Severe Foliar Damage Research Articles

The potential role of <i>Aureobasidium pullulans</i> in the development of foliar symptoms of Esca disease in grapevine

Esca belongs to the group of grapevine trunk diseases - fungal diseases present worldwide in all wine-growing regions. Some aspects of the disease, like the development of external symptoms, have still not been completely discovered and are believed to be affected by several factors, including interactions within the vine microbiome. The examination of the occurrence of the yeast-like fungus Aureobasidium pullulans in the healthy wood of Esca-diseased grapevines via both isolation and qPCR measurements showed a positive correlation between its abundance and the severity of foliar symptoms, suggesting the contribution of this fungus to Esca pathogenesis via an indirect action. In vitro confrontation tests revealed antagonistic interaction between A. pullulans and the Esca pathogen Phaeomoniella chlamydospora. Mutual growth inhibition and the induction of asexual sporogenesis were observed for both fungi without cytotoxic effects. In planta confrontation tests revealed that A. pullulans in combination with P. chlamydospora can lead to severe foliar damage in a strain-dependent manner. This phenomenon could be explained by the altered metabolism of the Esca pathogen in the presence of A. pullulans, or by the cumulative/synergistic effects of the secreted polysaccharides and/or proteins of the two fungi. The present study shows the importance of microbial interactions in the development of plant diseases, highlighting that even a non-pathogenic microorganism can act as a disease-enhancer.

Two-Stage Convolutional Neural Networks for Diagnosing the Severity of Alternaria Leaf Blotch Disease of the Apple Tree

In many parts of the world, apple trees suffer from severe foliar damage each year due to infection of Alternaria blotch (Alternaria alternata f. sp. Mali), resulting in serious economic losses to growers. Traditional methods for disease detection and severity classification mostly rely on manual labor, which is slow, labor-intensive and highly subjective. There is an urgent need to develop an effective protocol to rapidly and accurately evaluate disease severity. In this study, DeeplabV3+, PSPNet and UNet were used to assess the severity of apple Alternaria leaf blotch. For identifications of leaves and disease areas, the dataset with a total of 5382 samples was randomly split into 74% (4004 samples) for model training, 9% (494 samples) for validation, 8% (444 samples) for testing and 8% (440 samples) for overall testing. Apple leaves were first segmented from complex backgrounds using the deep-learning algorithms with different backbones. Then, the recognition of disease areas was performed on the segmented leaves. The results showed that the PSPNet model with MobileNetV2 backbone exhibited the highest performance in leaf segmentation, with precision, recall and MIoU values of 99.15%, 99.26% and 98.42%, respectively. The UNet model with VGG backbone performed the best in disease-area prediction, with a precision of 95.84%, a recall of 95.54% and a MIoU value of 92.05%. The ratio of disease area to leaf area was calculated to assess the disease severity. The results showed that the average accuracy for severity classification was 96.41%. Moreover, both the correlation coefficient and the consistency correlation coefficient were 0.992, indicating a high agreement between the reference values and the value that the research predicted. This study proves the feasibility of rapid estimation of the severity of apple Alternaria leaf blotch, which will provide technical support for precise application of pesticides.

