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The genus Trigonella (Fabaceae, tribe Trifolieae) includes potential new species for pasture legume production in phase farming systems of southern Australia. Performance under biotic stress is an important factor in selecting the most suitable species and genotypes for pasture legume breeding programs. Fifty-nine accessions representing 26 Trigonella species and two Medicago species (formerly with Trigonella) were evaluated for resistance to two aphid species, bluegreen aphid (Acyrthosiphon kondoi Shinji), and spotted alfalfa aphid (Therioaphis trifolii (monell) fm. maculata) in glasshouse experiments. An accession of Trigonella macrorrhyncha (Sa 32223) was found to be highly resistant to both the aphids. Accessions of T. coerulescens, T. cylindracea, T. gladiata, T. mesopotamica, T. schlumbergeri and Medicago monspeliaca were found to be resistant to bluegreen aphid, but susceptible to spotted alfalfa aphid. The resistance mechanism in T. macrorrhyncha involved both antixenosis (non-preference in a choice test) and antibiosis (reduced fecundity). The implications of these results for germplasm improvement are discussed. [ABSTRACT FROM AUTHOR]

The Matérn correlation function provides great flexibility for modeling spatially correlated random processes in two dimensions, in particular via a smoothness parameter, whose estimation allows data to determine the degree of smoothness of a spatial process. The extension to include anisotropy provides a very general and flexible class of spatial covariance functions that can be used in a model-based approach to geostatistics, in which parameter estimation is achieved via REML and prediction is within the E-BLUP framework. In this article we develop a general class of linear mixed models using an anisotropic Matérn class with an extended metric. The approach is illustrated by application to soil salinity data in a rice-growing field in Australia, and to fine-scale soil pH data. It is found that anisotropy is an important aspect of both datasets, emphasizing the value of a straightforward and accessible approach to modeling anisotropy. [ABSTRACT FROM AUTHOR]