australian journal of crop science   AJCS

Emergence and early development of tomato seedlings cv. santa clara in alternative substrates

A quality substrate is essential to ensure the proper conditions for the emergence and early development of seedlings. The aim of the present study was to evaluate different proportions of termite mound substrate in the emergence and early development of tomato seedlings. The experiment was performed in a completely randomized design, with five treatments constituted by the substrates, with four replications: T1: Washed sand (100%); T2: Washed sand (75%) + termite mound material (25%); T3: Washed sand (50%) + termite mound material (50%); T4: Washed sand (25%) + termite mound material (75%) and T5: termite mound material (100%). The Santa Clara cultivar (tomato) of Topseed® was used. The seeds were distributed in gerbox boxes. Emergence, emergence speed index, shoot height, number of leaves, shoot dry mass, root length and root dry mass of tomato seedlings development were evaluated after 25 days. The use of termite mound substrates is a viable alternative to the emergence and development of tomato seedlings. In general, the substrate of termite mound material (100%) was the most promising in the increment of all variables.

Breeding and characterization of Hibiscus hybrids in the Philippines was conducted to improve the local varieties for them to have unique flower colors and forms by introducing genes from foreign varieties. The Hibiscus hybrids are important ornamental genetic materials being used to honor outstanding Filipina achievers. The study aimed to characterize 5 new selected hybrids, test their pollen fertility and evaluate their graft compatibility with 2 known rootstock varieties. The important characteristics of the 5 selected hybrids are as follows: The flower of hybrid H. rosa-sinensis ‘Accession 20’ x H. rosa-sinensis ‘Gelia Castillo’ is solferino purple or red purple (RHCC 65B) with a ruby red (RHCC 59A) eye surrounded by grayish violet (RHCC N77C) halo, while the bloom of hybrid H. rosa-sinensis ‘Tandang Sora’ x H. rosa-sinensis ‘Connie S. Angeles’ is tuscan yellow (RHCC 162C) with ruby red (RHCC 59A) eye surrounded by reddish white (RHCC N1555A) halo. The petal of hybrid H. rosa-sinensis ‘Tarantella’ x H. rosa-sinensis ‘Golden Dubloom’ is rose red (RHCC 58B) surrounded with yellow orange (RHCC 20A) edging, while the eye is dark red rose (RHCC 61B). The flower of hybrid H. rosa-sinensis ‘Perla Santos-Ocampo’ x H. rosa-sinensis ‘Loren B. Legarda’, is spanish orange (RHCC 26B) with lemon yellow (RHCC 13B) eye and dark orange markings (RHCC N 25B) radiating from the eye going to the petals. In addition, the petal color of hybrid H. rosa-sinensis ‘Loren B. Legarda’ x H. rosa-sinensis ‘Tarantella’ is a combination of primrose yellow (RHCC4B) and neyron rose (RHCC 58C). Correlation analysis was conducted for the different floral and leaf traits such as corolla length, width, bloom length, receptacle diameter, style length, calyx lobe width, sepal length, style length, ovary width, petiole length, leaf length and width. Very high positive correlation (r = 0.9428) was detected on corolla length and bloom length. High correlation was observed on bloom length and corolla width (r=0.8663), corolla width and corolla length (r= 0.8727), style length and bloom length(r=0.7136), receptacle diameter and calyx lobe width (r=0.7861). Pollen viability of the 5 different Hibiscus hybrids when used as male parents in hybridization, as shown by potassium iodide structural staining was 61.62 to 70.0%, but significant differences on pollen viability were not detected among the different hybrids. However, significant differences between different sucrose concentrations added to the Brewbaker and Kwack’s (BK) medium for pollen germination test of H. rosa-sinensis ‘Accession 20’ x H. rosa-sinensis ‘Gelia Castillo’ were detected. Ten percent (v/v) sucrose as additive to BK medium was the optimum concentration for pollen germination at 70%. Good pollen germination, a prerequisite for pollen tube growth in the stigma going to the ovary, hence effective fertilization and development of the zygote and growth of the embryo in the hybrid seed, is necessary for successful hybridization. Furthermore, evaluation of the graft compatibility of the 5 Hibiscus hybrids to known rootstock varieties was conducted as a prerequisite for efficient asexual propagation. Significant difference (p ≤ 0.05) was detected between rootstock varieties H. rosa-sinensis ‘Reddy or Not’ and H. rosa-sinensis ‘Wilcox’ when side-grafted with the hybrid H. rosa-sinensis ‘Accession 20’ x H. rosa-sinensis ‘Gelia Castillo’. Rootstock variety H. rosa-sinensis ‘Wilcox’ promoted better grafting success by 65% when used for side-grafting H. rosa-sinensis ‘Accession 20’ x H. rosa-sinensis ‘Gelia Castillo’ compared to rootstock variety H. rosa-sinensis H. rosa-sinensis ‘Reddy or Not’. However, no significant difference in the grafting success was detected between H. rosa-sinensis ‘Wilcox’ and H. rosa-sinensis ‘Reddy or Not’ when side-grafted with the other Hibiscus hybrids. Overall, it is recommended that the 5 Hibiscus hybrids be used as potted and landscaping materials, and as parents for hybridization with other varieties, while the fertile pollen could be utilized for cross-pollination with other varieties to produce another set of Hibiscus hybrids.

