Number Of Healthy Plants Research Articles

First report of brown leaf spot on Juglans sigillata caused by Ophiognomonia leptostyla in Sichuan, China.

Juglans sigillata Dode (Iron walnut) is mostly distributed in southwestern China, and valued for wood and nuts (Feng et al. 2018). In April 2020, we surveyed a walnut garden located in Baisha Town, Wanyuan City, (Sichuan, China), where brown spot symptoms were observed on leaves of ten trees among of 100 plants, and this disease can result in a reduced growth potential when trees are severely infected. Necrotic and subcircular lesions with conidiamata were observed on diseased leaves. Symptomatic leaves were collected and taken back to the laboratory forfurther analysis. Using the single spore isolation technique developed by Chomnunti et al. (2014), five isolates were grown from the infected leaves on Potato Dextrose Agar medium (PDA). The five isolates had similar colony morphology, which was initially white, suborbicular, gradually turning yellowish with black spots, developing fluffy aerial mycelium. Morphological characteristics were examined using light microscopy on the PDA. Conidiogenous cells were subcylindrical to cylindrical, or ampulliform, hyaline, rarely branched. Macroconidia were lunate, reniform, hyaline, 1-3-septate, mostly 1-septate, distinctly constricted at the septum, the basal cell was bluntly rounded, the apical cell had an acute end, and the basal cell was equal to or larger than the apical cell, measuring 22 to 40.5 × 2.5 to 8.3 μm (mean = 32 × 6.2 μm, n = 50). Microconidia were botuliform, or subfusiform, hyaline, both ends were rounded, straight or curved, aseptate, and measured 10 to 28.5 × 1.9 to 3.7 μm (mean= 17.2 × 2.7 μm, n = 20). A multilocus approach was conducted for precise identification of a representative isolate SICAUCC 20-0012. The internal transcribed spacer regions (ITS), guanine nucleotide-binding protein subunit beta gene (MS204), and translation elongation factor 1-alpha (tef1-α) of isolate SICAUCC 20-0012 were amplified and sequenced as described by Sogonov et al. (2008) and Walker et al. (2012a). GenBank Accession Nos. for ITS, MS204, and tef1-α are MW250303, MW246773, and MW246775, respectively. Phylogenetic analyses showed 100% support with Ophiognomonia leptostyla (Fr.) Sogonov, and the morphology was consistent with the asexual stage of O. leptostyla documented by Walker et al. (2012b). To test Koch's postulates, five healthy plants of J. sigillata (2- to 3-year-old) with 5-8 leaves per plant were inoculated with conidial suspensions (104 conidia/mL) after wounded with a small pin as described by Desai et al. (2019), and the same number of healthy plants were wounded and sprayed with sterile distilled water as controls. Plants were sprayed regularly with distilled water every day and placed in a growth chamber at 25℃ with a 12-h fluorescent light/dark regimen. After 15 days, typical brown spot symptoms developed on inoculated leaves, but not on the controls. The fungus O. leptostyla was reisolated from the lesion as described above but not from non-inoculated leaves. O. leptostyla has been reported on some walnut trees; for example: J. ailantifolia, J. californica, J. cinerea, J. hindsii, J. major, J. mandshurica, J. nigra, and J. regia (Farr & Rossman 2020). However, to our knowledge, this is the first report of O. leptostyla causing brown leaf spot on J. sigillata. J. sigillata is an economically important tree in southwest China, and fungicide treatments should be considered to prevent the spread of this fungus before it becomes more widespread. Chunlin Yang, Yu Deng, and Feihu Wang contributed equally to this work. This research was supported by the Key Research and Development Project of Sichuan Province (2021YFYZ0032).

