Daniel I. Leskovar

Development of a codominant CAPS marker for allelic selection between canary yellow and red watermelon based on SNP in lycopene β-cyclase (LCYB) gene

Flesh color of watermelon is an agronomically important trait that is predominantly determined by a network of the carotenoid biosynthetic pathway, which also contributes to the nutritional value of the fruit through the health-promoting function of carotenoids. We have identified a key gene, lycopene β-cyclase (LCYB) that may determine canary yellow and red flesh color of watermelon and developed a zero-distance molecular marker that identifies a critical single nucleotide polymorphism (SNP) that distinguishes different alleles of the LCYB gene. Analysis of the flesh color inheritance in segregating populations indicated that a single gene determines the color difference between canary yellow and red flesh in watermelon. The sequence comparison of full-length cDNA of LCYB, which was isolated using degenerate PCR and RACE, identified three SNPs in the coding region of LCYB between canary yellow and red. These SNPs showed perfect co-segregation with flesh color phenotypes. One of the SNPs introduces an amino acid replacement of evolutionarily conserved Phe226 to Val, which may impair the catalytic function of LCYB. This SNP was used to develop a cleaved amplified polymorphic sequence (CAPS) marker, which perfectly cosegregated with flesh color phenotype. Our results strongly suggest that LCYB may be the genetic determinant for canary yellow or red flesh color and our CAPS marker will allow breeders to economically distinguish between canary yellow and red watermelon fruit color at the seedling stage.

Effect of nursery regimes and establishment irrigation on root development of Lotus creticus seedlings following transplanting

Summary The influence of irrigation and temperature regimes in the nursery on the dynamics of root development after being transplanted with minimum management conditions was investigated in Lotus creticus. In the nursery period (three months), plants were pot-grown in greenhouses, heated and unheated, located on the Southeast Mediterranean coast of Spain. Drip irrigation was used, with three irrigation treatments: T-6, plants watered 6.d a week at the water-holding capacity; T-3, plants watered 3.d a week; and T-2, plants watered twice a week. The total water applied over the whole nursery period was (in litres per plant): T-6, 7; T-3, 3.5; and T-2, 2.3. After the nursery period, plants were transplanted in a growth chamber into transparent containers (round acrylic tubes 8.cm diameter and 100.cm tall) and just one establishment irrigation was applied. Three treatments were applied, using three different amounts of water in the establishment irrigation: 10, 30 and 60.mm. The containers were kept in the growth chamber for one month, until the end of experiment. The harsher the conditions after transplanting (less water in the establishment irrigation) the more evident was the positive effect of hardening in the nursery. The regime involving least water and lowest temperature in the nursery period produced plants best adapted to stress at transplanting: a greater root length:shoot length ratio, higher percentage of brown roots and lower fresh weight:length ratio in shoots. All the plants survived transplanting. The most stressed plants in the nursery (least water and no heating) showed greater and more rapid root growth than the less stressed plants, especially when soil moisture was low.

Root growth and root-shoot interaction in transplants and direct seeded pepper plants.

Abstract The objectives of this work were to assess and describe pepper ( Capsicum annuum L.) root distribution in the soil profile and to relate root to shoot growth. Plants were field-grown from transplants, produced with either top or bottom irrigation, or from direct seeding using either primed or raw seeds. Dry weights were determined every 2 weeks beginning at 30 days post-planting. Root growth was measured at two soil levels, 0–10 cm and 10–20 cm and in three 10-cm wide positions within each level. Transplants and direct seeded plants had 150 and 100%, respectively, greater root mass in the upper than in the lower soil level. Root growth increase over 56 days was linear for transplants while in direct seeded plants root growth had a lag phase of approximately 14 days, with a sharp increase thereafter. At the end of the growth period, fruit, stem, leaf and root dry weight accounted for 66, 11, 19 and 4% for transplants and 39, 16, 33 and 12% for direct seeded plants. The coordination of growth between root and shoot changed after fruit set only in transplants, which indicates that transplants exhibited a greater fruit sink demand and fruit production than seeded plants.

