Occurrence of Canker and Wood Rot Pathogens on Stone Fruit Propagation Material and Nursery Trees in the Western Cape of South Africa

Plant Disease ◽  
2021 ◽  
Author(s):  
Rhona van der Merwe ◽  
Francois Halleen ◽  
Meagan Van Dyk ◽  
Vernon Guy Jacobs ◽  
Lizel Mostert
Keyword(s):  
South Africa ◽  
Management Practices ◽  
Phylogenetic Analyses ◽  
Fruit Trees ◽  
Fungal Species ◽  
Stone Fruit ◽  
Western Cape ◽  
Latent Infections ◽  
Nursery Trees ◽  
Propagation Material

Dieback and canker of young stone fruit trees can cause suboptimal growth and even death under severe conditions. One source of inoculum of canker pathogens could be through nursery trees harboring latent infections that would not be visible to inspections done according to the deciduous fruit scheme. The objectives of this study were to identify the canker and wood rot fungal pathogens present in nursery stone fruit trees as well as propagation material and to evaluate their pathogenicity. Isolations were made from scion and rootstock propagation material and from certified nursery stone fruit trees. The plant material sampled did not have any external symptoms. The certified nursery trees when cross-sectioned displayed brown discoloration from the pruning wound, bud union and often from the crown. Fungal species isolated were identified by sequencing of the relevant barcoding genes and phylogenetic analyses thereof. Canker and wood rot associated fungi were identified. Buds used for budding had low levels of infection, with 1.2% of dormant buds infected and 0.4% of green buds infected. The dormant rootstock shoots had canker pathogen incidence of 6.2% before it was planted in the nursery fields and increased as the ungrafted, rooted rootstock plants had 11.1% infection with canker and wood rot pathogens. Out of 1080 nursery trees, the canker and wood rot associated fungi infected 21.8% of trees. The canker causing pathogens that were isolated the most were Cadophora luteo-olivacea and Diplodia seriata. A low incidence of wood rot fungi was found with only 1.5% of nursery trees infected. In total 26 new reports of fungal species on stone fruit in South Africa were made. Of these, 22 have not been found on stone fruit world-wide. The pathogenicity trials’ results confirmed the pathogenic status of these newly reported species. All of the isolates tested formed lesions significantly longer than the control, 4 months after wound inoculation of 2-year-old shoots of two plum orchards. Lasiodiplodia theobromae was the most virulent species on both plum cultivars. The results of this research showed that nursery stone fruit trees and propagation material can harbor latent infections. Different management practices need to be evaluated to prevent these infections to ensure healthier stone fruit nursery trees.

scholarly journals Canker and Wood Rot Pathogens Present in Young Apple Trees and Propagation Material in the Western Cape of South Africa

Plant Disease ◽  
2019 ◽  
Vol 103 (12) ◽  
pp. 3129-3141 ◽  
Author(s):  
Minette Havenga ◽  
Greg M. Gatsi ◽  
Francois Halleen ◽  
Christoffel F. J. Spies ◽  
Rhona van der Merwe ◽  
...  
Keyword(s):  
South Africa ◽  
Management Practices ◽  
Vascular Tissue ◽  
Schizophyllum Commune ◽  
Fungal Species ◽  
Western Cape ◽  
Apple Trees ◽  
Nursery Trees ◽  
Propagation Material ◽  
Young Apple