Pages 1508-1519 | Read More| doi: 10.21475/ajcs.17.11.12.pne523

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Changes in the oxidative metabolism of cassava (Manihot esculenta Crantz) roots associated with cultivation managements

It is believed that sweet cassava root age and pre-harvest managements can modulate the oxidative metabolism and provide a longer shelf life. Moreover, the evaluation of enzymes envolved in oxidative protection regardingthe phenolic metabolism can be an additional approach to understand how the cultivation affects the post-harvest physiological deterioration tolerance in sweet cassava roots. Thus, the aim of this study was to evaluate the oxidative enzymatic protection associated to oxidation mediate by PPO and POD, in response to population density and harvest time of sweet cassava roots, cv. "Mossoró". The roots were cultivated in field conditions in the Brazilian Semiarid, under irrigation. The experimental design was a randomized complete block with three replications. Treatments corresponded to four harvest times (240, 300, 360, 420 days after planting - DAP) and four population densities (10,000, 12,500, 15,000 and 17,500 plants ha-1). Sweet cassava roots were sampled and the total soluble phenol content as well as soluble protein content were measured. Also, polyphenol oxidase (PPO), peroxidase (POD), superoxide dismutase (SOD), catalase (CAT) activity was evaluated. The roots showed higher total soluble phenol content at 300 and 360 DAP and higher protein content at 240, 300 and 360 DAP, for all densities avaluated. Planting densities extremes, of 10,000 and 17,500 plants ha-1, resulted in higher levels of phenolics compounds and SOD activity. However, did not promote difference in the levels of soluble proteins. There was a significant reduction at PPO, SOD and CAT activity with late harvest, which did not occur for POD activity. Therefore, younger roots have higher oxidative enzymatic protection when compared to older roots in Semiarid conditions.

This study evaluated the effect of the plant growth regulator trinexapac-ethyl on chemical composition and physiological quality of wheat seeds produced under fertilization for high yield potential. The experiment was performed under completely randomized design with five treatments (0; 200; 400; 600; 800 mL ha-1 of the commercial product Moddus®) and four repetitions. The plant growth regulator was applied at elongation via foliar spraying. Seeds were harvested at the end of crop cycle. Variables evaluated were 1000 seeds weight, germination and first count of germination, speed of germination index, seedling dry matter, electrical conductivity, accelerated ageing and the contents of total soluble sugars, starch, amino acids and proteins. The first count of germination increased until the higher dose. Electrical conductivity after three hours of imbibition reduced at the doses of 600 mL ha-1 and 800 mL ha-1, indicating greater seed physiological quality. Starch showed a trend of increase until the dose of 448 mL ha-1; amino acids until the dose of 243 mL ha-1 and protein until the dose of 417 mL ha-1. The content of total soluble sugars decreased with the increasing dose of the plant growth regulator. Therefore, wheat seeds produced from plants in which trinexapac-ethyl is applied present higher vigor and greater contents of starch, protein and amino acids, but lower content of total soluble sugars. Our results demonstrate that trinexapac-ethyl can be used for wheat management in seed production fields in the recommended dose (400 mL ha-1) with benefits in seed quality and composition.

Pages 1527-1533 | Read More| doi: 10.21475/ajcs.17.11.12.pne565

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Federal University of Viçosa, Department of Plant Science, Brazil

The yellow passion fruit is the most commonly cultivated species of the genus Passiflora in commercial plantations in Brazil. Obtaining accurate and easy to perform measurements for determination of leaf area in passion fruit is crucial to understand the interaction between the plant and the environment. The objective of this study was to develop reliable mathematical equations to directly estimate leaf area in passion fruit using linear measurements. Passion fruit leaves may exhibit varying morphology across phenological stages, with lanceolate, bilobed or trilobed leaves. For each morphological pattern, 100 leaves without defects were collected. The real leaf area was measured with a LI-COR 3100 area meter and regression equations were estimated for real leaf area and measurements of length, width, and their corresponding products, using a millimeter ruler. The results showed that determination of leaf area can be easily and accurately performed for passion fruit leaves of varying morphology, using the product of the linear measurements of length and width. The linear equations chosen for determining leaf area through the product of width and length were 0.25 + 0.64x (lanceolate), -4.82 + 0.69x (bilobed) and -0.81 + 0.54x (trilobed).