Deficit irrigation impact on lycopene, soluble solids, firmness and yield of diploid and triploid watermelon in three distinct environments

Summary Water conservation practices are critical for production and quality of watermelon [Citrullus lanatus (Thunb.) Matsum & Nakai] in southern regions of the USA. The objective of this experiment was to determine the effects of deficit irrigation and environment on lycopene content, total soluble solids, firmness, and yield of diploid and triploid watermelon. Irrigation rates were 1.0 evapotranspiration (ET), 0.75 ET, and 0.5 ET, which were calculated based on climatic parameters applied to the Penman-Monteith equation. Diploid cultivars were ‘Summer Flavor 710’ and ‘Summer Flavor 800’, and triploid cultivars were ‘Summer Sweet 5244’ and ‘Super Seedless 7187’. To investigate if there was a consistent response in cultivars across diverse environments, three studies were conducted in remote Texas locations: Uvalde in the Wintergarden, Weslaco in the Rio Grande Valley, and Lubbock in the High Plains. To isolate the environmental effects due to weather and soil type, all experiments used similar cultural strategies (plant spacing, subsurface drip irrigation, black plastic mulch, and containerized transplants), except for transplanting and harvesting dates. Deficit irrigation reduced total marketable yield by 36% at Uvalde, 30% at Lubbock, and 15% in Weslaco, increasing the yield of small fruits (<5 kg). Location and irrigation rates had major influences on yield of diploid and triploid watermelon. Soluble solids content increased with deficit irrigation at 0.5 ET rate in triploids, but not in diploids. Flesh firmness also increased in triploids compared to diploids. Fruit lycopene content increased with maturity (7 and 22 d after ripening) at all irrigation rates and cultivars. This work across three diverse Texas locations confirms that deficit irrigation directly reduced yield, but does not reduce lycopene development and fruit quality of triploid watermelon.

Development of an automated method for Folin-Ciocalteu total phenolic assay in artichoke extracts.

We developed a system to run the Folin-Ciocalteu (F-C) total phenolic assay, in artichoke extract samples, which is fully automatic, consistent, and fast. The system uses 2 high performance liquid chromatography (HPLC) pumps, an autosampler, a column heater, a UV/Vis detector, and a data collection system. To test the system, a pump delivered 10-fold diluted F-C reagent solution at a rate of 0.7 mL/min, and 0.4 g/mL sodium carbonate at a rate of 2.1 mL/min. The autosampler injected 10 μL per 1.2 min, which was mixed with the F-C reagent and heated to 65 °C while it passed through the column heater. The heated reactant was mixed with sodium carbonate and color intensity was measured by the detector at 600 nm. The data collection system recorded the color intensity, and peak area of each sample was calculated as the concentration of the total phenolic content, expressed in μg/mL as either chlorogenic acid or gallic acid. This new method had superb repeatability (0.7% CV) and a high correlation with both the manual method (r(2) = 0.93) and the HPLC method (r(2) = 0.78). Ascorbic acid and quercetin showed variable antioxidant activity, but sugars did not. This method can be efficiently applied to research that needs to test many numbers of antioxidant capacity samples with speed and accuracy.

White rust infection and leaf chlorosis in relation to crop strategies in spinach

Abstract The interaction of spinach ( Spinacia oleracea L.) crop management strategies on white rust caused by Albugo occidentalis G. W. Wils., leaf chlorosis, aphid numbers, root growth and yield were evaluated in 1992. Irrigation levels were low ( I-low ), medium ( I-med ) and high ( I-high ); fungicides were none ( F 0 ), metalaxyl at planting ( F 1 ), and metalaxyl at planting plus experimental CGA 2014 foliar ( F 2 ); and genotypes were ACX 5044 and ARK 88-354. The Gompertz model best described the white rust disease progress. At all irrigation levels, ACX 5044 had a higher rate of disease increase ( r G ) and an earlier disease onset than ARK 88-354. Metalaxyl delayed disease onset and r G in ACX 5044 only at I-low , but not at I-med and I-high . ARK 88-354 was the less sensitive genotype to fungicides. Chlorosis, estimated by spectrophotometry, was higher at I-med and I-high , while ARK 88-354 had less chlorosis than ACX 5044. Root diameter was increased with F 1 compared to F 0 . Lateral and tap root dry weights were higher for ARK 88-354. Yields for ARK 88-354 were significantly higher than ACX 5044. No treatments influenced the number of live green peach aphids [ Myzus persicae (Sulzer)] or aphids parasitized by Pandora neoaphidis (Remaudiere and Hennebert) Humber. Genotypes with partial resistance to white rust, superior leaf color and growth are recommended to use with minimum irrigation for winter plantings.

