Peter G. Alderson

The potential for underutilized crops to improve security of food production

Staple crops face major challenges in the near future and a diversification away from over-reliance on staples will be important as part of the progress towards the goal of achieving security of food production. Underutilized or neglected crops species are often indigenous ancient crop species which are still used at some level within the local, national or even international communities, but have the potential to contribute further to the mix of food sources than they currently do. The most cost-effective and easily disseminated changes that can be made to a crop are changes to the genetics, as these are contained within the seed itself and, for many species, the seed is a pure breeding, self-replicating, resource. This article focuses on the potential of underutilized crops to contribute to food security and, in particular, whether genetics and breeding can overcome some of the constraints to the enhanced uptake of these species in the future. The focus here is on overview rather than detail and subsequent articles will examine the current evidence base.

Targeted Dispersal of the Aphid Pathogenic Fungus Erynia neoaphidis by the Aphid Predator Coccinella septempunctata

The potential of adult and larval C. septempunctata to vector the aphid-specific entomopathogenic fungus E. neoaphidis was assessed through a series of laboratory and field experiments. The ability of coccinellids to vector conidia from a colony of E. neoaphidis -infected pea aphids, Acyrthosiphon pisum, to a colony of uninfected A. pisum was demonstrated in a laboratory study. Adult coccinellids which had previously foraged on plants infested with different densities of sporulating cadavers (1, 5, 15, 30 cadavers per plant) initiated infection in a proportion of uninfected pea aphids (4, 0, 2 and 8%, respectively) when subsequently allowed to forage on A. pisum infested bean plants. Further laboratory studies demonstrated that fourth instar larvae and adult coccinellids artificially inoculated with conidia initiated infection in 11 and 13% of an A. pisum population in which they foraged, respectively. Furthermore, a proportion of A. pisum placed on bean plants which had previously been foraged on by inoculated larval and adult coccinellids also died from infection (3 and 10% of A. pisum, respectively). However, although coccinellid adults inoculated with conidia initiated infection in 19% of A. pisum, cereal aphids, S. avenae , exposed to the inoculated coccinellids did not become infected. A further laboratory study demonstrated that infection of A. pisum only occurred if inoculated coccinellids were transferred to A. pisum populations immediately post inoculation. However, a proportion of A. pisum placed on bean plants which had been foraged on by inoculated coccinellids transferred 0, 4 and 24 h post inoculation died from infection (9, 3 and 7%, respectively). A field study further demonstrated the potential of coccinellids to vector E. neoaphidis. Single spring sown field bean plants (Long Hoos Experimental Plots, IACRRothamsted Farm) were enclosed within nylon mesh bags and 25 adult A. pisum were added to each bag with one of the following treatments: no further addition (control), coccinellid adult (control), inoculated coccinellid adult, inoculated A. pisum or sporulating A. pisum cadavers. No aphids died of E. neoaphidis in the control treatments; 5, 16 and 33% of aphids were infected with E. neoaphidis on the other treatments, respectively.

Effect of a novel edible composite coating based on gum arabic and chitosan on biochemical and physiological responses of banana fruits during cold storage.

The composite effects of gum arabic (GA) (5, 10, 15, and 20%) and chitosan (CH) (1.0%) on the biochemical and physiological characteristics of banana fruits stored at 13 ± 1 °C and 80 ± 3% relative humidity (RH) for 28 days and afterward for 5 days at simulated marketing conditions (25 °C, 60% RH) were investigated. Significant (P ≤ 0.05) differences were observed for the entire GA plus CH treatments as compared to the control. However, the results showed that after 33 days of storage, the weight loss and soluble solids concentration of fruits treated with 10% GA plus 1.0% CH composite coating were 24 and 54% lower, whereas fruit firmness, total carbohydrates, and reducing sugars were 31, 59, and 40% higher than the control, respectively. Furthermore, the composite edible coating of 10% GA plus 1.0% CH delayed color development and reduced the rate of respiration and ethylene evolution during storage as compared to the control. Similarly, sensory evaluation results also proved the effectiveness of 10% GA plus 1.0% CH composite coating by maintaining the overall quality of banana fruits. Consequently, the results of scanning electron microscopy also confirmed that the fruits coated with 10% GA plus 1.0% CH composite edible coating had very fewer cracks and showed a smooth surface. These findings suggest that 10% GA plus 1.0% CH as an edible composite coating can be used commercially for extending the storage life of banana fruits for up to 33 days.

Induction of bulbing of tulip shoots in vitro

Abstract Bulbing has been induced in adventitious shoots from floral stem explants of Tulipa ‘Merry Widow’. Incubation of 1-mm thick explants at 20°C on a medium containing 1 mg l−1 NAA and BAP for 14–18 weeks, followed by 4°C for 8 weeks, produced a consistent bulbing response in shoots after transfer back to 20°C. Bulbing was further enhanced by transfer to 25°C and by raising the concentration of sucrose in the medium. Microscopy indicated the presence of developing meristematic centres in shoots 12 weeks of age. Shoots over 16 weeks of age containing meristematic centres gave a variable bulbing response with applied gibberellins and cold incubation, depending on whether gibberellins were supplied continuously in the medium or via a brief soak in sterile gibberellin solutions before sub-culturing. A GA3 “soak” of 1.0 mg l−1 was optimum for bulb production. The possible mechanisms of cold and gibberellin effects are discussed.