Pages 1534-1538 | Read More| doi: 10.21475/ajcs.17.11.12.pne662

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Influence of water supply and fluctuations on yield and quality of lemon balm (Melissa officinalis L.)

The response of lemon balm (Melissa officinalis) on drought stress was investigated in a pot experiment in 2015-16. In treatment S1, plants grew in 40% saturation of soil water capacity (SWC) for six weeks. In treatment S2, the same level of water supply was used for three weeks, while the control plants received irrigation up to 70% SWC throughout the experimental period. In the second year, after the stress period, a 3 week re-hydration phase was also carried out. Growth, morphology, biomass, active components and antioxidant capacity of the plants were measured. Six weeks growth at reduced soil water content (40% soil water capacity) resulted in a significant decrease of all morphological features of lemon balm as well as the fresh mass of shoots, as compared to the control (70% SWC). The effect of the shorter drought treatment (3 weeks) was less characteristic. After the three week recovery period no significant difference concerning number of branches, leaf length and fresh shoot mass was detectable among the plants. Thus, the retarding effect of even the 6 week drought stress (S1) was reversible in lemon balm. The changes in active components (volatile compounds, phenolics, rosmarinic acid) and antioxidant capacity did not show meaningful changes due to the treatments. After a three-week re-hydration period a significant increase was found in each parameter. It was established that a six week period of water shortage (water content of 40% SWC) could threaten the yield of lemon balm, although re-hydration by regular irrigation may induce significant recovery. The impact of water shortage on the quality of the drug was less critical.

Pages 1539-1546 | Read More| doi: 10.21475/ajcs.17.11.12.pne665

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Chicory (Cichorium intybus L.) yield under water stress and estimation of leaf area using allometric relations

Leafy vegetables are mainly grown in small properties using empirical irrigation control and frequently applying excess water. Considering these aspects, this study aimed at (i) evaluating the chicory (Cichorium intybus L. cv. “Folha Larga”) production, grown in a greenhouse under different irrigation levels, proportional to the reference evapotranspiration (ET0) and (ii) adjusting models to estimate chicory leaf area from leaf linear measurements. For this, the chicory was grown in a 120 m2 greenhouse. A completely randomized experimental design was used, applying five irrigation treatments and nine repetitions per treatment. The irrigation treatments consisted of percentages of ET0, as follows: 45.6; 60.8; 76; 91.2 and 106.4% of ET0. Measurements of plant height, number of leaves, shoot fresh and dry mass and leaf area were taken. Measurements of 605 leaves were used to adjust ten initial models, from which four models were selected based on statistical coefficients. These models were then submitted to statistical analysis to obtain models which residuals present tendency to normality and homoscedasticity. Measures of 250 new leaves were used to apply the Bland-Altman graphical method. The results show that the increase in one percent of ET0 applied by irrigation increased the plants height in 0.148 cm, and 0.263 and 0.0158 g in the shoots’ fresh and dry mass (respectively) and decrease in 0.306 cm2 of the leaf area. Bland-Altman method revealed that the models estimated correlated but non-concordant data, pointing out to the need of adding the biases’ value of each model to the estimated values.

Aflatoxins are naturally occurring toxic metabolites produced by many Aspergillus particularly Aspergillus flavus and Aspergillus parasiticus in food and feed products. These toxins are hepatotoxic and mutagenic causing severe health disorders including hepatitis and hepatocellular carcinoma (HCC). Various physical and chemical strategies have been introduced to control the growth and aflatoxin production. However, due to safety concerns and potent toxicity of chemicals, researchers are seeking for cost-effective and non-toxic alternates of plant origins to prevent deterioration of grain crops. The aim of this study was to check the effect of natural spices products such as aniseed, black cumin, black pepper, cardamom and turmeric extracts on the growth of pathogenic strains and their ability to produce aflatoxin contamination. Antifungal activity of spices including black cumin, turmeric, black pepper, cardamom and aniseed were performed against aflatoxigenic strain of Aspergillus parasiticus. Water soluble extracts of these spices were prepared, agar diffusion assay was performed and zone of inhibition was measured after applying different concentrations of extracts against the above strain. Subsequently, aflatoxin inhibition assay was performed by inoculating sub-inhibitory concentrations of these extracts with aflatoxigenic strain in Czapek Dox liquid medium. After incubation, thin layer chromatography (TLC) was performed to detect and quantify aflatoxins. All extracts have shown concentration dependent antifungal activity and best results were obtained with cardamom which was active even at 0.005% concentration. In addition, it was also observed that the synthesis of toxin was inhibited by all extracts and maximum activity at the concentration of 0.00025% was shown by black cumin, black pepper and aniseed. Our study showed that these extracts are effective to control aflatoxigenic strains of Aspergillus and aflatoxin contamination and may be considered as an alternative to control post-harvest fungal diseases.

