Rice seedlings of the resistant variety Phalguna showed premature tillering, browning of central leaf, and tissue necrosis at the apical meristem following artificial infestation with avirulent biotype 1 of the Asian rice gall midge, Orseolia oryzae (Wood‐Mason) (Diptera: Cecidomyiidae). Tissue necrosis representing a typical hypersensitive reaction (HR), accompanied by maggot mortality, was observed within 4 days after infestation. However, reinfestation of secondary tillers subsequent to HR in primary tiller, did not lead to HR in secondary tillers though maggot mortality was seen. Artificial infestation with the weed gall midge O. fluvialis did not result in HR either in gall midge susceptible TN 1 or resistant Phalguna rice varieties. Resistance in Phalguna against the virulent biotype 4 could be induced by either prior, simultaneous, or subsequent infestation with the avirulent biotype 1. The duration of effectiveness of such induced resistance varied with the sequence and time lag between infestations.

Fourteen differential rice cultivars under four major donor groups were evaluated at 11 field locations in seven Indian states during 13 years against the rice gall midge, Orseolia oryzae (Wood-Mason) (Diptera:Cecidomyiidae). Three basic variations, which qualify to be called biotypes 1,2 and 3 could be identified based on overall reaction patterns against Eswarakora and Siam 29 differential groups. Biotype I cannot damage entries involving either Eswarakora or Siam 29. Biotype 2 is capable of damaging the group of Eswarakora and its derivatives but not able to damage the group of Siam 29. Biotype 3 can damage the Siam 29 group while being incapable of doing so with Eswarakora group.Resume-Quatorze varietes de riz provenant de quatre groupes differents ont ete evaluees pendant 13ans dans onze locations contre le moucheron du riz, Orseolia oryza (Wood-Mason) (Diptera:Cecidomyiidae). Trois differents Biotypes I, II et III ont put etre identifier en se bassant sur la possible reaction du moucheron contre le groupe Eswarakora et Siam 29. Le Biotype I n'a pas pu dommager les deux groupes, par contre le Biotype II est capable de s'attaquer au groupe Eswarakora et ses derivees sans en affecter Ie groupe Siam 29. Le Biotype III a une action contraire au Biotype II.

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