Ground penetrating radar for underground sensing in agriculture: a review

Abstract Belowground properties strongly affect agricultural productivity. Traditional methods for quantifying belowground properties are destructive, labor-intensive and pointbased. Ground penetrating radar can provide non-invasive, areal, and repeatable underground measurements. This article reviews the application of ground penetrating radar for soil and root measurements and discusses potential approaches to overcome challenges facing ground penetrating radar-based sensing in agriculture, especially for soil physical characteristics and crop root measurements. Though advanced data-analysis has been developed for ground penetrating radar-based sensing of soil moisture and soil clay content in civil engineering and geosciences, it has not been used widely in agricultural research. Also, past studies using ground penetrating radar in root research have been focused mainly on coarse root measurement. Currently, it is difficult to measure individual crop roots directly using ground penetrating radar, but it is possible to sense root cohorts within a soil volume grid as a functional constituent modifying bulk soil dielectric permittivity. Alternatively, ground penetrating radarbased sensing of soil water content, soil nutrition and texture can be utilized to inversely estimate root development by coupling soil water flow modeling with the seasonality of plant root growth patterns. Further benefits of ground penetrating radar applications in agriculture rely on the knowledge, discovery, and integration among differing disciplines adapted to research in agricultural management.

Vegetable Crops: Linking Production, Breeding and Marketing

Vegetable production has been a major and dynamic activity devised by diverse human cultures to sustain their livelihood for centuries. Vegetables, being several times more productive per unit area than cereals, can play a vital role in facing food security and nutrition challenges in the coming decades. However, the predicted climate change and increased demand on limited land and water resources makes water conservation a key component of vegetable production systems. At the same time, there is an increased global demand for healthy and nutritious vegetables. Dramatic improvements have been achieved through breeding for important abiotic stresses and quality traits in many vegetables. Thus, successful emerging small or large commercial farmers now apply integrated strategies from farm to table, including planting, grafting, irrigation, use of modern cultivars and innovative marketing tools. In this chapter we highlight some technological advances in vegetable production, with emphasis on stand establishment and irrigation management for water-limited areas. We discuss the impact of breeding and genetics on the improvement of abiotic stress tolerance and provide evidences on the use of improved germplasm and cultivars to enhance the quality of vegetables. Finally, we discuss the critical role of marketing and consumer trends for vegetable products.

Watermelon lycopene β-cyclase: promoter characterization leads to the development of a PCR marker for allelic selection

In the carotenoid biosynthetic pathway, lycopene β-cyclase (LCYB) catalyzes the cyclization that converts lycopene into β-carotene. Only a single copy of LCYB was identified and was suggested to encode a chromoplast-specific LCYB (CYCB type) in watermelon [Citrullus lanatus (Thunb.), Matsum & Nakai]. Splicing variants in the 5′-untranslated region were identified, but alternative splicing did not provide an explanation of the regulation of carotenoid accumulation in watermelon flesh. A quantitative assay using real time-PCR showed that differential expression was not detected between red- and canary yellow-fleshed watermelon cultivars. LCYB promoter regions were isolated and characterized, and a sequence difference was identified in the promoter region between red and canary yellow LCYB alleles. This polymorphism did not change the expression of LCYB, but does provide a reliable marker for discriminating LCYB alleles for red and canary yellow flesh. To develop a PCR-based marker to distinguish between the two LCYB alleles, we designed primers flanking the polymorphic region. The newly developed marker, designated Clcyb.600, co-segregated perfectly with flesh color phenotypes and single nucleotide polymorphism (SNP) markers developed in our previous study. Moreover, the Clcyb.600 marker offers easier discrimination of LCYB alleles than SNP or cleaved amplified polymorphic sequence markers, as it does not require restriction enzyme digestion for genotyping. Genotyping of LCYB promoter alleles in various commercial cultivars and plant introductions indicated that watermelon cultivars can be classified into two groups, those carrying a red LCYB allele or a canary yellow LCYB allele.

Organic soil amendments influence soil health, yield, and phytochemicals of globe artichoke heads

Abstract The objective of this study was to assess the influence of plant- and animal-based soil amendments on soil nutrient availability, CO2 respiration, yield and phytochemicals of artichoke (Cynara cardunculus cv. 179) heads. Four certified organic fertilisers: fish meal, blood meal, alfalfa meal and chicken manure, were used as experimental treatments. After two years of organic soil amended with the plant-based fertiliser (alfalfa meal), soil respiration and content of organic matter (OM) was higher than that in soil amended with animal-based fertilisers (fish meal, blood meal, and chicken manure), though the difference in OM between alfalfa and chicken manure was not statistically significant. The marketable yield from soil amended with chicken manure was higher than that amended with alfalfa meal and in the first year (2015) yields from both chicken manure and fish meal treatments were higher than that of the alfalfa treatment. Concentrations of phytochemicals in artichoke heads grown in soil amended with alfalfa treatment were higher than in those grown with animal-based fertilisers (for chlorogenic acid the difference was significant only in 2016). Conversely, the cost of the alfalfa meal was higher than that of the animal-based fertilisers. Overall, plant-based fertiliser can be an ideal option for improving soil and head quality of artichokes, but animal-based fertilisers may be an appropriate choice for organic farmers when yield and cost are the main concerns.