Canker and wood rot pathogens cause dieback and, in severe cases, the death of young apple trees. Recently, a higher occurrence of cankers was observed on 1-year-old apple trees in the Western Cape Province of South Africa. This study aimed to assess the phytosanitary status of nursery trees and propagation material as possible inoculum sources for canker pathogens. Thirteen 1-year-old apple orchards showing canker or dieback symptoms were sampled. Certified nursery apple trees were collected from four nurseries as well as scion and rootstock mother plant material. Isolations were made from the discoloration observed in the vascular tissue of the plant parts and from asymptomatic material. Possible canker and wood rot species were identified with PCR and sequence comparisons of the relevant gene regions and phylogenetic analyses. Similar canker and wood rot species were isolated from 1-year-old diseased apple trees, nursery apple trees, and the propagation material. Forty-five fungal species associated with canker or wood rot symptoms were identified. The top five most abundant fungal species found causing disease on commercial 1-year-old trees were also found in high numbers causing latent infection in certified apple nursery trees. These species were Didymosphaeria rubi-ulmifolii sensu lato, Diplodia seriata, Schizophyllum commune, Didymella pomorum, and Coniochaeta fasciculata, with D. rubi-ulmifolii sensu lato being the dominant species in both sampling materials. In all, 65% of certified nursery apple trees, 5% of scion shoots used for budding, and 21% of rooted rootstock cuttings from layer blocks had latent infections of canker and wood rot pathogens. Pathogenicity trials were conducted with isolates of 39 species, inoculated onto 2-year-old branches of 14-year-old Golden Delicious trees. All species caused lesions that were significantly longer than the control. This study confirmed the presence of canker and wood rot pathogens in apple propagation material as well as certified nursery apple trees, which will aid the improvement of management practices in nurseries.

scholarly journals Eutypa, Eutypella, and Cryptovalsa Species (Diatrypaceae) Associated with Prunus Species in South Africa

Plant Disease ◽  
2018 ◽  
Vol 102 (7) ◽  
pp. 1402-1409 ◽  
Author(s):  
Providence Moyo ◽  
Ulrike Damm ◽  
Lizel Mostert ◽  
Francois Halleen
Keyword(s):  
South Africa ◽  
Phylogenetic Analyses ◽  
Fruit Trees ◽  
Fungal Species ◽  
Stone Fruit ◽  
Prunus Species ◽  
Internal Transcribed Spacer Region ◽  
Eutypa Lata ◽  
Eutypa Dieback ◽  
Prunus Spp

Stone fruit trees (Prunus spp.) are economically important fruit trees cultivated in South Africa. These trees are often grown in close proximity to vineyards and are to a large extent affected by the same trunk disease pathogens as grapevines. The aim of the present study was to determine whether stone fruit trees are inhabited by Diatrypaceae species known from grapevines and whether these trees could act as alternative hosts for these fungal species. Isolations were carried out from symptomatic wood of Prunus species (almond, apricot, cherry, nectarine, peach, and plum) in stone fruit growing areas in South Africa. Identification of isolates was based on phylogenetic analyses of the internal transcribed spacer region and β-tubulin gene. Forty-six Diatrypaceae isolates were obtained from a total of 380 wood samples, from which five species were identified. All five species have also been associated with dieback of grapevine. The highest number of isolates was found on apricot followed by plum. No Diatrypaceae species were isolated from peach and nectarine. Eutypa lata was the dominant species isolated (26 isolates), followed by Cryptovalsa ampelina (7), Eutypa cremea (5), Eutypella citricola (5), and Eutypella microtheca (3). First reports from Prunus spp. are E. cremea, E. citricola, and E. microtheca. Pathogenicity tests conducted on apricot and plum revealed that all these species are pathogenic to these hosts, causing red-brown necrotic lesions like those typical of Eutypa dieback on apricot.

scholarly journals Identification of Pseudomonas Isolates Associated With Bacterial Canker of Stone Fruit Trees in the Western Cape, South Africa

Plant Disease ◽  
2020 ◽  
Vol 104 (3) ◽  
pp. 882-892 ◽  
Author(s):  
Khumbuzile N. Bophela ◽  
Yolanda Petersen ◽  
Carolee. T. Bull ◽  
Teresa. A. Coutinho
Keyword(s):  
South Africa ◽  
Pseudomonas Syringae ◽  
Bacterial Species ◽  
Fruit Trees ◽  
Stone Fruit ◽  
Bacterial Disease ◽  
Bacterial Canker ◽  
Western Cape ◽  
Vegetable Crops ◽  
Phylogenetic Groups

