Death Of Seedlings Research Articles

The role of exogenous proline in amelioration of lipid peroxidation in rice seedlings exposed to Cr(VI)

Lipid peroxidation was hydroponically investigated in rice seedlings (Oryza sativa L. cv. XZX 45) treated with different doses of hexavalent chromium (Cr(VI)) in the presence or absence of exogenous proline. Results showed that Cr(VI) induced lipid peroxidation was observed as indicated by higher accumulation of malondialdehyde (MDA) in roots of rice seedlings without application of proline. Cr(VI) also caused inhibition of relative growth rate and increase of root cell death of rice seedlings compared with control. Additionally, changes of roots phenotype traits were evident in roots of rice seedlings under Cr(VI) stress. Exogenous proline significantly increased Cr accumulation in roots, compared with rice seedings without proline treatment. However, less lipid peroxidation was detected in proline-treated rice seedlings as displayed by decreases in MDA content and root cell viability. Hierarchical cluster analysis was also performed using varieties of Cr accumulation, MDA content, root viability and root phenotype traits to further elucidate the role of exogenous proline in amelioration of lipid peroxidation. It is suggestive from the present study that exogenous proline is able to effectively reduce Cr(VI)-induced lipid peroxidation in rice seedlings.

Development of high-throughput methods to screen disease caused by Rhizoctonia solani AG 2-1 in oilseed rape

BackgroundRhizoctonia solani (Kühn) is a soil-borne, necrotrophic fungus causing damping off, root rot and stem canker in many cultivated plants worldwide. Oilseed rape (OSR, Brassica napus) is the primary host for anastomosis group (AG) 2-1 of R. solani causing pre- and post-emergence damping-off resulting in death of seedlings and impaired crop establishment. Presently, there are no known resistant OSR genotypes and the main methods for disease control are fungicide seed treatments and cultural practices. The identification of sources of resistance for crop breeding is essential for sustainable management of the disease. However, a high-throughput, reliable screening method for resistance traits is required. The aim of this work was to develop a low cost, rapid screening method for disease phenotyping and identification of resistance traits.ResultsFour growth systems were developed and tested: (1) nutrient media plates, (2) compost trays, (3) light expanded clay aggregate (LECA) trays, and (4) a hydroponic pouch and wick system. Seedlings were inoculated with virulent AG 2-1 to cause damping-off disease and grown for a period of 4–10 days. Visual disease assessments were carried out or disease was estimated through image analysis using ImageJ.ConclusionInoculation of LECA was the most suitable method for phenotyping disease caused by R. solani AG 2-1 as it enabled the detection of differences in disease severity among OSR genotypes within a short time period whilst allowing measurements to be conducted on whole plants. This system is expected to facilitate identification of resistant germplasm.

Serangan Ulat Jengkal (Hyposidra talaca Wlk.) Pada Bibit Pakoba (Syzygium luzonense (Merr.) Merr.) Di Persemaian

Obstace of pakoba (Syzygium luzonense (Merr.) Merr.) cultivation in nursery is twig caterpillar (Hyposidra talaca WLK) attacks. The Pest symptoms was holes in the leaves especially young leaves; twig caterpillar enable to attack all leaves of pakoba seed. Severe attacks cause death of seedlings. There are five blocks in pakoba nursery that were observed; 1014 pakoba seedlings were grown in these blocks. The average percentage of twig caterpillar’s attack was quite high, reached 49.34%. Twig caterpillar has been controlled by integrated pest management. Chemical control to decrease twig caterpillars attack in nursery has been done by using half dose of insecticide profenofos.

