Multi-platform metabolomics analyses of a broad collection of fragrant and non-fragrant rice varieties reveals the high complexity of grain quality characteristics

The quality of rice in terms not only of its nutritional value but also in terms of its aroma and flavour is becoming increasingly important in modern rice breeding where global targets are focused on both yield stability and grain quality. In the present paper we have exploited advanced, multi-platform metabolomics approaches to determine the biochemical differences in 31 rice varieties from a diverse range of genetic backgrounds and origin. All were grown under the specific local conditions for which they have been bred and all aspects of varietal identification and sample purity have been guaranteed by local experts from each country. Metabolomics analyses using 6 platforms have revealed the extent of biochemical differences (and similarities) between the chosen rice genotypes. Comparison of fragrant rice varieties showed a difference in the metabolic profiles of jasmine and basmati varieties. However with no consistent separation of the germplasm class. Storage of grains had a significant effect on the metabolome of both basmati and jasmine rice varieties but changes were different for the two rice types. This shows how metabolic changes may help prove a causal relationship with developing good quality in basmati rice or incurring quality loss in jasmine rice in aged grains. Such metabolomics approaches are leading to hypotheses on the potential links between grain quality attributes, biochemical composition and genotype in the context of breeding for improvement. With this knowledge we shall establish a stronger, evidence-based foundation upon which to build targeted strategies to support breeders in their quest for improved rice varieties.

Effect of sowing time and nitrogen on rice cultivars of differing growth duration in New South Wales. 1. Yield and yield components

New South Wales rice crops commonly take >180 days from sowing to harvest, and a reduction in crop duration is sought to increase the efficiency of rice production. The response of rice cultivars of differing growth duration to sowing time and N application was examined across 2 growing seasons. The highest yields were obtained at early sowing dates in each season. In season 2, the maximum yield of the short-duration cultivar M101 was not significantly different to the long-duration cultivars Calrose, Pelde, and M7, with yields >12 t/ha. However, yield of cv. M101 was significantly less than the long-duration cultivars at an early sowing date in season 1. Analysis of yield components did not clearly indicate the reason for reduced yield of the short duration cultivar. Damage by birds and mice before harvest, exacerbated by early maturity, is a possible cause.Later sowing reduced yields of all cultivars, with the short-duration cultivar-least affected. Optimum N application decreased with delay in sowing. At early sowings there was a positive yield response to increasing N, whereas at the latest sowings in each season the N response was negative for all cultivars. Where the yield response to applied N was positive, the yield component most associated with yield was the number of florets per unit area (r = 0.55). Where the yield response was negative, yield reductions were primarily caused by a reduction in the proportion of filled grains (r = 0.83). Minimum temperatures during the reproductive stage of each cultivar explained only a small amount of the variation in percentage of filled grain. Low minimum temperatures during the reproductive stage were not the sole cause of the reduction in proportion of filled grains of late-sown, high-N plots. The high yield potential of short-duration cultivars in The high yield potential of short-duration cultivars in the New South Wales rice-growing area is clearly demonstrated, as is the value of such cultivars where late sowing is unavoidable.