Submitted to: Phytopathology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/15/2009
Publication Date: 8/15/2009
Citation: Brown, C.R., Mojtahedi, H., Zhang, L.H., Riga, E. 2009. Independent Resistant Reactions Expressed in Root and Tuber of Potato Breeding Lines with Introgressed Resistance to Meloidogyne chitwoodi. Phytopathology. 99:1085-1089. Interpretive Summary: The potato crop is expensive to produce. Potatoes require a large investment of capital. A significant portion of the investment is in the form of biocides to kill or deter pests and pathogens. In the Columbia Basin, an important pest is the Columbia root-knot nematode. It is a small worm-like creature that invades roots, multiplies and then invades the developing tubers. The tubers sustain damage in the form of lumps and bumps on the skin and discoloration of the flesh rendering them unmarketable. At present the only remedy is to fumigate the soil with strong poisons that kill the nematodes. It is costly and serves as a source of contamination of the ground water. Resistance to the nematode is clearly a good option. In this research we found that resistance to this nematode can be separated into root and tuber resistances. It appears that the two resistances are Under separate genetic control, but the genetic factors are linked, or located close to each other on the same chromosome. This tuber resistance has not been described before. As a new discovery it is much welcome, because it improves the resistant qualities of the potatoes that has it. The combination of the two resistances provides the most durable solution. The resistance in the tubers so far has held up against many different types of the Columbia root-knot nematode. New potato varieties, with these traits incorporated into them, will save the growers money on input costs and spare the environment the contamination of fumigants.
Technical Abstract: Resistance to Meloidogyne chitwoodi was introgressed from Solanum bulbocastanum. into the cultivated gene pool of potato. A single dominant gene is responsible for resistance to race 1 reproduction on the root system. An additional form of resistance was discovered in certain advanced backcross clones. A BC5 clone, PA99N82-4, resisted invasion of tubers by available nematode juveniles whether supplied by weeds or by race 2 and several resistance-breaking pathotypes. This tuber resistance is inherited as a single dominant gene and is linked to RMc1(blb). Because this gene has been mapped to chromosome 11, tuber resistance is inferred to be on the same homologue in coupling phase. Among a 51 progeny derived from PA99N82-4, 3 recombinants comprising both types were found while other breeding lines were found to have only single root resistance. Therefore, the existence of these two genetic factors controlling independently expressed traits is confirmed. The combination of the two phenotypes is likely to be a sufficient level of resistance to avoid tuber damage from circumstances that provide exogenous juveniles proximal to the tubers in the soil. These factors are weed hosts of M. chitwoodi host races and pathotypes of M. chitwoodi that overcome RMc1(blb).