Puccinia horiana Hennings, the causal agent of chrysanthemum white rust, is a worldwide quarantine organism and one of the most important fungal pathogens of Chrysanthemum × morifolium cultivars, which are used for cut flowers and as potted plants in commercial production regions of the world. It was previously reported to be controlled by Lecanicillium lecanii, Cladosporium sphaerospermum, C. uredinicola and Aphanocladium album, due to their antagonistic and hyperparasitic effects. We report novel antagonist species on Puccinia horiana. Fungi isolated from rust pustules in a commercial greenhouse from Villa Guerrero, México, were identified as Cladosporium cladosporioides and Cladosporium pseudocladosporioides based upon molecular analysis and morphological characters. The antagonism of C. cladosporioides and C. pseudocladosporioides on chrysanthemum white rust was studied using light and electron microscopy in vitro at the host/parasite interface. Cladosporium cladosporioides and C. pseudocladosporioides grew towards the white rust teliospores and colonized the sporogenous cells, but no direct penetration of teliospores was observed; however, the structure and cytoplasm of teliospores were altered. The two Cladosporium spp. were able to grow on media containing laminarin, but not when chitin was used as the sole carbon source; these results suggest that they are able to produce glucanases. Results from the study indicate that both Cladosporium species had potential as biological control agents of chrysanthemum white rust.

RESUMEN El Tomato brown rugose fruit virus (ToBRFV) es un virus emergente que amenaza la producción de tomate y chile en todo el mundo. Esta investigación tuvo como objetivo evaluar el efecto de la infección del ToBRFV en la morfología de la planta y calidad de frutos en ocho variedades de chile y proponer una escala diagramática para evaluar la severidad en hojas infectadas considerando el porcentaje de área foliar afectada. Se probaron 16 tratamientos, que incluyeron ocho variedades de chile y dos condiciones experimentales (inoculado y no inoculado). Cinco días después del trasplante, cada variedad de chile se inoculó mecánicamente con ToBRFV y se evaluaron variables morfológicas y de calidad de frutos. La comparación de medias de cada variedad inoculada versus no inoculada se realizó con la prueba t-Student (P ≤ 0.05) para grupos independientes. El ToBRFV infectó a todas las variedades inoculadas ocasionando lesiones locales necróticas, clorosis, mosaico, moteado, necrosis de tallo, ampulación, deformación, enrollamiento y necrosis de hoja; asimismo, se observaron plantas asintomáticas. El ToBRFV afectó significativamente la altura, número de entrenudos, número de flores, peso fresco de raíz, peso promedio de fruto, número de semillas y diámetro polar-ecuatorial del fruto. La variedad chile habanero mostró la menor severidad, mientras que la mayor severidad se observó en la variedad de chile serrano ‘Tampiqueño’.

In Chiapas, Mexico, there are high-yielding coffee plants adapted to the local climatic conditions. The presence of microorganisms in the explants makes developing protocols for cloning these genotypes in vitro difficult. The objective of this work was to evaluate how field and in vitro microorganism management affected asepsis and the induction of callogenesis in leaf explants of agronomically important coffee plants. Drought-tolerant genotypes were obtained from aseptic explants and cell cultures using a participatory study, agronomic, and in vitro techniques. Five accessions (ITTGj 1-5) were selected from a 21-year-old Borbon cultivar. The present study was conducted over two flowering cycles, evaluating the effect of field management on explant asepsis on the first and the callogenic response caused by the culture medium, the transport solution, and the genotype, on the second. Sixty days before explant collection, biweekly applications of calcium polysulfide (10 % v v-1), copper oxychloride (2 g L-1), and Zingiber officinale extract (20 g L-1) reduced fungal contamination by 100 % and bacterial contamination by 90 %. Field explant transportation in 200 mg L-1 citric acid and ascorbic acid solution reduced oxidation in explants and in vitro cultures. Proembryogenic friable corns were formed with the combination of 4.4 µM BAP (6-benzylaminopurine) and 7.25 µM 2,4-D (2,4-dichlorophenoxyacetic acid) at 45 days of culture, with genotype four showing the best response. Field management was effective for the aseptic establishment of Coffea arabica cultures in vitro, and the combination of BAP and 2,4-D used was an appropriate growth regulator for the induction of callogenesis.

Parthenocarpy is the ability of the ovary to develop without the need for the stimulation of pollination so that the fruit forms and grows normally until physiological or commercial maturity. In this study, 46 parthenocarpic varieties of squash (Cucubita pepo L.) type round zucchini obtained at the Autonomous University of Chapingo were analyzed, the objective was to identify the diversity and genetic variability existing between the varieties and obtain the corresponding genetic fingerprints. Molecular markers type RAPD (random amplification of polymorphic DNA) were used, in which 14 primers of the Operon series A were tested, of which five were selected associated to a total of 44 loci. 84.1% of the loci were polymorphic, among the parthenocarpic varieties, this indicated few genetic variability. The dendrogram of genetic similarity yielded five groupings, the genetic distance was very close to one, with a range of 0.6573 and 0.9770, indicating that they are highly genetically related varieties; this genetic variation between loci was expressed with 95.45% of the polymorphism. The genotypes studied provide a valuable source of parthenocarpy base for the genetic improvement of zucchini for vegetables that do not require stimulation of pollination to develop, suitable for production under cover.