Influence of the aphid pathogen Pandora neoaphidis on the foraging behaviour of the aphid parasitoid Aphidius ervi

Abstract.  1. The parasitoid Aphidius ervi and the entomopathogenic fungus Pandora neoaphidis both require successful invasion of an aphid host to complete their life cycle. A shorter developmental period allows P. neoaphidis to out‐compete A. ervi. Aphidius ervi may reduce this fitness cost by avoiding aphid colonies containing P. neoaphidis. Here the response of A. ervi towards P. neoaphidis was assessed using sequential experiments designed to replicate different stages of parasitoid foraging behaviour.

Intraguild interactions between the entomopathogenic fungus Pandora neoaphidis and an aphid predator and parasitoid at the population scale.

The interactions that occur between the entomopathogenic fungus Pandora neoaphidis and a predator (Coccinella septempunctata) and a parasitoid (Aphidius ervi) were assessed in microcosm and polytunnel experiments. Transmission of P. neoaphidis to the pea aphid, Acyrthosiphon pisum, was enhanced in the presence of both C. septempunctata and A. ervi in microcosm experiments done under fixed abiotic conditions. In contrast, the reproductive success of A. ervi was reduced in the presence of P. neoaphidis. Despite the increased fungal transmission in the presence of C. septempunctata, there was no additional decrease in the aphid population indicating that P. neoaphidis is functionally redundant in the presence of the coccinellid. In polytunnel experiments the reproductive success of A. ervi was not affected by P. neoaphidis. These results do not support those of the microcosm and may be due to the more natural abiotic conditions in the polytunnel reducing the competitive advantage of the fungus. Microcosms therefore provide an arena in which the interactions between fungal pathogens and other aphid-natural enemies can be assessed however, further assessments at increased spatial scales under more natural abiotic conditions are also required to accurately determine the outcome of these interactions.

Genetic relationships and genotype tracing in date palms ( Phoenix dactylifera L.) in Oman, based on microsatellite markers

Microsatellite markers (SSRs) were used to screen and analyse the genetic diversity among clonal genotypes of date palm ( Phoenix dactylifera L.) derived by somatic embryogenesis in Oman. Twenty-one palms, representing 14 Omani, five Bahraini, one Iraqi and one Moroccan genotype, were screened with ten microsatellite markers. All primer pairs produced an amplification product in the expected size range and detected high levels of polymorphism among the analysed samples. Correspondence analysis revealed that the genotypes from Bahrain and Iraq showed a close relationship with accessions already grown in Oman. The genotype from Morocco (Medjool) appeared distinct from the rest of the material. Three independent clonal lines derived from a single Khalas Aldahra genotype were found to give identical genetic fingerprints. The value of this work for date palm production and conservation in Oman is discussed.

Transmission of deformed wing virus and slow paralysis virus to adult bees (Apis mellifera L.) by Varroa destructor

Summary To investigate the role of the parasitic mite Varroa destructorin the transmission of slow paralysis virus (SPV) and deformed wing virus (DWV) and to gain some insight into host-parasite-pathogen interactions, virus transmission experiments were carried out with adult honey bees in two periods of the year (early July and late September) using either five or ten mites exposed to bee pupae injected with either DWV or SPV for two different time periods of virus acquisition (five or ten days). No significant differences were observed between the proportions of bees becoming infected after mites were exposed to injected pupae for five or ten days regardless the type of virus (DWV or SPV). There was a significant difference in the proportion of bees subsequently infected in relation to the time of year at which the experiments were undertaken. For both DWV and SPV, a greater proportion of adult bees became infected by the mites during September trials than during July trials. Significantly more adult bees were infected with DWV in comparison with SPV. The results strongly support the suggestion that transmission of DWV and SPV occurs during the feeding activities of mites.

Effect of temperature integration on the growth and volatile oil content of basil (Ocimum basilicum L.)

Summary Sweet basil (Ocimum basilicum L.) is a warm climate plant. The optimum temperature for growth is 25°C and, at this temperature, the volatile oil content of leaves is enhanced. Plants grown at 25°C for 2 weeks were taller and had a higher dry matter content and larger leaves than plants grown at other temperatures. The total volatile oil contents in fresh leaves from plants grown at 25°C or 30°C for 2 weeks were three times the levels found in leaves of plants grown at 15°C. Temperature also affected the composition of the volatile oils. Warm conditions (25°C) resulted in the accumulation of eugenol and cis-ocimene, whereas cooler temperature (15°C) resulted in more camphor and trans- farnesene. There was no effect of temperature on the relative contents of 1,8-cineole and linalool. Treatments with alternating temperatures, that supplied the same accumulated ‘day-degrees’ but with a different sequence of temperatures, did not affect most plant growth parameters. In contrast, volatile oil content and composition were strongly affected by the temperature regime during the final 2 weeks of growth. For example, the higher the temperature before harvesting, the higher the volatile oil content and the greater the relative content of eugenol.

Role for Cytokinins in Somatic Embryogenesis of Pepper (Capsicum annuum L.)

The effects of cytokinins on somatic embryogenesis in pepper were studied using a Murashige and Skoog-based medium supplemented with 2 mg/L 2,4-dichlorophenoxyacetic acid and 10% sucrose. Compared to the medium without cytokinins, N6-(Δ2-isopentenyl)-adenine and kinetin had no significant effect, whereas benzylaminopurine and zeatin significantly reduced somatic embryogenesis. Coconut water (10%) either had no significant effect or it reduced embryogenesis as well. Induction of somatic embryogenesis was also dependent on genotype. Appearance of somatic embryos continued after removal of the embryos that developed first, especially on cultivars with a lower initial induction rate. Although somatic embryos germinated, the apical meristem did not elongate.