|Reighard, G - CLEMSON UNIVERSITY, SC|
Submitted to: Journal of Nematology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 5, 1998
Publication Date: N/A
Interpretive Summary: Root-knot nematodes are important pests of peach in the United States and other parts of the world if not controlled. Meloidogyne incognita and M. javanica are the predominant species on peach. Nemaguard peach rootstock is resistant to these 2 nematode species, but planting Nemaguard on orchard sites infested with both Meloidogyne sp. and ring nematode has proven to be futile for the peach industry in the Southeast. Lovell rootstock is recommended in situations where both root-knot and ring nematodes occur, even though Lovell is susceptible to root knot nematode. Finding a rootstock superior to Lovell that survives on peach tree short life sites, induced by ring nematode and also is root knot nematode resistant, would be of great value to the peach industry throughout the Southeast. Such a rootstock BY520-9 (Guardian), was identified in 1991 as providing greater peach tree short life tree survival than Lovell. Unfortunately, grower demand resulted in commercial release of Guardian before all root knot nematode evaluation testing had been examined critically. Current studies that Guardian was not a suitable host to M. incognita and M. javanica and that the mechanism of resistance to M. incognita was the result of the nematode not being able to complete its life cycle. These data provide useful insights into the potential utilization of Guardian rootstock in peach orchards infested with root knot nematode. Furthermore, these data were necessary for providing a complete understanding of how the two commercial Guardian seed sources, USDA Byron and Clemson University, did not differ in resistance to the two root knot nematode isolates found in the Southeast.
Technical Abstract: Guardian peach rootstock was evaluated for susceptibility to Meloidogyne incognita race 3 (Georgia-peach isolate) and M. javanica in the greenhouse. Both commercial Guardian seed sources tested were poor hosts to M. incognita and M. javanica. Reproduction as indicated by number of egg masses and eggs per plant, eggs per egg mass, and eggs per gram of root was a better measure of host resistance than number of root galls per plant. Penetration, development and reproduction of M. incognita in Guardian (resistant) and Lovell (susceptible) peach were also studied in the greenhouse. Differences in susceptibility were not attributed to differential degrees in penetration by the infective stage juveniles or the number of root galls per plant. Results indicate that M. incognita infective stage J2's penetrate Guardian roots, root gall formation occurs, but the majority of the nematodes fail to reach maturity and reproduce.