Comparative mapping of quantitative trait loci associated with waterlogging tolerance in barley (Hordeum vulgare L.)

<p>Abstract</p> <p>Background</p> <p>Resistance to soil waterlogging stress is an important plant breeding objective in high rainfall or poorly drained areas across many countries in the world. The present study was conducted to identify quantitative trait loci (QTLs) associated with waterlogging tolerance (e.g. leaf chlorosis, plant survival and biomass reduction) in barley and compare the QTLs identified across two seasons and in two different populations using a composite map constructed with SSRs, RFLP and Diversity Array Technology (DArT) markers.</p> <p>Results</p> <p>Twenty QTLs for waterlogging tolerance related traits were found in the two barley double haploid (DH) populations. Several of these QTLs were validated through replication of experiments across seasons or by co-location across populations. Some of these QTLs affected multiple waterlogging tolerance related traits, for example, QTL Q_wt4-1 contributed not only to reducing barley leaf chlorosis, but also increasing plant biomass under waterlogging stress, whereas other QTLs controlled both leaf chlorosis and plant survival.</p> <p>Conclusion</p> <p>Improving waterlogging tolerance in barley is still at an early stage compared with other traits. QTLs identified in this study have made it possible to use marker assisted selection (MAS) in combination with traditional field selection to significantly enhance barley breeding for waterlogging tolerance. There may be some degree of homoeologous relationship between QTLs controlling barley waterlogging tolerance and that in other crops as discussed in this study.</p

Combining ability of barley flour pasting properties

Malt extract is one of the major traits contributing to high malting quality and thus a major objective in malting barley breeding programs. Understanding the genetic behaviour of this trait could make selection more efficient. However, the measurement of this trait is very time-consuming and cannot be done in a single plant since it needs a certain amount of grain. In this paper, 10 different varieties with different malting quality were selected to make two 6 × 6 half-diallel crosses for the purpose of studying the genetic behaviour of flour pasting properties, in particular pasting temperature which has been shown to be closely related with malt extract. The pasting properties were measured with a Rapid ViscoAnalyser. Both Australian malting varieties showed significantly higher general combining ability for lower pasting temperature (higher malt extract). The Japanese malting variety also appeared to be a good parent for lower pasting temperature. All the other feed varieties which are used in the breeding programs for improving waterlogging tolerance or salinity tolerance showed significantly higher pasting temperature. Since specific combining ability was not significant, the selection of parents when breeding for pasting temperature can be based on the pasting temperature of the parents. Combined with the fact that only a small amount of grain is needed for the measurement of pasting temperature, the selection can be made in early segregating generations. Preliminary study showed that a major QTL associated with pasting temperature was located on chromosome 7H, indicating the possibility of marker assisted selection for this trait

The social learning potential of participatory water valuation workshops : A case study in Tasmania, Australia

Participatory water valuation workshops are useful for their valuation outcomes, but can they also foster social learning? Social learning involves changes in understanding through social interactions between actors, which go beyond the individual to become situated within wider social units. Participatory water valuation workshops involve dialoguing about knowledge, perspectives, and preferences, which may be conducive to social learning. In this paper, we assess the social learning potential of a participatory valuation workshop, based on a case study in Tasmania, where farmers, water managers, and a policy maker shared their personal perspectives on the past, current and future values of irrigation water. To assess the social learning potential of a single participatory valuation workshop, we analyzed drivers—that is, factors positively influencing social learning—and outcomes—that is, indications that social learning occurred. Data were collected through an exit survey, in-workshop reflections and semistructured interviews following 3 weeks and 6 months after the actual workshop. The results indicate that the workshop provided the drivers for social learning to occur. In addition, participants indicated to have learned from and with others, and that the workshop provided improved and extended networks. According to the participants, the workshop led to a shared concern about increasing prices for water licences and induced substantive outcomes related to the use, management, and governance of irrigation water. We conclude that participatory valuation workshops, such as the one analyzed here, can foster social learning.</p

