Distribution of free and glycosylated sterols within Cycas micronesica plants

Flour derived from Cycas micronesica seeds was once the dominant source of starch for Guam's residents. Cycad consumption has been linked to high incidence of human neurodegenerative diseases. We determined the distribution of the sterols stigmasterol and β-sitosterol and their derived glucosides stigmasterol β-d-glucoside and β-sitosterol β-d-glucoside among various plant parts because they have been identified in cycad flour and have been shown to elicit neurodegenerative outcomes. All four compounds were common in seeds, sporophylls, pollen, leaves, stems, and roots. Roots contained the greatest concentration of both free sterols, and photosynthetic leaflet tissue contained the greatest concentration of both steryl glucosides. Concentration within the three stem tissue categories was low compared to other organs. Reproductive sporophyll tissue contained free sterols similar to seeds, but greater concentration of steryl glucosides than seeds. One of the glucosides was absent from pollen. Concentration in young seeds was higher than old seeds as reported earlier, but concentration did not differ among age categories of leaf, sporophyll, or vascular tissue. The profile differences among the various tissues within these organs may help clarify the physiological role of these compounds.     

Effects of Cultivation after Planting on Yields of Seed Cotton

Abstract

Experiments carried out over several seasons showed that, on a soil prone to crusting, cultivations after the establishment of a cotton crop only increased yields in a season of low rainfall. This yield increase appeared to have been due to enhanced entry into the soil of the limited effective rainfall. In one season of high rainfall, deep cultivation significantly reduced yields.     

Plant Diseases

Abstract

Following declining numbers in some areas in the 1980s, Mute Swan numbers have shown a marked increase in recent years. In some areas, such as the Wylye Valley in Wiltshire, this increase has been accompanied by complaints of damage caused to farming and fishing interests. The population dynamics of this population of Mute Swans is described, including its habitat preferences, and these findings are related to possible management options. As the Wylye catchment already receives immigrants from unknown sources, culling and translocation are not appropriate solutions to prevent agricultural damage. A combination of scaring, repellents and the provision of alternative food sources could provide the most successful long‐term management. Whilst different techniques may be needed to resolve the fishing problem, it is considered that integration of selected management options is most likely to provide maximum benefit.     

Spider mite control and resistance management: does a genome help?

The complete genome of the two‐spotted spider mite, Tetranychus urticae, has been reported. This is the first sequenced genome of a highly polyphagous and resistant agricultural pest. The question as to what the genome offers the community working on spider mite control is addressed. Copyright © 2012 Society of Chemical Industry     

Landscape-scale assessment of tree crown dieback following extreme drought and heat in a Mediterranean eucalypt forest ecosystem

Mediterranean regions are under increasing pressure from global climate changes. Many have experienced more frequent extreme weather events such as droughts and heatwaves, which have severe implications for the persistence of forest ecosystems. This study reports on a landscape-scale assessment investigating potential associated factors of crown dieback in dominant tree species following an extreme dry and hot year/summer of 2010/11 in the Northern Jarrah Forest of Western Australia. Analyses focussed on the influence of (i) geology, (ii) topography, (iii) climate, and (iv) fire history. The results showed that trees on specific soils were more likely to show canopy dieback. Generally, trees on rocky soils with low water holding capacity were found to be affected more frequently. Other explanatory factors identified that dieback occurred (i) on sites that were close to rock outcrops, (ii) in areas that received a slightly higher amount of annual rainfall compared to the surrounding landscape, (iii) on sites at high elevations and (vi) on steep slopes, and (v) in areas that were generally slightly warmer than their surroundings. These results expand our understanding of how landscape-scale factors contribute to the effects of an extreme drought and heating event in Mediterranean forest ecosystems, and give indications of where changes are likely to occur within the landscape in the future. The analogues with other Mediterranean climate regions make the results of this study transferable and a starting point for further investigations.     

A study of the ecological variability in yield of selected clones of Arabica coffee (Coffea arabica L.) from the coffee-breeding programme in Kenya

Summary

Cherry yield of eleven elite clones of Arabica coffee was evaluated over a five-year period at three locations in a continuing study to detenriine the extent and influence of Clone X Environment interactions on coffee breeding lines developed in Kenya. Clone mean yield comparisons indicated a better performance of all the improved clones compared with the Standard. In analysis of variance (ANOVA) significant main effects and non-significant Clone X Environment interactions (P<0.05) were found. Interactions were however, further investigated using ecovalence values, the Eberhart and Russell (1966) regression model as well as the Additive Main effects and Multiplicative Interaction effects (AMMI) model. The clones were then clustered according to their response patterns using principal components and cluster analyses to obtain a delineation of ecological districts and more accurate predictions of clone performance. The main effects for clones reflected breeding advances with the standard variety having the smallest mean. Improved materials from the hybridization scheme appeared to do better than their pure-line counterparts with clones 8,3,1 and 2 being the most advanced of the 11 clones. Similarly, the main effects for the environment reflected the overall site/year quality with Kiambu having the best production conditions particularly due to the favourable weather in 1983. This indicates that the coffee growing upper zone may be favourable for the clones especially when they are raised by top-working old coffee. Makuyu environments had the least interaction effects.     

