Breeding for Salinity Resistance in Crop Plants: Where Next?

Abstract

Soil salinity is widely reported to be a major agricultural problem, particularly in irrigated agriculture, and research on salinity in plants has produced a vast literature. However, there are only a handful of instances where cultivars have been developed which are resistant to saline soils. Reasons for the lack of success in developing salt-resistant genotypes, and for the low impact that plant physiological research has made, are explored. We conclude that soil salinity has not yet become a sufficient agricultural problem, other than on a local scale, to make salt resistance a high priority objective for plant breeders. The limited success of simple selection, where this has been practised in breeding programs, can be accounted for by the fact that research has consistently shown salt resistance is a complex character controlled by a number of genes or groups of genes and involves a number of component traits which are likely to be quantitative in nature. We also conclude that the results of physiological research have been poorly marketed by physiologists and, understandably, have failed to impress plant breeders. We anticipate that the importance of salinity as a breeding objective will increase in the future. Our assessment of reports of the degradation of irrigation systems, together with projections of the future demands of irrigated agriculture, is that enhancing the salt resistance of at least some crops will be necessary. Salinity resistance will both help provide stability of yield in subsistence agriculture and, through moderating inputs, help limit salinisation in irrigation systems with inadequate drainage. It is emphasised that plant improvement and drainage engineering should be seen as partners and not alternatives. We conclude with a personal view of one way forward for developing salt-resistant genotypes, through the pyramiding of physiological characters.

A comparative <i>in vitro</i> study of salt tolerance in cultivated tomato and related wild species

“…According to the FAO Land and Nutrition Management Service (2008), over 6% of the world's land, more than 800 million ha, is affected by either salinity or sodicity. The percentage of cultivated land affected by salt is even greater with 23% of the cultivated land being saline and 20% of the irrigated land suffering from secondary salinization (Flowers 2004;Flowers and Yeo 1995;Ghassemi et al 1995). Population growth and land degradation by salinization have led plant researchers to the concept of developing salt-tolerant crops by different approaches (Cuartero et al 2006;Munns 2005;Munns et al 2006;Yamaguchi and Blumwald 2005).…”

“…Abiotic stresses such as salinity, drought, temperature, and flooding are some of the main causes of crop yield loss worldwide. Abiotic stresses can reduce the average yields of most major crops by more than 50% (Bray et al 2000;Flowers and Yeo 1995;Flowers et al 2000). In particular, high salinity is a serious threat to crop production.…”

Salt Modulates Gravity Signaling Pathway to Regulate Growth Direction of Primary Roots in Arabidopsis

“…Another major constraint to root system development is soil salinity, which limits the productivity of agricultural crops and the distribution of plant species (Flowers and Yeo, 1995;Zhu, 2002Zhu, , 2003Chinnusamy et al, 2005). Sodium accumulation in the cells and the resulting disturbed balance of ions is the primary cause for inhibition of plant growth and subsequent yield reduction (Zhu, 2003).…”

Stress-Tolerant Feedstocks for Sustainable Bioenergy Production on Marginal Land

“…Secondary salinity, resulting from irrigation or land clearing, affects 20 [125] to 50 % [118,126] of the irrigated land area globally. There is evidence that the land area affected by salinization is growing through anthropogenic causes [127] and due to changing hydrologic patterns related to climate change [128], resulting in an increasing proportion of marginal land.…”

“…Framing the Issue Salinity is a major environmental stressor affecting arid, semiarid, and irrigated land worldwide [118,119] and contributing to the abandonment or marginalization of land [118]. Salinization can occur naturally, through aerosolization, deposition, or contact with sea salts in coastal locations [120], or through proximity to saline seeps, shallow water tables, and degradation of parent rock materials inland [121,122].…”