Cylindrocladium spathiphylli de espatifilo: relação da patogênese com produção in vitro da enzima lacase

RESUMO O fungo Cylindrocladium spathiphylli causa podridão no colo e nas raízes de espatifilo. Fungos produzem enzimas extracelulares e muitas destas podem estar envolvidas na patogênese. Há poucos estudos procurando comprovar o papel de uma determinada enzima na patogênese, principalmente no patossistema C. spathiphylli e espatifilo. Assim, o objetivo do presente trabalho foi verificar a patogenicidade de diferentes isolados do fungo em espatifilo, em condições de BOD, e depois relacionar a patogênese com a produção in vitro da enzima extracelular lacase. O ensaio da patogenicidade foi inteiramente casualizado, com dois isolados normais e três isolados alterados por fungistase com seis repetições. Após a inoculação, avaliou-se a severidade da doença em mudas de espatifilo em quatro períodos (até 10 dias) com uma escala de notas (1,0 – sadia até 3,0 – morte de plantas). Aos 10 dias de avaliação, a severidade média da doença causada pelo isolado normal MMBF 01/01 e pelos isolados alterados MMBF 01/01 – 9 D e LFEEI016 – 3 D foi semelhante, enquanto que a severidade causada pelo isolado normal LFEEI016 não diferiu da testemunha. O isolado alterado MMBF 01/01 – 3 D apresentou severidade máxima da doença (nota média 3,0) aos sete dias de avaliação, diferindo dos demais. Quanto à enzima lacase, delineou-se ensaio inteiramente casualizado, com os mesmos isolados do fungo, em placa de Petri contendo meio específico para produção da enzima lacase com seis repetições. Mensurou-se a área da coroa circular da enzima formada no meio. A maior área média da enzima foi produzida pelo isolado alterado MMBF 01/01 – 3 D (2256,0 mm2), enquanto que as áreas dos isolados alterados LFEEI016 – 3 D e MMBF 01/01 – 9 D e do isolado normal MMBF 01/01 foram iguais e a menor área de lacase foi produzida pelo isolado normal LFEEI016 (747,2 mm2). Há uma relação quanto à quantidade da enzima lacase produzida in vitro com a severidade da doença causada pelos isolados na planta, o que reforça a necessidade de mais estudos in vivo para provar o papel da lacase na patogênese do fungo C. spathiphylli em espatifilo.

Assessment of molecular diversity and tolerance of increased salinity levels in irrigation of barley seedlings

Salinity is one of the biggest challenges that limit the productivity of crops. Therefore, Screening for more tolerant varieties is a top priority of breeders. Landraces are great source for genetic variability that would be used for improvement of new varieties. Thus, in this study five barley landraces genotypes were collected from different locations in the New Valley governorate of Egypt and two check varieties, Giza 123 (salt tolerant) and Beecher (salt sensitive) as a control were evaluated for their potentiality to salt stress tolerance and genetic variability, via exposure of seedlings to series graded salt concentrations course and inter simple sequence repeat (ISSR) molecular marker analysis. Survived seedlings were counted under both non-stress and stress conditions. Highly significant differences were observed among genotypes under salt stress conditions, whereas all genotypes were affected by salinity stress. Seedlings mortality varied among genotypes, where salt sensitive check (Beecher) variety was highly affected. While, L2 had the lowest seedlings death rate and distinct over salt tolerant check variety (Giza 123). Furthermore, ISSR molecular marker techniques were used for study of genetic diversity and similarity relationships among the seven genotypes. The polymorphism was 86.89%. L1 and L5 were the highest similar (0.74) genotypes, but the lowest similarity (0.45) was noted between L4 and Giza 123 genotypes. Moreover, dendrogram analysis gathered the highest salt tolerant genotypes in one group. Superiority of L2 genotype in comparison with check salt tolerant variety suggests that landraces could be beneficial tool for genetic improvement of barley stress tolerant lines.

Soil bacterial and fungal community dynamics in relation to Panax notoginseng death rate in a continuous cropping system.

