The Agricultural Research Service, United States Department of Agriculture, in cooperation with the Beet Sugar Development Foundation, announces the release of FC710 (4X) tetraploid, multigerm sugar beet germplasm.  This line was developed in the breeding program of L. Panella, and L. E. Hanson, Sugarbeet Research Unit, USDA-ARS, Fort Collins, Colorado.  This line has excellent resistance to root-rotting strains (AG-2-2) of Rhizoctonia solani K?hn.  It is also resistant to leaf spot caused by Cercospora beticola Sacc. It is released as a tetraploid pollinator, or population from which to select tetraploid pollinators with resistance to rhizoctonia root rot and cercospora leaf spot.  FC710 (4X) is released from seed production 20001022 and has also been tested as 971017.

FC710 (4X) (PI 633733) is tetraploid (2n = 4x = 36), multigerm (MM), non-O-type, pseudo-self-fertile, and has 29% green hypocotyls (93 plants counted).  It is a colchicine doubled version of FC710, which was registered in 1991 and FC710 (4X) performs comparably to FC710.  FC 710 was developed through two cycles of recurrent selection, with progeny tests for rhizoctonia root rot resistance and sucrose yield, and nine cycles of mass selection for rhizoctonia root rot.  It is 42% from C817 (synthetic from GW 359), 28% from breeding lines resistant to cercospora leaf spot and black root (caused by Aphanomyces cochlioides Drechs.) and 30% from reciprocal hybrids between elite sugarbeet breeding lines and Beta vulgaris subspecies maritima accessions (i.e., approximately 15% Beta vulgaris ssp. maritima germplasm).  Ninety-one colchicine treated seedlings with thickened or distorted hypocotyls were selected, transplanted, vernalized, and induced to flower.  Pollen from approximately 100 plants was sized to determine ploidy and seed was harvested individually (mother roots) from 34 tetraploid C₀ plants.  Five seeds of each mother plant were planted, vernalized, and induced to flower.  Again, pollen was sized to confirm ploidy and 75 tetraploid plants from 28 of the original C₀ mother roots harvested for seed to produce the C₁.  The C₁ seed was planted in the greenhouse and pollen sized to confirm ploidy level.  The C₂ seed was harvested from 48 tetraploid plants.  C₂ seed went through another cycle of seed production and pollen sizing in the greenhouse, 100 plants were grown and 91 plants harvested to produce C₃ seed.  This seed was tested in artificially created epiphytotics of rhizoctonia root rot and cercospora leaf spot, bulk increased in a field isolation plot in 1997 (180 plants) and again in 2000 (182 plants).  The increased seed was tested from 1998 through 2002.

FC710 (4X) exhibited excellent resistance to rhizoctonia root rot when tested under strong disease pressure.  FC710 (4X) performance was equal or superior to rhizoctonia-resistant checks in disease index (DI) ratings in 2000 and 2002 (DI of 0 = no root rot and 7 = all plants dead).  FC710 (4X) performed significantly better than the susceptible check (FC901/C817).  FC710 (4X) had mean DI=s of 3.6 and 2.4 (2000 and 2002), whereas the highly resistant check (FC705/1) had DI=s of 3.1 and 1.7, respectively.  Percentages of resistant plants (those rated 0 or 1) were 0 and 31 for FC710 (4X); and 13 and 58 for the highly resistant check.

 FC710 (4X) also exhibited good resistance to cercospora leaf spot when tested in an artificial epiphytotic.  In tests from 1999 and 2000, it was significantly better than the susceptible control and not significantly different from the resistant control.  The following DI ratings (DI of 0 = no leaf spot and 10 = all plants dead) represent the most severe rating (last of three or four ratings each season).  In 1999 and 2000, DIs of FC710 (4X) were 3.3 and 2.7; DIs of the resistant control (FC504CMS/FC502-2//SP6322-0) were 2.7 and 2.3; DIs of the susceptible control (SP351069-0) were 6.3 and3.7, respectively.  FC710 (4X) does not show tolerance to the curly top virus and has never been tested against black root.

In 2002, FC710 (4X) was yield tested for agronomic quality.  One-row plots, replicated six times were planted at the USDA-ARS Crops Research Lab-Fort Collins Research Farm, CO, on May 3rd.  Plots were 3.04 m long with 56 cm between rows and 20 to 25 cm within-row spacing.  Roots were harvested on October 8th and sent to the tare lab of Western Sugar Co. (in Scotts Bluff, NE) for analyses.  The average value of three commercial varieties - Beta 6045, HM1955, Monohikari - was used as a standard for comparison.  In percent sucrose, FC710 (4X) was 92.2% of the standard, and in sugar loss to molasses, FC710 (4X) was 118.2% of the standard.

Breeder seed of FC710 (4X) is maintained by USDA-ARS and will be provided in quantities sufficient for reproduction upon written request to Lee Panella (lpanella@lamar.colostate.edu), Sugar Beet Research, USDA-ARS,  Crops Research Laboratory, 1701 Center Ave., Fort Collins, CO  80526-2083.  Genetic material of this release has been deposited in the National Plant Germplasm System where it will be available for research purposes, including development and commercialization of new varieties/cultivars.  We request that appropriate recognition be made of the source when this germplasm contributes to a new cultivar.  U.S. plant variety protection will not be requested for FC710 (4X).

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