While tetraploid plants of red clover are taller, have thicker stems, and have broader leaves that altogether result in a higher forage yield compared to diploids, they generally have substantially lower seed yields than diploid plants. Tetraploid red clover can be induced chemically by colchicine or nitrous oxide (N2O) and sexually by union of unreduced gametes. The average seed yield of tetraploid red clover in Norway is 60% of the diploid yield, while in Sweden it is 75%. One objective of this paper was to examine whether there is a difference in seed yield among chromosome doubled tetraploids and crossed tetraploids. A second objective was to investigate differences in seed yield and seed yield components in Norwegian and Swedish tetraploid populations. The third objective was to study which yield component most correlates with the seed yield per hectare. Seed production experiments were established at Landvik and Bjørke in Norway and Svalöv and Lännäs in Sweden. Populations made by crossings of tetraploids gave significantly greater yield (p < 0.001) compared to populations that were made by chromosome doubling. On average, Norwegian and Swedish varieties had equal yields in both experimental years. Norwegian and Swedish varieties differed mostly in earliness traits. Swedish populations began flowering on average 4 d earlier than Norwegian populations. Genotypic correlations showed that seed yield per flower head was the component with the highest correlation (r = 0.956 and r = 0.977) with yield per hectare in both experimental fields. Results from the second experimental year indicate a trend towards improved seed yield after several cycles of recurrent selection for higher seed yield per flower head.

R ed clover (Trifolium praTense L.) is one of the most widely grown forage legumes in temperate areas, together with alfalfa (Medicago sativa L.) and white clover (Trifolium repens L.) (Boller et al., 2010). Red clover is cultivated in mixtures with grasses on approximately four million hectares worldwide (Isobe et al., 2014). Red clover in grass mixtures is important because its nitrogen-fixing ability, through symbiosis with Rhizobium leguminosarum biovar trifolii, reduces the need for nitrogen (N) input in fertilizers (Taylor and Quesenberry, 1996). Additionally, high content of crude protein and polyunsaturated fatty acids in red clover makes this species a popular component of legume-grass mixtures (Taylor and Quesenberry, 1996;Lee et al., 2009). Moreover, the high content of polyphenol oxidase (PPO) in red clover slows down the degradation of proteins in silage and thus reduces N losses from plant tissues (Lee et al., 2004;Sullivan and Hatfield, 2006).Forage legume cultivars often produce low seed yields or seeds of low viability. Both diploid and tetraploid red clover cultivars ABSTRACT Satisfactory seed yield of red clover (Trifolium pratense L.) cultivars is crucial for the availability of seeds on the market. Many breeders and researchers have used seed yield components to measure, compare, and explain differences in seed yield between diploid and tetraploid red clover cultivars and populations; however, the relative importance of each component varies between studies. In 2011 and 2012, single-plant trials with several tetraploid and one diploid red clover cultivar were established at the Norwegian plant breeding station at Bjørke. The goal was to study the impact of different seed-yield components on the seed yield of tetraploid plants. Seed weight per flower head was the seed-yield component that correlated best with the seed yield plant −1 (r = 0.91 and r = 0.68 in 2011 and 2012, respectively). Path coefficient analysis has also shown that the seed weight per flower head had the highest direct impact on seed yield plant −1 (direct path coefficients were 0. 867 and 0.783 in 2011 and 2012, respectively). In comparison, the direct path coefficients for calculated number of flower heads, which was previously highlighted as the most important seed-yield component, were lower and more variable (0.739 and 0.392 in 2011 and 2012, respectively). Since previously seed yield per flower head was also identified as the most important seed-yield component in dense plant canopy, this component might have the potential to select for improved seed yield of new cultivars based on single plants. However, further studies are required to confirm this conclusion.

This paper deals with the problem of how to utilize a large calibration set with 10 different analytes in order to make the best predictions possible on a routine basis. Ten different strategies of using the data set were studied with the use of numbers of principal components ranging from 4 to 12. We found positive effects of scatter correction for most of the analytes. On average, the local regression methods were superior to the others. The optimum number of samples for local regression seems to be between 50 and 100. The largest reduction in root mean square error of prediction (RMSEP), in comparison to results for the traditional method, was found on scatter-corrected spectra and a proposed local calibration with 50 calibration samples. The gain in RMSEP for neutral detergent fiber (NDF), acid detergent fiber (ADF), and crude fiber was about 25% and for protein and in vitro digestible dry matter digestibility (IVDMD) about 10%, compared to results for the traditional universal calibration method.

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Forage dry matter intake potential by ruminants is negatively associated with its cell wall constituent (CWC) concentration. The objectives of this study were to estimate genetic variance components and determine combining ability and heritability of CWC percent, and other associated quality traits in reed canarygrass (Phalaris arundinacea L.). Genotypic correlations were computed between paired characters. Twelve heterozygous clones used in two 6 ✕ 6 diallels and progenies from 30 crosses were grown for 2 years at two locations with three replicates arranged in randomized complete blocks. One plot consisted of six plants on 91 cm spacing in a row. Infrared spectroscopy was used to determine CWC, acid detergent fiber (ADF), acid detergent lignin (lignin), silica, crude protein, and in vitro digestible dry matter (IVDDM). Separate predictive equations were necessary for each year, probably due to yearly differences in drying procedures of samples. General (GCA) and specific combining ability (SCA) were estimated least squares analysis for one harvest in 1976, two harvests in 1977, and for the mean of the three harvests.Mean squares for GCA were significant for CWC, ADF, and lignin. Mean squares for SCA were significant for CWC, ADF, lignin, crude protein, and IVDDM. Estimates of variance components due to SCA were nearly twice as large or larger than the variance components due to GCA for CWC, ADF, lignin, crude protein, and IVDDM, indicating the presence of large amounts of nonadditive genetic variance under noncompetitive, spacedplant conditions. Broad‐sense and narrow‐sense heritabilities for CWC were 0.81 and 0.26, respectively.Estimates of genotypic correlations suggested that: (i) CWC was strongly positively correlated with ADF and lignin and strongly negatively correlated with protein and IVDDM; (ii) ADF had the highest correlation with IVDDM and was closely followed by lignin and CWC, which agreed with other reports using laboratory procedures for estimating these traits; (iii) none of the quality components was strongly correlated with spaced‐plant yield of first growth.