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Registration of CN12 and CN72 sugarbeet germplasm populations with resistance to cyst nematode.

Sugarbeet (Beta vulgaris L.) germplasm populations CN12 (Reg. no. GP-256, PI 636338) and CN72 (Reg. no. GP-257, PI 636339) were developed by the USDA-ARS in cooperation with the Beet Sugar Development Foundation (BSDF) and the California Beet Growers Association. They were released in 2005.

CN12 and CN72 are multigerm (MM), self-fertile ([S.sup.f]), genetic male-sterile (A_:aa) facilitated, random-mated populations that segregate for resistance to sugarbeet cyst nematode (SBCN) (Heterodera schachtii Schmidt). Based on greenhouse tests of individual plants, both populations have about 40% of their plants that are moderately to highly resistant to SBCN. The resistance factors were derived from different wild beet (Beta vulgaris subsp. maritima L.) accessions but these accessions may have initially come from the same or similar source. Inheritance of resistance has yet to be determined, but empirical results and performance of selections, progeny lines, and hybrids suggest that resistance is highly heritable, dominant, and due to one or a few genetic factors. Resistance may be similar to that reported from B. vulgaris subsp. maritima that conditions partial resistance (Heijbroek, 1977). Resistance is not from the wide crosses involving B. procumbens Chr. Sm. (Savitsky, 1975). Although considered to be partial resistance, this resistance gives a high level of protection against economic losses in field tests (Lewellen and Pakish, 2005).

CN12 is a multigerm, self-fertile population that segregates for genetic male sterility and hypocotyl color (75% red). CN12 segregates for resistance to SBCN, powdery mildew [caused by Erysiphe polygoni DC. (syn. E. betae Weltzien)] conditioned by Pm (Lewellen and Schrandt, 2001), and rhizomania (Beet necrotic yellow vein virus) conditioned by Rz1. Most, if not all, of the annualism (B) of the wild beet ancestry has been eliminated and CN12 has moderate nonbolting tendency. It has moderate resistance to Curly top virus, virus yellows (Beet chlorosis virus and Beet yellows virus), and sugarbeet Erwinia (caused by Erwinia carotovora subsp. betavasculorum Thomson et al.). Its developmental populations have shown good yield performance particularly under natural infection with SBCN and rhizomania. The precise frequency of resistance to SBCN has not been determined nor has the efficacy of this resistance been fully characterized in field and greenhouse tests.

Theoretically, CN12 is 12.5% wild beet (WB) (B. vulgaris subsp. maritima) with about equal proportions of WB97 (PI 546394) and WB242 (PI 546413). WB97 and WB242 were each crossed to breeding line C54 (PI 590802). In 1991, these [F.sub.1]s were combined and crossed to genetic-male-sterile plants from population 0747 (PI 590762). Population 0747 is similar to C37 (PI 590715) and one of the progenitors of population C931 (PI 636340). Plants within the [F.sub.1]B[C.sub.1] generation were selected under field conditions for resistance to powdery mildew and increased in bulk to produce population P202. Population P202 was grown in the field in 1993 under natural powdery mildew and SBCN conditions. When individual plants were examined and selected, it was observed that in addition to segregating for reaction to powdery mildew (Pm_:pmpm), some root systems were heavily infested with SBCN cysts and a few intermingled roots were completely free of visible cysts. The selected plants were divided into two groups, one that was free of cysts to become P402NR and one that had high resistance only to powdery mildew to become P402. P402 and P402NR were crossed to population C931.

Individual [F.sub.1]B[C.sub.2] families were grown under naturally infected rhizomania and powdery mildew conditions at Salinas in 1997. Plants resistant both to rhizomania and powdery mildew from both sets of families were combined and increased in bulk to produce P812. A second cycle of mass selection for resistance to powdery mildew and rhizomania, and for non-bolting and agronomic type was done to produce P912. Until this point, (population P912), selected plants had been increased in bulk in isolation and could have produced various combinations of sib matings and selfs to produce mixtures of [S.sub.0], [S.sub.1], and [S.sub.2] plants. P912 would likely have segregated for self-fertility, genetic male sterility, powdery mildew resistance, rhizomania resistance, hypocotyl color (R:rr), etc. Population P912 was mass selected two additional times in the field at Salinas under natural rhizomania, SBCN, and powdery mildew conditions to produce population N112 and in 2003, N312. In addition to resistance to diseases, roots were selected on the basis of agronomic type, size, and sugar concentration. Selection for resistance was done visually at harvest with only plants resistant to all three diseases selected, but it is likely that escapes, particularly for SBCN, occurred under these field conditions.

