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Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/21/2005 Publication Date: 3/1/2006 Citation: Timper, P., Wilson, J.P. 2006. Root-knot nematode resistance in pearl millet from west and east Africa. Plant Disease. 90:339-344. Interpretive Summary: Resistance to the southern root-knot nematode is important to provide stability to pearl millet production and to reduce nematode populations that can damage crops grown in rotation with pearl millet. The objectives of this study were to determine if resistance to the southern root-knot nematode exists in pearl millets from West and East Africa, and to determine if variation for resistance exists within selected varieties. Seventeen pearl millet varieties of diverse origin were evaluated. All African varieties expressed some level of resistance. P3Kollo was among the least resistant of the African varieties, Zongo and Gwagwa were intermediate, and SoSat-C88 was among the most resistant. Thirty selfed progeny from SoSat-C88, Gwagwa, Zongo, and P3Kollo were evaluated to determine whether the varieties contained both resistant and susceptible plant types. Each of the varieties contained plant types that were either resistant, susceptible, or intermediate in their reaction to nematode reproduction. Zongo and SoSat-C88 contained the highest frequency of resistant plants. Distinct resistant and susceptible plant types were identified in Zongo progeny, and it was estimated that two dominant genes for resistance are present in this variety. Averaged across the individual plants, nematode reproduction on the four varieties was less than on the susceptible hybrid HGM-100, but was not different from resistant hybrid TifGrain 102. If any of these pearl millet varieties are to be used as sources of nematode resistance for the U.S. or West Africa, it will be necessary to select resistant plant types from within the varieties for breeding programs or hybrid production. Technical Abstract: Resistance to Meloidogyne incognita is important to provide stability to pearl millet production and to reduce nematode populations that can damage crops grown in rotation with pearl millet. The objectives of this study were to determine if resistance to M. incognita exists in pearl millets from West and East Africa, and to determine if heterogeneity for resistance exists within selected varieties. Resistance was assessed as nematode egg production/g root in greenhouse trials. Seventeen pearl millets of diverse origin were evaluated as bulk (S0) populations. All African varieties expressed some level of resistance. P3Kollo was among the least resistant of the African varieties, Zongo and Gwagwa were intermediate, and SoSat-C88 was among the most resistant. Thirty selfed (S1) progeny selections from SoSat-C88, Gwagwa, Zongo, and P3Kollo were evaluated for heterogeneity of resistance within variety. Reactions were verified in 13 S2 progeny of each of the four varieties. In S1 evaluations, each of these varieties was heterogeneous for resistance. Progeny reaction varied from highly resistant to highly susceptible. Patterns of apparent segregation of resistance varied among the four varieties. Discreet resistant and susceptible phenotypes were identified in Zongo progeny, and it was estimated that two dominant genes for resistance segregated in this variety. Averaged across progenies, egg production on the four varieties was less (P < 0.001) than on the susceptible hybrid HGM-100, but was not different from resistant hybrid TifGrain 102. Reproduction of M. incognita on the S2 progeny tended to confirm the results from inoculations of S1 progeny. Heritability of nematode reproduction (standardized as the ratio of the value to HGM-100) determined by parent-offspring regression was 0.54. Realized heritability determined by divergent selection was 0.87. |
