Nursery Soil Research Articles

Effect of Calcium Cyanamide on Soil Fungal Community in Successive Tea-Cuttings Nursery

The effects of calcium cyanamide on the soil fungal communities in successive tea-cuttings nursery soils were investigated based on Illumina high-throughput sequencing. The field experiment was carried out with three treatments, including control (CK), flooding (F) and calcium cyanamide (CC). The treatment with calcium cyanamide increased pH (~1 unit) and reduced the accumulation of phenols (~50%), available phosphorus (~28%) and exchangeable Al (~90%) significantly, and improved soil quality. The predominant phylum in all treatments was Ascomycota. FUNGuild revealed that the dominant trophic mode was saprotrophy in tea-cuttings nursery soil. Plant pathogens had a low abundance in the calcium cyanamide treatment. Alpha diversity analysis showed lower richness in the calcium cyanamide than the other treatments. Network analysis showed a poorly connected but highly modularized network in the calcium cyanamide treatment, with the crucial OTUs functions related to anti-pathogenicity. The results showed that calcium cyanamide should be recommended for improving long-term tea nurseries by increasing the survival rate of tea seedlings due to increasing soil pH value, reducing aluminum toxicity, decreasing the accumulation of polyphenols, diminishing pathogenic fungi and making the taxa related to anti-pathogenicity occupy a more important niche.

Ecology, biology and enzymatic activity of the rhizosphere planted with Larix decidua seedlings after addition of vermicompost

The aim of this study was to determine the influence of Eisenia fetida vermicompost (VC) added to forest nursery soil. The chemical reaction in the soil and selected microorganisms, such as bacteria, fungi and nematodes, were assessed. Larch seedlings were cultivated for 2 years in pots with nursery soil as a control and VC-amended soil in two doses: 10% (V10) and 20% (V20) v/v. One important observation was the connection between the addition of VC and the improvement of the plant's biometry and a much higher level of mycorrhization with increasing Suillus sp. Vermicompost modified the nematode community by reducing plant parasitic nematodes, and significantly increasing bacterial and fungivorous, as well as predatory nematodes. Actinomycetes bacteria, which were present in a proportion of 2.2% in the control soil, increased to 10.5% in V10, and to 5.4% in V20. Bacillus spp. increased along with the amount of VC from <0.01% in the control to 2.2% in V10 and to 2.7% in V20. The C:P ratio correlated negatively while the C:K ratio and N-NH4 concentration correlated positively with the abundance of Bacillus spp. Toxigenic Penicillium spp. and Fusarium spp. were suppressed. The stability of VC-amended soil system with respect to enzymatic activity was rather high, except for o-diphenol oxidase which was strongly reinforced by the VC. The enzyme activity values for all enzymes were correlated with an improvement in the values of the microbiological, biometric and nematode parameters and increased mycorrhization. One favorable modification, which was manifested in better seedling growth, was the effect of VC on the development of Suillus-morphotype mycorrhizal fungi, fungal feeder nematodes and Bacillus spp. Vermicompost may therefore be recommended in practice as a method of sustainable management for soil protection in larch forest nurseries.

Effect of Potting Media on Growth and Quality parameters of &lt;i&gt;Juniperus polycarpos&lt;/I&gt; C. Koch Seedlings under Nursery Condition

A trial was conducted to study the effect of different potting media on the growth performance of Juniperus polycarpos under nursery condition. One year old seedlings of J. polycarpos raised in germination beds were transplanted in polybags filled with different combination of potting media with seven treatments comprising various combinations of soil, sand and farmyard manure and five replication in completely randomized design to study their effect on seedling growth and quality parameters. Significant differences were observed in shoot length, collar diameter, root length, number of roots, root and shoot biomass of J. polycarpos seedlings raised in different potting media. Maximum growth of various seedling parameters viz., shoot length (58.80cm), collar diameter (6.98mm), root length (55.24cm), number of roots (58.53) was recorded in treatment T 7 i. e. Soil + Sand + FYM (1:1:1) where as minimum growth of various seedling parameters was recorded in treatment T 1 i.e. nursery soil. Maximum fresh shoot biomass (32.35 g seedlings -1 ) was recorded in treatment T 4 , whereas fresh root biomass (9.08 g seedlings -1 ) and total fresh biomass (40.85g seedlings -1 ) was recorded in treatment T 7 . Maximum dry shoot biomass (17.33 g seedlings -1 ) was recorded in treatment T 5 whereas dry root biomass (4.60 g seedlings -1 ) and total dry biomass (21.86g seedlings -1 ) was recorded in treatment T 7 . Maximum value of various seedling quality parameters viz., root shoot ratio (0.27), volume index (2864.75) and Quality index (1.79) was also observed in seedling grown in treatment T 7 and whereas least value of sturdiness quotient (8.40) was observed in treatment T 1 (nursery soil) which is at par with treatment T 7 . The study recommended raising of seedlings of J. polycarpos in soil, sand and farm yard manure (1:1:1) for production of quality nursery stock.

