Robert A. Spotts

Reconstructing the early evolution of Fungi using a six-gene phylogeny

The ancestors of fungi are believed to be simple aquatic forms with flagellated spores, similar to members of the extant phylum Chytridiomycota (chytrids). Current classifications assume that chytrids form an early-diverging clade within the kingdom Fungi and imply a single loss of the spore flagellum, leading to the diversification of terrestrial fungi. Here we develop phylogenetic hypotheses for Fungi using data from six gene regions and nearly 200 species. Our results indicate that there may have been at least four independent losses of the flagellum in the kingdom Fungi. These losses of swimming spores coincided with the evolution of new mechanisms of spore dispersal, such as aerial dispersal in mycelial groups and polar tube eversion in the microsporidia (unicellular forms that lack mitochondria). The enigmatic microsporidia seem to be derived from an endoparasitic chytrid ancestor similar to Rozella allomycis, on the earliest diverging branch of the fungal phylogenetic tree.

Control of postharvest pear diseases using natural saprophytic yeast colonists and their combination with a low dosage of thiabendazole

Abstract Thirty-one morphologically different strains of yeasts and yeast-like fungi, isolated from the surface of pear fruits, were evaluated for biocontrol potential of blue mold on dAnjou pear fruits. Seven yeast strains (Cryptococcus albidus strain HRB2, C. infirmo-miniatus strain YY6, C. laurentii strain HRA5, Rhodotorula aurantiaca strain YCL5, and R. glutinis strains HRA3, HRA4 and HRB6) reduced incidence of blue mold on pears. C. laurentii HRA5 and R. glutinis HRB6 were most effective for reduction of incidence and severity of blue mold. C. laurentii HRA5 and R. glutinis HRB6 combined with a low dose of thiabendazole (TBZ) (15 μg ml−1) gave significantly better disease control at 5, 10 and 20 °C than either TBZ or the yeast alone and was comparable to disease control achieved using a commercially-recommended high dose of TBZ (525 μg ml−1). C. infirmo-miniatus strain YY6 was most effective for the control of Mucor rot of pears. C. laurentii HRA5, C. infirmo-miniatus YY6, and R. glutinis HRB6 reduced incidence and severity of gray mold of pears and were more effective when combined with a low dose of TBZ. Side rot of Bosc pears was completely controlled by C. laurentii HRA5, C. infirmo-miniatus YY6 and R. glutinis HRB6, whereas TBZ was ineffective. Bulls-eye rot of pears was completely controlled by all yeasts when they were combined with a low dose of TBZ. Populations of C. laurentii HRA5, C. infirmominiatus YY6 and R. glutinis HRB6 in pear wounds increased approximately 1.3 log units within 10 days at −1 °C and 1.7 log units in 2 days at 5, 10 and 20 °C. Addition of cell-free supernatants of yeast cultures to wounds did not suppress decay, and substances inhibitory to fungal germination were not detected on culture plates.

Wounding, wound healing and staining of mature pear fruit

Abstract Incidence of wounding in commercially-harvested `dAnjou and `Bosc pear fruit, healing of wounds to decrease decay caused by Botrytis cinerea, Mucor piriformis, Penicillium expansum, and Penicillium solitum at −1°C, 20°C, and 28°C, and formation of compounds potentially involved in resistance were determined. Use of a blue food coloring to make wounds on fruit more visible on packinghouse lines was evaluated. Over 4 years, an average of 2.9% of `dAnjou pear fruit were wounded during harvest and handling. In `Bosc pears, average incidence of wounding was 4.3% where fruit was harvested by workers paid by the hour, and 13.9% where workers were paid by the number of bins harvested. Susceptibility of wounds to infection by M. piriformis, P. expansum, and B. cinerea at −1°C decreased rapidly during the first 2 weeks, 4 weeks, and 8 weeks, respectively. The percent of wounds that stained well with food coloring was similar to the decay susceptibility curve for P. expansum at −1°C. Susceptibility of wounds to decay in fruit held at 20°C decreased almost linearly from 0 to 2 days. After 2 days at 20°C, 78% of the wounds absorbed stain, a significantly higher percent than were susceptible to decay. Prestorage heat treatment of fruit to 28°C for 24 h prior to inoculation decreased susceptibility of wounds to infection by both P. expansum and P. solitum. In commercial packinghouses, use of a 10% solution of blue food coloring to enhance visibility of wounds in pear fruit resulted in removal of 40% of punctured fruit compared with 22% removal without staining. Histochemical tests of cell walls near wounds showed an accumulation of callose, suberin, tannins and pectic substances, as well as gums and starch, within 4 days after wounding. Lignin was not detected in wound tissue.

