Matthew D. Kleinhenz

Application of calcium and nitrogen for mitigating heat stress effects on potatoes

This study was designed to investigate the effect of calcium and nitrogen application during heat stress on leaf calcium concentration, transpiration rate, membrane thermostability, and biomass accumulation and partitioning. Micropropagated Russet Burbank potato (Solanum tuberosum L). plants were transplanted into 20 L pots containing 1:1 (v/v) soil: perlite and exposed to 30/20C (D/N) temperatures for four weeks (weeks 9–12 after transplanting) in a controlled-environment growth room. The maximum temperature was maintained for 6 hr during the middle of the 14 hr photoperiod. The nutrition treatments were N before stress (NBS), N during stress (NDS) and Ca and N during stress (Ca+NDS). Calcium was supplied as Ca(NO3)2. All treatments received the same total amount of nitrogen. Native soil Ca level without amendment (550 mg Ca/kg soil) was sufficient for potato plant growth under normal temperatures.Plants given Ca and N during heat stress had the highest leaf Ca concentration and transpiration rate during and 2 weeks after conclusion of the heat stress period. When measured after 4 weeks of heat stress, area and fresh and dry weight of the most recently mature leaf was significantly greater in NDS and Ca+NDS plants compared to NBS plants. Cellular membrane thermostability (measured as ion leakage from heat-treated leaf disks) was not affected by any treatment prior to heat stress. However, leaf tissue from Ca+NDS plants exhibited significantly higher membrane thermostability compared to NBS plants after 2 and 4 weeks of heat stress. At harvest, NDS and Ca+NDS plants had significantly higher leaf/stem (fresh weight ratio) values compared to NBS plants. Also, Ca+NDS plants had significantly greater total tuber and biomass values than NBS and NDS plants. Results of this study suggest that some detrimental effects of heat stress on plant growth and stomatal function may be alleviated by Ca and N application during heat stress. The data also suggest that mitigation of heat stress by Ca and N application during heat stress may maintain plant productivity when optimum growing temperatures are restored.CompendioEl presente estudio fue diseñado para investigar el efecto de la aplicación de calcio y nitrógeno en la concentratión de calcio en las hojas, tasa de transpiratión, termo-estabilidad de membrana, y acumulación y distributión de biomasa durante estrés producido por altas temperaturas. Plantas de papa de la variedad Russet Burbank (Solanum tuberosum L.) fueron micropropagadas y luego transplantadas en macetas de 1 litro de capacidad conteniendo suelo y perlita (1:1 volumen). Las plantas fueron expuestas a tempeaturas de 30/20C (D/N) durante 4 semanas (9–12 semanas después de haber sido transplantadas) en una cámara de crecimiento con todos los factures medioambientales controlados. La temperatura máaxima fue mantenida por 6 horas a la mitad del fotoperíodo de 14 horas. Los tratamientos fueron nitrógeno antes del estrés (NBS), durante el estrés (NDS) y calcio y nitrogeno durante el estrés (Ca+NDS). El calcio fue aplicado en forma de nitrato de calcio (Ca(NO3)2). Todos los tratamientos tuvieron la misma cantidad total de nitrógeno. Los niveles de calcio del suelo sin alteratión (550 mg/Kg suelo) fueron suficientes para el crecimiento de las plantas de papa bajo temperaturas normales.Las plantas tratadas con calcio y nitrógeno tuvieron la concentratión más alta de calcio en las hojas así como también la tasa más alta de transpiratión durante y hasta dos semanas después del período de estrés causado por altas temperaturas. Después de 4 semanas del período de estrés, el área total así como los pesos seco y fresco fueron medidos en hojas de reciente maduración. Los resultados indicaron que éstos fueron significativamente mayores en plantas NDS y Ca+NDS que en plantas NBS. La termoestabilidad de la membrana celular (cuya medida es basada en la pérdida de iones de discos de hojas sometidas a altas temperaturas) no fue afectada por ningún tratamiento antes del estrés. Sin embargo, el tejido foliar de las plantas Ca+NDS exhibió una mayor termo-estabilidad de membrana comparada con la de las plantas NBS después de 2 y 4 semanas de estrés causado por altas temperaturas. En la cosecha, las plantas NDS y Ca+NDS tuvieron valores de hoja/tallo (tasa de peso fresco) significativamente mayores comparados con los de las plantas NBS. Asímismo, las plantas Ca+NDS tuvieron valores de biomasa y número de tubérculos significativamente mayores que los de las plantas NBS y NDS. Los resultados del présente estudio sugieren que algunos efectos negatives del estrés causado por altas temperaturas en el crecimiento de la planta y en la función de los estomas pueden ser aliviados mediante la aplicación de calcio y nitrógeno durante el estrés. Los datos también sugieren que dicho alivio puede mantener la productividad de la planta cuando las temperaturas óptimas para el crecimiento son restauradas.

