Development of plant-based emulsion formulations to control bacterial leaf blight and sheath brown rot of rice.

Bacterial leaf blight (BLB) and sheath brown rot (SBR), caused by Xanthomonas oryzae pv. oryzae (Xoo) and Pseudomonas fuscovaginae, respectively, are bacterial diseases that lead to substantial yield losses in rice. Natural plant-based products represent a sustainable alternative to combat bacterial diseases due to their biodegradability and overall safety. However efficient ways of delivering them are crucial to their success. In an attempt to maximize the antibacterial properties of botanical bactericides for the control of these pathogens, this study evaluated the efficiency of different emulsion formulations of Piper sarmentosum extracts. The emulsion formulations were demonstrated to be effective in controlling BLB and SBR of rice in in vitro plate assays and in planta under glasshouse conditions. The observed in vitro inhibition of the bacterial pathogens and significant disease suppression in planta indicate that these plant extract formulations represent promising alternatives to be adopted in management strategies for controlling rice diseases.

Strategic tillage in conservation agricultural systems of north-eastern Australia: why, where, when and how?

Farmers often resort to an occasional tillage (strategic tillage (ST)) operation to combat constraints of no-tillage (NT) farming systems. There are conflicting reports regarding impacts of ST and a lack of knowledge around when, where and how ST is implemented to maximise its benefits without impacting negatively on soil and environment. We established 14 experiments during 2012-2015 on farms with long-term history of continuous NT to (i) quantify the associated risks and benefits to crop productivity, soil and environmental health and (ii) explore key factors that need to be considered in decisions to implement ST in an otherwise NT system. Results showed that introduction of ST reduced weed populations and improved crop productivity and profitability in the first year after tillage, with no impact in subsequent 4 years. Soil properties were not impacted in Vertosols; however, Sodosols and Dermosols suffered short-term negative soil health impacts (e.g. increased bulk density). A Sodosol and a Dermosol also posed higher risks of runoff and associated loss of nutrients and sediment during intense rainfall after ST. The ST reduced plant available water in the short term, which could result in unreliable sowing opportunities for the following crop especially in semi-arid climate that prevails in north-eastern Australia. The results show that generally, there were no significant differences in crop productivity and soil health between tillage implements and tillage frequencies between ST and NT. The study suggests that ST can be a viable strategy to manage constraints of NT systems, with few short-term soil and environmental costs and some benefits such as short-term farm productivity and profitability and reduced reliance on herbicides.

Development of marker genes for jasmonic acid signaling in shoots and roots of wheat.

The jasmonic acid (JA) signaling pathway plays key roles in a diverse array of plant development, reproduction, and responses to biotic and abiotic stresses. Most of our understanding of the JA signaling pathway derives from the dicot model plant Arabidopsis thaliana, while corresponding knowledge in wheat is somewhat limited. In this study, the expression of 41 genes implicated in the JA signaling pathway has been assessed on 10 day-old bread wheat seedlings, 24 h, 48 h, and 72 h after methyl-jasmonate (MeJA) treatment using quantitative real-time PCR. The examined genes have been previously reported to be involved in JA biosynthesis and catabolism, JA perception and signaling, and pathogen defense in wheat shoots and roots. This study provides evidence to suggest that the effect of MeJA treatment is more prominent in shoots than roots of wheat seedlings, and substantial regulation of the JA pathway-dependent defense genes occurs at 72 h after MeJA treatment. Results show that the expression of 22 genes was significantly affected by MeJA treatment in wheat shoots. However, only PR1.1 and PR3 were significantly differentially expressed in wheat roots, both at 24 h post-MeJA treatment, with other genes showing large variation in their gene expression in roots. While providing marker genes on JA signaling in wheat, future work may focus on elucidating the regulatory function of JA-modulated transcription factors, some of which have well-studied potential orthologs in Arabidopsis.