scholarly journals Characterization and Pathogenicity of Botryosphaeriaceae Species Obtained from Avocado Trees with Branch Canker and Dieback and from Avocado Fruit with Stem End Rot in Chile

Plant Disease ◽  
2019 ◽  
Vol 103 (5) ◽  
pp. 996-1005 ◽  
Author(s):  
Ana L. Valencia ◽  
Pilar M. Gil ◽  
Bernardo A. Latorre ◽  
I. Marlene Rosales
Keyword(s):  
Vascular System ◽  
Persea Americana ◽  
Effective Control ◽  
Future Research ◽  
Severe Drought ◽  
Internal Transcribed Spacer Region ◽  
Avocado Fruit ◽  
Hass Avocado ◽  
Botryosphaeriaceae Species ◽  
Branch Canker

Several species of the Botryosphaeriaceae family have been associated with branch canker, dieback, and stem end rot in avocado (Persea americana Mill.). In Chile, the incidence of diseases affecting the avocado tree increased from 2011 to 2016, which coincided with a severe drought that affected avocado production. Moreover, distant countries importing avocados from Chile also reported an increase of stem end rot of ripe avocados. Therefore, the aims of this study were to identify the pathogen species associated with branch canker, dieback, and stem end rot of avocado in Chile and to study their pathogenicity. This study was conducted between 2015 and 2016 in ‘Hass’ avocado orchards located in the main avocado-producing regions in Chile. A diverse collection of fungal species was recovered from both necrotic woody tissue and necrotic tissue on harvested ripe fruit. On the basis of morphology and phylogenetic analyses of the internal transcribed spacer region (ITS1-5.8S-ITS2) and the translation elongation factor 1-α (TEF1-α) gene, eight species in the Botryosphaeriaceae family were identified: Diplodia mutila, D. pseudoseriata, D. seriata, Dothiorella iberica, Lasiodiplodia theobromae, Neofusicoccum australe, N. nonquaesitum, and N. parvum. For each of these species, pathogenicity studies were conducted on 1-year-old healthy Hass avocado plants. All isolates produced brown gum exudate and caused necrosis in the vascular system 3 weeks after inoculation. N. nonquaesitum, N. parvum, and D. pseudoseriata were the most virulent species. Necrotic lesions and cavities with white mycelia near the peduncle union were observed on Hass avocado fruit inoculated postharvest. L. theobromae, N. australe, and N. parvum were significantly more virulent than the other tested species in the Botryosphaeriaceae family. This study identified and characterized the pathogenicity of Botryosphaeriaceae species in Chile, which will prove useful to future research on these pathogens directed at establishing effective control strategies in avocado.

scholarly journals First Report of Black Spots on Avocado Fruit Caused by Neofusicoccum parvum in Mexico

Plant Disease ◽  
2012 ◽  
Vol 96 (2) ◽  
pp. 287-287 ◽  
Author(s):  
E. Molina-Gayosso ◽  
H. V. Silva-Rojas ◽  
S. García-Morales ◽  
G. Avila-Quezada
Keyword(s):  
Average Length ◽  
Black Spot ◽  
Persea Americana ◽  
Universal Primers ◽  
Internal Transcribed Spacer Region ◽  
Pathogenic Potential ◽  
Neofusicoccum Parvum ◽  
First Report ◽  
Black Spots ◽  
Avocado Fruit

