Messina (\u3cem\u3eMelilotus siculus\u3c/em\u3e)–A New Pasture Legume for Saltland

Messina (Melilotus siculus ((Turra) Vitman ex B.D. Jacks)) is a new annual pasture legume for saltland in temperate Australia and regions of the world that experience Mediterranean climates. Messina has greater tolerance to the combined stresses of salinity and water-logging than existing commercial pasture legumes. Coupled with desirable agronomic traits these characteristics give messina the capacity to rehabilitate saltland and increase productivity on land where existing legumes fail. This paper reviews the agronomic perform-ance of messina in relation to top soil salinity levels

Preliminary assessment reveals tolerance to salinity and waterlogging (and these stresses combined) in Tedera (Bituminaria bituminosa var. albomarginata)

Tedera (Bituminaria bituminosa var. albomarginata) is a promising herbaceous new drought tolerant perennial forage legume for southern Australia. In valley floors or high rainfall areas of southern Australia it is common for species to be exposed to transient waterlogging and/or salinity stresses. Tedera\u27s tolerance to these stresses is unknown. We are presenting the results of a hydroponic experiment in which four accessions were grown in an aerated nutrient solution for 20 days and then exposed to the following treatments: (i) stagnant, non-saline; (ii) aerated, 200 mM NaCl; (iii) stagnant, 200 mM NaCl; and (iv) aerated, non-saline control. After 27 days treatment, biomass of shoots and roots were measured and root morphology studied. Two of the accessions had the same shoot and root biomass in stagnant and control treatments, indicating good waterlogging tolerance. New lateral roots with aerenchyma were formed in the stagnant treatments, a typical response of waterlogging tolerant species. Both the aerated and stagnant saline treatments had significant reductions in shoot and root biomass; however, some plants were still green with no dead leaves and producing new shoots. These preliminary results are encouraging that there is variability within Tedera to select elite plants with enhanced tolerance to transient waterlogging and salinity

Growth responses of Melilotus siculus accessions to combined salinity and root-zone hypoxia are correlated with differences in tissue ion concentrations and not differences in root aeration

Soil salinity and root-zone hypoxia often occur together in saline landscapes. For many plants, this combination of stresses causes greater increases in Na+ and Cl− in shoots, and decreases in K+, than from salinity alone. These changes in ion concentrations from combined salinity and hypoxia can have more adverse consequences for growth than from salinity alone. The herbaceous forage legume Melilotus siculus naturally occurs in saline soils prone to waterlogging; however, accessions differ in their tolerances, although all form high levels of aerenchyma. We hypothesised that tolerance to combined salinity and hypoxia would be associated with either greater aerenchyma formation in roots or the innate ability of the accessions to regulate tissue ion concentrations. Fifteen accessions of M. siculus were grown in nutrient solution with two salinities (0 or 200 mM NaCl) and two aeration treatments (aerated or hypoxic) for 21 days. Dry mass (shoot and root), root porosity and ion concentrations (Cl−, Na+, K+) in shoots and roots were assessed. In the M. siculus accessions variation in the shoot dry mass under saline–hypoxic conditions was negatively correlated with shoot Cl− and Na+, and positively correlated with the shoot K+. Shoot ion concentrations under saline–hypoxic conditions were related to concentrations under saline–aerated conditions, but not to the porosity of the main root, which was relatively high (∼18 to 25%). Differences in the tolerance of M. siculus accessions to combined salinity and root-zone hypoxia were mediated by variation in the plants’ ability to regulate ions, and were not related to variation in root porosity, which was relatively high in all accessions. The interaction between salinity and hypoxia was not detrimental to M. siculus, a waterlogging tolerant species

Waterlogging tolerance is associated with root porosity in barley (Hordeum vulgare L.)

Tolerance to waterlogging is an important breeding objective for barley (Hordeum vulgare L.); however, it is a complex quantitative trait. It is difficult to screen large numbers of lines in the field due to environmental variability, and it is also challenging to screen large numbers in controlled conditions if yield data are to be collected. The direct measurement of traits that contribute to waterlogging tolerance, such as aerenchyma development in roots, may offer advantages especially if molecular markers can be developed to screen breeding populations. A doubled haploid population from a cross between Franklin and YuYaoXiangTian Erleng was screened for adventitious root porosity (gas-filled volume per unit root volume) as an indicator of aerenchyma formation. A single QTL for root porosity was identified on chromosome 4H which explained 35.7 and 39.0 % of phenotypic variation in aerated and oxygen-deficient conditions, respectively. The nearest marker was EBmac0701. This QTL is located in the same chromosomal region that contributed to tolerance when the same population was screened in an earlier independent soil waterlogging experiment. Comparative mapping revealed that this QTL is syntenic with the Qaer1.02-3 QTL in maize and the Sub1A-1 gene in rice, which are associated with aerenchyma formation (maize) and submergence tolerance (rice), respectively. This is the first report of a QTL for root porosity in barley which elucidates a major mechanism of waterlogging tolerance

Evaluation and breeding of tedera for Mediterranean climates in southern Australia

Tedera (Bituminaria bituminosa C.H. Stirton var. albomarginata and var. crassiuscula) has been identified as one of the most productive and drought-tolerant species of herbaceous perennial legumes based on 6 years of field evaluation in Western Australia in areas with Mediterranean climate and annual rainfall ranging from 200 to 600mm. Importantly, tedera demonstrated broad adaptation to diverse soils, and some accessions have shown moderate levels of tolerance to waterlogging and salinity. Tedera exhibits minimal leaf shedding during summer and autumn. Economic modelling strongly suggests that giving livestock access to green tedera in summer and autumn will dramatically increase farm profit by reducing supplementary feeding. The breeding program (2006-12) evaluated the available genetic diversity of tedera for its field performance in seven nurseries with 6498 spaced plants in total covering a wide variation in rainfall, soils and seasons. Best overall plants were selected using a multivariate selection index generated with best linear unbiased predictors (BLUPs) of dry matter cuts and leaf retention traits. The breeding program also evaluated tedera for grazing tolerance, grazing preference by livestock, waterlogging tolerance, seed production, cold tolerance, disease susceptibility and presence of secondary compounds. Tedera is a diploid, self-pollinated species. Therefore, 28 elite parents were hand-crossed in several combinations to combine outstanding attributes of parents; F1 hybrids were confirmed with the aid of highly polymorphic, simple sequence repeat markers. The F1s were progressed to F4s by single-seed descent breeding. Elite parent plants were selfed for two generations to be progressed in the breeding program without hybridisation. Over time, selections from the crossing and selfing program will deliver cultivars of three ideotypes: (i) drought-tolerant, (ii) cold- and drought-tolerant, (iii) waterlogging- and drought-tolerant