Salt Tolerance of Sego SupremeTM Plants

Sego SupremeTM is a designated plant breeding and introduction program at the Utah State University Botanical Center and the Center for Water Efficient Landscaping. This plant selection program introduces native and adapted plants to the arid West for aesthetic landscaping and water conservation. The plants are evaluated for characteristics such as color, flowering, ease of propagation, market demand, disease/pest resistance, and drought tolerance. However, salt tolerance has not been considered during the evaluation processes. Four Sego SupremeTM plants [Aquilegia barnebyi (oil shale columbine), Clematis fruticosa (Mongolian gold clematis), Epilobium septentrionale (northern willowherb), and Tetraneuris acaulis var. arizonica (Arizona four-nerve daisy)] were evaluated for salt tolerance in a greenhouse. Uniform plants were irrigated weekly with a nutrient solution at an electrical conductivity (EC) of 1.25 dS·m−1 as control or a saline solution at an EC of 2.5, 5.0, 7.5, or 10.0 dS·m−1 for 8 weeks. After 8 weeks of irrigation, A. barnebyi irrigated with saline solution at an EC of 5.0 dS·m−1 had slight foliar salt damage with an average visual score of 3.7 (0 = dead; 5 = excellent), and more than 50% of the plants were dead when irrigated with saline solutions at an EC of 7.5 and 10.0 dS·m−1. However, C. fruticosa, E. septentrionale, and T. acaulis had no or minimal foliar salt damage with visual scores of 4.2, 4.1, and 4.3, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. As the salinity levels of treatment solutions increased, plant height, leaf area, and shoot dry weight of C. fruticosa and T. acaulis decreased linearly; plant height of A. barnebyi and E. septentrionale also declined linearly, but their leaf area and shoot dry weight decreased quadratically. Compared with the control, the shoot dry weights of A. barnebyi, C. fruticosa, E. septentrionale, and T. acaulis decreased by 71.3%, 56.3%, 69.7%, and 48.1%, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. Aquilegia barnebyi and C. fruticosa did not bloom during the experiment at all treatments. Elevated salinity reduced the number of flowers in E. septentrionale and T. acaulis. Elevated salinity also reduced the number of shoots in all four species. Among the four species, sodium (Na+) and chloride (Cl–) concentration increased the most in A. barnebyi by 53 and 48 times, respectively, when irrigated with saline solution at an EC of 10.0 dS·m−1. In this study, C. fruticosa and T. acaulis had minimal foliar salt damage and less reduction in shoot dry weight, indicating that they are more tolerant to salinity. Epilobium septentrionale was moderately tolerant to saline solution irrigation with less foliar damage, although it had more reduction in shoot dry weight. On the other hand, A. barnebyi was the least tolerant with severe foliar damage, more reduction in shoot dry weight, and a greater concentration of Na+ and Cl–.

Springtime photoinhibition constrains regeneration of forest floor seedlings of Abies sachalinensis after a removal of canopy trees during winter

A clear-cutting of canopy trees during winter often causes severe foliar damage during the following spring in forest floor seedlings of Abies sachalinensis, a typical shade-tolerant evergreen coniferous species. The maximum photochemical efficiency of photosystem II after an overnight dark adaptation showed a temporary decrease immediately before budbreak in 1-year-old shoots of A. sachalinensis seedlings grown under full sunlight in a nursery, suggesting “springtime photoinhibition” related to the phenology of evergreen coniferous species. In the field, a greater rate of canopy tree cutting during winter was associated with more severe photoinhibition in the following spring, immediately before budbreak, which subsequently resulted in a reduction in carbon gain in 1-year-old shoots, and consequently suppressed the growth of current-year shoots. Although photoinhibition under low temperature is a well-known factor to determine the survival rate of tree seedlings during winter in cool regions, the present study additionally proposes that the temporary increase in the susceptibility to photoinhibition in springtime i.e. “springtime photoinhibition” would be a constraint for the regeneration of coniferous seedlings especially when the canopy trees are removed during winter.

Morphological and Physiological Responses of Nine Ornamental Species to Saline Irrigation Water

To provide more species for landscapes where poor-quality irrigation water is used, salt tolerance of commonly used landscape plants should be characterized. Nine ornamental species, including six herbaceous and three woody, were irrigated with nutrient solution at electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solution at EC of 5.0 or 10.0 dS·m−1 (EC 5 or EC 10) for 8 weeks and their growth and physiological responses were determined. Although growth was reduced in orange peel jessamine (Cestrum ‘Orange Peel’) and mexican hummingbird bush (Dicliptera suberecta) as salinity increased, no obvious signs of stress or injury were observed, indicating that orange peel jessamine and mexican hummingbird bush were the most salt tolerant. Flame acanthus (Anisacanthus quadrifidus var. wrightii), rock rose (Pavonia lasiopetala), and ‘Dark knight’ bluebeard (Caryopteris ×clandonensis ‘Dark Knight’) had more growth reduction than that of orange peel jessamine and mexican hummingbird bush with minimal or no foliar damage in EC 5 and slight foliar damage in EC 10. Cardinal flower (Lobelia cardinalis) and mexican false heather (Cuphea hyssopifolia) exhibited mortality rates of 30% and 20%, severe foliar damage, and greater than 70% reduction in leaf area and dry weight in EC 10 compared with their respective controls. Although the growth reductions in butterfly blue (Scabiosa columbaria) were not as great as cardinal flower and mexican false heather, 40% of butterfly blue plants were dead with moderate foliar damage in EC 10. Therefore, cardinal flower, mexican false heather, and butterfly blue plants were considered as moderately salt sensitive. Eastern red columbine (Aquilegia canadensis) was the most salt sensitive among the species investigated with moderate foliar damage in EC 5 and all plants died in EC 10. Four out of the nine species tested had significant differences in net photosynthetic rate (Pn), stomatal conductance (gs), and/or relative chlorophyll content between the control and EC 10, and the difference varied with species. Shoot ion concentrations of the nine ornamentals were also affected by salinity levels and varied among species.