Notoginseng (Panax notoginseng), a valuable herbal medicine, has high death rates in continuous cropping systems. Variation in the soil microbial community is considered the primary cause of notoginseng mortality, although the taxa responsible for crop failure remains unidentified. This study used high-throughput sequencing methods to characterize changes in the microbial community and screen microbial taxa related to the death rate. Fungal diversity significantly decreased in soils cropped with notoginseng for three years. The death rate and the fungal diversity were significantly negatively correlated, suggesting that fungal diversity might be a potential bioindicator of soil health. Positive correlation coefficients revealed that Burkholderiales, Syntrophobacteraceae, Myrmecridium, Phaeosphaeria, Fusarium, and Phoma were better adapted to colonization of diseased plants. The relative abundance of Fusarium oxysporum (R = 0.841, P < 0.05) and Phaeosphaeria rousseliana (R = 0.830, P < 0.05) were positively associated with the death rate. F. oxysporum was a pathogen of notoginseng root-rot that caused seedling death. Negative correlation coefficients indicated that Thermogemmatisporaceae, Actinosynnemataceae, Hydnodontaceae, Herpotrichiellaceae, and Coniosporium might be antagonists of pathogens, and the relative abundance of Coniosporium perforans was negatively correlated with the death rate. Our findings provide a dynamic overview of the microbial community and present a clear scope for screening beneficial microbes and pathogens of notoginseng.

Virulence of Bursaphelenchus mucronatus to pine seedlings and trees under field cownditions

SummaryBursaphelenchus mucronatus is a parasitic nematode of pine that is widely distributed in the natural pine forests of Asia and Europe. It has a very similar morphology and biology to that of Bursaphelenchus xylophilus, the causal agent of pine wilt disease, but has generally been considered to be non‐pathogenic to pine. However, in some provinces of China, B. mucronatus has been isolated from dead pine trees rather than B. xylophilus. Previous studies have shown that B. mucronatus can induce the death of pine seedlings under glasshouse conditions. To investigate the virulence of B. mucronatus, 2‐year‐old seedlings of Pinus massoniana and Pinus elliottii were inoculated with one of six isolates of B. mucronatus under field conditions in April 2014 and their condition was monitored over a year. The virulence of the six B. mucronatus isolates differed on the three host species: P. elliottii seedling mortality ranged from zero to six of the 18 inoculated seedlings, whereas P. massoniana seedling mortality ranged from four to 12 of the 18 inoculated seedlings. Three B. mucronatus isolates that appeared to cause different levels of mortality among the seedlings were used to inoculate 12‐year‐old Pinus thunbergii trees in August 2014. The trees were monitored for a year, during which time between 4 and 12 of the 18 inoculated trees in each treatment wilted and died. The average monthly temperature during the test period appeared to be similar to that of the historical average in the test areas; however, both study sites experienced above‐average rainfall. This study demonstrated that B. mucronatus has potential virulence on pine trees and provided experimental evidence that high temperatures or drought stress is not essential for the virulence of B. mucronatus.

Restoration Silviculture: An Ecophysiological Perspective - Lessons learned across 40 years

Involvement in forest restoration programs across North America for the past 40 years, dealing with nursery cultural practices, operational seedling quality programs and defining seedling performance on restoration sites has given me a unique perspective, which I have used to examine programs from both a research and operational perspective. Certain biological patterns and themes continually appeared across these programs and this paper discusses five of the most common themes.Learning To Think Like a Tree – It is important for practitioners to develop an understanding of the ecophysiological performance of tree species in a nursery or forest restoration program in order to understand how seedlings grow. This understanding leads to sound biologically based cultural decisions to improve seedling performance.Stress and the Cyclical Nature of Stress Resistance – Seedlings are exposed to stress when environmental conditions limit their performance. Plants develop physiological resistance attributes to mitigate stress and these attributes change throughout the seasonal cycle. Practitioners have developed hardening cultural practices that enhance seedling stress resistance, thereby improving seedling quality and site restoration success.Seedling Quality: Product versus Process – Seedling quality is an important component of successful restoration. Typically seedling quality is examined from a product perspective, thus defining functional integrity, operational grading or sometimes performance potential. An alternative approach monitors the process, with product quality the final output.Planting Stress and Seedling Establishment – Planting stress is prevalent in forest restoration. The act of planting can result in a seedling that does not have proper connections for water movement through the soil-plant-atmosphere continuum (SPAC). Seedling water stress, reduced growth performance and potentially death can occur if this SPAC connection is not restored.Seedling Death: Sometimes Simple and Sometimes Complicated – Seedling death can occur in restoration programs as a result of environmental extremes or incorrect management practices. Some problems can be easy to diagnose and correct practices can be implemented to rectify the problem. Other times, issues are complicated and it can be a challenge to define the potential factors causing seedling death.