Estimation of indoxacarb and thiamethoxam residues in chilli

ABSTRACT Supervised field trials were conducted for two consecutive years to estimate the dissipation and persistence of indoxacarb and thiamethoxam residues in chilliafter two foliar applications of Indoxacarb 14.5 SC @ 55 and 110 g a.i. ha−1 and seed treatment of Thiamethoxam 30 FS @ 2.1 and 4.2 g a.i. ha−1. The chilli fruit samples that were collected at different time intervals were processed by QuEChERS methodology, and residues of indoxacarb and thiamethoxam were determined by Gas Liquid Chromatography (GLC) and Gas Chromatography-Mass Spectrometry (GC-MS/MS). The average initial deposits of indoxacarb on green chilli fruits were found to be 2.75 and 5.93 mg kg−1 at single dose while 2.56 and 5.68 mg kg−1 at double dose, respectively, in years 2019 and 2020. These residues reached below the limit of quantification (0.01 mg kg−1) after 25 and 35 days, respectively, at both the doses. The mean residues of thiamethoxam in seedlings, green chilli fruits and red chilli fruits were observed to be below its limit of quantification (0.05 mg kg−1) while, in nursery soil, the residues remained detectable till 10 and 15 days after single and double doses. The half-life value of indoxacarb in green chilli was calculated to be 3.46–4.77 and 3.58–3.76 days while in soil, it was calculated to be 3.85 and 4.93 days, respectively, at single and double recommended doses.

Bioaccumulation and Translocation Factors of Lead in Mustard and Maize Plants in Soil Kurdistan Region _ Akre City

The aim of this study is to determine the Pb bioaccumulation and translocation factors in mustard (Brassica juncea) and maize (Zea mays L). growing in the pot experiment in Akre horticulture nursery soil. In present paper, about 1gm of root and shoot portions of the selected plant species that were growing in the site were separately collected. Besides, 10gm of soil samples were also collected from the pots at each sampling where the plants were previously sampled. The soil and plants were analyzed for Pb by atomic absorption spectrophotometer (AASP), type GBC 932AA. Bioaccumulation factor (BAF) was measured in the plant species and obtained from the ratio of Pb content in the plant root to that of extracted Pb content in the soil. And, Translocation factor (TF) was obtained from the ratio of Pb content in the plant shoots to that in the plant roots, from the results obtained, the two plant species had BAF and TF>1, suggesting their applicability in extraction of Pb polluted soil at the study site. Since Pb accumulation and translocation, factors in the two plants species were more than one so they regard as accumulator plants and suggest that the plants species having phytoextraction ability and could be used in restoring soil contaminated with Pb.

A new method for early detection of latent infection by ‘Candidatus Liberibacter asiaticus’ in citrus trees

Background: ‘Candidatus Liberibacter asiaticus’ (CLas) is a major causal agent of citrus greening disease. The disease primarily involves an asymptomatic, often latent infection of CLas. However, there is no effective technique to distinguish latent-infected trees from healthy ones. This study describes the development of a new detection method for latent CLas infection using cuttings. Methods: Root tissues regenerated from cuttings using symptomatic and asymptomatic citrus trees were prepared for real-time a polymerase chain reaction (PCR) test which was used to investigate latent CLas. When some of the regenerated roots were negative for CLas in the first real-time PCR assay, a subsequent cultivation in soils was performed using the CLas-negative cuttings. CLas development during cultivation was evaluated by a second real-time PCR assay using soil-grown roots from seedlings. Results: Previously, CLas had not been detected from leaves of the latent-infected trees in our greenhouse by real-time PCR. In this study, however, CLas was detected at a moderate frequency from the root tissues of cuttings derived from the latent-infected trees, by the same PCR test. For cuttings with regenerated roots that tested negative for CLas by real-time PCR, CLas was frequently detected from roots grown in nursery soil with autoclaving, after cultivation for a month or more. Conclusions: Latent infection with CLas was detectable by real-time PCR using root tissues regenerated by cuttings and roots grown in nursery soil with autoclaving. These results suggest that the new method of investigation would provide great opportunities for early detection of CLas in asymptomatic citrus trees from field surveys, and would accelerate the eradication practice of citrus greening.

DNA-Metabarcoding of Belowground Fungal Communities in Bare-Root Forest Nurseries: Focus on Different Tree Species.

