Differences in the resistance of sweet potato cultivars and lines to Melodogyne incognita populations

Abstract

Differences in the resistance of sweet potato cultivars and lines to Melodogyne incognita populations. Zen-ichi Sanol, Hideki Iwahoril, Yasushi Tateishil and Yumi Kai2.Differences in resistance of sweet potato cultivars to some populations of Meloidogyne incognita were examined in greenhouse assays. Twenty-four major sweet potato cultivars rooted in 200 g of potted soil were inoculated with approximately 500 juveniles of four M. incognita populations collected from different areas. Reproduction rates (eggs produced per J2 inoculated) were determined after 35 days of growth at 27t. Nine cultivars with reproduction rates higher than 11 were rated as susceptible and five cultivars with reproduction rates lower than one were rated as highly resistant to the four populations. However distinct differences were observed in reproduction rates of those populations on the other 10 cultivars. In an assay similar to the one described above with 13 newly developed cultivars or breeding lines, all four populations produced many egg-masses on three and produced only a few egg-masses on 6 of those cultivars or breeding lines. However, the remaining cultivars or breeding lines did not have a consistent response to the four populations. Among purple sweet potato cultivars grown primarily in Okinawa and Tanegashima Island, two similarly shaped cultivars, Bise and Tanegashima-murasaki 7, exhibited different levels of resistance to two populations as indicated by a marked difference between the numbers of egg masses produced. These results clearly demonstrate that resistance of sweet potato to populations of M. incognita distinctly differs with cultivars or breeding lines. Jpn. J. Nematol. 32 (2), 77-86 (2002).

Effect of Introducing Nematode-Resistant Sweet Potato Cultivars on Crop Productivity and Nematode Density in Sweet Potato-Radish Double-Cropping Systems

“…14 (K14). Cultivars K139 and M had been reported as highly resistant and susceptible cultivars, respectively, by Sano et al (2002), but they were moderately resistant in our experimental conditions. Two kinds of nematode-resistant cropping systems (CR1, CR2) and one susceptible cropping system (CS) were arranged.…”

“…These results show that the effects of the introduction of a highly nematode-resistant cultivar last only for 1 yr if a nematodesusceptible sweet potato cultivar is cultivated thereafter. Sano et al (2002) also demonstrated that J and S have high nematode resistance in 4 different M. incognita populations collected from different area. The populations included the Miyakonojo population from the Miyakonojo Research Station.…”

“…In the CR1 cropping system J, M, J and K14, and in the CR2 system K139, S, M, and K14 were cropped in 2003, 2004, 2005 and 2006, respectively *Three of the 6 plots of CR1 and CR2 were removed before radish cultivation in 2003 for another experiment which is not discussed in this paper. **We expected resistance of these cultivars with reference to the report of Sano et al (2002). Radish was excluded in this scheme, but was the same cultivar (Taibyousoubutori) in all systems and years.…”

“…The fi eld was naturally infested with RKNs, and the sweet potato cultivar "Kokei No. 14," which has been identifi ed as a nematode-susceptible sweet potato cultivar (Sano et al, 2002), was cultivated in 2002. The cropping sequence involved continuous annual double cropping of sweet potato in the summer and radish in the fall.…”

Resistance to Two Races of Meloidogyne incognita and Resistance Mechanism in Diploid Ipomoea trifida

“…The latter race reproduces on a differential sweet potato host, 'Norin No. 2', unlike the former (Sano et al 2002). These two races were raised from an egg-mass and maintained on tomato (cv.…”