Bacterial canker is a common bacterial disease of stone fruit trees. The causal agents responsible for the disease include several pathovars in Pseudomonas syringae sensu lato and newly described Pseudomonas species. Pseudomonad strains were isolated from symptomatic stone fruit trees, namely apricot, peach, and plum trees cultivated in spatially separated orchards in the Western Cape. A polyphasic approach was used to identify and characterize these strains. Using a multilocus sequence typing approach of four housekeeping loci, namely cts, gapA, gyrB, and rpoD, the pseudomonad strains were delineated into two phylogenetic groups within P. syringae sensu lato: P. syringae sensu stricto and Pseudomonas viridiflava. These results were further supported by LOPAT diagnostic assays and analysis of clades in the rep-PCR dendrogram. The pseudomonad strains were pathogenic on both apricot and plum seedlings, indicative of a lack of host specificity between Pseudomonas strains infecting Prunus spp. This is a first report of P. viridiflava isolated from plum trees showing symptoms of bacterial canker. P. viridiflava is considered to be an opportunistic pathogen that causes foliar diseases of vegetable crops, fruit trees, and aromatic herbs, and thus the isolation of pathogenic P. viridiflava from twigs of plum trees showing symptoms of bacterial canker suggests that this bacterial species is a potentially emerging stem canker pathogen of stone fruit trees in South Africa.

scholarly journals First Report of Leaf Rust of Blueberry Caused by Thekopsora minima on Vaccinium corymbosum in the Western Cape, South Africa

Plant Disease ◽  
2010 ◽  
Vol 94 (4) ◽  
pp. 478-478 ◽  
Author(s):  
L. Mostert ◽  
W. Bester ◽  
T. Jensen ◽  
S. Coertze ◽  
A. van Hoorn ◽  
...  
Keyword(s):  
South Africa ◽  
South African ◽  
Water Solution ◽  
Phylogenetic Analyses ◽  
The United States ◽  
Vaccinium Corymbosum ◽  
Tween 20 ◽  
Western Cape ◽  
The South ◽  
First Report

Southern highbush blueberry plants (Vaccinium corymbosum interspecific hybrids) showing rust-like symptoms were observed in July 2006 in Porterville in the Western Cape (WC), South Africa. Diseased plants were also found in Villiersdorp and George in the WC in 2007. In 2008, symptoms were observed in George, and in 2009, in all the previous reported areas. Cvs. Bluecrisp, Emerald, Jewel, Sharpblue, and Star were infected. Reddish-to-brown spots appeared on the adaxial surface of leaves and developed into yellow-to-orange erumpent uredinia with pulverulent urediniospores. Uredinia were hypophyllous, dome shaped, 113 to 750 μm wide, and occasionally coalescing. Urediniospores were broadly obovate, sometimes ellipsoidal or pyriform, with yellowish orange content, and measured 19 to 27 × 12 to 20 μm (average 24 × 15 μm, n = 30). Spore walls were echinulate, hyaline, 1 to 1.5 μm thick, and with obscure germ pores. No telia or teliospores were observed. Voucher specimens were lodged in the South African National Fungus Collection in Pretoria (PREM 60245). The isolate was initially identified as Thekopsora minima P. Syd. & Syd., based primarily on the absence of conspicuous ostiolar cells characteristic of Naohidemyces spp. (3). Genomic DNA was extracted from urediniospores. Approximately 1,400 bp were amplified spanning the 5.8S, ITS2, and 28S large subunit of the ribosomal DNA (1). The sequence (GU355675) shared 96% (907 of 942 bp; GenBank AF522180) and 94% (1,014 of 1,047 bp; GenBank DQ354563) similarities in the 28S portion, respectively, to those of Naohidemyces vaccinii (Wint.) Sato, Katsuya et Y. Hiratsuka and Pucciniastrum geoppertianum (Kuehn) Kleb, two of the three known rust species of blueberry (2). Although no sequences of T. minima were available for direct comparison, phylogenetic analyses of the 28S region strongly supported the South African blueberry rust as congeneric with T. guttata (J. Schröt.) P. Syd. & Syd. (GenBank AF426231) and T. symphyti (Bubák) Berndt (GenBank AF26230) (data not shown). Four 6-month-old cv. Sharpblue plants were inoculated with a suspension (approximate final concentration of 1 × 105 spores per ml) of fresh urediniospores in a water solution with 0.05% Tween 20. After incubation at 20°C for 48 h under continuous fluorescent lighting, the plants were grown in a glasshouse (18/25°C night/day temperatures). Identical uredinia and symptoms developed approximately 3 weeks after inoculation on the inoculated plants, but not on two control plants of cv. Sharpblue sprayed with distilled water and kept at the same conditions. The alternate host hemlock (Tsuga spp.) is not endemic to South Africa and not sold as an ornamental plant according to a large conifer nursery. Hosts of T. minima include Gaylussacia baccata, G. frondosa, Lyonia neziki, Menziesia pilosa, Rhododendron canadense, R. canescens, R. lutescens R. ponticum, R. prunifolium, R. viscosum, V. angustifolium var. laevifolium, V. corumbosum, and V. erythrocarpon (3). Visual inspection of possible hosts in the gardens in close proximity of Vaccinium production areas did not show any rust symptoms. To our knowledge, this is the first report of T. minima on blueberries outside of Asia and the United States (2). References: (1) M. C. Aime. Mycoscience 47:112, 2006. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Botany and Mycology Laboratory. Online publication. USDA-ARS, 2009. (3) S. Sato et al. Trans. Mycol. Soc. Jpn. 34:47, 1993.

