Using immunology and resistant sheep to beat the fly

New methods for controlling blowfly strike will be needed when mulesing is phased out and the availability or efficacy of insecticides for control of fly strike decreases. The Australian Sheep Industry CRC has pursued two approaches for the development of new methods to help control blowfly strike. In the first, genetic resistance of sheep to survival and growth of blowfly larvae was examined. Resistance to growth of larvae was heritable (0.29 ± 0.22). The trait was not associated with resistance to internal parasites, nor was it influenced by wool characteristics such as fibre diameter or coefficient of variation of fibre diameter. This new trait differs from resistance to fly strike associated with resistance to fleece rot. Because measurement of the trait is labour intensive, gene markers or correlated measures are needed before it will be suitable for industry adoption. The second approach examined the impact of larval products on the immmune system of the sheep. Larvae suppress the sheep immune system and thereby limit the ability of the sheep to reject the larvae. The immunosuppresive agent is being purified and strategies to abolish its activity are being explored. Abolition of immunosuppression would create opportunities for the development of new vaccines againts blowfly strike.

Temporal variation in arthropod sampling effectiveness: The case for using the beat sheet method in cotton

Predatory insects and spiders are key elements of integrated pest management (IPM) programmes in agricultural crops such as cotton. Management decisions in IPM programmes should to be based on a reliable and efficient method for counting both predators and pests. Knowledge of the temporal constraints that influence sampling is required because arthropod abundance estimates are likely to vary over a growing season and within a day. Few studies have adequately quantified this effect using the beat sheet, a potentially important sampling method. We compared the commonly used methods of suction and visual sampling to the beat sheet, with reference to an absolute cage clamp method for determining the abundance of various arthropod taxa over 5 weeks. There were significantly more entomophagous arthropods recorded using the beat sheet and cage clamp methods than by using suction or visual sampling, and these differences were more pronounced as the plants grew. In a second trial, relative estimates of entomophagous and phytophagous arthropod abundance were made using beat sheet samples collected over a day. Beat sheet estimates of the abundance of only eight of the 43 taxa examined were found to vary significantly over a day. Beat sheet sampling is recommended in further studies of arthropod abundance in cotton, but researchers and pest management advisors should bear in mind the time of season and time of day effects.

Banana agronomy – can unravelling the Musa genome help?

Unravelling the Musa genome allows genes and alleles linked to desired traits to be identified. Short stature and early flowering are desirable agronomic features of banana, as they are of bread wheat (Triticum aestivum). In wheat they were achieved through knowledge of the physiology and genetics of vernalization and photoperiod during development. Bananas and plantains have a facultative long-day response to photoperiod, as do wheat and wall cress (Arabidopsis thaliana). Using keyword searches of the genome of Musa acuminata 'Pahang' we found homologues of the genes of either T. aestivum or Arabidopsis that govern responses to vernalization and photoperiod. This knowledge needs to be interpreted in the context of plant development. Bananas have juvenile, mid-vegetative and reproductive phases of development. Leaf and bunch 'clocks' operate concurrently throughout the juvenile and mid-vegetative phases. In the mid-vegetative phase the plant becomes sensitive to photoperiod. Increased sensitivity to photoperiod reduces the overall pace of the bunch clock without affecting the leaf clock. Separation of the clocks changes the link between leaf number and time of flowering. The 'critical' quantitative trait for the time of flowering is the pace of the bunch clock up to bunch initiation. For bunch size it is the duration of the subsequent phase of female hand formation. Plants with either a short juvenile phase or a faster bunch clock in the mid-vegetative phase will produce fewer leaves and bunch early. In turn, independent manipulation of hand number per bunch and/or fruit per hand will provide manageable bunches with appropriate fruit size. Using published data we explore relationships between plant height, leaf number, bunch weight and hand number among bananas and plantains. Identifying and then manipulating the appropriate genes in Musa opens opportunities for earlier flowering, leading to plants with desirable agronomic qualities.

Host jumps shaped the diversity of extant rust fungi (Pucciniales)

* The aim of this study was to determine the evolutionary time line for rust fungi and date key speciation events using a molecular clock. Evidence is provided that supports a contemporary view for a recent origin of rust fungi, with a common ancestor on a flowering plant. * Divergence times for > 20 genera of rust fungi were studied with Bayesian evolutionary analyses. A relaxed molecular clock was applied to ribosomal and mitochondrial genes, calibrated against estimated divergence times for the hosts of rust fungi, such as Acacia (Fabaceae), angiosperms and the cupressophytes. * Results showed that rust fungi shared a most recent common ancestor with a mean age between 113 and 115 million yr. This dates rust fungi to the Cretaceous period, which is much younger than previous estimations. Host jumps, whether taxonomically large or between host genera in the same family, most probably shaped the diversity of rust genera. Likewise, species diversified by host shifts (through coevolution) or via subsequent host jumps. This is in contrast to strict coevolution with their hosts. * Puccinia psidii was recovered in Sphaerophragmiaceae, a family distinct from Raveneliaceae, which were regarded as confamilial in previous studies.