Livestock integration into soybean systems improves long-term system stability and profits without compromising crop yields.

Climate models project greater weather variability over the coming decades. High yielding systems that can maintain stable crop yields under variable environmental scenarios are critical to enhance food security. However, the effect of adding a trophic level (i.e. herbivores) on the long-term stability of agricultural systems is not well understood. We used a 16-year dataset from an integrated soybean-beef cattle experiment to measure the impacts of grazing on the stability of key crop, pasture, animal and whole-system outcomes. Treatments consisted of four grazing intensities (10, 20, 30 and 40 cm sward height) on mixed black oat (Avena strigosa) and Italian ryegrass (Lolium multiflorum) pastures and an ungrazed control. Stability of both human-digestible protein production and profitability increased at moderate to light grazing intensities, while over-intensification or absence of grazing decreased system stability. Grazing did not affect subsequent soybean yields but reduced the chance of crop failure and financial loss in unfavorable years. At both lighter and heavier grazing intensities, tradeoffs occurred between the stability of herbage production and animal live weight gains. We show that ecological intensification of specialized soybean systems using livestock integration can increase system stability and profitability, but the probability of win-win outcomes depends on management.

Improved Pastures Support Early Indicators of Soil Restoration in Low-input Agroecosystems of Nicaragua.

Pasture degradation hinders livestock production and ecosystem services that support rural smallholder communities throughout Latin America. Silvopastoral systems, with improved pasture cultivars (especially Brachiaria spp.) and multipurpose trees, offer a promising strategy to restore soils and improve livelihoods in the region. However, studies evaluating the impact of such systems on pasture productivity and soil health under realistic smallholder constraints are lacking. We evaluated the impact of improved pasture grass and tree establishment on a suite of soil health indicators in actively grazed, low-input, farmer-managed silvopastoral systems. In August 2013, paired pasture treatments (improved grass with trees vs. traditional pastures) were established on nine farms with similar land-use histories near Matagalpa, Nicaragua. On each farm, one treatment was left as traditional pasture with naturalized grass (Hyparrhenia rufa), while the adjacent treatment was sown with the improved grass (Brachiaria brizantha cv. Marandu) and planted with tree saplings without fertilizer. In August 2015, we measured standing biomass and a suite of chemical, biological, and physical soil health variables. Improved silvopastoral systems with B. brizantha produced more standing grass biomass and supported higher levels of earthworm populations and permanganate oxidizable carbon (POXC) compared to the traditional control. Correlations suggest that earthworms and POXC were associated with incipient improvements to soil aggregate stability and water holding capacity. We report measurable improvements to soil health just two years following the establishment of improved pasture systems under common smallholder management practices and suggest that these systems, even with minimal fertility inputs, have the potential to enhance regional sustainability.

Capturing candidate drought tolerance traits in two native Andean potato clones by transcription profiling of field grown plants under water stress.

Candidate traits for drought tolerance were targeted by analyzing water stress responses in two moderately drought-tolerant native Andean potato clones, SA2563 and Sullu (Solanum tuberosum L. subsp, andigena (Juz, Bukasov) Hawkes) under field conditions. SA2563 exhibited increased root growth under drought, while Sullu retained a higher relative leaf water content. Gene expression profiling using the TIGR 10 K microarray revealed 1713 significantly differentially expressed genes, 186 of these genes were up-regulated in both clones. In addition to these commonly up-regulated genes, each clone induced a specific gene set in response to drought. Gene expression and metabolite analysis pinpointed candidate traits for drought tolerance present either in one or both of the clones under investigation. These traits included osmotic adjustment, changes in carbohydrate metabolism, membrane modifications, strengthening of cuticle and cell rescue mechanisms, such as detoxification of oxygen radicals and protein stabilization. Many of the up-regulated genes have been identified previously in laboratory studies on model plants using shock treatments, and the present study confirms the importance of these factors under field conditions.

Self-excision of the antibiotic resistance gene nptII using a heat inducible Cre-loxP system from transgenic potato.

Resistance to antibiotics mediated by selectable marker genes remains a powerful selection tool for transgenic event production. However, regulatory agencies and consumer concerns favor these to be eliminated from food crops. Several excision systems exist but none have been optimized or shown to be functional for clonally propagated crops. The excision of the nptII gene conferring resistance to kanamycin has been achieved here using a gene construct based on a heat-inducible cre gene producing a recombinase that eliminates cre and nptII genes flanked by two loxP sites. First-generation regenerants with the Cre-loxP system were obtained by selection on kanamycin media. Following a heat treatment, second generation regenerants were screened for excision by PCR using nptII, cre, and T-DNA borders primers. Excision efficiency appeared to be at 4.7% depending on the heat treatment. The footprint of the excision was shown by sequencing between T-DNA borders to correspond to a perfect recombination event. Selectable marker-free sprouts were also obtained from tubers of transgenic events when submitted to similar heat treatment at 4% frequency. Spontaneous excision was not observed out of 196 regenerants from untreated transgenic explants. Biosafety concerns are minimized because the expression of cre gene driven by the hsp70 promoter of Drosophila melanogaster was remarkably low even under heat activation and no functional loxP site were found in published Solanum sequence database. A new plant transformation vector pCIP54/55 was developed including a multiple cloning site and the self-excision system which should be a useful tool not only for marker genes in potato but for any gene or sequence removal in any plant.