scholarly journals Preharvest Detection and Postharvest Incidence of Phlyctema vagabunda on ‘Cripps Pink’ Apples in South Africa

Plant Disease ◽  
2020 ◽  
Vol 104 (3) ◽  
pp. 841-846 ◽  
Author(s):  
Alana Den Breeyen ◽  
Jessica Rochefort ◽  
Andre Russouw ◽  
Julia Meitz-Hopkins ◽  
Cheryl L. Lennox
Keyword(s):  
South Africa ◽  
Management Practices ◽  
Molecular Detection ◽  
Disease Incidence ◽  
Postharvest Disease ◽  
Western Cape ◽  
Pome Fruit ◽  
Current Management ◽  
Detection Tool ◽  
Fruit Growing

Phlyctema vagabunda is responsible for significant postharvest losses in ‘Cripps Pink’ apples in South Africa. The first objective of this study was to determine the presence and incidence of P. vagabunda on stored commercial ‘Cripps Pink’ apple in five major pome fruit growing regions in the Western Cape. As the fungus remains latent until postharvest, the second objective was to develop a rapid molecular detection tool to determine the presence of P. vagabunda on asymptomatic ‘Cripps Pink’ apples from two commercial orchards. Postharvest disease incidence in ‘Cripps Pink’ apples in the Western Cape ranged from 0 to 73% in the 2010/2011, 0 to 6% in 2011/2012, and 0 to 30% in 2012/2013 seasons. P. vagabunda spores were also detected on ‘Cripps Pink’ fruit from December to February and from March to April. In December and January, P. vagabunda spores were detected on the ‘Hillieri’ crab apple pollinator. The knowledge that P. vagabunda conidia are present on the surface of ‘Cripps Pink’ apples and ‘Hillieri’ crab apples during the growing season could be applied to improving current management practices in the orchards.

Oviposition by the banded fruit weevil, Phlyctinus callosus (Schoenherr) (Coleoptera: Curculionidae), in deciduous fruit orchards in South Africa

1989 ◽  
Vol 79 (1) ◽  
pp. 31-40 ◽  
Author(s):  
B. N. Barnes ◽  
K. L. Pringle
Keyword(s):  
South Africa ◽  
Cover Crop ◽  
Plant Material ◽  
Soil Surface ◽  
Fruit Trees ◽  
Dispersion Pattern ◽  
Western Cape ◽  
Deciduous Fruit ◽  
Fruit Orchards ◽  
Oviposition Sites