Eric Xavier de Carvalho, Rômulo Simões Cezar Menezes, Ana Dolores Santiago de Freitas*, Everardo Valadares de Sá Barretto Sampaio, Djalma Elzébio Simões Neto, José Nildo Tabosa, Dário Costa Primo, Rodrigo Oliveira de Queiroz

Grasses such as sugarcane (Saccharum spp.), maize (Zea mays L.) and sorghum (Sorghum bicolor L. Moench) with C4 photosynthetic system are important crops that can host endophytic bacteria capable for biological nitrogen fixation (BNF). However, fixation measurements have yielded conflicting results. We determined BNF of five sugarcane and two sorghum varieties, maize and Guinea (Panicum maximum Jacq), elephant (Pennisetum purpureum Schum) and buffel (Cenchrus ciliaris L.) grasses in a pot experiment, using the 15N natural abundance technique, with a soil naturally rich in 15N (δ15N > 16 ‰) and two reference species (castor bean, Ricinus communis L., and cotton, Gossypium hirsutum L.) that absorb only N from the soil (average δ15N = 9.2 ‰). The initial results showed that no fixation occurred in elephant and buffel grasses. Sorghum, maize, Guinea grass and four sugarcane varieties had δ15N signals significantly lower than both reference species, indicating that they absorbed N from the atmosphere (δ15N = 0 ‰). The differences in signals from the reference species translates into proportions of plant N content originating from BNF varied from 12.8 to 19.4 % for sugarcane, 22.4% for maize, 20.9% for Guinea grass, and 24.7 to 31.2 % for sorghum. Nitrogen fixation by these species represents a potential of great fertilizer economy and high yields in low input agriculture.

Non-chemical methods to break seed dormancy of canafistula [Peltophorum dubium (Sprengel) Taubert (Fabaceae)]

Canafistula seeds have a naturally slow and irregular germination due to tegument impermeability. In this study, the efficacy of non-chemical methods was investigated to break the tegument dormancy and enhance the germination rate of canafistula [Peltophorum dubium (Spreng.) Taub. – (Fabaceae)] seeds. A completely randomized design with eight treatments of seed dormancy breaking and four replications of 25 seeds each was used. Different methods to break the seed dormancy were compared: T1: untreated seeds to break dormancy (control); T2: sanding; T3: soaked in hot water (95 oC) and cooled for 24 hours; T4: pre-soaking in boiling water (100 °C) for 5 minutes; T5, T6 T7 and T8: seeds exposed to dry heating in an oven at 40 °C for 24, 48, 72 and 96 hours, respectively. All seeds were germinated in sand, and kept in a greenhouse conditions for 25 days. The emergence capacity, emergence rate index, plant growth rate, dry matter partitioning into roots and shoots, and vigor index of canafistula seedlings were measured. Mechanical scarification (sanding) and soaking in hot water (95 oC) and cooled for 24 hours were efficient to breaking the tegument dormancy and enhanced the seed emergence rate and vigor of Peltophorum dubium (Fabaceae) seedlings.

The purpose of the present study was evaluation of the efficiency of the ‘Fixed area’, Strand, Prodan and Quadrat sampling methods to understand richness, diversity, floristic composition and horizontal structure of natural forest wood species. A census survey was carried out on a cerradão fragment, in which 27 fixed area plots were randomly established with dimensions of 20 × 20 meters. The center of each fixed area plot was considered a sampling point for the alternative methods of sampling, Prodan and Quadrat. For the Strand method, a line was established parallel to one side of the plot cutting it to the center. Richness and diversity of woody species in each method were evaluated by the rarefaction/extrapolation curves using the first three hill numbers. Finally, to characterize the horizontal structure, the Import Value Index percentage (IVI%) and the confidence interval of the basal area and number of individuals per hectare were calculated. The census survey registered a total of 82 species in the cerradão fragment, distributed among 59 genera and 33 botanical families. The study showed that the Fixed Area method was the best survey method regarding the richness, diversity and floristic composition. As for the horizontal structure of the forest, all methods differed, but the Fixed Area and Quadrat methods were the closest to the forestry survey census.

