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.

resUmenIdentificación mediante PCR del sexo de la papaya (Carica papaya L.), híbrido "Pococí". el objetivo de la presente investigación fue identificar plantas hermafroditas del híbrido de papaya "Pococí". Para la identificación del sexo de las plantas del híbrido "Pococí", se utilizó el protocolo descrito por Deputy et al. (2002), con algunas modificaciones. esta metodología emplea un Pcr múltiple que permite la amplificación simultánea de dos fragmentos (1.300 y 800 pb respectivamente) para plantas hermafroditas y de un solo fragmento (1.300 pb) para plantas femeninas. el aDn se extrajo a partir de hojas de plantas de invernadero o campo con dos metodologías de extracción, cTaB y lisis alcalina (NaOH). La amplificación por PCR del ADN extraído de muestras foliares de papaya híbrido "Pococí", con ambos métodos de extracción, produjo los fragmentos del tamaño esperado. La determinación del sexo de 1.500 plántulas en almácigo mostró un 46 % de plántulas hermafroditas y un 54 % de plantas femeninas. La proporción observada de plantas femeninas: hemafroditas no varió de la esperada (1:1) según la prueba de chi-cuadrado (p= 0,4237). Las plantas hermafroditas fueron llevadas al campo y al momento de la floración se determinó su sexo. La correspondencia entre el sexado por PCR y la expresión sexual en campo fue de un 98 %.Palabras clave: Plantas hembra, hermafroditas, marcadores moleculares, extracción de aDn, genes ligados al sexo. abstractSex determination of papaya (Carica papaya l.) "Pococí" hybrid by PCR. The objective of this work was to identify papaya hermaphrodite plants of the hybrid "Pococí" at the seedling stage using the Polymerase Chain Reaction (PCR). Sex identification was achieved according to the methodology described by Deputy et al. (2002) with some modifications. This methodology employs a multiplex-PCR assay that allows simultaneous amplification of two fragments (800 bp and 1300 respectively) for hermaphrodite plants and one fragment (1300 bp) for female plants. genomic Dna was extracted from leaves and two extraction protocols were evaluated, CTAB and rapid alkaline lysis (NaOH). The amplification reaction yielded the expected size of the fragments with both methods of DNA extraction. PCR sex determination of 1500 seedlings yielded 46 % of hermaphrodite and 54 % of female plants. The female: hermaphrodite plant ratio observed did not vary from the expected (1:1) ratio according to the chi-square test (p = 0.4237). Hermaphrodite plants were planted in the field in san carlos region, costa rica, and sex was determined at flowering. The correspondence between the PCR sexed plants and sexual expression in the field was 98 %.

