Citrullus lanatus (Thunb.) Matsum. & Nakai - Cucurbit Breeding ...

The goal of our QTL mapping experiment would be to identify at least two markers flanking each QTL
that explains large portions of the variation associated with resistance. Alternatively, should the single gene db
be regulated by minor QTLs, a single molecular marker linked to db would be a useful tool to plant breeders for
MAS. Ideally, the identification of a marker tightly linked to db and other markers detecting the presence of the
minor QTLs would provide enough information to predict the phenotype of the progenies of each cross.
Nevertheless, it could be difficult to achieve the correct mapping of these minor QTLs, due to the possibility
that each of them explains too little of the total variation.
Based on the results of this investigation, plant breeders could integrate MAS for the db gene and field
and greenhouse testing to select the progenies with the highest expression of resistance under natural and
artificial epidemics of gummy stem blight. Thus, minor QTLs could be selected directly by observation of the
level of resistance in phenotypic testing. Field testing would be necessary for yield and quality traits, so that
multiple years of trialing for disease resistance would be possible, prior to release of the best germplasm.
Literature Cited
Bruton, B.D. 1998. Soilborne diseases in Cucurbitaceae: pathogen virulence and host resistance, p. 143-166. In:
J.D. McCreight (ed.). Cucurbitaceae 98. ASHS Press.
Choi, H.K., D. Kim, T. Uhm, E. Limpens, H. Lim, J.H. Mun, P. Kalo, R.V. Penmetsa, A. Seres, O. Kulikova,
B.A. Roe, T. Bisseling, G.B. Kiss, and D.R. Cook. 2004. A sequence-based genetic map of Medicago
truncatula and comparison of marker collinearity with M. sativa. Genetics. 166: 1463-1502.
de Vienne, D. (ed.). 2002. Molecular markers in plant genetics and biotechnology. Institute National de la
Recherche Agronomique, Versailles, France.
Dhingra, O.D. and J.B. Sinclair. 1995. Basic plant pathology methods. CRC press, Boca Raton, FL.
Goodman, M.M. 2004. Plant breeding requirements for applied molecular biology. Crop Science. 44: 1913-
1919.
Guerra-Sanz, J.M. 2002. Citrullus simple sequence repeats markers from sequence databases. Molecular
Ecology Notes. 2: 223-225.
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