Resumen

ORTIZ, Aída et al. Current status in resistance of Ischaemum rugosum Salisb. to herbicide bispiribac-sodio in Venezuela. Bioagro [online]. 2013, vol.25, n.2, pp.79-89. ISSN 1316-3361.

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 Guárico 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.}

Palabras clave : Rice; Oryza sativa; ribbed murainagrass; wrinkle grass; herbicide resistance; ALS inhibitor.

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