Current status in resistance of Ischaemum rugosum Salisb. to herbicide bispiribac-sodio in Venezuela

摘要

Ischaemum rugosum is reportedly the most difficult to control weed in rice fields of Venezuela. The objective of this study was to evaluate the resistance of I. rugosum to bispyribac- sodium. Three experiments were established: (1) detection bioassay, (2) dose response and (3) control of resistant (R) accessions.  In the first experiment, 71 accessions and a susceptible (S) control were treated with 40 g?·ha-1 a.i of bispyribac-sodium (recommended rate); fresh weight percent was measured 21 days after application.. To quantify the resistance level, a dose response experiment was conducted with the R accessions IR37P, IR44P, IR75G, IR90G, IR82G and IR106G and the S accession IR143G; putatively R plants were treated with 0, 20, 40, 80, 160, 320, 640, 1280 g?·ha-1 a.i. of  bispyribac-sodium and S plants with 0, 2.5, 5, 10, 20, 40, 80 and 160 g?·ha-1 a.i.  We found that 26 ​​accessions from the State of Portuguesa, 13 from Gu??rico and 2 from Cojedes were R to bispyribac-sodium.  This test confirmed the resistance to bispyribac-sodium: IR37P; 106G; IR44P and IR82G showed resistance indices (RI = ED50R/ED50S) of 8, 44, 262.81 and 446.75 respectively, while RI values to quantify the high resistance of IR75G and IR90G could not be estimated (ED50R  1280 g?· ha-1 a.i.). Cross-resistance was assayed by treating the R accessions with 60, 30, 157, 160, 3360 and 988 g?·ha-1 a.i. of pirybenzoxim; nicosulfuron, imazethapyr + imazethapyr; profoxydim, propanil and oxadiazon, respectively. IR75G and IR90G were R to all herbicides used except oxadiazon.