Crop and Pasture Science
Volume 65 Number 11 2014
Forage Breeding for Changing Environments and Production Systems
White clover is the best available forage legume for grazed pastures in temperate zones, but it is not stress resistant and cannot grow in semi-arid, low fertility soils. Several closely related wild clover species are adapted to stressful environments and, although none of these cross naturally with white clover, successful use of tissue culture techniques and genetic bridges has enabled eleven forms of them to be hybridised with white clover. These inter-species hybrids are being used by plant breeders to select resilient new clovers for future-proofing legume-based pastures and expanding them into marginal zones.
Forage legumes, such as lucerne and white clover, lack foliar proanthocyanidins which leads to bloat, an often lethal condition costing the pastoral industry significant loss of earnings. By overexpressing an R2R3-MYB gene in these species, leaf PA accumulation is achieved; however, additional MYB genes involved in PA regulation have also been identified. Progress towards producing commercial cultivars of both species containing effective levels of PAs has begun as a viable option for mitigating bloat in pastoral agriculture-based farming systems.
The drought tolerant forage legume tedera is a very promising novel species for Mediterranean climates in southern Australia. The evaluation and breeding of tedera commenced in 2006 in Western Australia and the first cultivar was delivered to the seed industry in 2014. The availability of this new technology to Australian farmers will allow them to reduce supplementary feeding by filling the autumn feed-gap with a grazable forage legume.
Brazil has the largest commercial cattle herd in the world and is the largest exporter of beef, due to the vast area of pastures which confer good welfare conditions to the animals. New improved and adapted forage cultivars are necessary to sustain this production. The development of more productive and better quality pastures in the country involves more efficient breeding methodologies and tools, dynamic breeding programs and efficient technology transfer, resulting in progressively better meat and milk production from pastures.
Red clover is an important forage legume around the world. However, its main limitation is the lack of persistence of forage yield due to the low survival of plants. To improve this complex character in our breeding program, we have conducted five cycles of recurrent selection, using a modified among and within half-family methodology. The average realised genetic gain for forage yield has been 0.4–2.6% per year, depending on location, showing the effectiveness of the breeding methodology and approach used.
Our studies of diverse germplasm, derived from crosses between annual wheat and perennial Triticeae grasses, established that regrowth and grain harvest for a number of seasons is possible, provided at least one genome equivalent from the perennial donor parent is retained. Selected lines demonstrated substantially increased root biomass in the second season compared with resown annual wheat, and produced valuable forage biomass. A breeding strategy for establishing segregating populations and targeted trait improvement is proposed, which should assist in the realisation of projected economic and environmental benefits, resulting from the change to a perennial growth habit.
Perennials are a vital component for sustainable production in pastures of south-eastern Australia. Stresses related to climate, soils and grazing pressure often reduce the persistence even of well-adapted perennials in high production pasture systems but plant breeders have recently been able to improve the tolerance of the major grass species, phalaris, to acid soils and high grazing pressure. Continued plant breeding efforts combined with good management will be needed to maintain perennials such as phalaris in pastures of the future.
Genomic selection is now being used at an accelerating pace in many plant species. This review interprets results of plant genomic selection studies considering the factors that affect the accuracy of genomic selection, such as size of reference population, heritability and extent of genetic diversity. Differences between genomic breeding strategies for self-pollinated and open-pollinated species, and between-population level and within-family designs, are highlighted.
This paper reviews research conducted at the University of Florida for almost 30 years to enhance resistance to plant parasitic nematodes, primarily root-knot nematode species. We discuss germplasm screening methods, progress in selection for resistance, cultivar development, and look to the future for ways to enhance progress.
CP14039Forages for feedstocks of biorefineries in temperate environments: review of lignin research in bioenergy crops and some insight into Miscanthus studies
Miscanthus is a potential bioenergy crop for temperate regions and low-lignin Miscanthus cultivars are desirable for cost-efficient bioethanol production. Limited information on genetic regulation of lignin biosynthesis in Miscanthus led us to review previous studies of lignin biosynthesis in switchgrass and maize, to review current status of lignin research in Miscanthus, and performed preliminary study on characterisation of Miscanthus lignin genes. This review will help us in setting Miscanthus lignin research direction and also support breeding of low lignin Miscanthus cultivars that is suitable for bioethanol production.
CP14031Genetic improvement of subterranean clover (Trifolium subterraneum L.). 2. Breeding for disease and pest resistance
Subterranean clover, the most widely sown pasture legume in southern Australia, is attacked by a range of diseases and pests which reduce pasture productivity. The identification of genotypes with resistance to important diseases and pests has enabled development of cultivars with improved disease and pest resistance. The advent of new gene technologies has the potential to develop future subterranean clovers with multiple disease and pest resistances, provided skills in pasture plant pathology, entomology, pre-breeding and plant breeding are adequately resourced.
CP13384Estimating the value of genetic gain in perennial pastures with emphasis on temperate species
It has traditionally been difficult to put a value on genetic gain in pasture species as pastures are not a directly traded commodity. This paper includes a discussion of the principles and processes for valuing genetic gain in pasture species either through comparisons with the cost of obtaining the attributes of the pasture from another source or through the use of the pasture to provide improvements in farm productivity and production.
CP13361Resources and strategies for implementation of genomic selection in breeding of forage species
Genomic selection provides an attractive option for improvement of complex genetic traits in forage species. Strategies for implementation are constrained and informed by multiple biological characteristics of the target crop species. These factors are generally compared and evaluated, and influence on a number of representative species is discussed.