Artificial Inoculation Trials Research Articles

Biscogniauxia rosacearum: A newly identified pathogen of strawberry tree (Arbutus unedo L.) in North Africa

AbstractBiscogniauxia species are opportunistic pathogens primarily associated with Quercus species dieback in the Mediterranean basin. Among these species, Biscogniauxia mediterranea stands out as the only species previously documented in Tunisia, affecting Quercus suber and Erica multiflora. This study unveils a novel finding, reporting the presence of Biscogniauxia rosacearum on Strawberry trees in Tunisia. The identification of B. rosacearum isolates was confirmed based on DNA sequence data (ITS, TUB2 and ACT) and morphological traits. Artificial inoculation trials on leaves confirmed the pathogenicity of the fungus towards Arbutus unedo. This finding emphasizes the significance of implementing proactive measures to effectively combat this pathogen because of the polyphagous nature of Biscogniauxia species that raises concerns about its potential spread within vulnerable hosts in Tunisian oak forests.

A Decade of Variety Testing for Resistance of Red Clover to Southern Anthracnose (Colletotrichum trifolii Bain et Essary) at the Bavarian State Research Center for Agriculture (LfL)

Southern anthracnose is caused by the fungal pathogen Colletotrichum trifolii Bain et Essary and affects red clover (Trifolium pratense) cultivation, causing severe losses in plant stands. Artificial inoculation with the pathogen in the greenhouse has been proven to effectively differentiate varieties for their resistance based on the survival rates of plants. Additionally, this method was successfully used to improve red clover populations via recurrent selection. However, not much is yet known on its association with resistance behavior in the field. In this study, results from 10 years of artificial inoculation trials at the Bavarian State Research Center for Agriculture were analyzed and compared to official German variety descriptions that are based on field data. A good congruency between survival rates from the greenhouse and official susceptibility ratings were observed. Thus, data from greenhouse tests have great potential to complement official variety lists where gaps exist. It was shown that within only three generations of recurrent selection using the greenhouse test, an existing variety could be significantly improved in terms of its resistance to Southern anthracnose without changing its DUS characteristics. A continuously increasing resistance level in the varieties registered in Germany since 2005 indicates that breeders can successfully respond to the threat imposed by this relatively new disease.

Eucalyptus leaf diseases associated with Neofusicoccum spp. in North Africa

This study represents the first survey reporting the occurrence of Neofusicoccum species associated with Eucalyptus foliar diseases in semi-arid areas in North African countries. Based on morphological features and phylogenetic analyses of internal transcribed spacer (ITS) of nuclear ribosomal DNA (rDNA), translation elongation factor 1-alpha (TEF1) and β-tubulin (TUB2) genes, two species were identified: Neofusicoccum mediterraneum recovered from leaf spots on E. gillii in Tunisia and Neofusicoccum cryptoaustrale reported from leaf blight of E. torquata and E. odorata in Libya. Artificial inoculation trials on leaves confirmed the pathogenicity of the isolates to E. torquata, E. odorata and E. gillii. This report points out the threat posed by pathogens to non-native Eucalyptus in North Africa and suggests a likely movement of various pathogenic fungi from other hosts to Eucalyptus mainly E. ododrata trees that are totally infested by N. cryptoaustrale. Thus, it is recommended that E. odorata should not be planted in semi-arid areas. Further prospections of Eucalyptus arboretums are required to assess the incidence of foliar diseases on Eucalyptus plantations and to take appropriate and prompt measures against disease spread.

Resistance of New Zealand Provenance Leptospermum scoparium, Kunzea robusta, Kunzea linearis, and Metrosideros excelsa to Austropuccinia psidii.

Resistance to the pandemic strain of Austropuccinia psidii was identified in New Zealand provenance Leptospermum scoparium, Kunzea robusta, and K. linearis plants. Only 1 Metrosideros excelsa-resistant plant was found (of the 570 tested) and no resistant plants of either Lophomyrtus bullata or L. obcordata were found. Three types of resistance were identified in Leptospermum scoparium. The first two, a putative immune response and a hypersensitive response, are leaf resistance mechanisms found in other myrtaceous species while on the lateral and main stems a putative immune stem resistance was also observed. Both leaf and stem infection were found on K. robusta and K. linearis plants as well as branch tip dieback that developed on almost 50% of the plants. L. scoparium, K. robusta, and K. linearis are the first myrtaceous species where consistent infection of stems has been observed in artificial inoculation trials. This new finding and the first observation of significant branch tip dieback of plants of the two Kunzea spp. resulted in the development of two new myrtle rust disease severity assessment scales. Significant seed family and provenance effects were found in L. scoparium, K. robusta, and K. linearis: some families produced significantly more plants with leaf, stem, and (in Kunzea spp.) branch tip dieback resistance, and provenances provided different percentages of resistant families and plants. The distribution of the disease symptoms on plants from the same seed family, and between plants from different seed families, suggested that the leaf, stem, and branch tip dieback resistances were the result of independent disease resistance mechanisms.

