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CROP BREEDING, GENETICS & CYTOLOGY

Stability of Nonflowering Orchardgrass

^a USDA-ARS, U.S. Dairy Forage Research Center, Madison, WI 53706-1108
^b USDA-ARS, National Forage Seed Production Research Center, 3450 S.W. Campus Way, Corvallis, OR 97331-7102
^c Dep. of Crop and Soil Sci., 503 Bradfield Hall, Cornell Univ., Ithaca, NY 14853
^d Agriculture and Agri-Food Canada, Crops and Livestock Research Centre, 440 University Ave., Charlottetown, PEI, Canada C1A 4N6

^* Corresponding author (mdcasler{at}wisc.edu).

Orchardgrass (Dactylis glomerata L.) is a valuable pasture species in much of temperate humid North America. However, profuse and early flowering in spring creates management problems for graziers and reduces intake of livestock in a management-intensive rotational grazing system. The objectives of this study were to estimate environmental stability, genotypic variability, and frequency of nonflowering and sparse-flowering plants in two sparse-flowering orchardgrass populations. Seven cultivars and 299 half-sib families were evaluated for 2 yr at five locations between 42° and 47°N latitude. Sparse-flowering populations WO-SF-B and WO-SF-C were later in maturity, produced fewer panicles per plant, and had higher frequencies of sparse-flowering and nonflowering plants than the cultivars. Plants had varying levels of expression of the nonflowering trait, ranging from slightly sensitive (sparse flowering in one year) to highly sensitive (stable nonflowering across years), with highly sensitive plants found only within populations WO-SF-B and WO-SF-C. The nonflowering trait of orchardgrass appears to be controlled by floral-regulation genes that are turned off by short-day temperatures below a critical threshold. Such a threshold appears to exist for all orchardgrass plants, but is increased in those plants expressing the nonflowering trait.

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THIS ISSUE IN CROP SCIENCE

Crop Science 2004 44: 1507-1510. [Full Text]