Naturalization of Fragaria × ananassa Duch. in Western Siberia

The process of the Fragaria × ananassa naturalization in Western Siberia lasts approximately 80 years from the moment of the appearance of first garden strawberry cultivars at agricultural experimental stations in 1933. The species invasive status changed slightly for such a long period of time (from casual alien plants to naturalized plants), and it corresponds to colonophytes in regards to degree of naturalization. The ornitochory is one reason the F. × ananassa appears in natural phytocenoses. At present, the F. × ananassa naturalization occurs in two directions, including genetic transformations in long-living coenopopulations and the reinvasion of new ecotypes of the same species in natural phytocenoses. The high death of seedlings in naturalized F. × ananassa does not allow the species to actively occupy regeneration niches in natural phytocenoses, which precludes the invasive plant status for the F. × ananassa at this stage of the F. × ananassa naturalization in Western Siberia.

Sugar suppresses cell death caused by disruption of fumarylacetoacetate hydrolase in Arabidopsis.

Sugar negatively regulates cell death resulting from the loss of fumarylacetoacetate hydrolase that catalyzes the last step in the Tyr degradation pathway in Arabidopsis . Fumarylacetoacetate hydrolase (FAH) hydrolyzes fumarylacetoacetate to fumarate and acetoacetate, the final step in the tyrosine (Tyr) degradation pathway that is essential to animals. Previously, we first found that the Tyr degradation pathway plays an important role in plants. Mutation of the SSCD1 gene encoding FAH in Arabidopsis leads to spontaneous cell death under short-day conditions. In this study, we presented that the lethal phenotype of the short-day sensitive cell death1 (sscd1) seedlings was suppressed by sugars including sucrose, glucose, fructose, and maltose in a dose-dependent manner. Real-time quantitative PCR (RT-qPCR) analysis showed the expression of Tyr degradation pathway genes homogentisate dioxygenase and maleylacetoacetate isomerase, and sucrose-processing genes cell-wall invertase 1 and alkaline/neutral invertase G, was up-regulated in the sscd1 mutant, however, this up-regulation could be repressed by sugar. In addition, a high concentration of sugar attenuated cell death of Arabidopsis wild-type seedlings caused by treatment with exogenous succinylacetone, an abnormal metabolite resulting from the loss of FAH in the Tyr degradation pathway. These results indicated that (1) sugar could suppress cell death in sscd1, which might be because sugar supply enhances the resistance of Arabidopsis seedlings to toxic effects of succinylacetone and reduces the accumulation of Tyr degradation intermediates, resulting in suppression of cell death; and (2) sucrose-processing genes cell-wall invertase 1 and alkaline/neutral invertase G might be involved in the cell death in sscd1. Our work provides insights into the relationship between sugar and sscd1-mediated cell death, and contributes to elucidation of the regulation of cell death resulting from the loss of FAH in plants.