Effect of Secondary Metabolites Associated with Anaerobic Soil Conditions on Ion Fluxes and Electrophysiology in Barley Roots1[C]

The effects of secondary metabolites produced by waterlogged soils on net K+, H+, and Ca2+ fluxes were studied in the mature zone of roots of two barley (Hordeum vulgare) cultivars contrasting in their waterlogging (WL) tolerance using the noninvasive microelectrode ion flux measuring technique. In WL-sensitive variety ‘Naso Nijo’, all three lower monocarboxylic acids (formic, acetic, and propionic acids) and three phenolic acids (benzoic, 2-hydroxybenzoic, 4-hydroxybenzoic acids) caused a substantial shift toward steady K+ efflux, accompanied by an immediate net influx of H+. Detrimental effects of secondary metabolites on K+ homeostasis in root cells were absent in WL-tolerant ‘TX’ variety. Root treatment with Mn2+ caused only a temporary K+ loss that returned to the initial level 10 min after treatment. Phenolic acids slightly increased Ca2+ influx immediately after treatment, while other metabolites tested resulted in transient Ca2+ efflux from the root. In the long-term (24 h) treatment, all metabolites tested significantly reduced K+ uptake and the adverse effects of phenolic acids were smaller than for monocarboxylic acids and Mn2+. Treatment with monocarboxylic acids for 24 h shifted H+ from net efflux to net influx, while all three phenolic acids did not cause significant effects compared with the control. Based on results of pharmacological experiments and membrane potential measurements, a model explaining the effects of secondary metabolites on membrane transport activity is proposed. We also suggest that plant tolerance to these secondary metabolites could be considered a useful trait in breeding programs

Combining ability of salinity tolerance on the basis of NaCl-induced K+ flux from roots of barley

Salinity is a major abiotic stress affecting agricultural production. To understand the genetic behavior of salinity tolerance traits, a half-diallel cross was made among six barley cultivars (Hordeum vulgare L.), with contrasting levels of known tolerance, to study the combining ability of salinity tolerance on the basis of K+ loss from plant roots under saline conditions. The glasshouse pot experiments showed that the six parents were significantly different in salinity tolerance and those tolerances were highly correlated with the K+ flux measurements. The combining ability analysis showed that the variances of both general combining ability (GCA) and specific combining ability (SCA) were highly significant. Two tolerant cultivars, CM72 and Numar, showed significantly higher GCA for salinity tolerance (less K+ loss under salinity stress). Cultivars with medium GCA were YU6472 and Yan90260. Salinity tolerance was mainly controlled by additive effects with the tolerance allele showing partial dominance. High positive SCA was also found between two tolerant cultivars and between tolerant and medium-tolerant cultivars, indicating possible different tolerant genes or some minor genes in these cultivars. The combination of these genes from different sources of tolerant cultivars should produce cultivars with even greater tolerance

Participatory crossover analysis to support discussions about investments in irrigation water sources

Regional long-term water management plans depend increasingly on investments by local water users such as farmers. However, local circumstances and individual situations vary and investment decisions are made under uncertainty. Water users may therefore perceive the costs and benefits very differently, leading to non-uniform investment decisions. This variation can be explored using crossover points. A crossover point represents conditions in which a decision maker assigns equal preference to competing alternatives. This paper presents, applies, and evaluates a framework extending the use of the concept of crossover points to a participatory process in a group setting. We applied the framework in a case study in the Coal River Valley of Tasmania, Australia. Here, farmers can choose from multiple water sources. In this case, the focus on crossover points encouraged participants to engage in candid discussions exploring the personal lines of reasoning underlying their preferences. Participants learned from others' inputs, and group discussions elicited information and insights considered valuable for both the participants and for outsiders on the factors that influence preferences. We conclude that the approach has a high potential to facilitate learning in groups and to support planning.Peer reviewe