The production of tree seedlings in forest nurseries and their use in the replanting of clear-cut forest sites is a common practice in the temperate and boreal forests of Europe. Although conifers dominate on replanted sites, in recent years, deciduous tree species have received more attention due to their often-higher resilience to abiotic and biotic stress factors. The aim of the present study was to assess the belowground fungal communities of bare-root cultivated seedlings of Alnus glutinosa, Betula pendula, Pinus sylvestris, Picea abies and Quercus robur in order to gain a better understanding of the associated fungi and oomycetes, and their potential effects on the seedling performance in forest nurseries and after outplanting. The study sites were at the seven largest bare-root forest nurseries in Lithuania. The sampling included the roots and adjacent soil of 2–3 year old healthy-looking seedlings. Following the isolation of the DNA from the individual root and soil samples, these were amplified using ITS rRNA as a marker, and subjected to high-throughput PacBio sequencing. The results showed the presence of 161,302 high-quality sequences, representing 2003 fungal and oomycete taxa. The most common fungi were Malassezia restricta (6.7% of all of the high-quality sequences), Wilcoxina mikolae (5.0%), Pustularia sp. 3993_4 (4.6%), and Fusarium oxysporum (3.5%). The most common oomycetes were Pythium ultimum var. ultimum (0.6%), Pythium heterothallicum (0.3%), Pythium spiculum (0.3%), and Pythium sylvaticum (0.2%). The coniferous tree species (P. abies and P. sylvestris) generally showed a higher richness of fungal taxa and a rather distinct fungal community composition compared to the deciduous tree species (A. glutinosa, B. pendula, and Q. robur). The results demonstrated that the seedling roots and the rhizosphere soil in forest nurseries support a high richness of fungal taxa. The seedling roots were primarily inhabited by saprotrophic and mycorrhizal fungi, while fungal pathogens and oomycetes were less abundant, showing that the cultivation practices used in forest nurseries secured both the production of high-quality planting stock and disease control.

Seedling Production from Seeds of a Wild Ecotype of Vetiver Grass (&amp;lt;i&amp;gt;Vetiveria zizanioides&amp;lt;/i&amp;gt; L.) in Southern China

Vetiver grass (Vetiveria zizanioides L.) is widely used for soil and water conservation, and land management. In practice, all vetiver seedlings are propagated via ramets or tillers, which cannot meet the market demand and would also destroy the original habitat. Most vetiver genotypes flower but do not produce seeds. A wild ecotype of vetiver grass originated in southern China is fertile, but the rate of seed germination is very low. This study aimed to develop a novel method to improve its seed germination and seedling establishment. In the field, the inflorescences of wild vetiver were wrapped using a transparent plastic bag with a pot containing wet soils. The effects of inflorescence bagging and Tween 80 application on seed germination and seedling growth were examined. The results showed that seed development was characterized by low seed setting rate (19.2%), uneven maturity time, easy shedding (more than 95% of spikelets shed off 20 days after flowering), therefore difficult harvest of viable seeds. Bagging the inflorescence with moist soils in pot ensured the mature seeds falling onto the nursery soil surface and absorbing water for germination while the immature seeds continued to grow on the inflorescence. Bigging not only improved seed development and maturity, saved the procedure of seed collection and storage, but also provided a humid micro-environment for seed germination and seedling growth. Tween 80 as a surfactant promoted seed water absorption, germination and seedling growth. This simple and novel method has integrated the procedures of seed collection, storage, germination and seedling establishment, and enables the production of a large number of healthy seedlings. The possible reasons for the degeneration and disappearance of the original population were also discussed from the perspective of the disadvantages of vetiver propagation.

Field Evaluation of a Novel, Granular Soil Fumigant for Controlling Phytophthora ramorum in Field Nursery Soils

Phytophthora ramorum, the causal agent of Sudden Oak Death (SOD) and ramorum blight, infects a wide range of hardwood and nursery ornamental species. Chlamydospores of P. ramorum can survive for extended periods of time in soils. Two studies were conducted, including: 1) a laboratory study to evaluate two liquid disinfectants for controlling P. ramorum chlamydospores, and 2) a field study to evaluate a novel soil fumigation treatment as an alternative to soil steaming or methyl bromide soil fumigation. The liquid disinfectants were ElectroBiocide and Oxidate 2.0. The laboratory study resulted in complete inactivation of the P. ramorum chlamydospores after six minutes of contact time for both the liquid disinfectants The field study evaluated a chlorine dioxide granule formulation that was applied at two rates in a nursery soil. Rhododendron leaf discs were inoculated with P. ramorum, placed in permeable sachets and buried at two soil depths in a research nursery. Soil treatments also included saturated hydrogels (with and without gels) so that soil moisture effects on chlamydospore survival could be estimated. The sachets were recovered 5, 15 and 30 days after the soil treatment. Efficacy of the soil treatments was evaluated by the number of leaf discs showing P. ramorum growth recovered from the sachets. The soil fumigation treatment with highest efficacy occurred when the sachets were buried at the 5 cm soil depth, were treated with hydrogels, at the highest Z-series granule rate (800g/tube), and had a contact time of 30 days. The probability of P. ramorum growth for this soil treatment was 0.18, or 18%, i.e. the probability of that fumigation treatment inactivating the pathogen was 82%. Also, as the soil moisture increased, the efficacy of the fumigation treatments also increased.