Control of Postharvest Decay in Pear by Four Laboratory-Grown Yeasts and Two Registered Biocontrol Products

Control of blue mold decay in Bosc pears was studied with the laboratory-grown yeasts Rhodotorula glutinis, Cryptococcus infirmo-miniatus, and two strains of Cryptococcus laurentii, as well as registered biocontrol products Aspire, containing the yeast Candida oleophila, and Bio-Save 11 (now Bio-Save 110), containing the bacterium Pseudomonas syringae. Both thiabendazole (TBZ)-sensitive and TBZ-resistant strains of Penicillium expansum were used. Aspire treatment reduced the average lesion diameter by approximately 65 and 45%, and reduced decay incidence by 27 and 9% with TBZ-resistant and TBZ-sensitive P. expansum, respectively, in the first year of the study, but did not result in significant decay control in the second year. Bio-Save 11 reduced decay lesion diameter by 32 to 72% and incidence by 21 to 40% over the 2 years. In both years, TBZ-sensitive P. expansum was completely controlled by the combination of either C. laurentii (both strains), R. glutinis, or C. infirmo-miniatus with 100 ppm TBZ. With TBZ-resistant P. expansum, control of wound infection with these yeasts alone or with 100 ppm TBZ ranged from 62.9 to 100%. In a packinghouse trial, control by Bio-Save 110 + 100 ppm TBZ and Aspire + 100 ppm TBZ was not different than control by TBZ at 569 ppm, the maximum label rate. The amount of decay following Aspire + 100 ppm TBZ treatment was significantly less than the amount of decay following Bio-Save 110 + 100 ppm TBZ treatment.

Variability in postharvest decay among apple cultivars

The level of resistance to decay caused by four fungal pathogens, the force required to break the epidermis, and the extent of open sinuses as measures of potential decay resistance were determined for the fruit of several apple cultivars. No single cultivar was the most resistant to each of the four pathogens in this study. In addition, each cultivar that was the most resistant to one pathogen also was the most susceptible to one of the other pathogens. However, Royal Gala was the most resistant to the wound pathogens Botrytis cinerea, Penicillium expansum, and Mucor piriformis. Fuji and Oregon Spur II were more resistant than other cultivars to Pezicula malicorticis. The epidermis (skin) of Fuji and Granny Smith were the most resistant to puncture, requiring an average of 81.5 and 87.0 Newtons, respectively, to break the epidermal layer. Fuji had the highest percentage of fruits with open sinuses, with a mean of 38%, whereas Braeburn had 0% of fruit with open sinuses. The cultivar information presented herein may be a valuable measure of decay resistance and may be of use to the apple industry.

Integrated control of brown rot of sweet cherry fruit with a preharvest fungicide, a postharvest yeast, modified atmosphere packaging, and cold storage temperature

Abstract An integrated approach was studied for control of postharvest brown rot of sweet cherry fruit. System components included a preharvest application of propiconazole, a postharvest application of a wettable dispersible granular formulation of the yeast Cryptococcus infirmo-miniatus (CIM) Pfaff and Fell, storage in modified atmosphere, and storage at 2.8xa0°C for 20 days or −0.5xa0°C for 42 days. Preharvest propiconazole and postharvest CIM were similarly effective for control of brown rot. A significant propiconazole–CIM synergism was observed. Modified atmosphere significantly reduced brown rot compared to air-stored fruit. The storage temperature regime effect was inconsistent. This integrated decay control approach was effective and is especially relevant since postharvest fungicide options for cherry are limited.

Control of brown rot and blue mold of sweet cherry with preharvest iprodione, postharvest Cryptococcus infirmo-miniatus, and modified atmosphere packaging.

The effectiveness of preharvest iprodione and postharvest Cryptococcus infirmo-miniatus treatments alone and in combination for control of decay of sweet cherry fruit was studied. Also, the effect of a modified atmosphere on brown rot control was evaluated as a part of the iprodione-C. infirmo-miniatus combinations. A single preharvest application of iprodione at 1.13 kg a.i./ha reduced brown rot in stored sweet cherry fruit in both years of this study. Significantly better control of brown rot was obtained when cherry fruit that received a preharvest iprodione application also were treated with a postharvest dip in a suspension of C. infirmo-miniatus containing 0.5 to 1.5 × 108 CFU/ml. Brown rot was reduced by modified atmosphere packaging (MAP) alone and further reduced as a result of a C. infirmo-miniatus-MAP synergism. Incidence of brown rot was reduced from 41.5% in the control to 0.4% by combining preharvest iprodione and postharvest C. infirmo-miniatus treatments with MAP.