Growth, yield and nitrogen use efficiency of dry-seeded rice as influenced by nitrogen and seed rates in Bangladesh

The fertilizer N requirement of dry-seeded rice (DSR) grown with alternate wetting and drying (AWD) water management may differ from that of traditional puddled transplanted rice (PTR) grown under continuous flooding due to differences in N dynamics in the soil/water system and crop growth patterns. The effects of changing establishment method and water management on N fertilizer requirement may also vary between crops grown in the dry and rainy seasons. Therefore, field experiments were conducted over two years in both the boro (dry) and aman (wet) seasons in Bangladesh to evaluate the effects of N rate and seed rate on crop performance and N use efficiency. Four N rates were used in the boro (0, 100, 140, and 180kgha−1) and aman (0, 80, 120, and 160kgha−1) seasons, and five seed rates (20, 40, 60, 80, and 100kgha−1) were used in both seasons. There was a significant interaction between N rate and seed rate on grain yield of all crops. Maximum yield of all crops was achieved at the highest N rate with a seed rate of at least 40–60kgha−1, suggesting that DSR has a higher fertilizer N requirement than the recommended rate for PTR. However, there was lodging at physiological maturity of the aman crops at 20 and 40kgseedha−1 at the maximum N rate, but not at 60kgha−1, suggesting that at seed rates of 20–40kgha−1 a lower N rate than the maximum tested would be optimal. Agronomic fertilizer N use efficiency (15–20kggrainkg−1) and N recovery efficiency (35–40%) were low and comparable to the values reported in Asia for PTR, indicating the need for methods to improve fertilizer use efficiency of DSR. The boro crops sown in mid November suffered from cold damage, resulting in some seedling death in the first year, and substantial seedling death in the second year. In the second year, all boro sowings from mid November to mid January failed due to low temperature. The results suggest that dry seeding of boro rice in mid November is risky because of low temperature in December–January. However, delaying sowing to early February reduced yield due to high temperature during anthesis and low solar radiation during grain filling. Therefore, boro varieties with greater cold tolerance during the vegetative stage are needed to enable the switch from PTR to November-sown dry-seeded boro rice in the High Ganges River Floodplain of western Bangladesh.

Phytotoxicity of dimethyl sulfoxide (DMSO) to rice seedlings

The physiological responses of dimethyl sulfoxide (DMSO) exposure were investigated in rice (Oryza sativa L. cv. XZX 45) seedlings. The seedlings were hydroponically exposed to different concentrations of DMSO for 72 h. Results showed that a linear decrease in relative growth rate and water use efficiency was observed with rice seedlings with increasing DMSO concentrations. The estimation of cell death measured by Evans blue uptake also indicated DMSO-induced damage in root tissues. Negligible decrease in chlorophylls was noted, while significant reduction in carotenoids content was only observed at 13.54 mM DMSO. Although DMSO did not have any significant effect on protein content in roots, the protein content in shoots was significantly decreased in a dose-dependent manner. Proline content in both plant tissues was positively affected by DMSO exposure, responding an inverted U-shaped curve with DMSO concentrations. Results also showed that DMSO-induced accumulation of hydrogen peroxide (H2O2) was evident in roots rather than shoots. DMSO did not result in any significant changes in superoxide dismutase and peroxidase activities as well as malondialdehyde content. Catalase (CAT) activity in both roots and shoots was quite sensitive to changes in DMSO treatments than other enzymes, suggesting that CAT may play central role in the detoxification of H2O2 in rice seedlings under DMSO exposure. Results suggest that growth inhibition and cell death of rice seedlings caused by DMSO exposure were largely related to the accumulation of H2O2 in plant tissues.

EVALUATION OF SOME EGYPTIAN COTTON (Gossypium barbadense L.) VARIETIES AGAINST Fusarium ROOT-ROT UNDER GREENHOUSE CONDITION

