Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2005
Publication Date: 5/22/2005
Citation: Beedanagari, S.R., Dove, S.K., Wood, B.W., Conner, P.J. 2005. A first linkage map of pecan cultivars based on RAPD and AFLP markers. Theoretical and Applied Genetics. 110:1127-1137. Interpretive Summary: Genetic improvement of pecan, a long-lived perennial possessing a long juvenility phase, is handicapped by the inability to efficiently detect and manipulate genes controlling key horticultural traits. A relatively crude genetic linkage map was constructed for pecan cultivars based on DNA based markers. This map is a first step toward advancing additional genetic studies in pecan, enabling marker assisted selection of key horticultural traits, moving toward cloning of genes, and increasing the efficiency of pecan breeding.
Technical Abstract: We report here the first genetic linkage maps of pecan [Carya illinoinensis (Wandenh.) K. Koch], using random amplified polymorphis DNA (RAPD) and amplified fragment length polymorphism (AFLP) markers. Independent maps were constructed for the cultivars 'Pawnee' and 'Elliot' using the double pseudo-testcross mapping strategy and 120 F1 seedlings from a full-sib family. A total of 477 markers, including 217 RAPD, 258 AFLP, and two morphological markers were used in linkage analysis. The 'Pawnee' linkage map has 218 markers, comprising 176 testcross and 42 intercross markers placed in 16 major and 13 minor (doublets and triplets) linkage groups. The 'Pawnee' linkage map covered 2,227 cM with an average map distance of 12.7 cM between adjacent markers. The 'Elliot' linkage map has 174 markers comprising 150 testcross and 22 intercross markers placed in 17 major and nine minor linkage groups. The 'Elliot' map covered 1,698 cM with an average map distance of 11.2 cM between adjacent markers. Segregation ratios for dichogamy type and stigma color were not significantly different from 1:1, suggesting that both traits are controlled by single loci with protogyny and green stigmas dominant to potandry and red stigmas. These loci were tightly linked (1.9 cM) and were placed in 'Elliot' linkage group 16. These linkage maps are an important first step towards the detection of genes controlling horticulturally important traits such as nut size, nut maturity date, kernel quality, and disease resistance.