The degrees of susceptibility of oat cultivars Tachiibuki and Haeibuki to infection by 3 Meloidogyne species (M. incognita, M. arenaria, and M. hapla) were examined. Reproduction rates of 3 M. incognita populations on Tachiibuki in greenhouse experiments were low, and this confirmed our previous field experiments. The reproduction rates of 3 M. arenaria populations were low on Tachiibuki and on Haeibuki, whereas the latter is a suitable host for M. incognita. With regard to invasion of second-stage juveniles (J2), similar rates were observed for M. incognita and M. arenaria on Tachiibuki and Haeibuki roots 5 days after inoculation at 25°C. After 30 days, however, Tachiibuki roots inoculated with M. incognita or M. arenaria contained only a small number of mature females compared to the suitable nematode hosts. Most J2 nematodes on Tachiibuki roots were undeveloped and a relatively high percentage of males was observed. We conclude that the low rates of reproduction of these 2 root-knot nematode species on Tachiibuki can be attributed to the inhibition of development from the J2 stage to mature females. For the 3 M. hapla populations, reproduction was close to zero and root invasion was minimal on both oat cultivars.

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We investigated the interaction between infection of the root-knot nematode (RKN), Meloidogyne incognita, and activation of the jasmonic acid (JA) signaling pathway in Arabidopsis thaliana. We monitored the RKN infection response of various Arabidopsis mutants. In addition, we analyzed effects of methyl jasmonate (MeJA) treatment on RKN infection. The number of invading juveniles in the wild type (WT) was significantly reduced by the application of MeJA. RKN infection in the defective salicylic acid mutant (pr1-1) was similar to that of WT. JA over expresser mutants (sa2-1 and sa2-7) had a lower number of juveniles in roots than WT without MeJA treatment, and the repressing effect was not enhanced by MeJA treatment. A negative correlation was found between the activation of the JA related pathway and RKN infection. However, the repressing effect on RKN infection was not changed though JA related genes expressed more than a certain level. RKN infection was also repressed in the JA insensitive mutant (coi1-1). This result might suggest that the COI-1 signaling pathway related to plant reactions such as production of metabolites and gene expression is important for RKN infection into roots. These results also indicated that RKN may require the JA pathway for infection and RKN infection may be suppressed when the JA pathway is activated.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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Ref.: Nematological Research Vol. 40 No. 2, 27-40 (2010) There is a mistake of a scientific name in the legend to Figure 3. Correct legend to Figure 3 is given bellow. Fig. 3. Effect of different temperature conditions on mortality (mean ± SE, n = 3) of the middle instar larvae of Agrotis segetum, caused by treatment with eight isolates of Steinernema litorale and two isolates of S. feltiae. Mortality of larvae was recorded at 15 days (4- 10°C) and 10 days (15-30°C) after treatment. Means with the same lower case letter are not significantly different at 5% level between temperature conditions in each isolate according to Tukey's HSD test.

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