First Report of Root Rot Caused by Dactylonectria torresensis on Bletilla striata (Baiji) in Yunnan, China.

Bletilla striata (Thunb.) Rchb.f. (Orchidaceae family, known as Baiji in Chinese) is an endangered plant species with important medicinal value in China. Bletilla striata plants with symptoms of wilting, leaf yellowing and rotting on underground parts were found in Shizong (24.82822 N; 103.99084 E), Yunnan Province, China in July 2016. In the following years, this disease occurred and became prevalent when high temperature and high humidity prevailed in the fields from May to August. The incidence of the disease varied from 45 to 75%, with yield losses of 40 to 65% in different B. striata fields. To identify the causal agent of the disease, symptomatic vascular tissue fragments were soaked in 2% sodium hypochlorite for 2 min, rinsed twice with sterile distilled water, and then placed on 4% (w/v) potato dextrose agar (PDA) plates. The plates were incubated at 26°C in 12h light/dark for three days. Mycelia grown from the edges of the plant fragments were transferred to PDA plates and incubated at 26°C in 12h light/dark. After three days, hyphal tips were isolated from the edge of the colonies to PDA plates. Three hyphal-tip isolates from different plants were further studied. The colonies of these three isolates were dark red, with cottony mycelia of moderate density. Hyphae were transparent and branched. Numerous hyphae anastomosed frequently and formed hyphal coils. For further morphological analysis, sporulation was induced as described by Cabral et al. (2012) and Lombard et al. (2014). Macroconidia were abundant, 37.2 to 44.0 µm × 5.2 to 8.7 µm based on the measurement of 20 conidia from each isolate. Ascospores divided into two cells of equal size, ellipsoid to oblong-ellipsoid, 12.5 to 14.8 µm × 4.8 to 5.9 µm based on the measurement of 20 spores from each isolate. Conidiophores simple or complex, sporodochial. Simple conidiophores arising laterally or terminally from aerial mycelium, solitary to loosely aggregated, unbranched or sparsely brached, more or less cylindrical. These morphological characteristics were consistent with the description of Dactylonectria spp. by Cabral et al. (2012) and Lombard et al. (2014). From one isolate, the internal transcribed spacer (ITS) region of ribosomal DNA and the beta-tubulin (tub2) gene were amplified by polymerase chain reaction (PCR) using the primer pairs ITS1/ITS4 (White et al. 1990) and T1/Bt-2b (Cabral et al. 2012), respectively. PCR products were sequenced and deposited in GenBank with accession numbers MH458779 (ITS) and MH626485 (tub2). BLAST search revealed that both sequences showed 99 to 100% homology with the corresponding sequences of previously identified D. torresensis isolates. Specially, MH458779 shares 100% identity with the entire 463-base pair (bp) sequence of KP411806, the ITS sequence of a D. torresensis isolate identified from olive trees (Nigro et al. 2019); MH626485 shares 99% identity with the entire 320-bp sequence of KP411801, the tub2 sequence of the same olive tree isolate. In addition, the entire 609-bp sequence of MH626485 shares 99% identity with JF735478, the tub2 sequence of a D. torresensis isolate identified from grapevines (Cabral et al. 2012). To test the pathogenicity of the fungus, plants of B. striata in plastic pots filled with sterilized nursery soil were inoculated with each of the three isolates by placing a fungal-colonized wheat kernel adjacent to each health plant. Plants inoculated with noncolonized wheat kernels were used as controls. Plants in three pots (replicates), with one plant per pot, were inoculated by each isolate. The pots were maintained in a greenhouse with a 12h photoperiod at 25°C. Ten days after inoculation, black necrotic lesions identical to those observed in the field were evident on the roots of all inoculated plants. Using the same methods described above, fungi with identical morphologies as described above were isolated from lesions caused by each of the three isolates. The control plants remained healthy, and no fungus was re-isolated. This completed Koch's postulates. Based on the morphological characteristics and molecular identification, the pathogen was determined to be D. torresensis. To our knowledge, this is the first report of D. torresensis causing root rot of B. striata in Yunnan, China. It is important to further study the impacts of this new disease on B. striata production in China.

First Report of Damping-off on Sedum plumbizincicola Caused by Rhizoctonia solani AG 2-1 in China.

