The effects of Pratylenchus penetrans (Nematoda: Pratylenchidae) on the growth of six chrysanthemum cultivars

The effects of the root lesion nematode Pratylenchus penetrans on the growth of six chrysanthemum cultivars were investigated by using cell trays and pots. Of all the cultivars tested, the Iwa-no-hakusen cultivar was most heavily damaged by the nematode. At 20 days after nematode inoculation, the nematode number in the roots of the Shuho-nochikara cultivar was significantly higher than that in the other five cultivars. However, very few necrotic root lesions were observed on Shuho-no-chikara and the root growth and plant height were not retarded. The nematode number in the root system of the four Higogiku cultivars — Akebono-no-hikari, Zuisho, Senjin-no-umi, and Hourei was similar to each other and no significant difference was observed in the root growth of the four Higogiku cultivars at 20 days after nematode inoculation. Based on these results together with some additional information, we classified Iwa-no-hakusen, Shuho-no-chikara, and the four Higogiku cultivars as suitable/susceptible, suitable/tolerant, and unsuitable/tolerant hosts for P. penetrans, respectively.