Root-zone temperature and nitrogen affect the yield and secondary metabolite concentration of fall- and spring-grown, high-density leaf lettuce.

BACKGROUND Understanding the effects of temperature and nitrogen levels on key variables, particularly under field conditions during cool seasons of temperate climates, is important. Here, we document the impact of root-zone heating and nitrogen (N) fertility on the accumulation and composition of fall- and spring-grown lettuce biomass. A novel, scalable field system was employed. RESULTS Direct-seeded plots containing a uniform, semi-solid, and nearly stable rooting medium were established outdoors in 2009 and 2010; each contained one of eight combinations of root-zone heating (-/+) and N fertility (0, 72, 144, and 576 mg day(-1)). Root-zone heating increased but withholding N decreased biomass accumulation in both years. Low N supplies were also associated with greater anthocyanin and total antioxidant power but lower N and phosphorus levels. Tissue chlorophyll a and vitamin C levels tracked root-zone temperature and N fertility more closely in 2009 and 2010, respectively. CONCLUSIONS Experimentally imposed root-zone temperature and N levels influenced the amount and properties of fall- and spring-grown lettuce tissue. Ambient conditions, however, dictated which of these factors exerted the greatest effect on the variables measured. Collectively, the results point to the potential for gains in system sustainability and productivity, including with respect to supplying human nutritional units.

Field Management Effects on Damping-Off and Early Season Vigor of Crops in a Transitional Organic Cropping System

Transitioning farmland to certified organic vegetable production can take many paths, each varying in their costs and benefits. Here, the effects of four organic transition strategies (i.e., tilled fallowing, mixed-species hay, low-intensity vegetables, and intensive vegetable production under high tunnels), each with and without annual compost applications for 3 years prior to assessment, were characterized. Although transition cropping strategies differed in soil chemistry (P < 0.05), the magnitude of the changes typically were marginal and pairwise comparisons were rarely significant. In contrast, the compost amendment had a much greater impact on soil chemistry regardless of cropping strategy. For example, percent C and total P increased by 2- to 5-fold and K increased from 6- to 12-fold. Under controlled conditions, damping-off of both edamame soybean (cv. Sayamusume) and tomato (cv. Tiny Tim) was reduced from 2 to 30% in soils from the mixed-hay transition. In the field, damping-off of both crops was also significantly lower in plots previously cropped to hay (P < 0.05). Although not always significant (P < 0.05), this pattern of suppression was observed in all four of the soybean experiments and three of the four tomato experiments independent of compost application. The compost amendments alone did not consistently suppress damping-off. However, plant height, fresh weight, and leaf area index of the surviving seedlings of both crops were greater in the compost-amended soils regardless of the transitional cropping treatment used (P < 0.05 for most comparisons). These data indicate that mixed-hay cropping during the transition periods can enhance soil suppressiveness to damping-off. In addition, although compost amendments applied during transition can improve crop vigor by significantly enhancing soil fertility, their effects on soilborne diseases are not yet predictable when transitioning to certified organic production.

