Base molecular para resistência a fluazifop-p-butyl em capim-camalote (rottboellia cochinchinensis) da Costa Rica

Rottboellia cochinchinensis is an annual grass weed species known as itchgrass, or “caminadora” in America´s Spanish speaking countries, and has become a major and troublesome weed in several crops. The application of fluazifop-P-butyl at recommended rates (125 g a.i. ha-1) was observed to be failing to control itchgrass in a field in San José, Upala county, Alajuela province, Costa Rica. Plants from the putative resistant R. cochinchinensis population survived fluazifop-P-butyl when treated with 250 g a.i. ha-1 (2X label rate) at the three- to four-leaf stage under greenhouse conditions. PCR amplification and sequencing of partial carboxyl transferase domain (CT) of the acetyl-CoA carboxylase (ACCase) gene were used to determine the molecular mechanism of resistance. A single non-synonymous point mutation from TGG (susceptible plants) to TGC (putative resistant plants) that leads to a Trp-2027-Cys substitution was found. This Trp-2027-Cys mutation is known to confer resistance to all aryloxyphenoxyproprionate (APP) herbicides to which fluazifop-P-butyl belongs. To the best of our knowledge, this is the first report of fluazifop-P-butyl resistance and a mutation at position 2027 for a Costa Rican R. cochinchinensis population.Rottboellia cochinchinensis, espécie de planta daninha anual conhecida como capim-camalote, ou “caminadora”, em países de língua espanhola das Américas, tornou-se uma planta daninha significativa e problemática em diversas culturas. Observou-se que a aplicação de fluazifop-p-butyl nas doses recomendadas (125 g i.a. ha-1) não conseguiu controlar capim-camalote em uma região em San José, condado de Upala, província de Alajuela, Costa Rica. As plantas da população supostamente resistente de R. cochinchinensis sobreviveram a fluazifop-p-butyl quando tratadas com 250 g i.a. ha-1 (2X a dose do rótulo) na fase de três a quatro folhas em condições de estufa. Amplificação e sequenciamento de reação em cadeia da polimerase de domínio de transferase de ácido carboxílico parcial (TC) do gene acetil-CoA carboxilase (ACCase) foram utilizados para determinar o mecanismo molecular de resistência. Foi encontrada uma mutação de ponto não sinônimo individual de TGG (plantas suscetíveis) para TGC (plantas supostamente resistentes) que conduz a uma substituição de Trp-2027-Cys. Sabe-se que essa mutação de Trp-2027-Cys confere resistência a todos os herbicidas ariloxifenoxipropionatos (AFP) a que fluazifop-p-butyl pertence. Pelo visto, este é o primeiro relato de resistência a fluazifop-p-butyl de uma mutação na posição 2027 para uma população costarriquenha de R. cochinchinensisWest Florida Research and Education Center, University of Florida/[]//United States of AmericaUCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Agroalimentarias::Estación Experimental Agrícola Fabio Baudrit Moreno (EEAFBM

Studying some Aspects of Biology and Morphology of Root Tubers and Seeds of Ranunculus ficaria L.

Introduction: Ranunculus ficariais L. (Fig buttercup or Lesser Celandine) is an herbaceous perennial belongs to Ranunculaceae (buttercup family) that behaves as a ground cover. It is a spring ephemeral that grows from a cluster of tuberous roots in late winter or early spring. It has glossy, dark green (sometimes slightly mottled), fleshy leaves on long petioles, and cordate to oblong-cordate in shape. The margins can be entire or wavy (1, 28). Flowers 15-60 mm in diameter, solitary at the end of each stem branch. Flowers have 3 sepals (rarely more), 3 petals, bright, pale to golden yellow, very rarely orange, shining on inside, receptacle concave, with short, pale simple glandular hairs. Achenes either abortive or maturing in a globular cluster, when mature 2•5-5•0 x 1•7-3•5 mm, more or less globular or obovoid, usually with few to numerous very short simple glandular hairs. This invasive weed spreads primarily by vegetative means through abundant tubers and bulblets, each of which can grow into a new plant once separated from the parent plant. The prolific tubers may be unearthed and scattered by the digging activities of some animals, including well-meaning human weed pullers, and spread to new sites during flood events (28). This weed has two subspecies, R. ficaria Subsp. ficaria and R. ficaria Subsp. bulbilifer that the second is probably the only subspecies of mountainous regions in many areas. It is an abundant weed of lawns and gardens, where it spreads rapidly and is very difficult to eradicate. According to our observations probably R. ficaria spread by tubers from mountains to fields that near to mountains in Lorestan province of Iran. The Aim of this study was assessment of this weed to improve its management practices in the wheat fields. Materials and Methods: In order to study the some aspects of biology and morphology of tubers root and seeds of R. ficaria , two experiments were conducted at Laboratory of Gorgan University in 2011. For breaking root tubers dormancy, root tubers incubated for different storage time (7, 14, 21 and 28 days) and different storage temperature (2, 4 and 8˚C). To evaluate the effect of tuber size, six groups (very smal

No fitness cost associated with Asn-2041-Ile mutation in winter wild oat (Avena ludoviciana) seed germination under various environmental conditions

Abstract Knowledge about the fitness cost imposed by herbicide resistance in weeds is instrumental in devising integrated management methods. The present study investigated the germination response of ACCase-resistant (R) and susceptible (S) winter wild oat under different environmental conditions. The DNA of the plants was sequenced after being extracted and purified. The segregated F2 seeds were subjected to various temperatures, water potentials, NaCl concentrations, different pHs, darkness conditions, and burial depths. The results of the sequencing indicated that Ile-2041-Asn mutation is responsible for the evolution of resistance in the studied winter wild oat plants. The seeds were able to germinate over a wide range of temperatures, osmotic potentials, NaCl concentrations, and pHs. Germination percentage of R and S seeds under dark and light conditions was similar and ranged from 86.3 to 88.3%. The highest emergence percentage for both R and S plants was obtained in 0, 1, and 2 cm depths and ranged from 66.6 to 70.3%. In overall, no differences were observed in the germination response between the R and S winter wild oat plants under all studied conditions. No fitness cost at seed level indicates that control of R winter wild oats is more difficult, and it is essential to adopt crop and herbicide rotation to delay the further evolution of resistance