Diaporthe species associated with twig blight and dieback of Vaccinium corymbosum in Portugal, with description of four new species

ABSTRACTBlueberry, an increasingly cultivated fruit crop in Portugal, is known to be susceptible to twig blight and dieback caused by species of Diaporthe. The diversity of Diaporthe species associated with symptomatic and asymptomatic Vaccinium corymbosum plants in Portugal was assessed. A multilocus sequence analysis of the rDNA internal transcribed spacer (ITS) region and the translation elongation factor 1-alpha (tef1-α), β-tubulin (tub2), calmodulin (cal), and histone 3 (his3) genes revealed the presence of Diaporthe foeniculina, Diaporthe rudis, and four new species, which are described as Diaporthe crousii, Diaporthe phillipsii, Diaporthe rossmaniae, and Diaporthe vacuae. These new species were characterized in terms of their morphology, mating strategies, and temperature growth requirements. In artificial inoculation trials of V. corymbosum cv. Bluecrop plants, all Diaporthe species caused minor symptoms. Further, no differences in aggressiveness were apparent between species. This study provides the first survey of Diaporthe species associated with blueberry twig blight and dieback in Portugal. It disclosed the occurrence of a diverse assemblage of Diaporthe species, whose status and impact as pathogens of blueberry is not yet fully understood.

Pestalotiopsis biciliata, a new leaf pathogen ofEucalyptusspp. recorded in Italy

AbstractThe present paper describes new symptoms onEucalyptusspp. in Central Italy associated with the fungal pathogenPestalotiopsis biciliata. This fungal species has been previously recorded in Italy on grape associated with fruit rot. Artificial inoculation trials on leaves confirmed the pathogenicity of the fungus toEucalyptus camaldulensis.P. biciliatais included in the list ofPestalotiopsisspp. responsible for leaf disease on eucalypts worldwide.

FURTHER INSIGHTS INTO MALUS FUSCA FIRE BLIGHT RESISTANCE

The apple wild species accession Malus fusca MAL0045 had been found to be resistant to fire blight in artificial inoculation trials with Erwinia amylovora strain Ea222_JKI. Consequently, using a population derived by crossing MAL0045 with Idared, the corresponding fire blight resistance locus of M. fusca (Mfu10) was mapped on chromosome 10 explaining up to 66% of phenotypic variation at a logarithm of the odd (LOD) ratio of 31.0 with the strain Ea222_JKI. Moreover, the very aggressive strain Ea3049 only minimally affected MAL0045 but significantly affected the population although could not overcome the resistance of Mfu10. To further understand the resistance mechanism of M. fusca, we evaluated resistance of the original mapping population, comprised of 134 individuals, to E. amylovora strain ZYRKD3-1 which causes the breakdown of the resistance of M.×robusta 5 (Mr5) and the Mr5 fire blight resistance QTL on LG3. Our results showed that the major QTL of M. fusca on LG10 could still be detected at the same exact position with a higher effect on fire blight resistance, indicating that ZYRKD3-1 has no effect on Mfu10, although the mean percent lesion length of the population was almost doubled compared with Ea222_JKI.

Diversity and potential impact of Botryosphaeriaceae species associated with Eucalyptus globulus plantations in Portugal

Eucalyptus globulus, a non-native species, is currently the most abundant forest species in Portugal. This economically important forest tree is exploited mainly for the production of pulp for the paper industry. The community of Botryosphaeriaceae species occurring on diseased and healthy E. globulus trees was studied on plantations throughout the country. Nine species from three different genera were identified, namely Botryosphaeria (B. dothidea), Diplodia (D. corticola and D. seriata) and Neofusicoccum (N. australe, N. algeriense, N. eucalyptorum, N. kwambonambiense, N. parvum and Neofusicoccum sp.). Of these, N. algeriense, D. corticola and D. seriata are reported for the first time on E. globulus, while N. algeriense, N. eucalyptorum and N. kwambonambiense correspond to first reports in Portugal. The genus Neofusicoccum was clearly dominant with N. australe and N. eucalyptorum being the most abundant species on both diseased and healthy trees. In artificial inoculation trials representative isolates from all nine species were shown to be pathogenic to E. globulus but there were marked differences in aggressiveness between them. Thus, D. corticola and N. kwambonambiense were the most aggressive while B. dothidea and D. seriata were the least aggressive of the species studied.