Soil health as a predictor of lettuce productivity and quality: A case study of urban vacant lots

Urban agriculture offers a framework for local self-reliance and resilience in cities. However, there is a concern over the capacity of urban soil to provide sustainable and safe food production. We tested the effectiveness of several soil health indicators to predict food crop productivity and quality in vacant lots in a disadvantaged neighborhood in the city of Cleveland, Ohio. We defined soil health as a state of composite well being in terms of biological, chemical, and physical properties of the soil as they relate to crop productivity. Twelve city-owned vacant lots, three close to each of the four city schools, were selected for soil properties and plant growth analyses. Soil samples were analyzed for pH, moisture content (θv), soil texture, soil organic matter (SOM), active carbon (AC), ammonium (NH4-N), nitrate (NO3-N), microbial biomass N (MBN), and nematode community parameters including total (TNN), bacteria-feeding (BFN), fungal-feeding (FFN), and plant-parasitic (PPN) nematodes, number of nematode genera (NNG), and nematode food web enrichment index (EI) and structure index (SI). Lettuce was planted in the selected vacant lots and its growth was documented through measures of dry biomass, numbers of leaves/plant, and complementary subjective appearance scores related to physiological status. All measured parameters varied considerably among vacant lots except soil pH. Principal components analysis revealed that among the primary soil physical, chemical, and biological parameters, soil clay, NO3-N, MBN, SOM, AC, TNN, BFN, FFN, and PPN contributed most to the variance of the entire dataset. There were also several positive correlations among these key soil health predictor variables: AC was positively correlated with clay, SOM, MBN, TNN, BFN, FFN and PPN, and TNN was positively correlated with AC, SOM, MBN, BFN, FFN and PPN. Of the identified primary soil health indicators, only clay, SOM, and MBN positively correlated with lettuce dry biomass, which was also positively correlated with a secondary soil health indicator, the nematode food web EI. Lettuce leaf necrosis was negatively correlated with clay, AC, SOM, MBN, TNN, FFN, and PPN, and the proportion of withered leaves was negatively correlated only with SOM. It is concluded that AC, PPN, TNN, SOM, MBN, clay, and nematode food web EI can serve as important soil health indicators that have potential for predicting crop productivity and quality in urban soils. It is also concluded that lettuce can serve as an important indicator of soil health with respect to crop productivity and quality in vacant lots.

Impact of phytopathogen infection and extreme weather stress on internalization of Salmonella Typhimurium in lettuce

Internalization of human pathogens, common in many types of fresh produce, is a threat to human health since the internalized pathogens cannot be fully inactivated/removed by washing with water or sanitizers. Given that pathogen internalization can be affected by many environmental factors, this study was conducted to investigate the influence of two types of plant stress on the internalization of Salmonella Typhimurium in iceberg lettuce during pre-harvest. The stresses were: abiotic (water stress induced by extreme weather events) and biotic (phytopathogen infection by lettuce mosaic virus [LMV]). Lettuce with and without LMV infection were purposefully contaminated with green fluorescence protein-labeled S. Typhimurium on the leaf surfaces. Lettuce was also subjected to water stress conditions (drought and storm) which were simulated by irrigating with different amounts of water. The internalized S. Typhimurium in the different parts of the lettuce were quantified by plate count and real-time quantitative PCR and confirmed with a laser scanning confocal microscope. Salmonella internalization occurred under the conditions outlined above; however internalization levels were not significantly affected by water stress alone. In contrast, the extent of culturable S. Typhimurium internalized in the leafy part of the lettuce decreased when infected with LMV under water stress conditions and contaminated with high levels of S. Typhimurium. On the other hand, LMV-infected lettuce showed a significant increase in the levels of culturable bacteria in the roots. In conclusion, internalization was observed under all experimental conditions when the lettuce surface was contaminated with S. Typhimurium. However, the extent of internalization was only affected by water stress when lettuce was infected with LMV.

Use of stomatal index as a marker to screen backcross populations of two wild potato species segregating for freezing tolerance

