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David F. Chapman Cathal M. Wims Cameron I. Ludemann Barbara Kuhn-Sherlock 《Grass and Forage Science》2023,78(1):64-84
Perennial ryegrass (PRG, Lolium perenne L.) breeding effort in New Zealand (NZ) has increased since c. 1990, resulting in greater functional trait diversity (e.g. heading date, ploidy, and associated Epichloë endophyte strain) in commercial products. This study quantified the variation, associations and interactions in dry matter (DM) yield, nutritive value and persistence-related traits among commercial cultivar-endophyte combinations released between 1973 and 2012, as a basis for assessing gains in value being delivered to the pasture-based livestock industries. Twenty-four or 28 combinations were compared over 3 years in two trials in each of two regions: Waikato in northern NZ (dryland), and Canterbury in central eastern South Island (irrigated). Cultivar-endophyte combinations were sown in mixtures with white clover, and pastures were intensively grazed 8–11 times per year by dairy cows. Principal Component Analysis identified 4 distinct clusters for the DM yield variables and for metabolisable energy (ME) content in each of the four trials. A broadly-adapted group of three late-season flowering, AR37-infected diploids with NZ and Spanish breeding backgrounds dominated the highest-yielding clusters. Tetraploids dominated the high ME content clusters. Interactions with region were observed throughout the data set: the strongest of these was driven by endophyte strain effects in Waikato. High-yielding cultivar-endophyte combinations in these trials were also generally high-yielding in the standard cultivar merit testing system operated in New Zealand, as interpreted via the DairyNZ Forage Value Index. However, alignment was poorer for medium- and lower-yielding cultivar-endophyte combinations. Several implications for forage evaluation methods and end-user industries are identified. 相似文献
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David F. Chapman Cameron I. Ludemann Cathal M. Wims Barbara Kuhn-Sherlock 《Grass and Forage Science》2023,78(1):85-100
Perennial ryegrass (Lolium perenne) plant breeding has delivered several high performing and broadly adapted cultivar-endophyte (Epichloë) combinations for the New Zealand pasture-based livestock industries. However, the trends in key traits and the potential economic value being added to farm systems have not previously been addressed systematically. Rates of gain in yield, nutritive value, phenological and morphological traits, and the economic value of those traits, were estimated among and within ryegrass functional groups (heading date, ploidy) traded commercially between 1973 and 2012. Whole pasture dry matter yield improvements of c. 80 and 60 kg DM/ha per year were identified in in late-season heading diploids and tetraploids respectively. Trends in metabolisable energy were negative within functional groups, but positive when all cultivar-endophyte combinations were included in the analysis due to the addition of tetraploids and late-season heading diploids from the mid-1990s. The estimated trend in overall economic value (all cultivar-endophyte combinations included) was $7/ha per year based on DM yield only, about half the rate of gain previously estimated using small-plot merit testing data. The trend increased to $15/ha per year when ME was included due to the emergence of commercial tetraploids from the early 2000s onwards. Estimated economic gains were high within late-season heading diploids and tetraploids but not mid-season diploids. These trends suggest that, if high performing cultivar-endophyte combinations had been adopted in New Zealand dairy systems, then pasture utilization should have increased by ~1 t DM/ha above the current industry average. Reasons for this apparent discrepancy are discussed. 相似文献
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Maire Juliette Gibson-Poole Simon Cowan Nicholas Krol Dominika Somers Cathal Reay Dave S. Skiba Ute Rees Robert M. Lanigan Gary J. Richards Karl G. 《Precision Agriculture》2022,23(5):1743-1774
Precision Agriculture - Most nitrogen (N) lost to the environment from grazed grassland is produced as a result of N excreted by livestock, released in the form of nitrous oxide (N2O) emissions,... 相似文献
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