Avocado (Persea americana L.) production for export markets has increased in Mexico during the past 10 years. The production system, however, is affected by several sanitation factors, including diseases. During the spring of 2009, smooth, black, circular spots were noted on the surface of avocado fruit. A study was conducted during the winter of 2010 to ascertain the etiology and identify the fungus associated with black spot symptoms on avocado fruit in orchards of Nuevo Parangaricutiro County (19°25′00″ and 102°07′43″) in Michoacan, Mexico. Several fungal isolates were obtained on potato dextrose agar (PDA) from the margin of lesions on immature fruit. The internal transcribed spacer region (ITS) of the rDNA from representative isolates was sequenced with universal primers ITS5 and ITS4 (2). BLAST searches in GenBank showed 100% similarity of the nucleotide sequences with Neofusicoccum parvum (Pennycook & Samuels) Crous, Slippers & A.J.L. Phillips, GenBank Accession Nos. GU188001 to GU188007 and GU187985 to GU187987. A representative nucleotide sequence of this region was deposited in GenBank under the Accession No. JN203129. Strains of N. parvum produced aerial and compact mycelium on acidified PDA, the anamorph state of Botryosphaeria parva. Mycelium was initially white, turning gradually gray to black. Conidia were one celled, hyaline, ellipsoidal to fusiform, externally smooth, thin walled, nonseptate, with one or two septa with age, and an average length and width of 14.5 (9.5 to 19) × 5.8 (4.0 to 7.2) μm (n = 100). Pathogenicity tests were conducted with six avocado fruit cv. Hass. Fruit were inoculated at three evenly spaced locations on the fruit surface, either by wounding the tissue with a needle that had been dipped in a conidial mass from an 8-day-old monoconidial culture of N. parvum strain CIAD-021-11 or by placing 5 μl of 1 × 106 conidia ml–1 suspension on each inoculation site. Inoculated fruit were maintained in a moist chamber at 25°C for 2 weeks. Black lesions appeared on all wounded sites 2 days postinoculation (dpi) and on unwounded sites 4 dpi. The delay of symptom development was likely due to penetration through the lenticels, which took longer to initiate infection. No symptoms were observed in the control fruit. The pathogen was reisolated from the lesions of all inoculated fruit, thus fulfilling Koch's postulates. The results confirmed the pathogenic potential of this fungus and indicated its possible involvement in the etiology of black spot on avocado fruit. N. parvum is a cosmopolitan, plurivorous pathogen causing disease in several hosts of economic importance, such as grapes and kiwi, as well as causing stem-end rot of avocado fruit in New Zealand (1) and avocado twigs in Spain (3). To our knowledge, this is the first report of N. parvum causing black spots on avocado fruit in Mexico. References: (1) W. F. T. Hartill et al. N.Z.J. Crop Hortic. Sci. 30:249. 2002. (2) T. J. White et al. Page: 315 in: PCR Protocols: A Guide to Methods and Application. M. A. Innis et al., eds. Academic Press, San Diego, CA, 1990. (3) T. Zea-Bonilla et al. Plant Dis. 91:1052, 2007.

scholarly journals Avoiding Chilling Damage in ‘Hass’ Avocado Fruit by Controlled Atmosphere Storage at Higher Temperature

HortScience ◽  
2017 ◽  
Vol 52 (8) ◽  
pp. 1107-1110 ◽  
Author(s):  
Jeremy Burdon ◽  
David Billing ◽  
Paul Pidakala
Keyword(s):  
Skin Color ◽  
Storage Temperature ◽  
Persea Americana ◽  
Controlled Atmosphere ◽  
Storage Duration ◽  
Avocado Fruit ◽  
Significant Difference ◽  
Chilling Damage ◽  
Hass Avocado ◽  
Atmosphere Storage

Sea-freight distribution of ‘Hass’ avocado (Persea americana) is by refrigerated containers, sometimes supplemented by controlled atmosphere (CA). With both refrigeration and CA prolonging the storage life of the fruit, there is a question as to whether the technologies can be traded. That is, by using CA at warmer temperatures to extend storage without the risk of chilling damage. In this project, the potential to avoid chilling damage by storing fruit at 7 °C in 2% O2/2% CO2 CA instead of 5 °C in 2% O2/2% CO2 CA or air has been investigated for fruit stored for 4 or 6 weeks. Increasing the storage temperature from 5 °C to 7 °C did not affect the quality of fruit immediately out of CA storage, with no significant difference in skin color, firmness, or skin disorders. Both CA storage regimes, at 5 °C or 7 °C, resulted in better fruit quality than for fruit that had been stored in air at 5 °C. Overall, CA at 7 °C was less effective at retarding the progression of ripening in storage than CA at 5 °C, although after 4 weeks of storage, fruit from both CA regimes took longer to ripen than the air-stored fruit. After 6 weeks of storage, there was no difference in ripening time between fruit that had been stored in CA at 7 °C or in air at 5 °C, with fruit that had been in CA at 5 °C still taking longest to ripen. However, the incidence of diffuse flesh discoloration (DFD) in the air-stored fruit was high compared with that in fruit from CA at 7 °C or 5 °C. The main negative aspect to storing fruit in CA at 7 °C rather than at 5 °C was the higher incidence of rots in ripe fruit. While it was lower in the air-stored fruit, the incidence in fruit that had been stored in CA at 7 °C tended to be higher than that of the fruit stored in CA at 5 °C. It therefore appears that the potential for using CA at slightly higher temperatures to avoid chilling damage rests on the storage duration required and the risk of rots in the fruit.