AbstractOviposition sites of Phlyctinus callosus (Schoenherr) in an apple and a nectarine orchard in the South Western Cape, South Africa, were investigated. No eggs were found on the fruit trees, only in different fractions of the orchard floor, viz. in orchard weeds, leaf litter and soil. Significantly more oviposition took place in plant material on the orchard floor than in the top 20 mm of the soil. Microscopic dissection of samples of such plant material revealed that females prefer to oviposit in confined or hollow spaces in moist, live or decaying plant tissue on the soil surface or in weeds comprising the cover-crop. P. callosus females favoured certain weeds above others for oviposition. The dispersion pattern of eggs in the cover-crop was contagious. The implications of the observed ovipostion behaviour in terms of control strategy, and for exploitation in a monitoring system for this species, are discussed.

scholarly journals Thesium nautimontanum, a new species of Thesiaceae (Santalales) from South Africa

PhytoKeys ◽  
2018 ◽  
Vol 109 ◽  
pp. 41-51 ◽  
Author(s):  
Miguel Angel García ◽  
Daniel L. Nickrent ◽  
Ladislav Mucina
Keyword(s):  
South Africa ◽  
New Species ◽  
Phylogenetic Analyses ◽  
South American ◽  
Western Cape ◽  
Western Cape Province ◽  
Molecular Phylogenetic ◽  
Internal Transcribed Spacer Sequences ◽  
Conservation Concern ◽  
A New Species

ThesiumnautimontanumM.A. García, Nickrent & Mucina, a new species from the Matroosberg Mt. of Western Cape Province of South Africa, is described and illustrated. This species shows several morphological features unusual for the genus including stem sympodial branching, indeterminate spicate inflorescences subtended by numerous bracts and fleshy, non-trichome tissue lining the inside of the corolla lobes. Molecular phylogenetic analyses using nuclear ribosomal internal transcribed spacer sequences place this taxon as sister to all African, Madagascan and South AmericanThesiumspecies. Given that only two proximal populations are known, this species is of conservation concern.

scholarly journals Honeybush (Cyclopia spp.) phenology and associated arthropod diversity in the Overberg region, South Africa

Bothalia ◽  
2019 ◽  
Vol 49 (1) ◽  
Author(s):  
Eleonore L. Slabbert ◽  
Rhoda R. Malgas ◽  
Ruan Veldtman ◽  
Pia Addison
Keyword(s):  
South Africa ◽  
Management Practices ◽  
Cape Floristic Region ◽  
Arthropod Community ◽  
Western Cape ◽  
Baseline Knowledge ◽  
Medicinal Properties ◽  
High Level ◽  
Production Areas ◽  
Suction Sampling

Background: Cyclopia is endemic to regions of the Cape Floristic Region across the Eastern and Western Cape provinces of South Africa and is commonly known as honeybush. Honeybush has historically been used as an herbal tea, and has proven medicinal properties. Honeybush biomass and extracts are used in the functional foods and cosmetics sectors, both locally and overseas. The growing demand for honeybush calls for increased agricultural production and a shift away from the predominantly wild harvested supply.Objectives: The current study aimed to address the lack of baseline knowledge on honeybush phenology and its associated arthropod community to advance sustainable production of commercially valued plants in the genus.Method: The study was conducted on wild and cultivated Cyclopia species (Cyclopia maculata and Cyclopia genistoides) at respective sites in the Overberg region. Sampling took place from April 2014 to April 2015 using qualitative methods for recording seasonal honeybush phenology and suction sampling for aboveground arthropods. Focal insect taxa (Coleoptera, Hemiptera, Thysanoptera, Lepidoptera and Hymenoptera) were sorted and identified to family level and classified into functional feeding guilds.Results: Qualitative phenology observations of wild C. maculata and cultivated C. genistoides indicated a high level of congruency in seasonality of phenophase stages. Associated arthropod assemblages contained a diversity of families per functional feeding group, namely phytophagous, zoophagous and omnivorous taxa, with high seasonal variability.Conclusion: Findings highlight the complexity of ecological elements to be taken into consideration for ecologically sound honeybush cultivation. Outcomes can be applied to land management practices and governance policies promoting sustainable agroecosystems in honeybush production areas.

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