The purpose of this study was to investigate differences in stomatal index among backcross progeny ofSolanum commersonii (freezing tolerant) andSolanum cardiophyllum (freezing sensitive) to assess the feasibility of using this trait as a marker for screeningSolanum populations for freezing tolerance. Measurements were taken on three terminal fully-expanded leaflets per genotype by completing microscopic examination of epidermal impressions made in partially dissolved cellophane tape. Freezing tolerance was estimated in parallel studies on the same plant material.Values of SI were significantly greater (Fisher T-test, 0.05) for theS. cmm. group (parent + backcross progeny) compared with theS. cph. group. Stomatal index of the F1 was significantly greater than SI ofS. cph. parents and similar toS. cmm. parents. Values of SI for both backcross progenies were greater than parental values. Non-acclimated relative freezing tolerance values were in the following order:S. cmm. parents >S. cmm. backcrosses > F1 >S. cph. back-crosses >S. cph. parents. Stomatal index values followed a similar pattern with the exceptionS. cmm. backcross >S. cmm. parents. These data suggest: a) increased SI is inherited as a dominant trait, b) SI may be a useful screening marker in breeding programs interested in improving freezing tolerance.CompendioEl propósito de este estudio fue investigar las diferencias de los índices de estomas entre la progenie de retrocruzamiento deSolanum commersonii (tolerante a las heladas) ySolanum cardiophyllum (sensible a las heladas) para determinar la factibilidad de utilizar este atributo como un marcador para evaluar y seleccionar poblaciones deSolanum para tolerancia a las heladas. Se efectuaron mediciones sobre tres foliolos terminales, completamente expandidos, por genotipo, efectuando exámenes microscópicos de impresiones epidérmicas hechas en cinta de celofán parcialmente disuelta. La tolerancia a las heladas fue estimada en estudios paralelos sobre el mismo material vegetal.Los valores de IE (Indice de Estomas) fueron significativamente mayores (prueba T Fisher, 0.05) para el grupo deS. commersonii (progenitores + progenie de retrocruzamiento) en comparación con el grupo deS. cardiophyllum. El IE de la F1, fue significativamente mayor que el de los progenitores deS. cardiophyllum y similar al de los progenitores de S.commersonii. Los valores de IE para ambas progenies de retrocruzamiento fueron mayores que los valores para los progenitores. Los valores no aclimatados de tolerancia relativa a las heladas guardaron el siguiente orden: progenitoresS. commersonii > retrocruzamientos deS. commersonii > F1> retrocruzamientos de S.cardiophyllum > progenitoresS. cardiophyllum. Los valores de IE siguieron un esquema similar con la excepción de retrocruzamientos deS. commersonii > progenitoresS. commersonii. Estos datos sugieren: a) el incremento en el IE es heredado como una característica dominante, b) el IE puede ser un marcador muy útil de evaluación y selección en los programas de mejoramiento interesados en mejorar le tolerancia a las heladas.

Growth and yield of potato (Solanum tuberosum L.) cultivars Atlantic and Monona as influenced by seed type and size

Growth and yield of potato plants grown from several weight classes of whole “B” seed, unsorted “B” seed, and 56 g cut seed pieces were compared in Ohio in 1988 and 1989. Whole “B” seed classes were 8 g ranges with means of 35 g, 43 g, 51 g, and 58 g. Unsorted “B” seed was used as an experimental control. Treatment responses were inconsistent. Few significant differences were evident at bloom in leaf area, number of main stems, and total plant dry weight (without tubers) per hill. However, the number of tubers greater than 1 cm in diameter per hill at bloom was less for cut seed as compared with several whole seed treatments. Percent stand at four weeks was also less for cut seed compared with 51 g and 58 g whole tuber treatments. Significant differences in total and U.S. No. 1 yields were absent despite differences in several plant growth variables early in the 1988 and 1989 growing seasons.CompendioSe comparó el crecimiento y el ren dimiento de plantas de papa procedentes de semilla entera “B” de variados pesos, semilla “B” no clasificada, y porciones de 56 g de semilla cortada en Ohio, en 1988 y 1989. Las semillas “B” enteras tuvieron 8 g de diferencia con promedios de 35 g, 43 g, 51 g y 58 g. La semilla “B” no clasificada por peso fue utilizada como control experimental. Las respuestas de los tratamientos fueron inconsistentes. Algunas diferencias sisgnificativas fueron evidentes al momento de la floración, en área de hoja, número de tallos principales y peso seco total de planta (sin tubérculos) por mata. Sin embargo, el número de tubérculos de más de 1 cm de diámetro por mata, el momento de la floración, fue menor para los tubérculos cortados en comparación con varios tratamientos de semilla entera. El porcentaje de plantas establecidas a las cuatro semanas también fue menor para la semilla cortada en comparación con los tratamientos con tubérculos enteros de 51 g y 58 g. No se encontraron diferencias significativas en los rendimientos totales y de U.S. No. 1 a pesar de las diferencias entre diversas variables del crecimiento de las plantas en las temporadas de cultivo de 1988 y de 1989.

