ISHS Acta Horticulturae 738: International Symposium on Biotechnology of Temperate Fruit Crops and Tropical Species
MOLECULAR GENETICS OF WALNUTS - A BREEDER'S PERSPECTIVE |
| Author: | G. McGranahan |
| Keywords: | Juglans regia, molecular markers, genetic engineering, rootstocks |
| Abstract:
Nut crops lag behind many other crops in the field of molecular genetics and genomics. In Persian walnuts, molecular genetics has been used primarily for problem solving. Marker-assisted selection is used to identify hypersensitivity to the cherry leafroll virus in young seedlings in the walnut backcross breeding program. The marker was derived by bulked segregant analysis. Microsatellite (SSR) markers have been used for genetic analysis and cultivar identification. Several techniques have been used to evaluate genetic diversity and relationships among walnut cultivars. These include randomly amplified polymorphic DNA (RAPD) markers, restriction fragment-length polymorphism (RFLP) markers, and inter-simple sequence repeat (ISSR) markers. Gene transfer techniques are well developed, and trees expressing rolABC, Bt CryIA(c), and Xa21 have been tested in the field. RolABC affected tree structure but did not increase rootability; husks from trees expressing the Bt gene were effective in killing codling moth; and Xa21 had no effect on walnut blight caused by Xanthomonas. Recently, RNAi gene silencing was used to block plant IAAM expression preventing the gall formation characteristic of Agrobacterium tumefaciens infection. | |
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