Abstract
Growth of ten isolates of Catenaria anguillulae on linseed oil-cake agar medium was studied at 10, 13, 15, 20, 25, 30, 35, 40, 44 and $46^{\circ}C$. The cardinal temperatures of these isolates were also determined. Observations clearly revealed that the isolates differed in their temperature requirements. Isolate GA was found to grow best at $40^{\circ}C$, whereas VF isolate showed best growth at 35 and $40^{\circ}C$. Isolates PA, KA, CHP, KO, MA and SWP grew best at $35^{\circ}C$. The other isolates(KP and MMT) showed their best growth at $30^{\circ}C$. Based on radial growth, isolates were categorized as fast growing, medium growing and slow growing. Studies on effect of different temperatures on pathogenicity was made using only three isolates: VF, KP and MA against Xiphinema basin. VF isolate caused maximum infection at $40^{\circ}C$, whereas KP and MA isolates caused maximum infection at $30^{\circ}C$. The morphology of sporangia varied with temperature in isolates producing elongate-elliptical or filamentous sporangia. In VF isolate the sporangia were largely iilamentous to elongate elliptical at $30^{\circ}C$. The width of the sporangia increased with increasing and decreasing temperatures. At $44^{\circ}C$ the sporangia of this isolate were mostly broadly elliptical or spherical. This clearly indicates that sporangia vary in morphology with temperature. From the morphometrical studies it was understood that sporangial morphology was more consistent and reliable for grouping of isolates. Based on the morphology of sporangia the isolates of C. anguillulae were characterized in three groups viz., Mamentouslelongate elliptical(VF, KA, GA and SWP), spherical(PA, KP, MA and MMT) and vertically elongate sporangia(CHP and KO).