ARS | Publication request: TAKING A CLOSER LOOK AT GUARDIAN® PEACH ROOTSTOCK SUSCEPTIBILITY TO ROOT-KNOT NEMATODE

Submitted to: Southeastern Regional Peach Newsletter
Publication Type: Other
Publication Acceptance Date: March 29, 2006
Publication Date: April 1, 2006
Citation: Nyczepir, A.P., Beckman, T.G., Reighard, G.L. 2006. Taking a closer look at Guardian® peach rootstock susceptibility to root-knot nematode. Southeastern Regional Peach Newsletter. 6(2):5-6.

Interpretive Summary: Root-knot nematodes are an important pest of peach in the U.S. and other parts of the world. Four major Meloidogyne spp. have been reported to cause damage to stone fruits throughout the world, but Meloidogyne incognita and M. javanica are the predominant species found on peach and plum. In a previous long-term field microplot study, the growth of Guardian® SC 3-17-7 peach rootstock was not affected by M. incognita infection even though root galls were detected 23 months after inoculation. Since this report, it has been observed that larger than normal root galls were detected on certain trees of Guardian® line SC 3-17-7 under commercial orchard conditions. The objective of this follow-up research was to evaluate the effect of M. incognita (GA-peach isolate) on susceptibility of SC 3-17-7 using increased replication (i.e., 50 reps/treatment) to get a better handle on the genetic variability occurring with this line under controlled conditions. Two greenhouse studies were initiated to examine the susceptibility of the advance selection of Guardian® SC 3-17-7 to M. incognita. Guardian® SC 3-17-7 was compared to Lovell and Nemaguard peach rootstocks and each rootstock treatment replicated 50 times. Results indicate that root galling was just as abundant on SC 3-17-7 as on Lovell. However, the majority of galls on Lovell were associated with egg masses, whereas many of the galls produced on SC 3-17-7 were not associated with egg masses in both tests. These data provide useful insights into the potential recommendation of Guardian® rootstock in peach orchards infested with the root-knot nematode, M. incognita. Our findings also indicate that even though some root-knot nematode species produce galls on Guardian® SC 3-17-7 roots, many of the galls are non-reproductive and Guardian® appears to be resistant/tolerant to the root-knot nematode isolate tested.

Technical Abstract: The advance selection of Guardian® SC 3-17-7 rootstock was evaluated for susceptibility to Meloidogyne incognita (GA-peach isolate) 111 days after inoculation in the greenhouse. The experiment was repeated one time. Results indicate that SC 3-17-7 was a poor host to the population of M. incognita tested. Reproduction by M. incognita as indicated by number of egg masses per plant, number of eggs per gram of dry root, and number of eggs per egg mass was less (P < 0.0001) on SC 3-17-7 and Nemaguard (known resistant) than on Lovell (known susceptible). There were no differences in reproduction between Nemaguard and SC 3-17-7 in Test 1, but differences were detected in number of egg masses per plant and number of eggs per egg mass in Test 2. Based on the number of egg masses recovered in both tests (i.e., 1-2 egg masses), SC 3-17-7 would be rated resistant/tolerant to M. incognita (GA-peach isolate) infection.