Nutritional Yield: A Proposed Index for Fresh Food Improvement Illustrated with Leafy Vegetable Data

Consumer interest in food products, including fresh vegetables, with health promoting properties is rising. In fresh vegetables, these properties include vitamins, minerals, dietary fiber, and secondary compounds, which collectively impart a large portion of the dietary, nutritional or health value associated with vegetable intake. Many, including farmers, aim to increase the health-promoting properties of fresh vegetables on the whole but they face at least three obstacles. First, describing crop composition in terms of its nutrition-based impact on human health is complex and there are few, if any, accepted processes and associated metrics for assessing and managing vegetable composition on-farm, at the origin of supply. Second, data suggest that primary and secondary metabolism can be ‘in conflict’ when establishing the abundance versus composition of a crop. Third, fresh vegetable farmers are rarely compensated for the phytochemical composition of their product. The development and implementation of a fresh vegetable ‘nutritional yield’ index could be instrumental in overcoming these obstacles. Nutritional yield is a function of crop biomass and tissue levels of health-related metabolites, including bioavailable antioxidant potential. Data from a multi-factor study of leaf lettuce primary and secondary metabolism and the literature suggest that antioxidant yield is sensitive to genetic and environmental production factors, and that changes in crop production and valuation will be required for fresh vegetable production systems to become more focused and purposeful instruments of public health.

Important Cabbage Head Traits and Their Relationships at Five Points in Development

We set out to document events and relationships among key traits throughout cabbage head formation, particularly in early stages, in order to help develop and implement efficient strategies to increase crop yield and quality. Head traits used as indicators of horticultural maturity and crop quality were documented at five stages of development in 3 commercial fresh market/slaw and processing cabbage cultivars grown in 2001 and 2002 at The Ohio State University, Ohio Agricultural and Development Center in Wooster, Ohio. Seedlings containing 2–4 true leaves were planted in June of both years. Trait measurement began 35 days prior to the estimated market maturity date for each cultivar and continued weekly for five weeks. Harvest timing affected all head traits evaluated. Head weight, diameter, volume, and density and core volume generally increased with harvest date, while the ratio of head polar to equatorial diameter and the percent of head volume occupied by the core decreased. A strong curvilinear relationship between head mean diameter and head weight was found. Developmental changes in head density, in contrast to weight and size, were found to be largely independent of thermal time. Information gained in this study adds to our understanding of cabbage crop development. It also strongly suggests that accurate assessments of developmental stage during the scheduling of harvest are required to maximize head quality. The results also indicate that head growth and maturation should be viewed as separate and distinct concepts in discussions of head development.

Insect management and herbicide tolerance in near-isogenic sister lines of transgenic and non-transgenic sweet corn.

Abstract Pest management systems were evaluated in three near-isogenic lines of transgenic and non-transgenic sweet corn. The genetic transformation was reputed to confer resistance to corn earworm ( Helicoverpa zea ) and European corn borer ( Ostrinia nubilalis ), and increase tolerance to the herbicide glufosinate. Plots were planted with either a transgenic line or a non-transgenic sister line. Transgenic and non-transgenic varieties were treated with a herbicide; either glufosinate or bentazon, respectively, applied post-emergence. Ears of the non-transgenic varieties were protected by spraying insecticides every 3–4 days. Transgenic varieties were not sprayed. Glufosinate caused temporary chlorosis (5% or less) and stunting (6% or less) of transgenic sweet corn in one experiment. Bentazon did not injure non-transgenic varieties. Corn earworm and European corn borer control in transgenic sweet corn was superior to that achieved in non-transgenic varieties sprayed with insecticides. Damaged ears of transgenic varieties ranged from 0% to 6% and most damage was restricted to the tip of the silk end. A few small, moribund larvae were recovered. In contrast, 40% of non-transgenic varieties, on average, had damaged ears, despite regular spraying of insecticides. Ears of non-transgenic varieties were damaged more severely and many late-instar larvae were recovered.