Effect of temperature on teliospore germination in Tilletia indica under simulated conditions and its relevance in pest risk analysis in wheat
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Authors
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J. KUMAR*, M.S. SAHARAN, A.K. SHARMA and S. NAGARAJAN
Keywords:
Wheat, Karnal bunt. Tilletia inciica, teliospore germination, pest risk analysisAbstract
Incubating teliospores of T.indica at extreme temperatures -5, 5, and 10°C (low) as well as 35 and 40°C (high) continuously for 30 days resulted in abnormal germ tubes either lacking macrosporidia or bearing only scanty of them, while tested further for germination at 20°C. Intermediate temperatures of 15, 20, 25 and 30°C did favour production of normal germ tubes bearing plenty of macrosporidia. However, the maximum production of sporidia occurred at incubation temperatures of 20 and 25°C (at par). Both high and low extremes of temperature induced a periodicity dependent lethality among teliospores since majority of them lost the ability to produce the germ tubes while incubated at these regimes. Such a lethal effect took place after exposure of teliospores for 10, 15, 30,15,10 days (periodicity) respectively at -5, 5, 10, 35 and 40°C. Such lethal periodicities (low temperature extremes) occurred several times during 1999 and 2000 in Lahaul and Kullu valleys of Himachal Pradesh and possibly debilitated the germination potential of teliospores (0%) contained in the infected grains brought there from Punjab and stored in FCI godowns.However, the teliospores belonging to the samples of Punjab brought to Karnal (Haryana) from same area and at the same time did not lose their potential to germinate. Teliospores did not lose their germinability at Karnal since lethal periodicities of both low and high temperature did not take place there. Understanding relationship between temperature and teliospore germination which is an incipient phase of Karnal bunt (KB) pathogenesis may find its utility in conjecturing KB establishment in a new area.
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