Sedum plumbizincicola X.H. Guo et S.B. Zhou sp. nov. is a plant species of the family Crassulaceae that has the ability to hyperaccumulate cadmium and zinc in high concentrations (Liu et al. 2017). In April of 2018 and 2019, a disease of damping-off was observed on S. plumbizincicola seedlings in a nursery in Changsha (28°13'N; 112°56'E), the Hunan Province of China, in which nearly 1 million seedlings were planted. Approximately 40% of the surveyed plants were infected. The affected plants displayed water-soaking on the shoots and stems, and chlorosis on the leaves. As the disease spread upward, leaf stalks or the whole plants became wilted and collapsed. Five diseased stem and leaf samples were collected. Symptomatic tissues were excised and surface sterilized with 70% ethanol for 10 s, and 0.1% HgCl2 for 2 min, washed with sterile distilled water for three times, and then cultured on potato dextrose agar (PDA) at 26°C in darkness. Fungal colonies were similar in morphology: white, light gray to brown, with hyphae branched at nearly right angles, septa near the branching point and constrictions at the base of hyphal branches. After 10 days, white-gray to brown sclerotia were produced. The morphological characteristics were consistent with those of Rhizoctonia solani J.G. Kühn (Sneh et al. 1991). Genomic DNA of a representative isolate was extracted using the cetyltrimethylammonium bromide method. The internal transcribed spacer (ITS) region of rDNA was amplified and sequenced with the primer pairs ITS4/ITS5 (White et al. 1990). When analyzed by the BLASTn program, the ITS sequence (GenBank Accession No. MN961664) had 100% identity to the corresponding gene sequence of R. solani anastomosis group (AG) 2-1(Accession Nos: LC202869.1 and MH862641.1). In addition, primers Rhsp1/ITS4B and Rhsp2/ITS1F specific for R. solani, and AG21sp/ITS4B specific for R. solani AG 2-1 were also used (Salazar et al. 2000). Results revealed that our isolate was R. solani AG 2-1. Pathogenicity was confirmed via in vivo inoculation of one-month-old S. plumbizincicola seedlings in sterilized nursery soil with four representative isolates. For each pot, five 5-mm-diameter mycelial plugs from 7-days old colonies on PDA were placed in the soil near the base of the stems. Plants inoculated with agar plugs without mycelium served as controls. The inoculated plants were kept in a growth chamber at 25°C with a 12/12 h light/dark cycle. Pathogenicity tests were performed twice, with three replicative potted plants for each isolate in each test. Approximately 25 days after inoculation, the damping-off symptoms resembling those observed in the field were displayed on the inoculated plants, while no obvious symptoms were observed on the control plants. R. solani was re-isolated from all infected plants and molecularly characterized, thus confirming Koch's postulates. R. solani has been previously reported as the pathogen of damping-off disease in many plants, such as canola (Paulitz et al. 2006) and oat (Zhang et al. 2016). However, to the best of our knowledge, this is the first report of R. solani causing damping-off of S. plumbizincicola in China. S. plumbizincicola is widely planted for heavy metal pollution treatment in China. The occurrence of this disease could seriously affect the production of the seedlings, and management strategies should be developed.

An evaluation of selected chemical, biochemical, and biological parameters of soil enriched with vermicompost

The aim of this study was to assess the changes in chemical and microbial properties and enzymatic activity of soil enriched with vermicompost derived from household waste. The vermicompost was tested in the rhizosphere of Larix decidua seedlings cultivated in 10-L pots in: (i) nursery soil (as the control), (ii) soil with 10% v/v vermicompost, and (iii) with 20% v/v vermicompost. The impact of vermicompost was assessed in terms of soil C/N ratio; bacterial, fungal, and nematode counts; and enzymatic activity. It was found that vermicompost increased the C/N ratio from 21 to 32, as well as the content of nitrate from 78 to 134 mg kg−1, of ammonium from 14 to 139 mg kg−1, of phosphorus from 92 to 521 mg kg−1, and of potassium from 142 to 1912 mg kg−1, compared with the control soil. The abundance of beneficial bacteria was increased (from 8.61 × 107 to 37.9 × 107), along with decreases in microbiological ratios of fungi and bacteria (e.g. fungi/Bacillus from 0.18818 to 0.00425). A significant 2- to 4-fold increase was observed compared with the control in the number of beneficial nematodes belonging to bacterivorous, fungivorous, and predatory groups with no change in the abundance of plant-parasitic nematodes. Addition of vermicompost brought about a change in soil enzyme activity. Vermicompost reduced the activity of alkaline phosphatase only. Both doses of vermicompost led to an increase in the activity of acid phosphatase, inorganic pyrophosphatase, dehydrogenases, β-glucosidase, and urease. Only the higher dose had an effect on increasing the activity of o-diphenol oxidase and proteases. No significant change was observed for nitrate reductase. Also, the presence of antibiotics produced by bacteria was detected depending on the dose of vermicompost, e.g. iturin (ituC) and bacillomycin (bmyB) were found in soil with a dose of 20% v/v vermicompost. Overall, vermicompost produced from household waste can be an excellent organic fertilizer for larch forest nurseries.

