Timing of Triazole-Based Spray Schedules for Managing Mungbean Powdery Mildew in Australia: a Meta-Analysis

Powdery mildew (PM), caused by two fungal species, Podosphaera xanthii and Erysiphe vignae, is a yield limiting foliar disease commonly found in mungbean (Vigna radiata) cropping areas of eastern region of Australia. Effective control of the disease relies largely on fungicide applications, mainly of the triazole group. Uncertainty in the current fungicide spray schedule recommendations, which advise commencing with a spray at the first signs of PM, prompted this study to evaluate PM severity and crop yield data obtained from fungicide trials which also tested spray schedules starting before (early) or after (late) first signs, applied singly or combined with a follow-up spray. A meta-analytic approach was employed to obtain mean differences of the PM severity and crop yield between plots sprayed with specific triazole-based spray schedules and nontreated plots. From 26 trials, 14 and 15 met the criteria for inclusion in the respective PM severity and yield analyses. The schedule with the first spray starting at first sign, with a follow-up spray 14 days later, resulted in significantly lower disease severity compared to all other schedules. However, the yield protected was only numerically higher and not statistically different compared to: single-spray at first sign, single-spray late or two-spray starting late. PM severity and yield in the early sprayed plots did not differ from the nontreated plots. These findings support the current recommendations and provide additional evidence that yields are still protected when delaying the first spray up to a week after disease onset. They also suggest that additional sprays may not always be necessary, thus reducing direct fungicide costs, indirect costs due to fungicide insensitivity and potential adverse effects to the environment

Inhibition of Gap Junction Communication at Ectopic Eph/ephrin Boundaries Underlies Craniofrontonasal Syndrome

Mutations in X-linked ephrin-B1 in humans cause craniofrontonasal syndrome (CFNS), a disease that affects female patients more severely than males. Sorting of ephrin-B1–positive and –negative cells following X-inactivation has been observed in ephrin-B1(+/−) mice; however, the mechanisms by which mosaic ephrin-B1 expression leads to cell sorting and phenotypic defects remain unknown. Here we show that ephrin-B1(+/−) mice exhibit calvarial defects, a phenotype autonomous to neural crest cells that correlates with cell sorting. We have traced the causes of calvarial defects to impaired differentiation of osteogenic precursors. We show that gap junction communication (GJC) is inhibited at ectopic ephrin boundaries and that ephrin-B1 interacts with connexin43 and regulates its distribution. Moreover, we provide genetic evidence that GJC is implicated in the calvarial defects observed in ephrin-B1(+/−) embryos. Our results uncover a novel role for Eph/ephrins in regulating GJC in vivo and suggest that the pleiotropic defects seen in CFNS patients are due to improper regulation of GJC in affected tissues

Climate change will create winners and losers in the fight against plant disease

Slides for a presentation delivered by Associate Prof. Adam H. Sparks, DPIRD and USQ, and Dr. Paul Melloy, USQ, to CHaBits (Consortium for Heat and Biotic Stresses) organised by Dr Krishna Jagadish, Kansas State University, Manhattan, KS, USA on the effects of climate change on plant disease. The video recording can be found on the CHaBits YouTube: https://youtu.be/PO958Vhdiss

The role of conidia in the dispersal of Ascochyta rabiei

Ascochyta rabiei asexual spores (conidia) were assumed to spread over short distances (~10 m) in a combination of rain and strong wind. The potential distance of conidial spread was investigated in three rainfall and three sprinkler irrigation events. Chickpea trap plants were distributed at the distances of 0, 10, 25, 50 and 75 m from infected chickpea plots before scheduled irrigation and forecast rainfall events. Trap plants were transferred to a controlled temperature room (20 °C) for 48 h (100% humidity) after being exposed in the field for 2–6 days for rainfall events, and for 1 day for irrigation events. After a 48 h incubation period, trap plants were transferred to a glasshouse (20 °C) to allow lesion development. Lesions on all plant parts were counted after 2 weeks, which gave an estimate of the number of conidia released and the distance travelled. Trap plants at all distances were infected in all sprinkler irrigation and rainfall events. The highest number of lesions on trap plants were recorded closest to the infected plots –the numbers decreased as the distance from the infected plots increased. There was a significant (p < 0.05) relationship between the amount of rainfall and the number of lesions recorded. A generalised additive model was developed that efficiently described spatial patterns of conidial spread. With further development, the model can be used to predict the spread of A. rabiei. This is the first systematic study to show that conidia distribute A. rabiei over longer distances than previously reported