Pseudomonas chlororaphis and organic amendments controlling Pythium infection in tomato

To create more resilient growing systems for greenhouse crops, the efficacy of different organic amendments alone and in combination with the biocontrol strain Pseudomonas chlororaphis 4.4.1 was tested to suppress Pythium disease in tomato plants. Four independent greenhouse experiments were performed with young tomato plants in potting soil. Inoculating the pathogen Pythium aphanidermatum to the potting soil prior to sowing resulted in significant losses of tomato plants; i.e. 94–98% healthy plants in pathogen-free control compared to 43–68% healthy plants when the pathogen was added. P. chlororaphis 4.4.1 inoculations increased the number of healthy plants in the potting soil up to 80% on average; soil and seed treatment were both effective. Numbers of P. chlororaphis in the rhizosphere had increased 4 to 100 fold 3 weeks after its inoculation (qPCR detection). All compost types reduced Pythium disease in potting soil resulting in 80–95% healthy plants. Animal bone char was not effective against P. aphanidermatum, whereas with plant-based biochar there was an effect, although not significantly different from the control treatment. Phosphorous and potassium uptake by the plants were elevated by the different organic amendments. These results demonstrate the potential of the organic amendments to enhance sustainability of growing media such as potting soil by increasing its disease suppressiveness, the re-use of nutrients and replacement of peat by using organic amendments. In addition, inoculating the growing medium or tomato seeds with the biocontrol strain P. chlororaphis 4.4.1 enhanced Pythium control in the susceptible growing media.

Biometric and Microbiological Approach to the aAsessment of the State of Young Plantations Hippophae Rhamnoides l. Subsp. Chinensis Rousi on Disturbed Highlands of Hongyuan County, Sichuan Province, China

This research looks at the results of the assessment of the state of young plantations Hippophae rhamnoides L. subsp. chinensis Rousi on disturbed highlands of Hongyuan County using biometrical and microbiological approaches. It was found that the growth dynamics of young seedlings corresponds to the initial stages of ontogenesis, but has some features. Plantations of H. rhamnoides L. subsp. chinensis Rousi are classified as healthy with signs of weakening. The number of healthy plants is 60.5 %. Soils under plantations are characterized by high heterogeneity of microbiological conditions. The ratio of the main taxonomic and ecological-trophic groups of microorganisms indicates the poverty of the soil with available nitrogen. It is predicted that further these plantations will be able to perform environmental functions.

Acclimatization of micropropagated Musa cavendischii cultivar roatan plants submitted to doses of fertigation and auxin

Micropropagation of banana is suggested to produce great number of healthy plants but the success depends on the ability to transfer plants from in vitro conditions to greenhouse or field environment, at low cost and with high survival rates. In this study, the effects of the fertilization and indolebutyric acid (IBA) applied in the nutritive solution on growth of Musa cavendischii plantlets were evaluated during acclimatization process in greenhouse. First, in vitro plantlets of M. cavendischii were transplanted to pots of 150 cm3 containing perlite and transferred to greenhouse for their acclimatization during 11 weeks. The experiment was established according to a completely randomized design with 5 treatments and 20 replications per treatment. The experimental unit was one plant transplanted in each pot, resulting from the combinations of daily applications of 10 ml of the Steiner’s nutritive solution at 10, 25, 50, 75 and 100%, respectively (Factor A), without and with 1 mgL-1 of the auxin IBA (Factor B). After 11 weeks of acclimatization, the results shows that, the higher plants with respect to plant fresh, dry weight and height, and leaf width corresponded to the treatments from 75 to 100% of the Steiner’s solution. The IBA application had no significant effects on the growth of the M. cavendischii plants. There was no significant interaction between fertigation and IBA applications. The plants fertigated at 100% of nutriments concentration had 27.7 cm of height, 259.9 cm2 of foliar area, and 1.01 mg of chlorophyll g-1 of foliar fresh weight. Key words: Acclimatization, fertilizer, micropropagation, indolebutyric acid, plant nutrition.