RESUMENCombate químico de la antracnosis de Sansevieria trifasciata var. Hahnii en un sistema de hojas separadas. El objetivo de este trabajo fue evaluar fungicidas para el combate de antracnosis en Sansevieria trifasciata var. Hahnii. Se evaluaron doce fungicidas (solos o en mezcla) sobre la infección y severidad de C. sansevieriae en un sistema de hojas separadas. Los fungicidas utilizados fueron azoxistrobina, boscalid + piraclostrobina, carbendazina + mancozeb, difenoconazol, epoxiconazol + carbendazina, folpet, imazalil, metil tiofanato + mancozeb, miclobutanil y prochloraz. El estudio se llevó a cabo en el Laboratorio de Biotecnología de Plantas del Centro de Investigaciones Agronómicas, Universidad de Costa Rica, durante el primer semestre del año 2012. La aplicación de los tratamientos se realizó por aspersión el día de la inoculación o tres días después de esta (0 y 3 ddi). A los siete, once y quince días después de la inoculación se evaluó el número y diámetro de las lesiones. El fungicida, el momento de aplicación, la interacción fungicida x momento de aplicación y la interacción fungicida x día de evaluación afectaron significativamente (p<0,0001) las variables evaluadas. Azoxistrobina, boscalid + piraclostrobina, carbendazina + mancozeb, epoxiconazol + carbendazina y metil tiofanato + mancozeb proveyeron un 100% de protección de las hojas de Sansevieria durante todo el período de evaluación (quince días), cuando se aplicaron el mismo día de la inocualción (0 ddi). A los 3 ddi, solo epoxiconazol + carbendazina inhibió en un 100% el establecimiento del patógeno (incidencia cero), en las tres evaluaciones. Con los tratamientos azoxistrobina y carbendazina + mancozeb también se obtuvo un 0% de incidencia a los siete y once días de evaluación para el primero y a los siete días para el segundo.Palabras clave: Lengua de suegra, Colletotrichum sansevieriae, fungicidas para C. sansevieriae. ABSTRACTChemical control of anthrachnose of Sansevieria trisfasciata var. Hahnii on a detached-leaf system. The objective of this work was to assess fungicides to combat Sansevieria trifasciata var. Hahnii anthracnose. Twelve fungicides (alone or in mixture) were evaluated on the infection and severity of C. sansevieriae on a detached-leaf system. Fungicides used were azoxystrobin, boscalid + pyraclostrobin, carbendazim + mancozeb, difenoconazole, epoxiconazole + carbendazim, folpet, imazalil, thiophanatemethyl + mancozeb, myclobutanil, and prochloraz. The study was carried out at the Plant Biotechnology Laboratory of the Agricultural Research Center of the University of Costa Rica, during the first semester of 2012. Each chemical treatment was applied by aspersion on the day of inoculation (0 dai) or three days after it (3 dai). The number and diameter of the lesions were evaluated after seven, eleven and fifteen dai. Fungicide, application moment, fungicide x application moment interaction and fungicide x evaluation moment interaction significantly affected (p<0,0001) both evaluated variables. Azoxystrobin, boscalid + p...

Common bean is a crop recalcitrant to in vitro regeneration and therefore it lacks an efficient transformation protocol that can be reproduced using A. tumefaciens. The main goal of this study was to establish a protocol for A. tumefaciens mediated transformation of Phaseolus vulgaris var. Brunca by marker genes (gusA and nptII) together with the gene for trehalose-6-phosphate synthase from Saccharomyces cerevisiae (TPS1) used in other species to increase tolerance to abiotic stress. The β-glucuronidase activity was detected in 45 % of the LBA4404 ElectroMAX® pCAMBIA1301 infected explants. Transformed explants regenerated new shoots after four to five months period in a kanamycin rich media. Surviving plants were evaluated by PCR and presented an 0.5 % efficiency of transformation. The established protocol for genetic transformation of common bean has two additional advantages with respect to previous reports: (1) it allows for obtaining transformed regenerants and (2) the genetic transformation was stable for the selective gene.

Itchgrass [Rottboellia cochinchinensis (Lour.) Clayton] is recognized as one of the most noxious and troublesome annual weeds in tropical and subtropical regions. Acetyl-coenzyme A carboxylase (ACCase)-inhibiting herbicides have been frequently used for managing R. cochinchinensis POST in a variety of crops, resulting in evolved resistance to these herbicides. Recently, resistance to fluazifop-P-butyl has been demonstrated for this weed, as the result of a G-to-C single-nucleotide polymorphism (SNP) that leads to the Trp-2027-Cys substitution in the ACCase enzyme. This study was conducted to develop a high-resolution melting analysis (HRMA) for the detection of the mutation underlying the Trp-2027-Cys substitution. The HRMA assay allowed differentiating between fluazifop-P-butyl-resistant (C mutant) and susceptible (G wild type) R. cochinchinensis plants. HRMA accuracy was confirmed with DNA sequencing of the target-site mutation, and no false positives or negatives were observed. Our results illustrated how HRMA is effective detecting the Trp-2027-Cys substitution in an R. cochinchinensis resistance, and how this technique can be of great value for developing high-throughput programs for monitoring evolution and dispersion of target site-based herbicide resistance at large scales.