To develop simple sequence repeat (SSR) markers for the hexaploid forage grass timothy ( Phleum pratense L.), we used four SSR-enriched genomic libraries to isolate 1,331 SSR-containing clones. All four libraries contained a high percentage of perfect clones, ranging from 78.1% to 91.6%. From these clones, we developed 355 SSR markers when tested from 502 SSR primer pairs. Using all 355 SSR markers we tested one screening panel consisting of eight timothy clones to detect the level of polymorphism and identify a set of loci suitable for framework mapping. The SSR markers detected 90.4% polymorphism between the parents of a pseudo-testcross F(1) population. These SSR markers will provide an ideal marker system to assist with gene targeting, QTL (quantitative trait locus) mapping, and marker-assisted selection in timothy.

Timothy (Phleum pratense L.) is the most important perennial forage grass grown in Hokkaido, Japan. Hence, the improvement of its nutritive value by breeding could be effective in enhancing animal productivity in the region. Effective improvement of the nutritive value of the grass requires a study on how the relative genotype ranking of the nutritive value changes in different environments. The objective of the present study was to investigate the magnitude of genotype × year interaction (G × Y) and genotype × location interaction (G × L) in the nutritive value of timothy. We grew 15 early‐maturing clones of timothy in Kunneppu in 2004 and 2005 to estimate G × Y and 11 early‐maturing clones in Kunneppu and Nakashibetsu in 2007 to estimate G × L, and analyzed the first crops by near‐infrared reflectance spectroscopy. The ratio of low‐digestible fiber content to organic cell wall content (Ob/OCW), Ob content and water‐soluble carbohydrate (WSC) content were significantly correlated between the 2 years and between the two locations, with non‐significant effects of G × Y and G × L. We conclude that the relative ranking of genotypes in different years and at different locations should be consistent for the traits and that selection for the traits in a single environment should be useful in effective improvement of the nutritive value of timothy.

While breeding methods to exploit only general combining ability (GCA) have been widely adopted in perennial and self‐incompatible forage crops, maize breeders have had great success in improving maize yield by developing hybrid breeding, whereby not only GCA but also specific combining ability (SCA) can be effectively exploited. A number of trials to apply hybrid breeding to such crops have not been successful because of severe inbreeding depression and/or ineffectiveness in commercial seed production. The objective of this study was to evaluate the potential of ‘clone and strain synthesis’ (CSS), a method in which both GCA and SCA can be exploited effectively to breed perennial and self‐incompatible crops. CSS consists of two procedures: (i) harvest of syn‐1 seeds from two seed parental clones after mating of each clone with a pollen parental strain under separate, isolated conditions; and (ii) even mixing of the syn‐1 seeds to produce subsequent generations, as is done to develop conventional synthetic strains from a number of parental clones. Therefore, the yield of a strain developed by CSS depends partly on combining ability, including SCA, among the three parental materials. Fifteen timothy (Phleum pratense L.) strains were developed by CSS for verification. The productivity test results indicated that four strains in the syn‐2 had significantly higher yield levels than the commercial variety adopted as their pollen parent, suggesting the potential of CSS to breed high‐yield varieties for forage, biofuel, or other uses. Yield of the strains was applied to a diallel analysis to evaluate the relative importance of SCA toward GCA; the results suggested that SCA was important in determining yield level.

Flooding due to worldwide climate change can drastically affect crop production. To overcome the detrimental effects of flooding during maize growth, we have been developing flooding-tolerant maize via DNA marker-assisted selection using a flooding-tolerant teosinte, Zea nicaraguensis, as a donor parent. Over the last decade, quantitative trait locus (QTL) information on flooding-tolerancerelated traits in Zea species has been obtained at the NARO Institute of Livestock and Grassland Science, and near-isogenic lines containing one or more QTLs have been developed for several flooding-tolerance-related traits, such as the capacity to form constitutive aerenchyma, tolerance to flooding under reducing soil conditions, and ability to form adventitious roots at the soil surface. In field trials, we have been accumulating data demonstrating the effectiveness of teosinte-derived QTLs on flooding tolerance, and are preparing to release a flooding-tolerant F 1 maize hybrid within a few years. In addition, we have just started a project to clone Qft-rd4.07-4.11 by using next-generation sequencing, which would make it possible to extend the use of this QTL to other upland crops.

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