A simplified protocol to obtain transgenic tomato plants was established. The effects of culture media composition and Agrobacterium concentration were evaluated. The highest shoot-forming capacity index (5.6) was observed when leaf explants were cultured for 6 weeks with 2 mg·L−1 zeatin, 0.1 mg·L−1 indoleacetic acid, and 300 mg·L−1 timentin. Shoot elongation and root formation were performed in one step on growth regulator-free media. The highest percentage (82%) of fully developed plantlets was obtained when shoots were cultured for 4 weeks with 0.5× Murashige and Skoog (MS) media and 15 g·L−1 sucrose. A 100% of plant survival rate was observed after 4 weeks of being transplanted to ex vitro conditions followed by fruit production (15 fruits/plant) after 2 more weeks. Transient expression of β-glucuronidase was visualized in 100% of the leaf explants infected with Agrobacterium at an OD600 = 0.5 and cocultured for 48 h with 2 mg·L−1 benzylaminopurine, 0.1 mg·L−1 naphthaleneacetic acid, and 100 μM acetosyringone. Stable transformation was confirmed by histochemical glucuronidase assay and polymerase chain reaction (PCR) analysis with a total efficiency of 19.1%. The complete protocol, from shoot induction to fruit production of soil-adapted transgenic plants can be accomplished in only 4 months, and it seems to be very useful for both micropropagation and genetic transformation purposes.
Abraham Cruz-Mendívil, Javier Rivera-López, Lourdes J. Germán-Báez, Melina López-Meyer, Sergio Hernández-Verdugo, José A. López-Valenzuela, Cuauhtémoc Reyes-Moreno, and Angel Valdez-Ortiz
Jesús Enrique Retes-Manjarrez, Sergio Hernández-Verdugo, Carlos Alfonso López-Orona, Raymundo Medina-López, José Antonio Garzón-Tiznado, and Jesús Enrique Retes-Cázarez
Pepper huasteco yellow vein virus (PHYVV) is a major disease in pepper (Capsicum annuum) that causes quantitative and qualitative losses to the crop in Central America and part of North America. To date, no resistant cultivars are available, and breeding is hampered by the lack of knowledge of the inheritance of this trait. Sources of resistance to PHYVV have been identified in the wild peppers of Mexico. The objectives of this study were to determine the grade of dominance, to analyze the maternal influence, and to estimate the number of genes involved in this resistant trait to PHYVV in the resistant wild pepper accession UAS12. Three susceptible parent lines—‘Anaheim’ (Ana), ‘Ancho Gigante’ (AG), and ‘Yolo Wonder’ (YW)—were crossed with resistant UAS12 accession to develop F1 (reciprocal), F2, and BC1 progenies in three families. Plants from this study were inoculated with PHYVV through Bemisia tabaci, evaluated phenotypically, and the segregation of disease scores was studied. A single recessive gene was found to control resistance to PHYVV in the resistant UAS12 accession, although segregation patterns suggested that other minor genes could participate in the expression of this resistant trait. No proof was found for maternal inheritance of PHYVV resistance. The gene symbol phv is proposed for PHYVV resistance in UAS12 accession in pepper. These results provide useful information for the design of pepper breeding programs in the introgression of this trait into commercial pepper backgrounds.