In addition to mother root selection and bulk increase, individual plants from population P912 were selfed to produce N112-# progenies. These selfed progeny families were evaluated for performance at Salinas and Brawley under both diseased and nondiseased conditions. At Brawley, the progeny test was under severe SBCN conditions. Based on line performance in these tests, individual stecklings from within the selected progenies were bulked and increased by selfing to produce a second cycle of selfed progeny families called N212-#. The second cycle progenies were also evaluated at Brawley and Salinas in a series of tests that evaluated performance, bolting tendency, and disease resistance. From 48 second cycle families, stecklings from 14 families were selected and bulked. This bulk was combined with stecklings from N312 in approximately equal proportions and recombined through the segregating genetic male steriles to produce population N412, released as CN12.

CN72 is a multigerm, self-fertile population that segregates for genetic male sterility and hypocotyl color (58% red). It has approximately 25% wild beet germplasm. CN72 segregates for resistance to SBCN and rhizomania conditioned by Rz1. Most of the annualism of the wild beet ancestry has been eliminated. The precise frequency of resistance to SBCN has not been determined. It is not known if the resistance in CN72 is identical to that in CN12. The wild beet source of resistance to SBCN was a Salinas accession from Europe that had been reported to be tolerant or resistant to SBCN. The accessed line had been selected for resistance to SBCN in Germany from material they had obtained from the Netherlands. It is possible that the original source was collected in the Loire fiver estuary in France and known as LePouliguen. The increase of this accession at Salinas in 1994 was called N499 (PI 599349). In 1997, plants from N499 were crossed to genetic male sterile plants from population C931. [F.sub.1] plants selected for resistance to rhizomania were backcrossed to C931 to produce population N972. N972 was developed in parallel with P912 (see above). The same criteria of selection were used except N972 does not segregate for Pm that conditions high powdery mildew resistance. Identical kinds of populations and selfed progenies were produced. After two cycles of mass or bulk selection and increases, populations N172 and then N372 were produced. Similarly, after two cycles of selfed family selection from N972, progeny lines N272-#s were produced. Because N972 would have segregated for genetic male sterility and self-fertility and pollination was not controlled within the isolation chambers, N372 could have been composed of [S.sub.o], [S.sub.1], and/or [S.sub.1] plants. Stecklings of N372 and from 10 selected families out of 24 of N272-# S2s were combined in approximately equal numbers and recombined through the genetic male steriles to produce N472, released as CN72.

CN12 and CN72 are being released as possible sources of resistance to SBCN in enhanced backgrounds. Selections from CN12 may lead to potential parental lines but CN72 retains too many wild beet influences for this purpose. Both populations will likely need to be further backcrossed to advanced sugarbeet parental lines. These populations may be useful for biological and agronomic tests to evaluate the efficacy of these sources of SBCN resistance and to establish progenies to search for molecular markers.

Breeder seed is maintained by the USDA-ARS and will be provided to sugarbeet researchers in quantities adequate for reproduction, on request to the author. U.S. Plant Variety Protection will not be requested for CN12 and CN72.

Acknowledgments

The technical assistance of L.M. Pakish, J.A. Orozco, D.L. Lara, and D. Puga is gratefully acknowledged.

References

Heijbroek, W. 1977. Partial resistance of sugar beet to beet cyst eel-worm (Heterodera schachtii Schm.). Euphytica 26:257-262.

Lewellen, R.T., and L.M. Pakish. 2005. Performance of sugarbeet cyst nematode resistant cultivars and a search for sources of resistance. p. 122-123. In Proc. Am. Soc. Sugar Beet Technol., Palm Springs, CA. 2-5 Mar. 2005. Am. Soc. of Sugar Beet Technologists, Denver.

Lewellen, R.T., and J.K. Schrandt. 2001. Inheritance of powdery mildew resistance in sugar beet derived from Beta vulgaris subsp. maritima. Plant Dis. 85:627-631.

Savitsky, H. 1975. Hybridization between Beta vulgaris and B. procumbens and transmission of nematode (Heterodera schachtii) resistance to sugar beet. Can. J. Genet. Cytol. 17:197-209.

R.T. LEWELLEN *

USDA-ARS, U.S. Agric. Res. Stn., Crop Improvement and Production Res., 1636 E. Alisal St., Salinas, CA 93905. Cooperative investigations by the USDA-ARS, the Beet Sugar Development Foundation, and the California Beet Growers Association. Registration by CSSA. Received 15 Oct. 2005. * Corresponding author (rlewellen@pw.ars.usda.gov).

doi:10.2135/cropsci2005.10-0373

Published in Crop Sci. 46:1414-1415 (2006).
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Title Annotation:REGISTRATIONS OF GERMPLASMS
Author:Lewellen, R.T.
Publication:Crop Science
Geographic Code:1USA
Date:May 1, 2006
Words:1548
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