Cotton breeders in Egypt pay a great attention to development hybrids has resistance to several diseases and pests and give good yield. Pathogenicity tests of four Fusarium species ,namely: Fusarium poae; Fusarium oxysporum; Fusarium subglutinane and Fusarium solani (isolated from diseased cotton seedling). The diseases evaluation had spot line on the susceptibility of thirteen cultivars of Egyptian cotton (Gossypium barbadense L.), including Giza45, Giza70, Giza80, Giza81x83, Giza83, Giza84, Giza85, Giza86, Giza87, Giza88, Giza89, Giza86x89 and Giza90 under greenhouse conditions. The obtained results revealed that at least every cultivar was resistant for one of Fusarium spices. Giza85 was the most susceptible cultivars (26.67; 40; 13.33 and 40 %, respectively) pre-emergence% for all tested Fusarium species. At the same time, Giza88 recorded resistance reaction ( 0.0; 6.67; 20 and 6.67% respectively). Fusarium oxysporum was the most pathogenic species (25.64% seedling death) followed by Fusarium solani and Fusarium poae (18.46 and 17.95%, respectively). The minimum incidence was noted in Fusarium subglutinane (9.74%), compared to 2.56% in check treat.

Detection of Mycoflora and Aflatoxin B1 in the Seeds of Inodorous Melons (Cucumis melo L.)

Twenty-two seed samples of inodorous melons, collected from the areas of Peshawar, Swabi, Tordher, Fatu-chuk, Mardan, Karachi, Islamabad, Ghotki, and Mandibahauddin, yielded 75 species of 36 fungal genera, isolated through ISTA (International Seed Testing Association) techniques. The agar plate method was chosen as being best for the qualitative and quantitative isolation of fungi, followed by the standard blotter method. The agar plate method yielded 64 species of 29 genera, while the blotter method yielded 24 species belonging to 14 genera. The deep-freezing method yielded only 2 species belonging to 2 genera. Aspergillus niger , followed by A. flavus , Chaetomium globosum , and Rhizopus stolonifer were the most dominant fungi in all 3 methods used. Forty species belonging to 25 genera had not been previously reported from Pakistan. Seven seed samples, which were highly infected with fungi, were grown in test tube slants, included samples from Tordher (1), Ghotki (1), Mandibahauddin (1), Karachi (2), Islamabad (1), and Fatu-chuk (1). Aspergillus flavus was the most dominant fungi, causing pre-emergence rot of seedlings. Fusarium oxysporum caused 3.6 % of seedling deaths after 10 - 12 days of incubation. Seed samples from Islamabad, Mandibahauddin, and Swabi were highly infected with A. flavus . The level of aflatoxin B 1 estimated through CD-ELISA for the 3 samples was 32.64 ppb (Swabi), 11.48 ppb (Islamabad), and 7.30 ppb (Mandibahauddin), respectively, of which the seed sample from Swabi contained the highest level of aflatoxins. Surface sterilization of seeds with 1 % Calcium hypochlorite (Ca (OCl) 2 )greatlyreduced the incidence of both saprophytic and superficial pathogenic fungi. doi: 10.14456/WJST.2016.3

GFP-fluorescent protein on the study of blister spot in coffee plants

In Brazil, Colletotrichum gloeosporioides is associated with a complex of symptoms in coffee culture. Although this pathogen had its pathogenesis observed and identified, its importance has still been questioned due to its several endophytic forms, raising doubts as to the real importance of the pathosystem. The aim of this study was to demonstrate, by using an isolate transformed with the gene gfp, the infection and colonization capability of C. gloeosporioides in coffee seedlings. After the fourth day of inoculation, manifestation of symptoms as punctual necrosis could be observed, which progressed during the evaluation period, culminating in the death of seedlings. Epifluorescence microscopy confirmed the presence of the pathogen in the seedlings, as well as the visualization of internal colonization of tissues, acervulus formation and conidium production, confirming that it was responsible for the observed symptoms.

DNA-protein cross-links involved in growth inhibition of rice seedlings exposed to Ga.

