Breeding for Tolerance

The improvement of crop performance in saline, waterlogged and inundated environments through conventional breeding programmes has been a challenging pursuit. While significant increases in crop yields were achieved in drought and hot environments during the post-Green Revolution era (Lantican et al., 2003) large areas of land subject to salinity, waterlogging and inundation are still to benefit from such a powerful and sustained research thrust. Genetic progress in breeding for tolerance to these stresses has been slow, as the physiological components of plant response are complex and the genetic basis for these responses is largely unknown (Flowers, 2004). Furthermore, the complexity of the environment and response of plants to subtle differences in environmental conditions, such as the timing, duration and intensity of stress (Munns, 2002; Setter and Waters, 2003), confound the identification of beneficial loci. In spite of the challenges, there remain good prospects for improvements in crop production on salt-, waterlogging- and inundation-prone soils through improvements in land management (Adcock et al., 2007; Bhutta and Smedema, 2007; Singh, 2009; Hobbs and Govaerts, Chapter 10, this volume) and plant breeding. Flowers and Yeo (1995) list three possible solutions to the development of crops for saline/waterlogged soils: (i) seek improvement within existing crop genomes; (ii) incorporate genetic information from halophytes into crop species; and (iii) domesticate halophytes (Fig. 6.4). These approaches may help to genetically improve the tolerance of crops for salinity, waterlogging and inundation.

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