INVITRO CULTURE OF SUBANGUINA-PICRIDIS IN ACROPTILON-REPENS CALLUS, EXCISED ROOTS, AND SHOOT TISSUES

The knapweed nematode Subanguina picridis is a foliar parasite that is of interest as a biological weed control agent of Russian knapweed. Attempts were made to culture the nematode in callus, excised roots and in shoots derived from roots of Russian knapweed. In callus tissues, the nematode developed from second-stage, juvenile to adult but failed to reproduce; it developed only to the fourth stage in excised roots. However, S. picridis was successfully cultured in vitro in shoots derived from roots. The nematode induced galls on the leaves, petioles, and shoot apices and developed and reproduced inside the galls. Gibberellic acid increased the development rate of the nematode and promoted the formation of males. This is the first gnotobiotic culture of a nematode used for biological weed control.