Hydroponic experiments were conducted with rice seedlings (Oryza sativa L. cv. XZX45) exposed to gallium nitrate (Ga(3+)) to investigate the accumulation of Ga in plant tissues and phytotoxic responses. Results showed that phyto-transport of Ga was apparent, and roots were the dominant site for Ga accumulation. The total accumulation rates of Ga responded biphasically to Ga treatments by showing increases at low (1.06-8.52 mg Ga/L) and constants at high (8.52-15.63 mg Ga/L) concentrations, suggesting that accumulation kinetics of Ga followed a typical saturation curve. Higher amount of Ga accumulation in plant tissues led to significant inhibition in relative growth rate and water use efficiency in a dose-dependent manner. DNA-protein cross-links (DPCs) analysis revealed that overaccumulation of Ga in plant tissues positively stimulated formation of DPCs in roots. Likewise, the measure of root cell viability evaluated by Evan blue uptake showed a similar trend. These results suggested that Ga can be absorbed, transported, and accumulated in plant materials of rice seedlings. Overaccumulation of Ga in plant tissues provoked the formation of DPCs in roots, which resulted in cell death and growth inhibition of rice seedlings.

First Report of Chestnut Blight Caused by Cryphonectria parasitica in a Chestnut Orchard in Andalusia (Southern Spain)

In Europe, chestnut blight caused by Cryphonectria parasitica (Murrill) Barr was first seen in Italy in 1938 (1). In Spain, the disease was first detected in Basque country in 1947 and later in other areas of northern Spain: Galicia, León, Navarra, and Catalonia, and in Trás-os-Montes in Portugal (2). In November 2012, in an orchard (2 ha) in Almonaster la Real (Huelva, Spain), approximately 20 cankered Castanea sativa (sweet chestnut) trees cv. Vazqueño, 40 to 50 years old, were observed. The trees were grafted 2 years before. In May and June 2013, six new disease focuses were detected near the first one. Five focuses were located in the same village and the other in Jabugo (a neighboring village). Diseased trees exhibited sunken cankers, cracked bark with mycelial fan spreads under the bark, and in some cases, orange fungal sporulation was visible on the bark. Samples were collected from two affected trees and symptom-bearing bark pieces were then placed in moist chambers at 20°C for up to 8 days to induce fungal sporulation. Cultures were made from spore masses extruding from the cankered bark and from the edge of necrotic lesions visible in the phloem of cankered bark tissue onto potato dextrose agar (PDA). Monoconidial fungal isolates were obtained from both trees. The morphological structure of two isolated fungi was identical to that described as C. parasitica (3). Species identity was confirmed by analysis of nucleotide sequences of the internal transcribed spacer (ITS) rDNA, using ITS1-ITS4 (4) as primer pairs, respectively. BLAST searches showed a high similarity between collected isolates' DNA sequences and C. parasitica sequences found on GenBank (96% coverage, 99% identity). Our isolates have been included in GenBank as KF220298 and KF220299. The pathogenicity assay of these two isolates was conducted using two cultivars of sweet chestnut (seedlings from Huelva and Granada nurseries). Isolate pathogenicity was tested on 3-year-old chestnut seedlings in a growth chamber at 25°C (day) and 20°C (night) with a 14-h photoperiod. The isolates were cultured on PDA at 25°C for 7 days. Stems were wounded at 10 cm height with a drill. Each isolate was inoculated to 25 replicates per cultivar by placing a mycelia agar plug (4 to 5 mm diameter) in the hole and wrapping the stem with Parafilm. Plants treated identically with sterile agar plugs were used as controls. Plants were then maintained at 100% relative humidity for 2 h. Both isolates induced diseases symptoms and death of seedlings of both cultivars at a mean time of 37.5 days after inoculation. No significant differences between isolates or between cultivars were detected. Twenty control plants similarly treated with sterile PDA discs did not display symptoms. C. parasitica was re-isolated from lesions, confirming Koch's postulates. Andalusia has 14,000 ha of chestnut crops with high commercial value due to their precocity. Dispersion of chestnut blight in this zone can reduce crop productivity. To our knowledge, this is the first report of C. parasitica causing chestnut blight in Andalusia (southern Spain), one of the few areas left in southwestern Europe free of chestnut blight.