First Report of Fusarium xylarioides Causing Root and Stem Rot on Aloe vera in China.

Aloe vera (L.) Burm f. is a perennial herb belonging to the family liliaceae. It is widely grown for medicinal, cosmetic and vegetable use. In 2018 and 2019, a root rot disease occurred on potted A. vera plants in a nursery in the Hunan Province of China. Symptoms of the disease include water soaking lesions, brown spots on taproot or basal part of the stem. The plants were easy to pull out when the taproot is rotten or necrotic. As the disease progressed upward, leaves in the basal part of stems became red-brown and gradually fell off. In severe cases, the whole plants became rotten and wilted. For isolation purposes, diseased tissues were excised from the lesion margins, surface disinfested with 70% ethanol for 10 s, 0.1% HgCl2 for 2 min, rinsed with sterile water thrice, and then placed on potato dextrose agar (PDA) and incubated at 26°C for 3 days in the dark. When cultured on PDA, fungal strains with similar morphology were consistently isolated and purified by single spore isolation. Colonies showed thick, pink aerial mycelium with a growth rate of 1.3 cm /day. The pigmentation was more intense in the colony center and became pale orange and white at the edge of colony. When cultured on SNA (Spezieller Nährstoffarmer agar), the fungus showed less pigmentation and thinner hyphae. Microconidia were abundantly produced, clavate and oval to kidney shaped, 7.1 to 15.2 μm × 2.5 to 5.1 μm, with 0 to 1 transverse septa. Macroconidia were sickle shaped, slender, slightly incurved in apical cell and foot-shaped in the basal cell, measured 27.9 to 53.2 μm × 2.5 to 3.5 μm, with 3 to 5 septa. These morphological characteristics were similar with those of Fusarium spp. (Booth 1971). For molecular identification, genomic DNA of the fungus was extracted by cetyl trimethyl ammonium bromide method. A portion of EF-1α (translation elongation factor 1-α) and RPB1 (the largest subunit of RNA polymerase) genes were amplified and directly sequenced using the EF-1/EF-2 and Fa/G2R primers (O'Donnell et al. 2010). The EF-1α and RPB1 were deposited in the GenBank with accession numbers MT755386 and MT755387. The EF-1α and RPB1 had 97.14% (ID FD_01334) and 99.62% identity (FD_03853), respectively, to F. xylarioides strains in the Fusarium-ID database (Geiser et al. 2004). In addition, the EF1-a showed 96.825% identity to the F. lateritium CBS 119871(AM295281) (a synonym of F. xylarioides), and the RPB1 showed 99.623% identity to the F. xylarioides NRRL 25486 (JX171517.1). Accordingly, the fungus was putatively identified to be F. xylarioides. For pathogenicity assay, A.vera seedlings were pot planted using sterilized nursery soil and inoculated with conidia suspension (1 × 105 conidia/ml), which were eluted from 7-day-old PDA cultures with sterilized water, according to the method described previously (Vakalounakis et al. 2015). The collar of each potted plant was poured with 20 ml of conidia suspensions. Plants mock inoculated with sterile water were used as control. All the inoculated plants were placed in a growth chamber at 25°C under 12/12 h light/dark cycle. The inoculation assays were carried out twice, with each one had three replicated plants. After 30 days, rot symptoms seen from the roots and basal part of stems were observed on the inoculated plants, but no visible symptoms were observed on control plants. The fungus was re-isolated from the inoculated plants and identified to be F. xylarioides by morphological and molecular characteristics, thus confirming Koch's postulates. As we know, many Fusarium species have been reported to cause root and stem rot disease in A.vera such as the F. oxysporum (Ji et al. 2007) and F. solani (Vakalounakis et al. 2015). However, to the best of our knowledge, this is the first report of F. xylarioides causing root and stem rot disease of A.vera in China. The identification of the pathogen fungus might provide a foundation for taking appropriate control strategies to this disease.