Biochemical response of Tachi-branco (Tachigali vulgaris L.G. Silva & H.C. Lima) in function of sources and doses of nitrogen

Abstract

This study aimed to evaluate the effects of application of nitrogen sources and doses in the biochemical response of seedlings of Tachigali vulgaris L. G. Silva & H. C. Lima. The seedlings were grown in pots containing 3 dm3 of soil. Nitrogen sources such as urea [(NH₂)₂CO], ammonium nitrate (NH4NO3), ammonium sulfate [(NH4) 2SO4] and calcium nitrate [Ca (NO3)2] were tested in five doses of 0, 75, 150, 225 and 300 mg/dm³. They were applied as a solution in four portions, 25, 50, 75 and 100 days after transplanting. The experimental unit consisted of a vase and a randomized block design (RBD) in factorial scheme (4 × 5), corresponding to 4 sources and 5 doses, with four replications, totally 80 vessels. The biochemical analyzes were performed at the end of the experiment and nitrate levels, nitrate reductase enzyme activity, free ammonium, total soluble amino acids, total soluble proteins, carbohydrates, sucrose and chlorophylls were determined. There was a reduction in the concentration of protein in leaf and root, with the application of ammonium nitrate and calcium nitrate. The conversion of nitrate into the root in amino acids shown to be dependent to the oxidation of carbohydrates, causing the reduction of the concentration of this solute increases with the supply NO3-. The results showed that for production of Tachigali vulgaris seedlings the dose of 150 mg dm-3 of N, applied in a piecemeal manner, at 25, 50, 75 and 100 days of transplanting with the ammonium nitrate fertilizer can be recommended.

Pages 1579-1587 | Read More| doi: 10.21475/ajcs.17.11.12.pne741

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Plants favour a variety of signaling networks that maintain physiological functions of the plants for managing stressful conditions. Glutathione (GSH), a non-protein thiol compound, plays an important role in maintaining redox signaling in plants against stress conditions. However, a gap remains to state the functional activities of glutathione on hormonal signaling and growth of plants under stress conditions. In the past centuries, GSH gradually gained significant interest and importance to the researchers due to diverse functional activities in plants. To date, researches and reviews documented the protective role of GSH in plants against stress conditions. Nevertheless, signalling behaviour of GSH is still lacking with regards to the mechanism of GSH underlying the hormonal signaling to the plants. This review highlights the improvements made on the functions of GSH to the hormonal signaling in plants under stressful conditions.

Department of Exact Sciences and Engineering, Regional University of the Northwest of Rio Grande do Sul State, Ijuí, Rio Grande do Sul, Brazil

Departament of Plant Science, Federal University of Santa Maria, Santa Maria, Rio Grande do Sul, Brazil

Maize is one of the most important cereals in the world. The productive potential of this crop is closely associated with nitrogen (N) fertilization, thus, studies focused on this subject are important in the development of cropping strategies. The aim of this work was to evaluate the effects of N split and different type of urea on important agronomic traits of the maize crop. A randomized complete block design in a 2×2+1 factorial treatment design with four replications was used. The factorial levels were composed of two types of urea (common and coated) and two nitrogen splits (V3 and V3+V8), plus the control treatment (without urea application). Important agronomic traits such as grain yield, biological productivity, and yield components were assessed. It was verified that there is no difference between the common or coated urea on grain yield and its components. On the other hand, the split of nitrogen into V3 and V8 stages is an efficient strategy to improve grain yield as well as important features as the number of rows per ears and harvest index. Thus, by using this management system farmers can achieve a more efficient nitrogen use.

IICAR Instituto de Investigaciones en Ciencias Agrarias de Rosario, Argentina

CONICET Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina

Plant phenotyping links genomics with plant ecophysiology and agronomy. It is usually performed by non-destructive, automated and image-based technology and generates information for efficient and searchable digital characterization of crop that can be performed during routine, periodical regeneration of accessions in germplasm collections. In the present work, ninety-two accessions of Pisum from different species and subspecies were studied during 2015 and 2016. Size and colour traits were measured using digital images from a Samsung CLX 3300 scanner and analysed with appropriate software; also seed weight, plant height and days to flowering were measured. Highly significant differences between accessions and species and subspecies for all these traits were found. When distances among species and subspecies are calculated, P. sativum subsp. sativum showed the greatest distance with P. fulvum (8.02) followed by P. abyssinicum (7.13); while the smallest distance was found between P. fulvum and P. sativum subsp. transcaucasicum (3.16). A Neighbour-joining tree with a cofenetic r of 0.985 was obtained. Seed and pod characteristics as colour parameters and size, obtained by digital phenotyping, have proved to be suitable markers for genetic diversity evaluation and they are useful in evolutionary analysis, allowing the discrimination of the main wild and cultivated species in the genus Pisum.

