ARS | Publication request: UNIQUE SOURCES OF LATE-BLIGHT RESISTANCE IN MEXICAN SOLANUM SPECIES

Submitted to: Proceedings Wisconsin Annual Potato Meetings
Publication Type: Abstract Only
Publication Acceptance Date: February 1, 2003
Publication Date: March 15, 2003
Citation: Kuhl, J.C., Norby, M., Hanneman Jr, R.E., Hamernik, A.J., Havey, M.J. 2003. Unique sources of late-blight resistance in mexican solanum species. Proceedings Wisconsin Annual Potato Meetings.

Technical Abstract: The late-blight fungus (Phytophthora infestans) is indigenous to the central highlands of Mexico. In this area there exist many wild Solanum species showing high levels of late-blight resistance. The most widely used sources of late-blight resistance for potato originated from the Mexican 6x(4EBN) S. demissum. There are many other sources of late-blight resistance among Mexican species, especially 2x(1EBN) wild potato Mexican germplasm. Although these species cannot be crossed directly with the cultivated potato, transfer of late-blight resistances to potato is possible by ploidy manipulations, bridge crosses, or resistance gene cloning. We identified late-blight resistant and susceptible plants from the Mexican 2x(1EBN) Solanum pinnatisectum (pnt) and Solanum cardiophyllum subsp. cardiophyllum (cph), respectively. Replicated detached leaf tests were completed using the P. infestans isolate MSU96 (US-8 A2). F1 hybrids from an interspecific cross between S. pinnatisectum and S. cardiophyllum plants segregated for resistance. A backcross family was generated between a resistant F1 progeny and the susceptible S. cardiophyllum parent. Segregation of 42 resistant to 57 susceptible BC1 progeny supported a single dominant locus controlling resistance. Linkage analysis using molecular markers located the resistance locus (named Rpnt) on the long arm of chromosome 7, a region previously unassociated with late-blight resistance. Inoculation of the MSU96 isolate onto a complete set of potato late-blight differentials revealed that this isolate carries the avirulence gene corresponding to R9 from S. demissum. We generated crosses between the R9 differential (LB3) and the susceptible cultivar 'Ranger Russett' to map R9 and compare its location with that of Rpnt. The long-term goal of these experiments is to determine if the same resistance loci exist in both 6x(4EBN) S. demissum and Mexican 2x(1EBN) Solanum species or if these wild species possess independently inherited sources of late-blight resistance.