scholarly journals Botryosphaeriaceae Species Associated with Avocado Branch Cankers in California

Plant Disease ◽  
2011 ◽  
Vol 95 (11) ◽  
pp. 1465-1473 ◽  
Author(s):  
Virginia McDonald ◽  
Akif Eskalen
Keyword(s):  
Internal Transcribed Spacer ◽  
Management Strategies ◽  
Internal Transcribed Spacer Region ◽  
Canker Disease ◽  
The Family ◽  
Fusicoccum Aesculi ◽  
Botryosphaeriaceae Species ◽  
Β Tubulin ◽  
Branch Canker ◽  
Future Management

Members of the family Botryosphaeriaceae cause branch cankers and dieback on California avocado trees. More intensive pruning, a practice associated with high-density planting that is becoming more common in the California avocado industry, may increase the occurrence of branch canker. This study was undertaken to identify and characterize the Botryosphaeriaceae spp. involved in the branch canker disease complex in order to develop future management strategies. From 2008 to 2009, branch cankers were sampled from four or five trees from each of eight avocado groves in five California counties. Six Botryosphaeriaceae spp. were identified based on morphology as well as phylogenetic analysis of the internal transcribed spacer region (ITS1-5.8S-ITS2) and a partial sequence of the β-tubulin gene. These six species included Neofusicoccum australe, N. luteum, N. parvum, an unknown Neofusicoccum sp., Fusicoccum aesculi, and Dothiorella iberica. Members of the Botryosphaeriaceae were isolated from all avocado-growing regions sampled in California; however, incidence and distribution of species varied. This report is the first description of the isolation of D. iberica from avocado branch cankers in California.

scholarly journals Reduction of Chilling Injury in Stored `Hass' Avocado Fruit by 38 °C Water Treatments

HortScience ◽  
1997 ◽  
Vol 32 (7) ◽  
pp. 1247-1251 ◽  
Author(s):  
Allan B. Woolf
Keyword(s):  
Electrolyte Leakage ◽  
Chilling Injury ◽  
Persea Americana ◽  
Hot Water ◽  
Skin Tissue ◽  
Heat Treated ◽  
Avocado Fruit ◽  
Temperature Damage ◽  
Hass Avocado ◽  
Water Treatments

`Hass' avocado (Persea americana Mill.) fruit were heat treated in water at 38 °C for 0 to 120 minutes, and stored at 0.5 °C for up to 28 days. After storage, fruit were ripened at 20 °C and their quality evaluated. External chilling injury (CI) developed during storage in nonheated fruit. Skin (exocarp) sectioning showed that browning developed from the base of the exocarp, and with longer storage, this browning moved outwards toward the epidermis. Longer durations of hot water treatment (HWT) progressively reduced CI; 60 minutes was the optimal duration that eliminated external CI, while best maintaining fruit quality. Concomitantly, electrolyte leakage of heated skin tissue increased ≈70% during storage, whereas electrolyte leakage of nonheated skin tissue increased ≈480% over the same period. Thus, significant protection was conferred by HWTs against low temperature damage to avocados and these effects are reflected in the morphology and physiology of the skin tissue.

scholarly journals Pretreatments at 38 °C of `Hass' Avocado Confer Thermotolerance to 50 °C Hot Water Treatments

HortScience ◽  
1997 ◽  
Vol 32 (4) ◽  
pp. 705-708 ◽  
Author(s):  
Allan B. Woolf ◽  
Michael Lay-Yee
Keyword(s):  
Gene Expression ◽  
Water Treatment ◽  
Heat Shock ◽  
Heat Shock Protein ◽  
Persea Americana ◽  
Hot Water ◽  
Hot Water Treatment ◽  
Avocado Fruit ◽  
Hass Avocado ◽  
Water Treatments

`Hass' avocados [Persea americana Mill.] were pretreated in water (38 °C for up to 120 min) immediately before 50 °C hot water treatments of up to 10 min. Fruit were stored for 1 week at 6 °C and ripened at 20 °C. External browning was evaluated immediately upon removal from cold storage, and fruit quality evaluated when fruit were ripe. Pretreatments at 38 °C tended to reduce the levels of external browning, skin hardening, and internal disorders, such as tissue breakdown and body rots, that were associated, and increased, with longer hot water treatments. A pretreatment of 60 min was the most effective for eliminating external browning, and reducing hardening of the skin when fruit were ripe following hot water treatment. Examination of heat shock protein (hsp) gene expression in avocado skin tissue, showed that levels of hspl7 and hsp70 homologous mRNA increased with increasing pretreatment duration. The results demonstrate that 38 °C pretreatments increase the tolerance of avocado fruit to subsequent hot water treatments.

