Genetic Opportunities to Improve Cereal Root Systems for Dryland Agriculture

Abstract

Understanding the major limitations to root growth is very important if we are to maximize water and nutrient use and increase yields. Limitations may be insufficient rooting depth, root diseases, nutrient deficiencies, toxicities and soil hardness. An understanding of these limitations will lead to more precisely identifying traits for which to select and breed. Examples of successfully overcoming limiting factors to improve crop performance by breeding and selection are given for cereal cyst nematodes in wheat, soil acidity and salinity. The importance of altered crop management practices to reduce limitations is also stressed. These have resulted in a more effective and healthier root system, which results in more water use and greater yields. Opportunities to genetically increase the size of the root system in dryland systems where water and nutrients are not all used by the crop are given.

Changes in durum wheat root and aerial biomass caused by the introduction of the Rht-B1b dwarfing allele and their effects on yield formation

“…In the Mediterranean Basin, one of the largest durum wheat producers in the world, more than 50 % of the total grain of durum wheat is produced in arid and semi-arid conditions, with severe drought most years (Loss and Siddique 1994;Araus et al 2003;García del Moral et al 2005). In dryland agricultural systems, a large root system that promotes access to soil water and nutrients is regarded as beneficial for plant growth (Richards 2008), although under terminal drought a greater investment in fine roots at depth would improve yield due to the better access to water and nitrogen (King et al 2003). Accordingly, root dry weight at depth has been related to drought adaptation (Lopes and Reynolds 2010).…”

Ppd1, Vrn1, ALMT1 and Rht genes and their effects on grain yield in lower rainfall environments in southern Australia

“…Climatically, this is a mostly Mediterranean-type environment with predominantly winter rainfall, but with an increasing proportion of summer rainfall with decreasing latitude in New South Wales and substantial seasonal variability in rainfall and temperature (Farrer 1898;Passioura 2006;Nidumolu et al 2012). Insufficient seasonal rainfall and high temperatures during grain filling can limit grain yield (Hochman et al 2009;Kirkegaard and Hunt 2010), as can soil constraints that limit root growth and access to soil water (Richards 2008;McDonald et al 2012). From the time of Farrer (1898), substantial effort has been made to develop wheat cultivars adapted to these lower rainfall environments, and the effort continues.…”

Genotypic Variations in Responses of Lateral Root Development to Transient Moisture Stresses in Rice Cultivars

“…In rice water-saving systems with intermittent irrigations, for example, the soil water potential fluctuated between 0 and -30 KPa (Belder et al, 2005). We assumed that such soil moisture fluctuations partially contributed to the observed rice yield reductions by 15-19% under watersaving systems compared to continuously flooded system (Belder et al, 2005;Bouman et al, 2005) because severe changes in soil moisture have marked effects on the soil condition, availability of nutrients and water, root development and functions (Kondo et al, 2005;Iijima et al, 2007;Kato et al, 2007;Richards, 2008;Siopongco et al, 2008), and thus, are very crucial for crop growth and yield. In this aspect, the ability of root traits to change developmentally and functionally in response to the changing conditions was suggested to be one of the most important traits for adaptation (Ingram et al, 1994;Yamauchi et al, 1996;Wang and Yamauchi, 2006).…”