Pages 1599-1605 | Read More| Supplementary Data| doi: 10.21475/ajcs.17.11.12.pne771

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Can industrial cleaning procedures make Urochloa ruziziensis seeds nematode free?

Seeds for agriculture should be pathogens free e.g. from plant-parasitic nematodes that if present in seed lots may be transferred to other clean areas as inoculum to infest other host plants. The aim of this work was to identify and quantify active forms of nematodes during the cleaning procedures of Urochloa ruziziensis seeds and also to evaluate its efficiency in turning the seeds nematodes free. Three seed lots with distinct origins were used. They were sampled four times in different parts of the process such as the reception and during the cleaning procedures consisting of the following treatments: unclean seeds, after using air screen cleaner, after using gravity separator (clean seeds) and the dust particles (seed covers and empty seeds). Identification and quantification of nematodes were done in each of the samples. The results showed that there is reduction in active number of Aphelenchoides and Ditylenchus nemaodes after cleaning procedures of seeds. However, this reduction does not meet the standards to be disseminated as pathogen free seeds for commercialization. The active Meloidogyne form was found only in one seed lot, but the cleaning procedures was effective to eliminate the parasites from the clean commercial seed. Others control forms need to be introduced into the system to turn pasture seed free of nematodes.

This study aims to analyze the production components and the water-use efficiency of corn cultivated with irrigation depths, and also to verify the utilization of multivariate analysis is suitable to highlight the relevant information. Hybrid corn AG 7088 was used as plant material. Two experiments were conducted under field conditions at two different experimental periods between the months of April and December 2015 in a randomized block design with six irrigation depths [50, 75, 100 (control), 125, 150, and 175% replacement of evapotranspiration - ET0] and four replications. At 120 days after sowing, the following variables were evaluated: mass of one thousand grains, number of spikes per plot, yield of dry grains, ear length, ear diameter, number of lines per ear, number of grains per line, number of ears grain per spike, grain mass per spike, cob mass, spaghetti mass, and mass of straws. The results showed that production components and water use efficiency of hybrid corn AG 7088 were not affected by the varying water depths in the first experimental period. In the second period, the increase in water depth supported a gain in the mass of a thousand grains, dry grain yield, grain number per row, grain number per ear, corn cob mass and mass of dehusked ear, reducing the efficiency of water use. The use of multivariate analysis was able to reduce the multi-dimensional space of the set of variables in the three Principal Components with relevant information to highlight differences between irrigation depths and experimental periods.

Leaf is a sensitive plant organ in responding to abiotic stresses, especially drought stress. Objective of this research was to evaluate changes of relative leaf expansion rate (RLER) and other leaf-related indicators as affected by gradual drought stress. The stress was induced by withholding water supply to chili pepper (Capsicum annum L.) for up to 12 days. Afterward, the crops were allowed to recover. The research was conducted in two stages. The first stage was for finding a reliable leaf area (LA) estimation model. The second stage was for evaluating relevance of RLER, specific leaf fresh weight (SLFW), specific leaf water content (SLWC), and total leaf area (TLA) as indicators for drought stress in chili pepper. Combinations of five regression models (linear, zero-intercept linear, quadratic, zero-intercept quadratic, and power) and three predictors, i.e. leaf length (L), leaf width (W), and LW were evaluated as candidates of LA estimation model. Selection of the models was based on coefficient of determination (R2) and geometrical principles. The selected model was used for calculating RLER, SLFW, SLWC and TLA. Results of this study indicated that dynamic changes of RLER were mainly driven by daily day-night cycle rather than long-term gradual drought stress. SLFW and SLWC did not significantly decrease during drought stress period. However, drought stress significantly inhibited TLA in chili pepper. Chili pepper was able to recover from short-term (4 days) exposure to drought stress; yet, this crop was unable to recover after 8 days exposure to drought stress or longer.

Combining effects of ozone and Xanthomonas oryzae pv. oryzae on antioxidants and phytoalexins in rice (Oryza sativa L.)

