other novel traits. Accurate and rapid selection for certain traits that are recessive, environmentally variable or otherwise difficult to assess is challenging in a large breeding programme. The time, labour, field space and other expenses required to conduct selection are limiting factors in any plant breeding operation. Technologies such as molecular markers and HTP approaches can help breeders to address some of these limitations. Despite the great amount of diversity in cultivated sorghum, some genes
Advanced technologies to accelerate sorghum breeding
Advanced technologies to accelerate sorghum breeding
or traits of interest are simply not found within this primary gene pool, and this presents another challenge for the breeder. Technologies for incorporating genetic diversity from outside the primary sorghum gene pool include wide crossing and transgenic technology. Wide crossing has been used for many years in sorghum, while transgenic technology has only recently been developed for this crop and is not yet widely used. The existing sorghum genome can also be altered to create de novo genetic diversity through mutagenesis in a somewhat haphazard manner, or more precisely through newer genomeediting technologies. The time required to develop new cultivars is also a challenge for any plant breeder. Commercial competition or an immediate need to release cultivars with resistance to the latest disease or insect outbreak necessitates that breeders develop new cultivars in a timely manner. With the use of an off-season nursery, a sorghum breeder can achieve two generations in a year, or perhaps three with fast-maturing lines in a greenhouse. Doubled haploid breeding is currently being used in maize (Zea mays L) and other crops to speed up the process of developing inbred lines. This technology is still in its infancy for sorghum, but there is good potential for it to develop into a mature technology to expedite sorghum improvement. This chapter first reviews some of the technologies that are currently in common use among the sorghum breeding community with specific examples of how these technologies have been used in cultivar development. This is followed by an exploration of some emerging technologies in various stages of development that have potential for direct application in sorghum improvement.