scholarly journals Regulation of Fermentative Metabolism in Avocado Fruit under Oxygen and Carbon Dioxide Stresses

1995 ◽  
Vol 120 (3) ◽  
pp. 481-490 ◽  
Author(s):  
Dangyang Ke ◽  
Elhadi Yahia ◽  
Betty Hess ◽  
Lili Zhou ◽  
Adel A. Kader
Keyword(s):  
Carbon Dioxide ◽  
Lactate Dehydrogenase ◽  
Pyruvate Dehydrogenase ◽  
Nicotinamide Adenine Dinucleotide ◽  
Lactate Concentration ◽  
Pyruvate Decarboxylase ◽  
Persea Americana ◽  
Fermentative Metabolism ◽  
Avocado Fruit ◽  
Hass Avocado

`Hass' avocado (Persea americana Mill.) fruit were kept in air, 0.25% O2 (balance N2), 20 % O2 + 80% CO2, or 0.25% O2 + 80% CO2 (balance N2) at 20C for up to 3 days to study the regulation of fermentative metabolism. The 0.25% 02 and 0.25% 02 + 80% CO2 treatments caused accumulations of acetaldehyde and ethanol and increased NADH concentration, but decreased NAD level. The 20% O2 + 80% CO2 treatment slightly increased acetaldehyde and ethanol concentrations without significant effects on NADH and NAD levels. Lactate accumulated in avocadoes kept in 0.25 % 02. The 80% CO, (added to 0.25% O2) did not increase lactate concentration and negated the 0.25% O2-induced lactate accumulation. Activities of PDC and LDH were slightly enhanced and a new isozyme of ADH was induced by 0.25% O2, 20% O2 + 80% CO2, or 0.25 % O2 + 80% CO2; these treatments partly reduced the overall activity of the PDH complex. Fermentative metabolism can be regulated by changes in levels of PDC, ADH, LDH, and PDH enzymes and/or by metabolic control of the functions of these enzymes through changes in pH, ATP, pyruvate, acetaldehyde, NADH, or NAD. Chemical names used: alcohol dehydrogenase (ADH), adenosine triphosphate (ATP), lactate dehydrogenase (LDH), nicotinamide adenine dinucleotide (NAD), reduced NAD (NADH), pyruvate decarboxylase (PDC), pyruvate dehydrogenase (PDH).

scholarly journals Postulated Physiological Roles of the Seven-carbon Sugars, Mannoheptulose, and Perseitol in Avocado

2002 ◽  
Vol 127 (1) ◽  
pp. 108-114 ◽  
Author(s):  
Xuan Liu ◽  
James Sievert ◽  
Mary Lu Arpaia ◽  
Monica A. Madore
Keyword(s):  
Carbon Allocation ◽  
Calvin Cycle ◽  
Threshold Level ◽  
Threshold Concentration ◽  
Pentose Phosphate ◽  
Persea Americana ◽  
Fresh Weight ◽  
Primary Products ◽  
Avocado Fruit ◽  
Hass Avocado

Avocado (Persea americana Mill.) tissues contain high levels of the seven-carbon (C7) ketosugar mannoheptulose and its polyol form, perseitol. Radiolabeling of intact leaves of `Hass' avocado on `Duke 7' rootstock indicated that both perseitol and mannoheptulose are not only primary products of photosynthetic CO2 fixation but are also exported in the phloem. In cell-free extracts from mature source leaves, formation of the C7 backbone occurred by condensation of a three-carbon metabolite (dihydroxyacetone-P) with a four-carbon metabolite (erythrose-4-P) to form sedoheptulose-1,7-bis-P, followed by isomerization to a phosphorylated d-mannoheptulose derivative. A transketolase reaction was also observed which converted five-carbon metabolites (ribose-5-P and xylulose-5-P) to form the C7 metabolite, sedoheptulose-7-P, but this compound was not metabolized further to mannoheptulose. This suggests that C7 sugars are formed from the Calvin Cycle, not oxidative pentose phosphate pathway, reactions in avocado leaves. In avocado fruit, C7 sugars were present in substantial quantities and the normal ripening processes (fruit softening, ethylene production, and climacteric respiration rise), which occurs several days after the fruit is picked, did not occur until levels of C7 sugars dropped below an apparent threshold concentration of ≈20 mg·g-1 fresh weight. The effect of picking could be mimicked by girdling the fruit stalks, which resulted in ripening on the tree. Again, ripening followed a decline in C7 sugars to below an apparent threshold level. Taken together, these data indicate that the C7 sugars play important roles in carbon allocation processes in the avocado tree, including a possible novel role as phloem-mobile ripening inhibitors.