Root-rot and Stem-canker Control in Faba Bean Plants by Using Some Biofertilizers Agents

Some biofertilizers agents i.e. Rhizobium leguminosarum var. fabae, Bacillus megaterium var., phosphaticum and Trichoderma harizianum play important roles in enhancing the plant growth and controlling several diseases i. e. root rot and stem canker disease. In this work, under greenhouse conditions, Rhizoctonia solani caused dampingoff and death of all faba bean seedlings, however the three tested microorganisms resulted good biocontol role against the pathogenic fungus and the application of T. harizianum gave the best result in this trend. The treatment of T. harizianum and R. leguminosarum var. fabae to the soil infested with Rhizoctonia solani showed significant increase in leaves number of faba bean plants compared with the untreated plants or which treated plants or which treated with Bacillus megaterium var., phosphaticum after 40 days from planting. Application of T. harizianum and R. leguminosarum var. fabae gave the best plant growth while the presence of the pathogenic fungus showed significant decrease in fresh weight, dry weight and nodules number on roots of faba bean plants. Also, polyphenols and antioxidants contents in the shoots and roots were decreased in the presence of the pathogen compared with the untreated plants. Application of R. leguminosarum resulted significant increase in the roots and shoots total nitrogen and protein.

Allelopathic effect of essential oils of medicinal plants in Bidens pilosa L.

We determined the inhibitory allelopathic effects of the volatile extracts of Cinnamomum zeylanicum Ness, Lippia sidoides Cham. and Cymbopogum nardus L. on seed germination and root growth of seedlings of Bidens pilosa. The experiment was conducted at the Seed Analysis Laboratory of the Department of Plant Science, Federal University of Ceará. For this end, we used oils at the concentrations of 0.01, 0.02, 0.04 and 0.08% (v/v). Five treatments were used for each of the oils arranged in a completely randomized design with four replications of 25 seeds. The seeds were sown in Petri dishes lined with filter paper moistened with distilled water and, aiming at the indirect contact with each oil, two sheets of filter paper were placed on top of the lid, in which three (3) mL of each oil solution were added. Then, the dishes were incubated in a germination chamber at 25°C. The pH did not contribute to alter the results; the volatile extracts of essential oils of C. zeylanicum, L. sidoides and C. nardus inhibited seed germination and root growth of seedlings of B. pilosa, which shows allelopathic potential; and the concentration of 0.08% of oils caused the overall deterioration of the roots and death of seedlings of B. pilosa.

English

Moringa oleifera seed germinates poorly and most seedlings die during early establishment. To solve this problem, the effects of pH and growing medium type on the susceptibility of M. oleifera to fungal diseases during seed emergence and early seedling establishment were evaluated in a 3 x 6 factorial experiment arranged as a randomized complete block design with three replications in a greenhouse experiment. Six growing medium types (sandy soil, clay soil, pine bark, clay + sandy soil, clay + pine bark and sand + pine bark) were evaluated at pH 6.2, 8.2 and in situ pH for each growing medium type. The control was the sterilised media of in situ pH. Seed viability tests showed 90% viability. Analysis of the seed showed the presence of Fusarium spp., Pythium spp., Dreschlera spp., Rhizopus spp. and Chactomium spp. Thus, seed was sterilised prior to planting to eliminate any pathogen from the surface of the seed. Media and pH were found to have a significant effect on the emergence of seeds. In situ, sterilised pine bark and clay gave the highest emergence. After emergence, no seedlings showed any infection indicating that reported seedling deaths could be a result of seed borne diseases. Observations indicated Fusarium spp. infection in the seed that had failed to germinate, whilst those in the sterilised media showed no evidence of fungal attack. This means media used for Moringa ought to be sterilised with hypochlorite or another material or procedure to ensure good seed emergence. Key words: pH, susceptibility, viability, media, pathogens, emergence, sterilised, Fusarium spp.