Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), is an important sugar-beet disease worldwide and can result in severe losses of root yield and sugar content. We have identified a major QTL for BNYVV resistance from a new source in a segregating population of 158 individuals. The QTL explained an estimated 78% of the observed phenotypic variation and the gene conferring the partial resistance is referred to as Rz4. AFLP was used in combination with bulked segregant analysis (BSA) to develop markers linked to the resistance phenotype. AFLP marker analysis was extended to produce a linkage map that was resolved into nine linkage groups. These were anchored to the nine sugar-beet chromosomes using previously published SNP markers. This represents the first anchored sugar-beet linkage map to be published with non-anonymous markers. The final linkage map comprised 233 markers covering 497.2 cM, with an average interval between markers of 2.1 cM. The Rz4 QTL and an Rz1 RAPD marker were mapped to chromosome III, the known location of the previously identified BNYVV resistance genes Rz1, Rz2 and Rz3. The availability to breeders of new resistance sources such as Rz4 increases the potential for breeding durable disease resistance.

Efficient conversion of grazed pasture and supplementary feeds into milk is essential to the profitability of dairy farming in southern Australia as costs of production continue to rise. The application of diet formulation approaches to the nutritional management of grazing dairy cows provides unique challenges in predicting the interactions that occur between grazed herbage and supplementary feeds. How feed intake and associative effects between feeds in lactating dairy cows grazing pasture might affect estimated metabolisable energy supplied by the diet are examined. The effects of increasing feed intake in high-producing dairy cows on decreasing the digestibility of energy, and the compensatory effects of reduced methane production, are reviewed. The factors affecting intake of grazing cows and possible effects on digestibility are considered, and include characteristics of the pasture/forage and amounts and forms of concentrates. Estimates of the potential magnitude of negative associative effects in dairy cows have been made using 2 datasets from recent experiments. Finally, the potential importance of understanding and predicting the magnitude of associative effects for efficient pasture-based dairy production is discussed. It is concluded that although associative effects between feeds in grazing dairy cows cannot be predicted with certainty, and although they involve complex interactions among a number of variables, ignoring their occurrence can lead to significant errors in both feed evaluation and ration formulation.

Sugar beet is a valuable arable crop providing a large proportion of world sugar supplies. It is susceptible to a range of fungal and viral diseases, to most of which there is inadequate genetic resistance. Control instead relies largely on the use of pesticides. To increase the sustainability of sugar-beet cultivation, strong and durable genetic resistance is urgently needed. This review describes an IACR-Broom's Barn programme devoted to evaluating Beta germplasm for novel resistance to major viral and fungal diseases, and its progress in elucidating the numbers and locations of the genes responsible.

Feed costs are the major component of the variable costs and a significant component of the total costs of milk production on Australian dairy farms. To improve farm productivity, farmers need to understand how much feed is being consumed and the nutritive characteristics of the diet. This paper reviews an existing simple approach, the ‘Target 10’ approach, which is commonly used by the dairy industry in Victoria to estimate annual forage consumption. An alternative approach – the ‘Feeding Systems’ approach – is then introduced. The ‘Feeding Systems’ approach is compared with estimated forage consumption measured under experimental conditions. An analysis of the sensitivity of both approaches to incremental changes in key variables is presented. The ‘Feeding Standards’ approach was concordant with estimated forage consumption measured under experimental conditions. Sensitivity analysis has highlighted key variables which may have considerable influence over simulated forage consumption using this approach. Given that none of the key variables tested in this analysis can be varied in the ‘Target 10’ approach, we feel confident that the ‘Feeding Standards’ approach provides an improved method of back-calculating annual on-farm forage consumption. Using a robust approach to calculate forage consumption which fully accounts for metabolisable energy requirements is important where farmers are using home-grown forage consumption as an indicator of farm feeding system performance. It is also important to understand the assumptions involved in estimating metabolisable energy supply from either supplements or forage.

Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), is an important sugar-beet disease worldwide. The aim of this study was to investigate and map BNYVV resistance from the WB258 source. Presence of a major resistance gene (termed Rz5) was indicated by 1 : 1 segregation of virus levels in a population of 170 individuals derived from WB258. The maximum logarithm of odds (LOD) position for Rz5, identified by interval mapping, explained 81% of the phenotypic variance. Rz5 was mapped alongside the previously identified Rz4 from the R36 source. Rz4 and Rz5 were located to 6.9 cM and 6.0 cM regions, respectively, on chromosome III by interval mapping. These locations corresponded well to the position of the widely deployed Rz1 gene, suggesting that the three genes could represent an allelic series. Physical mapping is probably required to confirm this however. BNYVV resistance genes from novel sources are potentially important in breeding for more durable resistance either as separate genes or as BNYVV race-specific alleles.