Glyphosate behavior was examined in Italian ryegrass plants from Chile that were sensitive (S) and resistant (R) to this herbicide. In order to explain the resistance to glyphosate, contact angles, spray retention, foliar uptake, herbicide translocation, and target enzyme activity were studied. Contact angles of glyphosate solutions at a field concentration were 40° to 45° on the abaxial surface of R leaves as compared to 70° on S. Glyphosate spray retention by R plants was 35% lower than by S plants. Glyphosate uptake by the abaxial leaf surface of R plants was about 40% lower than that of S plants. In addition, in the R plants more glyphosate migrated to the tip of the treated leaves. The target enzyme in R and S plants was sensitive to the herbicide. Based on these and previous results, it is concluded that resistance in this Italian ryegrass biotype results from lower spray retention, lower foliar uptake from the abaxial leaf surface, and altered translocation pattern. The decreases in spray retention and foliar uptake constitute new mechanisms of glyphosate resistance.

Whole-plant response of two suspected resistant Avena fatua biotypes from Chile and Mexico to ACCase-inhibiting herbicides [aryloxyphenoxypropionate (APP), cyclohexanedione (CHD), and pinoxaden (PPZ)] and the mechanism behind their resistance were studied. Both dose-response and ACCase enzyme activity assays revealed cross-resistance to the three herbicide families in the biotype from Chile. On the other hand, the wild oat biotype from Mexico exhibited resistance to the APP herbicides and cross-resistance to the CHD herbicides, but no resistance to PPZ. Differences in susceptibility between the two biotypes were unrelated to absorption, translocation, and metabolism of the herbicides. PCR generated fragments of the ACCase CT domain spanning the potential mutations sited in the resistant and susceptible biotypes were sequenced and compared. A point mutation was detected in the aspartic acid triplet at the amino acid position 2078 in the Chilean biotype and in isoleucine at the amino acid position 2041 in the Mexican wild oat biotype, which resulted in a glycine triplet and an asparagine triplet, respectively. On the basis of in vitro assays, the target enzyme (ACCase) in these resistant biotypes contains a herbicide-insensitive form. This is the first reported evidence of resistance to pinoxaden in A. fatua.

Herbicide and Fusarium effect on red clover root rot, Ceballos et al. 142 BENTAZON-MCPA EFFECT ON ABSTRACTIn Chile, the main factor in red clover (Trifolium pretense L.) stand decline is fusariumroot rot, which results in a reduction in yield. Fusarium oxysporum (Schlect.) is the most prevalent pathogen recovered from diseased red clover roots plants. Agronomical management of red clover includes application of broadleaf herbicides such as MCPA and bentazon. This study was conducted to evaluate the effects of bentazon and bentazon/MCPA mixture on phytotoxicity and root rot as caused by F. oxysporum on red clover, under greenhouse conditions. In addition, in vitro mycelial growth and conidial germination of F. oxysporum was studied. A reduction of 40% in crown diameter and 57% shoot dry weight was observed 30 days after treatment with a high rate of bentazon/MCPA and F. oxysporum inoculum. The bentazon -F. oxysporum interaction reduced root dry weight by 57% at 1X rate and 42% with 2X rate at 20 and 30 of evaluation. Bentazon caused a significant increase in phytotoxicity at the high rate and the mixture bentazon/MCPA increased root rot severity and phytotoxicity at the high rate. The conidial germination and mycelial growth were significantly reduced by bentazon/MCPA. These results suggest that red clover growth and persistence could be adversely affected by F. oxysporum after bentazon and bentazon/MCPA application.

Este documento pretende dar una visión general sobre la situación, evolución y perspectivas de las actividades de preinversión, inversión y financiamiento agrícola y rural en América Latina y el Caribe, fundamentalmente mediante intervenciones del sector público, la banca nacional, las instituciones financieras de desarrollo y la banca multilateral. Luego se focaliza en la experiencia conceptual, metodológica y operativa del Instituto Interamericano de Cooperación para la Agricultura (IICA), sobre el desarrollo rural con enfoque territorial, con énfasis en la asignación de recursos en el marco de los cuatro pilares del enfoque: (i) cadenas agroproductivo–comerciales; (ii) territorios rurales; (iii) innovación institucional; y (iv) el desarrollo de capacidades estratégicas para el desarrollo rural. Se culmina con las consideraciones finales y lecciones aprendidas. La presentación incluye dos casos: (i) Análisis sobre el desarrollo fronterizo Costa Rica–Nicaragua; y (ii) La experiencia del IICA: lecciones aprendidas del desarrollo rural con enfoque territorial en Brasil.

REsuMEnLa nutria neotropical Lontra longicaudis Olfers, 1818 es un carnívoro de tamaño mediano con amplia distribución en América. Generalmente habita ambientes ribereños entre 0 y 1.700 metros de elevación. En Ecuador, se puede encontrar en áreas tropicales y subtropicales al este y oeste de los Andes. En este trabajo reportamos una nueva localidad en el valle interandino al sur de Ecuador, que confirma su presencia en ecosistemas con climas templados y altoandinos.