Hye-Ji Kim

Root Interactions in a Maize/Soybean Intercropping System Control Soybean Soil-Borne Disease, Red Crown Rot

Background Within-field multiple crop species intercropping is well documented and used for disease control, but the underlying mechanisms are still unclear. As roots are the primary organ for perceiving signals in the soil from neighboring plants, root behavior may play an important role in soil-borne disease control. Principal Findings In two years of field experiments, maize/soybean intercropping suppressed the occurrence of soybean red crown rot, a severe soil-borne disease caused by Cylindrocladium parasiticum (C. parasiticum). The suppressive effects decreased with increasing distance between intercropped plants under both low P and high P supply, suggesting that root interactions play a significant role independent of nutrient status. Further detailed quantitative studies revealed that the diversity and intensity of root interactions altered the expression of important soybean PR genes, as well as, the activity of corresponding enzymes in both P treatments. Furthermore, 5 phenolic acids were detected in root exudates of maize/soybean intercropped plants. Among these phenolic acids, cinnamic acid was released in significantly greater concentrations when intercropped maize with soybean compared to either crop grown in monoculture, and this spike in cinnamic acid was found dramatically constrain C. parasiticum growth in vitro. Conclusions To the best of our knowledge, this study is the first report to demonstrate that intercropping with maize can promote resistance in soybean to red crown rot in a root-dependent manner. This supports the point that intercropping may be an efficient ecological strategy to control soil-borne plant disease and should be incorporated in sustainable agricultural management practices.

Economic analysis of aquaponics and hydroponics production in the U.S. Midwest

ABSTRACT This article examined the profitability of aquaponics in the U.S. Midwest. Three sources of data were considered for the study: (1) three active aquaponics farms, (2) a university greenhouse experiment, and (3) published research. The first analysis compares the economics of aquaponics and hydroponics systems under similar operations. Results suggest that the aquaponics system requires higher investment and operating cost but has lower production of vegetables compared with the hydroponics system. However, if aquaponics vegetable production is managed as an organic production, and the produce is sold at 20% premium price, aquaponics becomes profitable. The second analysis constructed three different representative farm sizes of aquaponics production of basil and tilapia—small, medium, and large. The production of basil provides better economic returns than the fish. All farm sizes are feasible when the basil price is above

Reactive oxygen species and nitric oxide induce senescence of rudimentary leaves and the expression profiles of the related genes in Litchi chinensis

10.00 per kg. The larger farm has the best results because of lower cost of production.

Ethylene insensitivity impedes a subset of responses to phosphorus deficiency in tomato and petunia

Litchi is one of the most important subtropical evergreen fruit trees in southern Asia. Previous studies indicated that high-temperature conditions encourage growth of rudimentary leaves in panicles and suppress flowering. We have demonstrated that methyl viologen dichloride hydrate (MV) and sodium nitroprusside (SNP) promoted flowering in litchi partially by inhibiting the growth of rudimentary leaves via reactive oxygen species (ROS) and nitric oxide (NO). In the present study, we examined the microstructure and ultrastructure, programmed cell death (PCD) ratio, nuclei morphology of the rudimentary leaves, and the expression of senescence-related genes after the treatment with ROS or NO. The results showed that chromatins of the ROS- or NO-treated cells in the rudimentary leaves were condensed. Fusion of the cytoplasm-digesting vesicles with the vacuole and degradation of cytoplasm forming scattered debris were found in those of the treated cells. Treatment with ROS or NO increased the cell PCD ratio. Morphology of the nuclei stained by propidium iodide (PI) showed that nuclei shape became irregular after the ROS or NO treatment. Further, the expression levels of LcRboh, LcMC-1-like, and LcPirin were higher in the ROS- and NO-treated rudimentary leaves than those in the control ones, suggesting that these genes may be involved in the ROS and NO-induced senescence and abscission of the rudimentary leaves in litchi. Our results suggested that ROS and NO play an important role in inducing the senescence of the rudimentary leaves, and ROS- and NO-induced PCD may be involved in the regulation of the rudimentary leaf growth in litchi.Climate change: tricking the treesWarmer winter temperatures suppress flowering of litchi trees, threatening fruit production, but researchers have found another way to trigger litchi trees to reproduce. In litchi, spring buds contain both flower and leaf primordia, and cold cues the plants to shed the young leaves, allowing the flower primordia to develop. With recent warmer winters, the leaves are crowding out the flowers. Biyan Zhou at South China Agricultural University investigated whether spraying with compounds that make the trees produce stress-signaling molecules, such as nitrous oxide, would mimic the effects of a cold winter. Following treatment, the trees shed their rudimentary leaves and flowers developed. Microscopic examination of buds showed that the leaf shedding process looked similar to cold-triggered shedding. This study offers a method to induce litchis to flower and fruit, even in a changing climate.