Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 24, 2000
Publication Date: N/A
Interpretive Summary: A new virus-resistant berseem clover germplasm, BYMVRB, was released in 1998 by the US Department of Agriculture's Agricultural Research Service and the Mississippi Agricultural and Forestry Experiment Station. The BYMVRB germplasm was developed for resistance to bean yellow mosaic virus (BYMV). BYMV causes the most widespread and serious virus disease of berseem and other annual clovers in the southeastern US. In the absence of resistance, BYMV, which is transmitted from plant to plant by feeding aphids, spreads rapidly within clover plantings. The virus reduces forage and hay yields, and reduces the effectiveness of winter clover cover crops in controlling soil erosion. Researchers discovered the new virus disease resistance within a broad range of exotic berseem clovers stored in the US germplasm collection. The new germplasm should be useful to plant breeders in producing BYMV-resistant cultivars. Small quantities of seed are available to qualified researchers.
Technical Abstract: BYMVRB berseem clover (Trifolium alexandrinum L.) germplasm, was released in 1998 by the USDA-ARS and the Miss. Agric. and Forestry Expt. Station. BYMVRB was developed from intercrosses of berseem clover plant introduc- tions (PIs) selected for resistance to bean yellow mosaic potyvirus (BYMV). Seedlings of 96 PIs and the cultivars `Multicut' and `Bigbee' were grown in the greenhouse in winter 1993-94 and mechanically inoculated with BYMV-kY204-1. Individual plant reactions were scored. Scores from 30 plants were averaged for each PI. Scores for Bigbee and Multicut were determined for six subsamples of 30 plants each for each cultivar. In fall 1996, nine PIs which had shown high levels of resis- tance in the 1993-94 tests, were chosen for further selection. The PIs and their respective cultivar names were: 468401, Lage; 220147, Frontier; 291548, Hustler; 291549, Musquawi; 468402, Balem; 420811, Eitan; 163315, Barain; 445875, Lyallpur Late; and 445882, "late flowering." Seventy seedlings of each PI were grown in the greenhouse and mechanically inoculated twice with BYMV. In spring 1997, 115 symptomless plants, representing all nine lines, were polycrossed with honey bees,Apis mellifera L., to produce first generation BYMVRB germplasm. Progeny tests, of 264 BYMVRB seedlings and 23 Bigbee seedlings showed 78% and 0% symptomless plants, respectively. In fall 1997, 100 BYMVRB seedlings were grown in the greenhouse without further selection, transplanted into pots, grown through the winter and clipped twice. In spring 1998, plants were moved outside into a screened cage with honey bees to produce second generation BYMVRB polycross seed for distri- bution. BYMVRB resembles Multicut in growth habit and should be useful as a source of BYMV resistance for selection and cultivar development.