Department of Natural Resources and Environment Faculty of Agriculture Natural Resources and Environment, Naresuan University, Muang, Phitsanulok, 65000 Thailand

College of Agriculture, Ibaraki University,3-21-1Chuo, Ami, Ibaraki 300-0393, Japan

Ozone is the most oxidative air pollutant and considered as an abiotic stress which harm to vegetation and crop. Similarly, biological stressor such as plant pathogen could cause severe damage to crops. Combination effects from both stresses will potentially lead to economic loss. Basically, plants will response to both abiotic stress and pathogenic stressor by generate antioxidants and phytoalexins. The concentration of these chemical indicate stress level in plant and also defence system response. This research is aimed to investigate the combination effects of ozone and Xanthomonas oryzae pv. oryzae on antioxidants and phytoalexins in rice (Oryza sativa L. cv. KDML 105). In this study, 45-day-old rice plants were used. Ozone was elevated at concentrations of 100, 200 and 300 ppb in the fumigating chambers for 12 hours. Xanthomonas oryzae pv. oryzae which caused bacterial blight disease in rice was selected as plant pathogen. Combining effects of ozone and Xanthomonas oryzae pv. oryzae were examined using ozone at a concentration of 100 ppb and Xanthomonas oryzae pv. oryzae 1x108 cells/ml inoculation. The experimental design was a completely randomized design with 2×2 factorials treatment and three replications required. Temperature, relative humidity and light intensity in fumigating chambers were controlled. The results of the combining effects showed the amount of antioxidants and phytoalexins were higher than those in single treatment. The experimental data indicated that the combining effects will result in more stress in rice. This suggests that, in rice plantation area with experience of ozone episode, pathogenic resistance rice strain should be considered to reduce combining effects.

Abstract

It was presumed that shallow water table restricted leaf growth and some water-related parameters; therefore, they can be used as indicators of plant stress due to the water table condition. Objective of this research was to evaluate morphological stress indicators in tomato plants exposed to shallow water table. The research was conducted in two stages: (1) developing reliable LA estimation model from June to September 2016; as pre-requisite for (2) calculating and evaluating the morphological indicators for stress due to shallow water table treatments, conducted from February to May 2017. Treated plants were placed inside experimental pools. Each treatment was done by partially submerging growing substrate to the targeted water tables at 5 cm and 10 cm below surface of the substrate. Untreated control plants were kept outside the pools. Zero-intercept linear model was the selected model for leaf area estimation after evaluating 15 combinations of five regression models and three predictors. Results of this study indicated that steady water table at 5-cm and 10-cm depth did not restrain relative leaf expansion rate (RLER) and there was no significant difference in specific leaf fresh weight (SLFW) and specific leaf water content (SLWC) between treated and untreated plants, measured prior to, during, and after recovery from shallow water table treatments. In conclusion, if position of water table was steady, the shallow water table at 5-cm depth or deeper did not affect tomato growth.

Pages 1635-1641 | Read More| doi: 10.21475/ajcs.17.11.12.pne808

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Nutritional status of orange tree ‘Pêra Rio’ variety after Huanglongbing disease infection, leaf spray fertilization and application of resistance-inducing bioinductors

Federal University of Campina Grande, Academic Unit of Agricultural Engineering, Campina Grande, 58109-970, Paraíba, Brazil

Paulista State University, Department of Soils and Fertilizers, Jaboticabal, 14884-900, São Paulo, Brazil

Federal University of Sergipe, Department of Agronomic Engineering, São Cristóvão, 49100-000, Sergipe, Brazil

Federal University of Campina Grande, Department of Animal Science, Patos, 58708-110, Paraíba, Brazil

State University of Paraíba, Coordination of the Post-Graduate Program in Agricultural Sciences, Campina Grande, 58429-570, Paraíba, Brazil

Federal University of Alagoas, Department of Plant Production, Maceió, 57072-900, Alagoas, Brazil

