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Latest From Hazel Blake
Researchers from the US University of Illinois (Urbana-Champaign) have found that the presence of specific gut bacteria species allow some western corn rootworms (Diabrotica virgifera virgifera) to survive crop rotation between maize and soybeans. Rotation-resistant populations of the rootworms developed some 20 years ago, and the trait is spreading. Analysis of gut micro-organisms in rotation-resistant rootworms showed that bacterially-produced enzymes improved the rootworm’s ability to digest soybean leaves and reduced the toxic effects of soybean plant defences. Overwintering adults were able to survive long enough to lay eggs that hatched in maize planted the following year. The study’s findings show that gut microbes are not just passive residents of the rootworm gut, but play an active part in insect adaptation, the researchers point out. Details of the study have been published in the journal, Proceedings of the National Academy of Sciences.
Researchers have developed genetically modified potatoes resistant to cucumber mosaic virus (CMV). The potatoes express a gene silencing construct comprising a mutated CMV replicase that confers resistance to CMV strains O and Y. The researchers used the RNAi construct to transform a CMV-susceptible potato cultivar to produce plants with complete or high levels of resistance to the viral pathogen. In those plants with high levels of resistance, infectivity of CMV-O was lower than that of CMV-Y. Details of the study have been published in the journal, Transgenic Research.
The first genome sequence of an ash tree with high resistance to the fungal disease, ash dieback (Chalara fraxinea), has been completed by an Anglo-Danish research consortium. The sequence is derived from a specimen, Tree35, growing in Denmark. Ash dieback has been present in mainland Europe since 1992 and has recently spread to the UK. No fungicides are available to treat infected trees. The sequence data have been published on the crowdsourcing website, OpenAshDieBack. The research team has previously completed sequencing the genome of C fraxinea. Data showed a high level of genomic variability in fungal strains from infected trees in UK woodlands, indicating that more than one "seeding event" was likely involved in the spread of the disease. Researchers hope that the sequence data will aid in identifying other resistant trees that can be used to establish lines with low susceptibility to the fungus.
Results from a study on the efficacy of insect-specific neurotoxins derived from spiders and scorpions against aphids indicate that most are effective only when injected into the insect body cavity. The researchers compared the effects of seven spider or scorpion toxins to that of the 28 kDa Bacillus thuringiensis Cyt1Aa toxin on pea aphids (Acyrthosiphon pisum) and the green peach aphid (Myzus persicae). Toxins were selected to represent different modes of electrophysiological action, including activity on voltage-gated calcium channels, calcium- and voltage-activated potassium channels, chloride channels, and voltage-gated sodium channels. The arachnid proteins range in size between 3.62 and 7.38 kDa.
Researchers from China and Australia have completed a draft genome sequence for the narrow-leaved or sweet lupin (Lupinis augustifolius). Lupins are the most recently domesticated crop in major agricultural cultivation. Data from the study have enabled researchers to identify, among others, a candidate gene associated with resistance to the major lupin disease, anthracnose (Colletotrichum lupini). The researchers sequenced the genomes of the high-yielding, disease-resistant cultivar, Tanjil, which is resistant to phomopsis stem blight (Diaporthe toxica), grey leaf spot (Stemphylium botryosum), cucumber mosaic virus transmission, and aphid colonisation. Details of the study have been published in the journal, PloS One.
Results from a study of the variation in aggression of rice blast (Magnoporthe oryzae) isolates indicate that the best way to limit yield losses from the fungal pathogen may be to target control of the disease in leaf rather than neck tissue. Leaf epidemics tend to occur early in the crop cycle, during the vegetative stage, with disease peaking at maximum tillering followed by a sharp decline and a very low level from flowering until harvest. Neck blast appears later in the crop cycle, at flowering, and yield losses are much greater than those associated with leaf blast epidemics.