Etiology of Bull's Eye Rot of Pear Caused by Neofabraea spp. in Oregon, Washington, and California

A collection of Neofabraea isolates from pear fruit grown in Oregon, Washington, and California was screened with species-specific primers in a multiplex polymerase chain reaction (PCR). Neofabraea alba was identified most frequently in samples from Oregon and California, whereas N. perennans was found most frequently in samples from Washington. N. alba also was identified from tissue of small cankers and pruning stubs on pear trees using PCR. Bulls eye rot pathogens were isolated from fruit of nine different European pear cultivars, Asian pear, and quince. Overall, N. alba was the most prevalent species in 2001 whereas N. perennans was more prevalent in 2002. An undescribed species of Neofabraea was identified in samples from Medford, OR that corresponds to a species previously found by others using molecular methods. This information increases the known geographic distribution of this undescribed species.

Populations of Botrytis cinerea and Penicillium spp. on Pear Fruit, and in Orchards and Packinghouses, and Their Relationship to Postharvest Decay

The aims of this study were to examine the sources and population sizes of Botrytis cinerea and Penicillium spp. in dAnjou pear orchards, packinghouses, and storage, and to determine the relationship between population sizes and postharvest decay. Densities of B. cinerea ranged from nondetectable to 4.0 CFU/cm2 on fruit, nondetectable to 3.1 CFU/liter in orchard air, and nondetectable to 1,167 CFU/g in orchard litter. The majority of packinghouse air and orchard soil samples collected yielded no B. cinerea inoculum. Densities of Penicillium spp. ranged from nondetectable to 2.7 CFU/cm2 on pear fruit, nondetectable to 3.13 CFU/liter in orchard air, nondetectable to 11.8 CFU/liter in packingline air, nondetectable to 3.9 CFU/liter in cold-storage air, 38 to 431 CFU/g in orchard soil, and 131 to 1,128 CFU/g in orchard litter. The mean incidence of gray mold in stored dAnjou pear fruit ranged from 0.7 to 10.7%. Incidence of blue mold ranged from 0 to 16.5%. Significant positive correlations were observed between decay and fruit surface populations of B. cinerea and Penicillium spp. In conclusion, inoculum levels of these important postharvest pathogens in orchard and packinghouse air, and orchard soil and litter, cannot be used as indicators of postharvest decay; whereas the inoculum level on fruit surfaces may be a useful predictor of decay.

Description of Cryptosporiopsis kienholzii and species profiles of Neofabraea in major pome fruit growing districts in the Pacific Northwest USA.

The objectives of this study were i) to give a taxonomic description of a fungus phylogenetically related to Neofabraea and assign the name Cryptosporiopsis kienholzii to this fungus, ii) to expand previous Neofabraea species profiles from infected apple and pear fruit collected from major pome fruit production districts in Oregon and Washington, and iii) to determine the sensitivity of Neofabraea alba, Neofabraea malicorticis, Neofabraea perennans, and C. kienholzii to a range of fungicides. A name is given herein to the anamorph of the fungus previously called Neofabraea sp. nov. in the literature, and the fungus is designated as C. kienholzii. The teleomorph of this fungus has never been observed in vivo or in vitro. N. alba, N. perennans, and C. kienholzii accounted for 61.3, 35.6, and 3.1 %, respectively, of 608 isolates obtained from pear fruit and 6.0, 81.3, and 12.7 % of 150 isolates from apple fruit. N. alba was the most common species in Oregon and N. perennans was most common in Washington. N. malicorticis was not found in any of the districts and may be limited to the wet climates west of the Cascade mountain range. C. kienholzii occurs in pome fruit orchards from southern Oregon to North Central Washington, and this is the first report of C. kienholzii in the state of Washington. The four most effective fungicides for control of bulls-eye rot caused by all species were thiabendazole, thiophanate-methyl, pyrimethanil, and pyraclostrobin+boscalid. Other fungicides gave acceptable control of some species of Neofabraea but not others. There was good agreement of the microbioassay with fungicide evaluations using wound-inoculated pear fruit for five of seven fungicides, but the microbioassay was not consistent enough for determination of the sensitivity of Neofabraea species to new fungicides.