Morphological, physio-biochemical and molecular response of grapevine rootstocks to moisture and salinity stress-A review

Rootstock usage in grape cultivation in most of the grape growing regions of the world was started in Europe in late 1800’s when thousands of acres of grapes were affected by incidence of soil borne pest namely phylloxera root louse. From then onwards use of rootstocks was inevitable in those countries to overcome many biotic stresses such as nematodes, root rots, diseases etc. But, in many of the semiarid and arid climatic conditions where grape is grown on large scale, abiotic stresses such as soil and water salinity, water scarcity are the major constraints. Poor vine growth, severe foliar damage due to excess salt accumulation coupled with drastic reduction in productive life span of own rooted grapevines necessitated the use of rootstocks to combat these abiotic stresses also. Many of the grape rootstocks are known to possess drought and salt tolerant traits which can be seen on grafted scions through several mechanisms at both cellular and whole plant level. The present review focuses on mechanism of rootstocks to overcome adverse situations of moisture stress and salinity stress at morphological, physio-biochemical, nutritional and molecular level.

English

Alternaria blight (Alternaria brassicae) causes severe foliar damage to Indian mustard in Uttarakhand. Ten (10) isolates of A. brassicae were collected from different hosts and characterized for cultural, morphological, pathogenic and molecular variations. A. brassicae colonies varied in their cultural behaviour ranging from cottony, flurry to feathery, with smooth to rough margins. Colour of colonies ranged between white, off white to light brown. Colony growth varied from slow, medium to fast with fast growth in isolate KM and least in JD on the potato dextrose agar (PDA) medium. Significant morphological variations in conidia length, conidia width, and number of horizontal septa were observed in the isolates. Average conidial size ranged from 105 to 135 × 10 to 20 μm. Isolates exhibited variations in disease index, number and size of the lesions. The dendrogram analysis, based on molecular (random amplification of polymorphic DNA, RAPD) basis revealed two groups at 15% similarity coefficient. Group I was composed of seven isolates namely, VR, DV, P7, LM. P10, KR and ND with 18% similarity (82% dissimilarity) while group II was composed of only three isolates namely, JD, KA and AS with only 24% similarity (76% dissimilarity).   Key words: Pathogenic variability, Brassica, Alternaria brassicae, RAPD-PCR.

English

Alternaria blotch (Alternaria mali) causes severe foliar damage to apple trees in Kashmir. Twenty one (21) isolates of A. mali were collected from different locations and characterized for cultural, morphological, pathogenic and molecular variations. A. mali colonies varied in their cultural behaviour ranging from velvety to cottony, mostly appressed, with regular to irregular margins. Colour of colonies ranged between light to dark olivacious. Isolates impregnated media with colour ranging between grey to brown. Growth rate of isolates was between 5.86 to 8.21 mm/day with fast growth in isolate Am-13 and least in Am-5. Morphological variations in size, shape and septation of hyphae, conidiophore and conidia were observed in the isolates with significant variations in conidiophore and conidial septation. Average conidial size ranged from 21.36 to 31.74 x 8.34 to 14.48 µm. Isolates exhibited variations in incubation period, number and size of the lesions were produced. The dendrogram analysis, based on cultural, morphological and pathogenic studies, revealed variation within A. mali population. At 67% similarity matrix, all the isolates formed 2 clusters with 12 and nine isolates in cluster I and II, respectively. However, dendrogram on molecular (random amplification of polymorphic DNA, RAPD) basis revealed five clusters at 68% Dice similarity coefficient. There was no congruence between RAPD pattern and cultural, morphological and pathogenic characters. Isolates identical for one spectrum were often dissimilar for other spectrum. The results demonstrate existence of considerable variation in cultural, morphological, pathogenic and molecular characters of A. mali isolates prevalent in Kashmir valley.

