The tomatillo, Physalis ixocarpa Brot. (2n = 2x = 24), is an important crop in Mexico, and it is becoming appreciated in other countries. Polyploidy induction is expected to increase its breeding potential. The objective of this work was to develop and characterize tomatillo autotetraploids through colchicine-based induction. Young seedlings of the Rendidora cultivar were treated for 24 h with colchicine in concentrations ranging from 0.04% to 0.20%, and ploidy levels were tested by cytological and flow cytometry techniques. Autotetraploidy was induced with colchicine concentrations of 0.12% and 0.16%, with success rates of 67% and 65%, respectively. Presence of univalents, bivalents and multivalents was observed in prophase I and metaphase I. The basic genome size was not altered in the third generation progeny from treated plants. Autotetraploid plants were fertile and productive, but their pollen development was lower than their diploid counterpart. The polyploid plants showed higher values for life cycle length, plant height, fruit weight and equatorial diameter, fruits per plant, and soluble solid concentration. This is the first report of an autopolyploid cultivated tomatillo. Its genome duplication is readily induced with production of fertile plants, and may be valuable to introduce genetic plasticity in this crop.

Piquin pepper (Capsicum annuum var. glabriusculum) is an important species that supports the economy of rural households; it is part of Mexican gastronomy and it is a highly valuable phytogenetic resource. There has been recent interest in domesticating and exploiting piquin pepper commercially, which has been limited until now due to the low germination rate, and this work had the purpose of promoting germination and determining the physiological capacity of genotypes. Ten piquin pepper genotypes from different geographical origins in Mexico were submitted to 11 pre-germination treatments. A completely randomized experimental design was carried out with arrangement in split-plot. The large plot had the treatments and the small plot had the genotypes. The results showed differences (p < 0.01) among treatments, genotypes, and treatment-genotype interaction. On one hand, treatments gibberellic acid (GA) and mechanical scarification + gibberellic acid (MSGA) increased the physiological potential of genotypes, reaching the highest values of germination speed (GS), germination index (IG) and germination percentage (GP); as well as the lowest values of dead seeds (DS) and hard Seeds (HS). In turn, the genotypes that presented the same condition were G8, G7, and G10. Regarding the interaction, each variable had a different condition. In conclusion, we can increase the physiological potential and solve the dormancy of piquin pepper seed by applying gibberellic acid. Likewise, the best genotypes were G8 and G10.

No abstract

4Autor para la correspondencia: varoto@prodigy.net.mx Resumen: Con el objetivo de estudiar el impacto de la autopoliploidía en la viabilidad de polen y el tamaño y frecuencia estomá-tica del tomate de cáscara (Physalis ixocarpa) se analizó el polen, tamaño y número de estomas de cinco poblaciones diploides y cinco autotetraploides formadas con colchicina. Las diez poblaciones se establecieron en campo, bajo un diseño de bloques al azar con cuatro repeticiones. Para el estudio de viabilidad de polen, éste fue colectado y coloreado con acetocarmín al 1%. Los granos de polen redondeados y coloreados de rojo se consideraron viables y los constreñidos y sin teñir, no viables. Además, se estimó la densidad e índice estomático, largo y ancho de células oclusivas de estomas de la superfi cie adaxial y abaxial de la hoja. Los diploides tuvieron valores de viabilidad de polen y densidad estomática, signifi cativamente mayores que los autotetraploides (P ≤ 0.05); sin embargo, los diploides tuvieron granos de polen y estomas signifi cativamente más pequeños que los autotetraploides. Por lo tanto, la poliploidía si afectó la viabilidad del polen, ocasionado pérdida de fertilidad. Sin embargo, esta característica se puede evitar por selección de plantas con estabilidad meiótica, para incrementar la fertilidad de los autotetraploides. El aumento del tamaño celular muestra que los autopoliploides tienen el potencial de generar plantas más vigorosas, pero con una disminución en la fertilidad, aunque esta característica puede mejorarse al paso de varias generaciones, por lo que este tipo de estudios abre la posibilidad de iniciar nuevas estrategias para el mejoramiento del tomate de cáscara. Palabras clave: abaxial, adaxial, granos de polen, poliploidía, tomate de cáscara.

Vegetable production in greenhouses is preferred when soil quality is degraded by high salinity or incidence of pests and diseases. In these soils with abiotic and biotic issues, it is a challenge to increase the yield and quality of fruits. The use of rootstocks and organic substrates are effective and environmentally friendly techniques to solve that challenge. The objective was to study the effect of rootstocks on yields and quality in bell peppers (Capsicum annuum L.) grown in either soil or coconut fiber substrate, in greenhouses. Using a randomized block design with three repetitions, the resulting treatment groups consisted of three rootstocks (Foundation-F1, Yaocali-F1, CLX-PTX991-F1 (Ultron), and non-grafted controls) with four hybrids as scions (Lamborghini, Bambuca, DiCaprio, and Ucumari). The yield of fruit per plant (YFP) and number of fruit per plant (NFP) obtained in coconut fiber were 85% and 55% greater, respectively, than in soil. The CLX-PTX991-F1 rootstock was superior to the hybrids without rootstock (p ≤ 0.05) in YFP and NPF (30% and 19.5%, respectively). The Lamborghini hybrid had significantly greater YFP and NFP than the Ucumari. We concluded that the use of coconut fiber significantly improves the yields of bell pepper and that the use of rootstock improves plant vigor and plant yield.