Growth Performance of Jatropha curcas Cultivated on Local Abandoned Bauxite Mine Soil

Lack of regulation in bauxite mining has caused land contamination in Malaysia. Land rehabilitation requires plants with excellent adaptability to adverse conditions. Inedible, economical viable crops with environmental co-benefits, like phytoremediation, are preferred. In this study, Jatropha curcas was evaluated for its growth performance in bauxite mine soil. Topsoil and exposed subsoil were sampled from a bauxite mine at Bukit Goh, Kuantan and used for growing J. curcas for 90 days under greenhouse conditions. The soil physicochemical properties, plant growth parameters (increase in number of leaves, plant height, and basal diameter), and oil yield were determined. The findings showed that the mine soils had lower nutrient status than unmined soil as reflected by the total C, N, P, and K values. Al, Fe, and Pb were relatively high in topsoil and subsoil. Plants grown in both mine soils recorded significantly lower increases in plant height and basal diameter but higher increases in number of leaves than that of nursery soil. Oil yield was significantly different between the plants grown in subsoil (46.54%) and topsoil (41.65%). The study demonstrated that J. curcas has the potential to be cultivated as an alternative crop in bauxite mine soil.

Effect of chemical alternatives to methyl bromide on soil-borne disease incidence and fungal populations in Spanish strawberry nurseries: A long-term study.

Chloropicrin (PIC) mixtures of 1,3-dichloropropene and chloropicrin (DD:PIC), dazomet, and metam sodium (MS) have been applied as chemical alternatives to methyl bromide (MB) in Spanish strawberry nurseries since MB was banned as a soil fumigant in 2005. These chemical alternatives were applied to soil in two Spanish strawberry nurseries between 2003 and 2017 to test their efficacy against the main crown and root disease and soil fungal populations in comparison with the use of MB and PIC (MB:PIC). These chemicals were applied at several doses with different application methods under plastic films. Crown and root disease incidence was calculated as the percentage of plants with symptoms caused by soil-borne pathogens. Soil fungal populations were estimated as colony forming units per gram of dry soil. All chemicals significantly reduced soil-borne fungal disease incidence and fungal population in both nurseries over the years. Phytophthora cactorum and Fusarium spp. were the main pathogens causing soil-borne diseases, followed by Verticillium spp. MB:PIC remained the treatment that best controlled P. cactorum. MS and DD:PIC controlled Fusarium disease to a lesser extent than MB:PIC and dazomet in both nurseries. MB:PIC and PIC were the two treatments that most reduced Verticillium spp. The population of Verticillium spp. declined and the presence of other species such as Colletotrichum spp. and Rhizoctonia spp. was minimal during the study. Chemicals are necessary to obtain healthy strawberry plants. The use of chemical alternatives to MB has resulted in changes in the incidence of soil-borne diseases and soil fungal populations in strawberry nurseries. Dazomet was an effective alternative to MB as a soil-borne disease control, except against Verticillium spp. MB alternatives in strawberry nursery soils have caused Fusarium spp. to displace Verticillium spp.

Monitoring of biological activity indicators of forest nursery soils in Siberia

The universality, comprehensiveness and adequacy of biological soil diagnostics methods make them widely used in monitoring studies of anthropogenic effects on the soil. Soil samples of forest nurseries have been studied, directly under seedlings and in the steam field. Anthropogenic loading changes the biological parameters of the soil, leading to a decrease in soil fertility. The results of the assessment of the biological state of forest nursery soils used for the planting material of coniferous seedlings in Siberia by the level of enzymatic activity are presented. Analysis of soil quality by methods of research of oxidative and hydrolytic enzymes was carried out. Monitoring of enzymatic activity indicators of soils of forest nurseries of Krasnoyarsk region showed that by activity of catalase, invertase of urease they belong to medium-enriched. It has been established that in the soil of Uyarsky, Kansky and Kuraginsky forest nurseryscientists there is the highest rate of proteolytic activity. Low level of catalase enzyme activity revealed in Kazatinsky nursery against the background of high soil contamination with phytopathogenic microorganisms.

English

Symptoms of Phytophthora seedling blight disease of cacao were found on 3 weeks old cacao seedlings at the nursery of Seed Production Division of Ghana Cocoa Board in New Tafo-Akim during routine surveys of cacao diseases in the Eastern Region of Ghana. Survey of seedlings in the nursery was conducted to determine disease incidence (DI). Heat sterilization of soil and drenching with Ridomil Gold plus 66 WP (6% metalaxyl-M and 60% copper (I) oxide) and Champion (77% cupric hydroxide) fungicides were evaluated for disease management. Symptoms of the disease started as vertical brown lesions above the cotyledon toward the top of cacao seedlings, causing the stems and leaves to wilt. Out of a total of 135,000 inspected cacao seedlings at the nursery, 2,525 (DI = 1.8%) seedlings were infected within one week of disease identification. Isolations from samples of infected tissues yielded Phytophthora palmivora. The fungicides were effective in disease control but heat sterilization of nursery soil before sowing cocoa beans was found to be the ideal control method. Key words: Seedling blight, cacao, Phytophthora palmivora, fungicides. &nbsp