Long term losses caused by foliar diseases on growth and survival of Eucalyptus globulus in Uruguay

Eucalyptus globulus is the most important forest species in Uruguay, with more than 250,000 ha of commercial plantations. Despite its high susceptibility to diseases, production losses caused by foliar diseases have not been properly quantified in this country. This study analyzes the effects of foliar damage on growth and survival using data from a progeny test of E. globulus naturally infected by Teratosphaeria leaf disease and eucalypt rust (Puccinia psidii). The severity of leaf spots and defoliation were quantified 8 months after planting and tree growth and mortality were evaluated 2, 4 and 6 years later. The trial had a high incidence of foliar damage, with a mean leaf spot severity of 28.7% and a mean defoliation of 37%. The greatest impact of foliar damage, both on growth rate and mortality, occurred in the first 2 years after damage was assessed. During this period, leaf spot severity less than 40% and defoliation below 50% did not affect growth, while survival was affected when leaf damage was 70% or greater. By the sixth year both stem growth and survival were affected by severe foliar damage (spotting or defoliation of 80% or more), with a loss of up to 25% in diameter and an accumulated mortality over 70%. It has been established for the first time that under the intensive Uruguayan productive conditions, E. globulus trees can tolerate a relatively high degree of leaf spotting or defoliation but severe foliar damage in the first months can cause considerable production losses, putting at risk the economical viability of this species.

First Report of Anthracnose Disease of Ornamental Feather Reed Grass (Calamagrostis × acutifolia 'Karl Foerster') Caused by Colletotrichum cereale.

Calamagrostis × acutifolia 'Karl Foerster' (feather reed grass) is a cool-season grass grown extensively as an ornamental plant throughout the United States. In July 2005, severe foliar damage was observed in feather reed grasses in a residential garden in Barrington, NJ. Symptoms were observed as small, yellowish brown, oval to irregularly shaped spots on the blades, with spread and coalescence of spots leading to eventual necrosis and plant death. Numerous acervuli with black setae diagnostic of fungi in the genus Colletotrichum were present on necrotic lesions. Two distinct fungi were isolated from diseased tissue by plating small sections of infested leaf tissue on potato dextrose agar (PDA) supplemented with 40 μg/liter each of penicillin, ampicillin, gentomycin, and streptomycin. The first fungus was identified as Colletotrichum gloeosporioides based on morphological, cultural (2), and molecular characteristics. Variable colonies of gray-white mycelia with masses of pink-to-salmon hued conidia formed at 25°C on PDA under constant light. Conidia were hyaline, aseptate, straight, and cylindrical with rounded apices (11.0 to 18.5 × 2.5 to 5.0 μm). Sequencing of the internal transcribed spacer (ITS) rDNA region showed the fungus to be most similar to C. gloeosporioides (GenBank Accession No. EU979125). The second fungus was identified as C. cereale based on morphological, cultural, and molecular characteristics (1). Variable colonies of gray-tan-white mycelia formed at 25°C on PDA under constant light and salmon-colored conidial masses surrounded numerous setae. Conidia were hyaline, aseptate, falcate, fusiform, and guttulate (15.0 to 21.5 × 2.5 to 4.5 μm). Hyphal appressoria were ovoid, sometimes lobate or multilobate (10.5 to 13.5 × 7.5 to 10.0 μm). Maximum likelihood phylogenetic analysis of the ITS sequence (GenBank Accession No. DQ126193) and fungal mating type idiomorph Mat1-2 HMG box (GenBank Accession No. DQ131962) identified the fungus as C. cereale (1). Pathogenicity was determined by inoculating healthy feather reed grasses (11.4-liter pots) established 61 cm off-center in a mulched bed. Three replicate plants per treatment were sprayed with a 20-ml conidial solution (5 × 104 conidia/ml in 0.1 potato dextrose broth) of either C. cereale or C. gloeosporioides and an uninoculated control. Temperatures ranged from 19 to 36°C and humidity varied between 31 and 79%. No symptoms were observed in uninoculated controls or plants inoculated with C. gloeosporioides. Plants inoculated with C. cereale developed disease symptoms within 21 days; the fungus was subsequently reisolated from symptomatic leaves and confirmed as C. cereale. To our knowledge, this is the first report of anthracnose of feather reed grass caused by C. cereale (formerly known as C. graminicola). Although C. cereale is known to inhabit numerous cool-season grass hosts, this is the first description of this fungus as a pathogen of an ornamental grass. Given the recent emergence of anthracnose epidemics caused by C. cereale on golf course turfgrass, the identification of this fungus as a pathogen of Calamagrostis × acutifolia highlights the need for nurseries and regulatory personnel to screen ornamental grasses such as feather reed grass for the presence of C. cereale so that the disease does not become problematic.