scholarly journals Mitochondrial Self-restoration as an Index to the Capacity of Avocado Fruit to Sustain Atmospheric Stress at Two Climacteric States

1995 ◽  
Vol 120 (4) ◽  
pp. 643-649 ◽  
Author(s):  
Takaya Moriguchi ◽  
Roger J. Romani
Keyword(s):  
Strong Association ◽  
Respiratory Control ◽  
Persea Americana ◽  
Direct Exposure ◽  
Avocado Fruit ◽  
Pathogen Suppression ◽  
Hass Avocado ◽  
Atmosphere Storage

A strong association is implicit between mitochondrial function and the energy demands of cells responding to stress. Yet, the dynamics of this organelle-cellular dependency have been difficult to resolve. This study examines a new diagnostic parameter namely, mitochondrial maintenance and self-restoration as exhibited by the course of respiratory functions (states 3 and 4 respiratory rates, respiratory control) of mitochoudria extracted during and after exposure of intact `Hass' avocado (Persea americana) fruit to different stress atmospheres: anoxia (100% N2) or high (25% and 75%) CO2 for varying durations. Comparisons are made with direct exposure of the mitochondria themselves to similar atmospheres. In general, exposure of the fruit to CO2 rich atmospheres enhanced the capacity of their mitochondria to restore energy-linked functions whereas anoxia caused irreparable damage. The physiological (climacteric) state of the fruit also affected the stress capacity of the mitochondria contained therein, anaerobiosis being more harmful to mitochondria in riper fruit. In contrast to their effects in vivo, in vitro anoxia appeared to sustain mitochondrial energy-linked functions, whereas high CO2 was clearly harmful. These and other observations are discussed in the context of mitochondrial self-restoration or homeostasis and its relevance to postharvest stress-atmosphere storage for purposes such as pathogen suppression or insect control.

scholarly journals Effects of Elevated Carbon Dioxide on Key Mitochondrial Respiratory Enzymes in `Hass' Avocado Fruit and Fruit Disks

1997 ◽  
Vol 122 (2) ◽  
pp. 238-244 ◽  
Author(s):  
Diana L. Lange ◽  
Adel A. Kader
Keyword(s):  
Carbon Dioxide ◽  
Pyruvate Dehydrogenase ◽  
Ethylene Production ◽  
Physiological State ◽  
Visual Quality ◽  
Persea Americana ◽  
Respiratory Enzymes ◽  
Climacteric Fruit ◽  
Avocado Fruit ◽  
Hass Avocado

Preclimacteric avocado [Persea americana (Mill.) cv. Hass] fruit or fruit disks as well as fruit harvested in either June (midseason) or August (late season) and partially ripened were kept in air (21% O2 + 78% N2), 20% CO2 + 17% O2 (63% N2), or 40% CO2 + 13% O2 (47% N2) at either 10 or 20 °C. Ethylene production by preclimacteric fruit was completely inhibited during CO2 exposure, whereas there was only partial inhibition of ethylene production when partially ripened fruit were exposed. Compared to the fruit stored in air, O2 uptake of fruit stored in 20% CO2 was decreased by 20%, whereas the fruit stored in 40% CO2 showed 25% more O2 uptake than air-stored fruit. Fruit subjected to a storage regime of 40% CO2 at 10 °C followed by 2 d in air had the best visual quality. In general, climacteric fruit treated with 20% CO2 at 10 °C showed increased pyruvate dehydrogenase (PDH) activity and decreased cytochrome oxidase (CytOx) activity. Fruit stored in 40% CO2 had reduced CytOx activity compared to air-stored fruit, and PDH activity was variable depending on the harvest season of the fruit. Our results show that the effect of elevated CO2 on a given enzyme depends on concentration of CO2, duration of exposure, physiological state of the fruit, and type of tissue exposed.

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