Fellow of CNPq Research Productivity, level 2, Brazil

Fellow of CNPq Research Productivity, level 1B, Brazil

Citrus industry is widespread in the world. The Huanglongbing is an important disease of citrus species and has been spread around the world. This research analyzed the nutritional status of tree ‘Pêra Rio’ variety infected with Candidatus Liberibacter spp., under leaf nutrients spray and bioinductors of resistance. The experiment was carried out from September 2013 to June 2014, in a citrus commercial orchard located in the city of Ibitinga (SP). A completely randomized design was used in a factorial 3 × 4 × 6, consisting of three plants status (healthy, infected with asymptomatic HLB, and symptomatic HLB), four rates of spray solutions (0, 2, 4 and 6 L ha-1), six application stages (A1, A2, A3, A4, A5, and A6 with intervals of 45 days between each stage) and four replications. Macro and micronutrients leaf levels were quantified. Data were submitted to exploratory factor analysis with multivariate statistics. Three factors were extracted from the variables, namely, Factor 1 formed by variables S, Cu, Fe, and Zn; Factor 2 by N, K and B, and Factor 3 by Ca, Mg, and Mn. ‘Pêra Rio’ plants nutritional status was destabilized with the infection of Candidatus Liberibacter spp. Progressive treatment with leaf fertilization and resistance bioinductors temporarily re-established nutritional standards of plants affected by Huanglongbing but did not promote stability of the plants nutritional status.

Productive viability of sweet pepper (Capsicum chinense [J.] cv. Lupita) using water management with different soil water tensions

Green pepper has a great prominence in the cuisine of Pará. This plant is cultivated using a low technological level along its production chain. However, in the last few years, there has been an increase in planted area due to a national and international recognition of this vegetable, because it is a substitute for bell pepper. This study aims to evaluate the effects of different soil water tension on the productivity of green pepper cv. Lupita. The experiment design was randomized blocks with four replications. The treatments consisted of five soil water tensions: 15, 25, 35, 45 and 55 kPa as indicative for the moment of irrigation. It is concluded that, to obtain high yield and large fruit sizes (longitudinal and transversal diameter), irrigation should be carried out at the moment when soil water tension is close to 33 kPa at a depth of 0.20 m. To obtain a better efficiency in water use, the irrigation should be performed at a tension close to 30 kPa.

Application of different nitrogen doses to increase nitrogen efficiency in Mombasa guinegrass (Panicum maximum cv. mombasa) at dry and rainy seasons

Nitrogen is the nutrient that most influences productivity and pasture quality but nitrogen fertilization efficiency still needs to be increased. The objective of this work was to study the efficiency of nitrogen sources and doses (N) on the yield of Panicum maximum cv. Mombasa applied during rainy and dry periods. The soil of the experimental area is an ultisol with a sandy texture. The experimental design was a randomized block in a factorial scheme with four replications, two sources of nitrogen: urea and ammonium nitrate and five N doses (0, 50, 100, 150 and 200 kg ha-1 per cutting), in total 0, 300, 600, 900 and 1200 kg ha-1 per season–dry or rainy, respectively). The dry matter yield (DMY) and nitrogen use efficiency (NUE), agronomic efficiency (AE), recovery of applied nitrogen (RAN) and physiological efficiency (PE) were evaluated. The results showed that N source did not influence DMY, NUE, AE, RAN and PE. However, the N doses influenced DMY positively, and negatively NUE, AE, RAN and PE. Generally, the increase was occurred in DMY with the increase of N doses and decrease in NUE, AE, RAN and PE. As the N source did not influence the analyzed attributes, it is recommended to use urea, because it is a fertilizer with the highest N concentration and lowest cost per unit of nutrient, at a dose of 100 kg ha-1 per cut, favoring DMY gain. In addition this urea assists with the management and maintenance of the Mombasa guineagrass.

Agricultural crops are severely affected by salinity. Recent studies have shown that salt stress signaling components affect plant metabolism and stimulate the accumulation of organic osmolytes and antioxidant substances. This work aimed at assessing the growth and development of lemon balm, Melissa officinalis L., subjected to salt stress, as well as its antioxidant response, essential oil composition, and essential oil yield (%). A completely randomized experimental design was conducted under greenhouse conditions, where 30-days-old lemon balm plants were treated with different NaCl concentrations (0, 50, 100, 150 and 200 mM) for sixty days. The highest concentrations (150 mM and 200 mM NaCl) caused significant reductions in shoot height, shoot fresh mass, relative water content, water activity and chlorophyll production due to changes in osmotic activity. The activities of superoxide dismutase (SOD) and catalase (CAT) increased in plants subjected to salinity. In addition, membrane damage (DM) increased with increase in NaCl concentration. The yield of the essential oils decreased but the number of compounds increased in all the NaCl treatments. The compounds neryl-acetate and geranyl-acetate were detected at 100, 150 and 200mM NaCl, suggesting that under salt stress, lemon balm plants activate the metabolic pathways for the production of terpenoids, consequently producing monoterpenes. Salinity negatively affected most of the parameters evaluated in lemon balm plants. Our results show that lemon balm plants are tolerant to low concentrations of salinity (up to 50mM) as proved by their distinct metabolic responses.