Plant-derived protein hydrolysates (PHs) have gained prominence as plant biostimulants because of their potential to increase the germination, productivity and quality of a wide range of horticultural and agronomic crops. Application of PHs can also alleviate the negative effects of abiotic plant stress due to salinity, drought and heavy metals. Recent studies aimed at uncovering the mechanisms regulating these beneficial effects indicate that PHs could be directly affecting plants by stimulating carbon and nitrogen metabolism, and interfering with hormonal activity. Indirect effects could also play a role as PHs could enhance nutrient availability in plant growth substrates, and increase nutrient uptake and nutrient-use efficiency in plants. Moreover, the beneficial effects of PHs also could be due to the stimulation of plant microbiomes. Plants are colonized by an abundant and diverse assortment of microbial taxa that can help plants acquire nutrients and water and withstand biotic and abiotic stress. The substrates provided by PHs, such as amino acids, could provide an ideal food source for these plant-associated microbes. Indeed, recent studies have provided evidence that plant microbiomes are modified by the application of PHs, supporting the hypothesis that PHs might be acting, at least in part, via changes in the composition and activity of these microbial communities. Application of PHs has great potential to meet the twin challenges of a feeding a growing population while minimizing agriculture’s impact on human health and the environment. However, to fully realize the potential of PHs, further studies are required to shed light on the mechanisms conferring the beneficial effects of these products, as well as identify product formulations and application methods that optimize benefits under a range of agro-ecological conditions.

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Soil erosion due to annual cropping on highly erodible farmland is a major ecological concern in the wheat growing regions of Washington State. In response to requests from farmers, the winter wheat breeding program at Washington State University has been developing perennial wheat selected from crosses between wild wheatgrass species and commonly grown annual wheat cultivars. In 2005/06, we conducted field trials of the most promising perennial wheat breeding lines derived from interspecific crosses between tall wheatgrass (Thinopyrum elongatum) and bread wheat (Triticum aestivum). Thirtyone perennial breeding lines and two annual winter wheat cultivars were evaluated for nutritional value in the form of grain mineral concentration, multiple baking and milling quality traits, and ease of grain threshability. The objective of this study was to identify the strengths and weaknesses of these post-harvest traits in the perennial wheat lines derived from these interspecific crosses. Mineral nutrient concentrations in the perennial lines were 44, 40, 24, 23, 32, 30 and 33% higher than the annual control cultivars for calcium, copper, iron, magnesium, manganese, phosphorus and zinc, respectively. The annual cultivars had a higher grain mineral content per unit area of land than the perennial lines, due primarily to the higher grain yields of the annual cultivars. Compared to the annual wheat cultivars, the perennial lines produced grain with smaller seed size, lower test weight and reduced flour yield, mix time and loaf volume. Protein content was 3.5-4.5% higher in the perennial lines than in the annual cultivars. The threshability index (TI) ranged from 0.63 to 0.89 in the perennials (m = 0.75); significantly lower than the mean TI of the annual cultivars (m = 0.97). The significant genotyperlocation interaction found for TI suggests that the variation in annual precipitation positively influenced some perennial lines to express greater threshability. In addition to transferring traits important to the perennial growth habit in wheat, the wild wheatgrass species also introduced beneficial characteristics (i.e. increased protein and mineral concentration) and deleterious traits (poor threshing grain and inferior baking qualities). This research gives researchers a platform from which to direct further research and selection in the development of perennial wheat.

Use of high tunnel crop production is expected to increase to meet the growing demand for locally produced fresh market vegetables. These structures have the potential to offer many production benefits; however, managing soil quality in these structures is challenging and work in the area is limited. In this 3-year study, we compared the impacts of organic and inorganic fertility amendments on soil quality, nutrient availability, and the productivity of chard (Beta vulgaris L.) and sweet peppers (Capsicum annuum L.) produced in high tunnel and open field systems. Fertility amendments included a green manure treatment [hairy vetch (Vicia villosa Roth) and dehydrated alfalfa meal], partially composted and pelletized chicken litter, urea, and an unfertilized control. Chard was grown in 2011, and peppers were grown in 2012 and 2013. Soil nutrients, microbial activity, active carbon, pH, electrical conductivity (EC), total soil organic matter, and yield were quantified. Chard yield was lower in the high tunnel compared with the open field in 2011, but pepper yield was greater in the high tunnel in 2012 and 2013. Productivity of chard was lower in the green manure compared with urea in 2011 across high tunnel and open field production systems, but no difference in pepper yield was observed between plants receiving fertility inputs in either 2012 or 2013. Repeated application of green manure and chicken litter resulted in soils with increased microbial activity and active carbon, but the green manure was the only treatment successful at accruing carbon in the high tunnel over time. High tunnel production resulted in greater EC compared with the open field, but levels were not considered inhibitory for chard or peppers. High tunnels can increase vegetable crop productivity in the midwest United States, and organic fertility amendments can improve soil quality as measured by soil microbial activity and active carbon in high tunnel and open field production systems.

Fresh produce, viewed as an essential part of a healthy life style is usually consumed in the form of raw or minimally processed fruits and vegetables, and is a potentially important source of food-borne human pathogenic bacteria and viruses. These are passed on to the consumer since the bacteria can form biofilms or otherwise populate plant tissues, thereby using plants as vectors to infect animal hosts. The life cycle of the bacteria in plants differs from those in animals or humans and results in altered physiochemical and biological properties (e.g., physiology, immunity, native microflora, physical barriers, mobility, and temperature). Mechanisms by which healthy plants may become contaminated by microorganisms, develop biofilms, and then pass on their pathogenic burden to people are explored in the context of hollow fiber microfiltration by which plant-derived microorganisms may be recovered and rapidly concentrated to facilitate study of their properties. Enzymes, when added to macerated plant tissues, hydrolyze or alter macromolecules that would otherwise foul hollow-fiber microfiltration membranes. Hence, microfiltration may be used to quickly increase the concentration of microorganisms to detectable levels. This review discusses microbial colonization of vegetables, formation and properties of biofilms, and how hollow fiber microfiltration may be used to concentrate microbial targets to detectable levels. The use of added enzymes helps to disintegrate biofilms and minimize hollow fiber membrane fouling, thereby providing a new tool for more time effectively elucidating mechanisms by which biofilms develop and plant tissue becomes contaminated with human pathogens. Biotechnol. Bioeng. 2017;114: 1403-1418. © 2017 Wiley Periodicals, Inc.