Variable rate application of fertiliser (VR) is a practice underpinning a profitable grains industry in Australia. We updated the extent of VR adoption through a national survey (n = 1 130) covering all grain growing regions. Three smaller regionalbased surveys (n = 39-102) collected detailed information on the nature and reasoning behind the use of various forms of the technology. We analysed the constraints to the adoption of each step using adoption theory. Surveys showed that 20% of grain growers have adopted some form of VR (varied from 11-35%), up significantly from \5% found 6 years earlier. Adopters are more than likely to have larger farms with a higher area in cropping. Many non-adopters were convinced of the agronomic and economic benefits of VR. A significant proportion of growers were managing within-field variability with manually-operated systems rather than more sophisticated VR technology, and have adopted some form of VR without yield maps, preferring to use soil tests, electro-magnetic induction or their own knowledge of soil and yield variation to define management. The rate of adoption is expected to continue to rise based on greater awareness of the benefits of the technology. The constraints to adoption were technical issues with equipment and software access to service provision and the incompatibility of equipment with existing farm operations.

Storage protein gene expression, characteristic of mid-to late embryogenesis, was investigated in microspore embryos of rapeseed (Brassica napus). These embryos, derived from the immature male gametophyte, accumulate little or no detectable napin or cruciferin mRNA when cultured on hormone-free medium containing 13% sucrose. The addition of abscisic acid (ABA) to the medium results in an increase in detectable transcripts encoding both these polypeptides. Storage protein mRNA is induced at 1 micromolar ABA with maximum stimulation occurring between 5 and 50 micromolar. This hormone induction results in a level of storage protein mRNA that is comparable to that observed in zygotic embryos of an equivalent morphological stage. Effects similar to that of ABA are noted when 12.5% sorbitol is added to the microspore embryo medium (osmotic potential = 25.5 bars). Time course experiments, to study the induction of napin and cruciferin gene expression demonstrated that the ABA effect occurred much more rapidly than the high osmoticum effect, although after 48 hours, the levels of napin or cruciferin mRNA detected were similar in both treatments. This difference in the rates of induction is consistent with the idea that the osmotic effect may be mediated by ABA which is synthesized in response to the reduced water potential. Measurements of ABA (by gas chromatography-mass spectrometry using [2H6]ABA as an internal standard) present in microspore embryos during sorbitol treatment and in embryos treated with 10 micromolar ABA were performed to investigate this possibility. Within 2 hours of culture on high osmoticum the level of ABA increased substantially and significantly above control and reached a maximum concentration within 24 hours. This elevated concentration was maintained for 48 hours after culturing and represents a sixfold increase over control embryos. The ABA-treated embryos accumulated the hormone very quickly, but ABA concentrations retumed to basal levels within 72 hours after treatment. The possibility that embryosynthesized ABA may be a mediator of effects of osmotic stress on gene expression in Brassica embryos is discussed.several studies on the regulation of gene expression in developing seeds (9, 10). In B. napus it has been shown that exogenous ABA treatment can have profound effects on the accumulation of transcripts and gene products of the major seed storage proteins (9), lipid profiles (8), and on levels of oil-body associated proteins (20). Many ofthe responses stimulated by ABA are also affected by water stress or elevated osmotica (7,8).The relationship between ABA effects and osmotic effects in developing seeds is not yet clear and has yielded results with contrasting interpretations (23). Bray and Beachy (2) suggested that the accumulation of soybean storage proteins, which is enhanced by culturing soybean embryos on high osmotica, is a consequence of elevated ABA content. In B. napus, on the other hand, Finkelstein and Crouch (7)

