Abstract

                                Twenty nine rice varieties were tested for their tolerance to herbicides. At normal doses (3.5 kg a. i./ha) propanit did not cause mortality of plant but inflicted a mild chloro- sis in Karuna, Co. 36, Krishna, Vaigal, IR. 8. Kannski, TKM, 6. Cauvery, ADT. 27 and GEB, 24 and severe chlorosis in PTB, 10, ASD. 5, BAM. 3. Bhavani, IR. 5, Jaganath, Pennal, Bale, IR, 22 and IR. 20. However all these varieties recovered from chlorosis within 10 days after application. Benthiocarb was highly selective on IR, 20, SR. 26, B. BAM. 3. GEB. 24, Kannaki and Vaigai whereas the varieties Bhavani, IR. 22. PTB. 10. TKM. 6. Co. 32 and ADT. 27 were found to be less tolerant. Varieties IR. 22, GEB. 24, IR. 8, Bala, Kanchi and Bhavani were highly susceptible to the herbicide butachlor whereas varieties Karuna, ADT, 27, Karikalan and Annapoorna were tolerant even to high dose (8 kg a.i./ha). Those tolerant japonica derivatives were susceptible to benthiocarb while the susceptible variety Ponni wes tolorant to benthiocarb.

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