APPLICATION OF SALT DURING SEVEN YEARS TO AN ASPARAGUS PLANTATION AFFECTED BY FUSARIUM

Salt application to the soil in asparagus plantations is an old practice which has been recommended to improve the asparagus crops damaged by Fusarium. A trial was established on a 5-year-old 'UC 157' planting in a soil of volcanic origin at Chillan (36°32’S; 71°55’W) to evaluate the effect of salt application in a sector affected by Fusarium spp. The experimental design was randomized complete blocks with five replications. Four doses of sodium chloride: 0, 600, 1200, and 1800 kg ha-1 were applied during summer (January) for seven years (2002 to 2008). There was no effect of salt application on asparagus yield during the seven harvest seasons, not also on the number of plants and number of stalks per plant at the end of each growing season. The number of healthy plants diminished from year 2002 to 2004 in all treatments, being constant the following years. On the other hand, the number of fern stalks per plant has increased in all treatments with passing of the years. The stability of soil aggregates was also evaluated in three opportunities of the year 2007: before, 15 days, and 30 days after salt application. Although there was no effect of the treatments on this parameter, a decrease of the stability in the time was observed (P <= 0.05), being more severe with the highest salt doses (1200 and 1800 kg ha-1).

Dynamical analysis of plant disease models with cultural control strategies and economic thresholds

In this paper plant disease models including impulsive cultural control strategies were developed and analyzed. The sufficient conditions under which the infected plant free periodic solution with fixed moments is globally stable are obtained. For the model with an economic threshold (ET) of infected plants, detailed investigations imply that the number of healthy plants either goes to extinction or tends to infinity, and the maximum value of infected plants is always less than the given ET. In order to prevent the healthy plant population going to extinction, we further propose a bi-threshold-value model, which has richer dynamical behavior including order 1-k or order k-1 periodic solutions with k ≥ 1 . Under certain parameter spaces, the infected plant free periodic solution is globally stable for the bi-threshold-value model. The modeling methods and analytical analysis presented can serve as an integrating measure to identify, evaluate and design appropriate plant disease control strategies.

MYCOBIOTA OF SOLARIZED AND UNSOLARIZED CUCUMBER SOILS AND ROLE OF SOLARIZATION IN CONTROLLING OF SCLEROTINIA SCLEROTIORUM (LIB.) de BARY UNDER GREENHOUSE CONDITIONS

Soil mycoflora play an important role in agri-cultural economy of a country. The current study was made to have the knowledge about soilborne fungi associated with cucumber crop in solarized and unsolarized soils. Solarization exerted various effects, some of which are biological, others are chemical and still others are physical. All together these changes affected directly or indirectly the mycoflora of the soil, especially the soilborne pathogenic ones. Forty-nine fungal species belong to thirty genera have been isolated from solarized and unsolarized soils. The diversity as well as the count was greatly affected by solarization. By comparison of the species lists of the fungal flora of solarized and unsolarized soils it was evident that soil fungi behave differently toward soil solar-ization, while some new species developed e.g. Absidia, Acrophialophora, Talaromyces, Glio-cladium, some remained unaffected e. g. Aspergil-lus, Penicillium, Chaetomium, Botryotrichum, still others disappeared e. g. Acremonium, Cephali-ophora, Eurotium and others. Regarding solariza-tion for controlling white cucumber rot caused by Sclerotinia sclerotiorum, the obtained data clearly show that solarization had led to a marked in-crease in the number of healthy plants up to 72.5%.

The spread of a viral infection in a plantation

AbstractWe consider a plantation subject to viral infection, in which infected plants are replaced by plants from a nursery, also subject to a minor degree of infection. A discrete time Markov chain model for the spread of infection in the plantation is proposed, and its consequences derived. The expected number of healthy plants in the plantation is obtained in the stationary case, and some conclusions drawn about the effect of the level of infection in the nursery on that in the plantation. Copyright © 2004 John Wiley &amp; Sons, Ltd.

The validity ofin vitroscreening methods in the search for fungal antagonists ofSclerotinia sclerotiorumcausing wilt of sunflower

A multi‐test screening system identified 63 fungal isolates with high in vitro biocontrol activity against Sclerotinia sclerotiorum. A bioassay method was developed, using sunflower seedlings growing in an unsterilized loam mixture. Twenty‐six isolates were tested in a series of five bioassay tests and a significant correlation (P < 0.01) was found between sclerotial infection in vitro and the number of healthy plants in vivo. Conversely, activity in an in vitro mycelial overgrowth test was not significantly correlated with activity in vivo. However, some isolates showing only mycelial activity still exerted significant disease control in both the bioassays at Littlehampton and in three additional bioassays at Sittingbourne. Only one isolate not previously reported showed significant activity in both sets of bioassays and the lack of consistency in disease control activity by all other isolates, and biocontrol agents in general, was deemed a major barrier to their use.