S7N OW9 (S.R. A.) l h e properties of two enantiomeric synthetic acetylenic abscisic acid (ABA) analogs (PBI-51 and PBI-63) in relation to ABA-sensitive gene expression are reported. Using microspore-derived embryos of Brassica napus as the biological material and their responsiveness to ABA in the expression of genes encoding storage proteins as a quantitative bioassay, we measured the biological activity of PBI-51 and PBI-63. Assays to evaluate agonistic activity of either compound applied individually showed a dose-dependent increase in napin gene expression on application of PBI-63. Maximal activity of about 40 p~ indicated that PBI-63 was an agonist, although somewhat weaker than ABA. PBI-63 has a similar stereochemistry to natural ABA at the junction of the ring and side chain. In contrast, PBI-51 showed no agonistic effects until applied at 40 to 50 p~.Even then, the response was fairly weak. PBI-51 has the opposite stereochemistry to natural ABA at the junction of the ring and side chain. When applied concurrently with ABA, PBI-63 and PBI-51 had distinctly different properties. PBI-63 (40 p~) and ABA (5 PM) combined gave results similar to the application of either compound separately with high levels of induction of napin expression. PBI-51 displayed a reversible antagonistic effect with ABA, shifting the typical ABA dose-response curve by a factor of 4 to 5. This antagonism was noted for the expression of two ABA-sensitive genes, napin and oleosin. To test whether this antagonism was at the leve1 of ABA recognition or uptake, ABA uptake was monitored in the presence of PBI-51 or PBI-63. Neither compound decreased ABA uptake. Treatments with either PBI-51 or PBI-63 showed an effect on endogenous ABA pools by permitting increases of 5-to 7-fold. It is hypothesized that this increase occurs because of competition for ABA catabolic enzymes by both compounds. l h e fact that ABA pools did not decrease i n the presence of PBI-51 suggests that PBI-51 must exert its antagonistic properties through direct competition with ABA at a hormone-recognition site.

Greenhouse-grown oilseed rape (Brasskca napus, annual Canola variety 'Westar') plants were harvested at six dates from the vegetative phase until the early pod (silique)-fill/late flowering stage. Endogenous gibberellin (GA)-like substances were extracted from stems, purified, and chromatographed on silica gel partition columns prior to bioassay in serial dilution using the 'Tan-ginbozu' dwarf rice microdrop assay. The concentrations of total endogenous GA-like substances were low during vegetative stages (1 nanogram GA3 equivalents/gram dry weight), and rose 300-fold by the time of floral initiation. After floral initiation the concentration of GA-like substances fell, then rose again during bolting to maximal levels during the early pod-fill stage (940 nanograms per gram dry weight). The qualitative profiles of GAlike substances varied across harvests, with higher proportions of a GAr-like substance at the early pod-fill stage. In a second study stems were similarly harvested at eight dates and the concentrations of endogenous GA1, the principal bioactive native GA of oilseed rape, were determined by gas chromatographyselected ion monitoring using [17,17-2H]GAI as a quantitative intemal standard. The concentration of GA1 increased at about the time of floral initiation and then subsequently fell, thus confirming the pattem noted above for total GA-like substances. The exogenous application of paclobutrazol (PP333), a persistent triazole plant growth regulator (PGR) which blocks GA biosynthesis, or another triazole, triapenthenol (RSW0411), prevented flowering as well as bolting; plants remained at the vegetative rosette stage. These results imply a causal role for endogenous GA, in the control of bolting, which normally precedes anthesis. Further, the rise in the concentration of total endogenous GA-like substances, including GA,, which was associated with floral initiation, and the prevention of visable floral development by the triazole PGRs, also indicates a role for endogenous GAs in the regulation of flowering in B. napus.

Borger CPD, Michael PJ, Mandel R, Hashem A, Bowran D & Renton M (2012). Linking field and farmer surveys to determine the most important changes to weed incidence. Weed Research52, 564–574. Summary An understanding of weed species incidence and patterns of change in incidence is vital in developing weed management strategies and directing future research endeavours. Weed incidence in fields in the south‐west of Western Australia was surveyed in 1997 and repeated in 2008 to determine any changes. In 2008, farmers were also surveyed to determine their perception of changes to weed incidence and severity. The field survey identified a total of 194 weed species (or groups of species within a genus) in the combined survey data set (i.e. 956 sites from both field surveys). The majority of survey sites were utilised for cropping, and 152 weed species were identified within cropped fields. Between 1997 and 2008, noticeable decreases in incidence (in cropped fields) were observed for Vulpia spp. (−25%), Aira caryophyllea (−21%), Bromus diandrus (−20%), Avena fatua (−18%) and Austrostipa spp. (−13%), with only Raphanus raphanistrum (11%) and Arctotheca calendula (7%) significantly increasing in frequency. Farmer perception of the most severe weed problems did not always coincide with survey results of weed incidence. For example, an exceptionally common weed like A. calendula (with increasing incidence) was of less concern to farmers than the extremely rare Conyza spp. The main conclusion of this research is that the prevalence of a weed species is not always an indication of whether the species is of economic concern to industry. Therefore, it is vital to link field survey results to industry perception of weed species severity, when directing future research efforts into weed management.