Response of Albizia lebbeck to Moisture Stress on Seed Germination and Moisture Gradient on Seedling Growth

The polyethylene glycol (PEG 6000) was used under laboratory conditions. The studied parameters viz., germination percentage, mean daily germination, peak value, germination value and hypocotyls length was significantly reduced with increase in moisture stress. The control treatment T1 had highest Germination percentage, mean daily germination, peak value, and germination value and hypocotyls length. There were decreases in the values of all the studied germination parameters with increase in moisture stress created by use of different concentration of polyethylene glycol (PEG 6000). The different irrigation interval (days) followed for seedling production in nursery exhibited that different moisture gradients in nursery soil effected significantly seedling growth parameters viz., seedling height, collar diameter, number of leaves, leaf area, number, fresh shoot weight, fresh root weight, chlorophyll a content, chlorophyll b content, nutrient uptake in leafs (N,P,K) and root: shoot ratio were significant. There was decrease in all the studied growth parameters (except root shoot ratio) recorded with increase in moisture stress caused by irrigation interval studied. Out of the three container size of hyco-trays studied, the container size T3 (300 cc) had significantly the highest seedling height, collar diameter, number of leaves, leaf area, fresh shoot weight, fresh root weight, total chlorophyll, nitrogen content in leaf, phosphorus content in leaf, potassium content in leaf and root; shoot ratio as compared to container size T1 (93 cc) and T2 (150 cc).There were increase in all the studied growth parameters (except root shoot ratio) studied with increase in size of root containers, which could be attributed to more growing media and nutrients, and higher water holding capacity in large sized containers.

Biological Control of Pythium Damping –off in Seedlings with Streptomyces Sp.

Damping-off is one of the severe diseases caused by soil-borne pathogens notably Pythium sp. the causative agent of this infection in raising tree saplings in forest nurseries. Biological control is an eco-friendly approach in disease management compared to chemical fungicides which in turn affects the soil environment. Biocontrol of Pythium sp. has been emphasized in vegetable nurseries than forest nurseries. The present research work is focused on identification of effective antagonistic organism from forest nursery soils against Pythium aphanidermatum. Bacteria were isolated from various forest soils collected from Boluvampati, Sirumugai and Mettupalayam forest nurseries in Coimbatore district and soil samples were screened for antifungal activity against Pythium aphanidermatum by dual culture technique. Among 245 bacterial isolates, one isolate KUMB1.1 exhibited clear zone of inhibition of 1cm and it was identified by 16S rDNA sequencing as Streptomyces sp. Solvent extraction was performed to isolate an active compound using ethyl acetate, dichloromethane, n-butanol, hexane and chloroform in the ratio 1:1. The antifungal activity of compound was performed by well plate method against Pythium sp. and n-butanol extract exhibited zone of inhibition. The antifungal activity of Streptomyces sp. was tested in a model plant Solanum lycopersicum (Tomato) seeds raised in Pythium aphanidermatum infested soils in seed trays under in vitro conditions. Pre-emergence and post-emergence disease incidences were observed, and the results exhibited promising efficacy of Streptomyces sp. against the fungal pathogen Pythium aphanidermatum. Seedbed study was carried out in Gmelina arborea seeds, where the seeds are treated with Streptomyces culture broth. In which seed treatment shows 43% increase in germination compared with control.

Evaluation of Biocontrol Efficacy of Herbal and Bioformulations against Root Rot Pathogen Fusarium Solani in Tomato

Background/Objectives: Fusarium solani cause various plant diseases that usually weaken or destroy plant tissues and reduce crop yields varying from 30-40% and root diseases are estimated to cause 10-15% yield losses annually in the world Soil borne pathogen Fusarium solani which causes root rot at the seedling stage itself leading to wide loss of the crop. Solanum lycopersicum (tomato) is one of the most versatile vegetable with wide usage in Indian culinary tradition. Since the use of chemical fungicides cause environmental pollution and adverse effect on human health, there is need to shift to biological control. Methods: Bacterial isolates were obtained from forest nursery soil samples and screened against F. solani. Of which one isolate showed promising efficacy against the pathogen. Preparation of oil based liquid bioformulation using glycerol, coconut oil and culture filtrate of biocontrol agent and herbal formulation using neem, garlic, ginger and clove blended together with water in the ratio 1:2 showed inhibitory effect on F.solani. Findings: Biocontrol agent was identified by 16S rDNA sequencing as Bacillus velezensis FZB42. Tomato seeds were coated with Gum Arabic as adhesive along with liquid bioformulation and herbal formulation showed great inhibitory effect against the F. solani in invitro conditions, increased the germination percentage of seeds and also the germination was faster when compared with the control. Applications: Technology transfer of application of this formulation to the farmers will be initiated which will help them to raise the seedlings in an ecofriendly method.