Assessment and rationalization of genetic diversity of Papua New Guinea taro (Colocasia esculenta) using SSR DNA fingerprinting

Taro (Colocasia esculenta) accessions were collected from 15 provinces of Papua New Guinea (PNG). The collection, totalling 859 accessions was collated for characterization and a core collection of 81 accessions (10%) was established on the basis of characterization data generated on 30 agro-morphological descriptors, and DNA fingerprinting using seven SSR primers. The selection of accessions was based on cluster analysis of the morphological data enabling initial selection of 20% accessions. The 20% sample was then reduced and rationalized to 10% based on molecular data generated by SSR primers. This represents the first national core collection of any species established in PNG based on molecular markers. The core has been integrated with core from other Pacific Island countries, contributing to a Pacific regional core collection, which is conserved in vitro in the South Pacific Regional Germplasm Centre at Fiji. The core collection is a valuable resource for food security of the South Pacific region and is currently being utilized by the breeding programmes of small Pacific Island countries to broaden the genetic base of the crop.

Genotypic variation in seedling root architectural traits and implications for drought adaptation in wheat (Triticum aestivum L.)

Root system characteristics are of fundamental importance to soil exploration and below-ground resource acquisition. Root architectural traits determine the in situ space-filling properties of a root system or root architecture. The growth angle of root axes is a principal component of root system architecture that has been strongly associated with acquisition efficiency in many crop species. The aims of this study were to examine the extent of genotypic variability for the growth angle and number of seminal roots in 27 current Australian and 3 CIMMYT wheat (Triticum aestivum L.) genotypes, and to quantify using fractal analysis the root system architecture of a subset of wheat genotypes contrasting in drought tolerance and seminal root characteristics. The growth angle and number of seminal roots showed significant genotypic variation among the wheat genotypes with values ranging from 36 to 56 (degrees) and 3 to 5 (plant-1), respectively. Cluster analysis of wheat genotypes based on similarity in their seminal root characteristics resulted in four groups. The group composition reflected to some extent the genetic background and environmental adaptation of genotypes. Wheat cultivars grown widely in the Mediterranean environments of southern and western Australia generally had wider growth angle and lower number of seminal axes. In contrast, cultivars with superior performance on deep clay soils in the northern cropping region, such as SeriM82, Baxter, Babax, and Dharwar Dry exhibited a narrower angle of seminal axes. The wheat genotypes also showed significant variation in fractal dimension (D). The D values calculated for the individual segments of each root system suggested that, compared to the standard cultivar Hartog, the drought-tolerant genotypes adapted to the northern region tended to distribute relatively more roots in the soil volume directly underneath the plant. These findings suggest that wheat root system architecture is closely linked to the angle of seminal root axes at the seedling stage. The implications of genotypic variation in the seminal root characteristics and fractal dimension for specific adaptation to drought environment types are discussed with emphasis on the possible exploitation of root architectural traits in breeding for improved wheat cultivars for water-limited environments.

Strawberry breeding in a subtropical environment

Strawberry breeding aims to provide cultivars that maximise consumer satisfaction and producer profitability in a changing environment. In this paper some concepts of profitability, consumer satisfaction and sustainability are explored for a subtropical climate using Queensland Australia, and Florida USA, as examples. The typical production environment is annual autumn planting of bare rooted runners into polythene covered raised beds at about 40000 plants/ha. Harvesting is late autumn to early spring, with fruit arriving at the major markets up to 2000km away from the production area within 1-4 days of harvest. The basic premise in the breed-big work is that consumers must enjoy the experience of eating strawberries, and that perceived flavour, sweetness, and juiciness are the major contributors to this experience. Using market chain information, we developed a basic value model comprised of costs, returns, and sustainability of market. To this basic outline are applied operational descriptors, such as 'speed of harvest', and associated plant characteristics, such as 'fruit display'. The expression of each plant characteristic is ascribed a value or level and together numerically describe the phenotype. This description is mathematically manipulated to provide a 'value index' for the cultivar. Nine cultivars including 'Strawberry Festival', 'Kabarla', 'DPI Rubygem' and 'Sweet Charlie' are described, and environmental issues that may impact on the subtropical strawberry breeding objectives are discussed. Product differentiation and the use of exotic germplasm as a new source of genes for flavour and resistance to disease and environmental stress will likely be the cornerstones of future progress in subtropical strawberry breeding. This approach should satisfy both consumers and producers.

Defining the unique flavours of Australian native foods

Australian native plant foods provide new and exciting eating experiences for consumers and have the potential to re-position ‘Australian cuisine’ as a contemporary food choice for consumers worldwide. The development of a common set of flavour and aroma descriptors and characteristics was identified as a key priority for the Australian native food industry. This research assists in the development and supply of product information to support market access and market growth for this emerging industry. This work was targeted so that a concise, consistent and accurate marketing message of the flavours of these ingredients could be delivered to customers. This report details the results of the development of the first ‘Australian native flavour wheel’ and sensory descriptions for sixteen of the key commercial native food species including fruits, berries, herbs, spices and seeds.