Covariation Judgment: Systematic Rule Use in Middle Childhood

SHAKLEE, HARRIET, and PASZEK, DONALD. Covariation Judgment: Systematic Rule Use in Middle Childhood. CHILD DEVELOPMENT, 1985, 56, 1229-1240. Research in causal reasoning and probability judgment indicates that children may show some simple understanding of event covariations by the early elementary school years. The present experiments use a rule-analysis methodology to investigate covariation judgments of children in this age range. Second-, third-, and fourth-grade children saw pictured information illustrating combinations of alternative event states of 2 potentially related events (e.g., plants healthy or not healthy; plant food present or absent) and were asked to identify the direction of the relationship. With increasing age, children were more likely to make judgments based on the pictured event-state combinations. Most common among these judgment strategies was a comparison of frequencies of the target event with and without the covariate (e.g., number of healthy plants with plant food vs. number of healthy plants without plant food, strategy a vs. b). Experiment 2 was a training study designed to investigate possible origins of this rule. Children's posttest performance showed that simply directing their attention to the frequencies of the 2 relevant event-state frequencies was not sufficient to elicit the use of the rule. Additional explicit instructions to compare the two frequencies did lead to use of the a vs. b rule. It was concluded that this simple covariation judgment rule can be used by children in the early elementary school years.

Covariation Judgment: Systematic Rule Use in Middle Childhood

SHAKLEE, HARRIET, and PASZEK, DONALD. Covariation Judgment: Systematic Rule Use in Middle Childhood. CHILD DEVELOPMENT, 1985, 56, 1229-1240. Research in causal reasoning and probability judgment indicates that children may show some simple understanding of event covariations by the early elementary school years. The present experiments use a rule-analysis methodology to investigate covariation judgments of children in this age range. Second-, third-, and fourth-grade children saw pictured information illustrating combinations of alternative event states of 2 potentially related events (e.g., plants healthy or not healthy; plant food present or absent) and were asked to identify the direction of the relationship. With increasing age, children were more likely to make judgments based on the pictured event-state combinations. Most common among these judgment strategies was a comparison of frequencies of the target event with and without the covariate (e.g., number of healthy plants with plant food vs. number of healthy plants without plant food, strategy a vs. b). Experiment 2 was a training study designed to investigate possible origins of this rule. Children's posttest performance showed that simply directing their attention to the frequencies of the 2 relevant event-state frequencies was not sufficient to elicit the use of the rule. Additional explicit instructions to compare the two frequencies did lead to use of the a vs. b rule. It was concluded that this simple covariation judgment rule can be used by children in the early elementary school years.

Influence of irrigation on survival of Poa pratensis infected by Ustilago striiformis and Urocystis agropyri

Irrigation increased the number of surviving plants of Poa pratensis 'Merion' infected with Ustilago striiformis (stripe smut) and Urocystis agropyri (flag smut) and stimulated the production of healthy shoots from infected plants. These effects were more pronounced with plants infected by U. striiformis. Nonirrigated plants infected by U. agropyri had died by the end of the second growing season: irrigation increased the survival of some U. agropyri infected plants to a third growing season and increased the survival of many U. striiformis infected plants for the same period. The number of healthy plants established from irrigated plants infected by U. striiformis also was much greater than those established from plants infected by U. agropyri. The pattern of development for healthy shoot production from infected plants differed for the respective pathogens. The reaction of U. striiformis and U. agropyri to irrigation suggests that U. agropyri is the more destructive of the two pathogens. The production of healthy shoots from infected plants may provide a means for evaluation of P. pratensis for resistance to U. striiformis.

Biological control of a soil-borne pythium infection by seed inoculation

1. A three-fold effect was produced on white mustard seedlings grown in soil infected withPythium sp. Seed germination, the number of healthy plants which survived and the fresh weight of the shoots were reduced.