Genetic solutions to postharvest crop loss can reduce cost and energy inputs while increasing food security, especially for banana (Musa acuminata), which is a significant component of worldwide food commerce. We have functionally characterized two banana E class (SEPALLATA3 [SEP3]) MADS box genes, MaMADS1 and MaMADS2, homologous to the tomato (Solanum lycopersicum) RIN-MADS ripening gene. Transgenic banana plants repressing either gene (via antisense or RNA interference [RNAi]) were created and exhibited specific ripening delay and extended shelf-life phenotypes, including delayed color development and softening. The delay in fruit ripening is associated with a delay in climacteric respiration and reduced synthesis of the ripening hormone ethylene; in the most severe repressed lines, no ethylene was produced and ripening was most delayed. Unlike tomato rin mutants, banana fruits of all transgenic repression lines responded to exogenous ethylene by ripening normally, likely due to incomplete transgene repression and/or compensation by other MADS box genes. Our results show that, although MADS box ripening gene necessity is conserved across diverse taxa (monocots to dicots), unlike tomato, banana ripening requires at least two necessary members of the SEPALLATA MADS box gene group, and either can serve as a target for ripening control. The utility of such genes as tools for ripening control is especially relevant in important parthenocarpic crops such as the vegetatively propagated and widely consumed Cavendish banana, where breeding options for trait improvement are severely limited.

Publisher Summary This chapter highlights commercial micropropagation from an engineering point of view rather than the biological side. The combination of automated systems with modern visual intelligence aided by computer technology would properly counter the high cost of manual labor in micropropagation and open the path for efficient in vitro plant production. The process of micropropagation requires a mesh of integrated processes extending from explantation, media preparation, sterilization of media and vessels, media pouring, cutting the propagules in the multiplication stage, planting in a new vessel, growing the plants in environmentally controlled growth rooms, screening out contaminated vessels, size sorting, and hardening. A significant expense in micropropagation laboratories is related to energy, which is due to its consumption in air conditioning, air filtration, and lights. Micropropagation techniques reduce or even eliminate the population of beneficial microorganisms such as mycorrhizal fungi and plant growth promoting bacteria in the rhizosphere, at least during the early stages of the post in vitro acclimation.

The A genome segment of the highly virulent Infectious bursal disease virus (IBDV) was amplified using long and accurate-RT-PCR (LA-RT-PCR). The entire sequence region encoding VP2, VP4, and VP3 in that order was cloned and sequenced. Following subcloning into the Escherichia coli expression vector pET21a under the T7 promoter, viral proteins were expressed and processed as demonstrated by Western blot analysis. Virus-like particles could be visualized by immuno-electron microscopy in IPTG-induced cells suggesting that viral assembly can take place in E. coli. Induction of anti-IBDV antibodies was detected in chickens immunized with purified recombinant IBDV by intra muscular (i.m.) injection. Furthermore, the vaccinated chickens were protected when challenged with the Gep 5 isolate of IBDV.

The high incidence of “off-types” produced by banana meristem culture is a major concern to commercial growers. At the same time, somaclonal variation is an important tool for the improvement of banana germplasm. Banana plant propagators and researchers have learned, over the years, to reduce the frequency of “off-types” to a manageable level. The majority of the banana “off-types” in the “Cavendish” variety appear as ‘dwarf’ or ‘giant’. It has been demonstrated that both are associated with sensitivity to gibberellic acid (Cote et al., 1990). However, the specific genes responsible for these mutants have not been identified so far. Several gibberellin insensitivity mutants have been isolated and characterized in other plant species, but none of these have been associated with somaclonal variation. Unlike “Cavendish” types, an array of phenotypic variations was reported in plantains. Most variations in plantains were related to the morphology of the inflorescence and fruit (Vuylsteke et al., 1991). Thus, it seems that the highly frequent types of variation are genotype specific.