In vitro propagation of ‘Arka Ravi’ chrysanthemum on growth regulator-free medium harbouring endophytic bacteria

Summary

To develop a micropropagation protocol for the elite chrysanthemum cultivar, ‘Arka Ravi’, in vitro cultures were established using surface-sterilised nodal microcuttings (1.0 – 1.2 cm) on semi-solid MS medium. Microbial contamination was observed in 22% of cultures during the initiation phase. Cultures that were devoid of obvious contamination were transferred to culture bottles containing MS medium supplemented with 30 g l^–1 sucrose, 2.5 g l^–1 Phytagel^® and either benzyl adenine (BA) or kinetin (KIN) supplied at 0, 1, 5, 10, or 20 µM, and were monitored, over eight in vitro passages, for their growth and microbial association. Shoot-tip and nodal microcuttings yielded a single shoot, coupled with rooting, in medium devoid of BA or KIN which was the best medium for continuous micropropagation. Rooting was inhibited with increasing concentrations of BA or KIN, and one or more shorter shoots with condensed internodes were induced, resulting in low rates of propagation. Culture indexing (i.e., testing the medium and tissue from visibly clean cultures using enriched bacteriological media) revealed quiescent endophytic bacteria associated with 80 – 100% of such cultures. Three distinct colony morphotypes were isolated and were identified as Ralstonia, Enterobacter, and Methylobacterium spp., based on their 16S rRNA gene sequences. These endophytes did not interfere with normal micropropagation, but tended to grow actively and outgrow older cultures, especially at higher cytokinin concentrations. Stable micropropagation of ‘Arka Ravi’ chrysanthemum for ≥ 2 years, with their resident endophytic bacteria in a covert form, was achieved on basal MS medium with > 90% shoot growth and rooting, a four-to-five-fold propagation rate at each 2 – 3 week sub-culture cycle, and with > 90% establishment of rooted plantlets ex vitro. These results suggest that in vitro cultures of chrysanthemum often harbour endophytes with no obvious indications of their presence or with possible hidden effects during micropropagation.     

Field scale spatiotemporal analysis of surface soil moisture for evaluating point-scale in situ networks

Soil moisture is an intrinsic state variable that varies considerably in space and time. From a hydrologic viewpoint, soil moisture controls runoff, infiltration, storage and drainage. Soil moisture determines the partitioning of the incoming radiation between latent and sensible heat fluxes. Although soil moisture may be highly variable in space and time, if measurements of soil moisture at the field or small watershed scale are repeatedly observed, certain locations can often be identified as being temporally stable and representative of the an area average. This study is aimed at determining the adequacy of long term point-scale surface soil moisture measurements in representing local field scale averages which may ultimately serve as in situ locations for the calibration and validation of remotely sensed soil moisture. Experimental data were obtained by frequency-domain reflectometry (FDR) sensors permanently installed in two agricultural fields, AS1 and AS2 (2.23 and 2.71 ha, respectively) at a depth of 5 cm. Twenty additional FDR sensors, spaced 35 m apart, were installed horizontally at a depth of 5 cm in each field with automated data collection being transmitted every 30 min from July 15 through September 20, 2009. Additionally, meteorological data were obtained from existing weather stations in each field. The FDR sensors revealed persistent patterns in surface soil moisture within each field and identified sites that were temporally stable. The locations that were optimal for estimating the area-average field water contents were different from the permanent sensor locations in both fields. Permanent sensor data showed approximately 4 and 10% mean relative differences for fields AS1 and AS2, respectively, with relatively large standard deviations. Thus, minimum offset values could be applied to the temporally stable field sites to obtain representative field average values of surface soil moisture. However, use of permanent sensor data for offset estimates gave poor results. These findings are of relevance for applications of geospatial surface soil moisture data assimilation in hydrologic modeling when only point-scale observations are available, as well as, remotely sensed surface soil moisture calibration and validation studies.