The Effect of Chlormequat Chloride, Ancymidol, BAS 106, and SD8339 on Selected Dianthus Cultivars

Abstract Experiments were conducted during the summer and fall to evaluate the effects of various concentrations of chlormequat chloride, ancymidol, BAS 106, and SD8339 on the height and plant quality of potted Dianthus cultivars ‘Snowfire’, ‘Indian Carpet’, and ‘Persian Carpet’. The effects of the growth retardants on the height and number of vegetative shoots were extremely diverse. The greatest height reduction was from BAS 106 applied at 3.6 mg a.i. per plant. As a result of this treatment, ‘Snowfire’ height was reduced by 70.0%, ‘Persian Carpet’ by 42.7%, and ‘Indian Carpet’ by 67.3%; however, both BAS 106 and SD8339, applied at concentrations that significantly reduced plant height, resulted in severe foliar damage. Chlormequat chloride and ancymidol reduced the height of ‘Snowfire’ at all treatment levels. ‘Snowfire’ height was reduced by 16.4% with 3000 ppm of chlormequat chloride and 47.5% with 144 ppm of ancymidol. Initial phytotoxic damage on ‘Snowfire’ from chlormequat chloride and ancymidol was not evident at the time of harvest. Chlormequat chloride and ancymidol applied to ‘Persian Carpet’ and ‘Indian Carpet’ in amounts to reduce plant height significantly resulted in severe foliage damage. Chemical names used: 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat chloride); α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol); 5-(4-chlorophenyl)-3,4,5,9,10 pentaaza-tetracyclo-5,4,102,6,08,11-dodeca-3-9-diene (BAS 106); and N-(phenylmethyl)-9-(tetrahydro-2H-pyran-2-yl)-9H-purin-6-amine (SD8339).

Postharvest Effects of Temperatures during Simulated Transit on Quality Factors of Two Ficus Species1

Abstract Ficus benjamina L. and Ficus lyrata Warb. were held at 4.4°, 21°, or 37°C during simulated transit (ST) for 3, 6, or 9 days. Both species were adversely affected during ST by 4.4° or 37°, with leaf loss increasing with exposure. Foliar damage was severe for all plants exposed to 37° for 6 or 9 days. Plant grade was lowest for both species when exposed to 37°. Plants held at 21° for 3, 6, or 9 days showed no foliar damage and only a slight loss of plant quality. After 8 weeks in a simulated interior environment (SIE), no plants had recovered from being held at 4.4° or 37° during ST, but showed even greater leaf loss and more severe foliar damage. Both species were lowest in dry weight and plant grade when held at 37° for 6 or 9 days. Chlorophyll content decreased as temperature increased from 4.4° to 21°.

Effect of Two Growth‐Regulating Chemicals on Yield and Water Use of Three Perennial Grasses1

AbstractGrowth responses of smooth bromegrass (Bromus inermis Leyss), Kentucky‐31 tall fescue (Festuca elatior L.), and common Kentucky bluegrass (Poa pratensis L.) to the growth‐regulating chemicals F‐529 (N‐pyrrolidinosuccinamic acid) and Cycocel (2‐chloroethyltrimethylammonium chloride) were studied. Growth of grasses was reduced to near zero when Cycocel was applied at a concentration of 0.584M, with at least some retardation occurring up to 100 days after application.F‐529 was less effective than Cycocel in retarding grass growth. Maximum reduction occurred at the 0.45M concentration where growth was reduced to 35% of the control, and at 70 days following application there was no reduction. Recovery from both chemicals was generally followed by a period of stimulated growth.Water use, in general, was highly correlated with amount of top growth.Food reserves of plants as determined by eiolated growth were significantly reduced only at the 0.292M and 0.584M concentrations of Cycocel, where severe foliar damage had occurred.