Development and commercialisation of the Pinus patula × P. tecunumanii hybrid in response to the threat of Fusarium circinatum

During the last 20 years a program to develop and commercialize the Pinus patula × Pinus tecunumanii hybrid, as a replacement for P. patula, has been successfully implemented. The first crosses were initiated during the early 1990s and lead to establishment of field trials across a wide variety of sites. This work gained further impetus when it became apparent that Fusarium circinatum, was causing poor post-planting survival of newly established stands of P. patula. P. tecunumanii, has been shown to be tolerant to this disease and thus a second, more comprehensive hybrid testing phase was implemented. Improvements in controlled pollination techniques and propagation methods, as well as access to genetically improved parent-stock and the use of molecular marker technology for fingerprinting was effectively utilized to greatly improve the process during this second phase. The use of artificial inoculation trials have demonstrated that the hybrid, in particular when using the low elevation (LE) provenances of P. tecunumanii, had substantially greater tolerance to F. circinatum than P. patula and survival figures from field trials support these results. Four-year volumes also indicate large growth improvements, although frost damage on certain sites presents a challenge for deployment on colder sites; and this is being tackled through breeding and accurate mapping of frost risk. Large-scale controlled pollinations and vegetative multiplication are now utilized commercially to produce the P. patula × P. tecunumanii (LE) hybrid as an alternative to P. patula.

Response of cucurbit rootstocks to Pythium aphanidermatum

Damping-off and vine decline diseases affect most greenhouse cucumber crops in Oman, with losses frequently exceeding 25% of seedlings and adult plants. As a consequence of some recent reports that disease control using metalaxyl fungicides were ineffective, seven local and introduced rootstocks were assessed for their response to Pythium aphanidermatum. The rootstocks were also tested for grafting compatibility and production potential under greenhouse conditions. During artificial inoculation trials, no damping-off symptoms were observed in the Hercules and Titan varieties, ridge gourd or sponge gourd. In three separate greenhouse trials, Titan, Hercules and squash var. Magda showed no damping-off or vine decline symptoms up to 45 days after transplanting. When cucumber was grafted onto the seven rootstocks, no symptoms were observed in the cucumber plants grafted onto Titan and Hercules rootstocks, whereas the cucumber grafted onto the other rootstocks showed varying levels of damping-off and vine decline diseases (10–40%). The Titan and Hercules rootstocks significantly increased the vegetative growth and the fruit number, weight and length compared to the self-grafted cucumbers, non-grafted cucumbers and cucumbers that were grafted onto the other rootstocks (P < 0.05). To the best of our knowledge, this study is the first to examine the influence of grafting on the resistance to Pythium and on the vegetative growth and yield of greenhouse cucumbers.

Breeding for resistance to ear rots caused by Fusarium spp. in maize – a review

With 2 tablesAbstractEar rots caused by different Fusarium spp. are one of the most dangerous food and feed safety challenges in maize production. At present, the majority of the inbreds and hybrids are susceptible. Gibberella and Fusarium ear rots (caused by Fusarium graminearum and Fusarium verticillioides, respectively) are the two main diseases, but more than 10 further Fusarium spp. cause ear rots. Natural infection is initiated by a mixture of the local Fusarium spp., but usually one species predominates. Many maize breeders rely on natural infection to create sufficient levels of disease severity for selection‐resistant genotypes; however, there are few locations where the natural infection is sufficiently uniform to make this selection efficient and successful. Thus, an artificial inoculation method normally performed with one fungal species is now used by more breeders. Most published papers on breeding for ear rot resistance are focused on either F. graminearum or F. verticillioides, and reports involving both or more Fusarium spp. are rare. Several reports support the hypothesis that resistance to multiple species especially F. graminearum, F. culmorum and F. verticillioides may be common. Significant differences in genotypic resistance after inoculation exist. Resistance to the two major modes of fungal entry into the ear, via the silk or through kernel wounds, is not correlated in all genotypes. The reason is not clear. When silk channel resistance was assessed, the data from natural and artificial inoculation trials correlated well. Analogous data relating to kernel resistance have not been published. Both native and exotic sources of resistance are important, but surprisingly little information is available. Few papers report on the use of artificial inoculation during inbred development. Most of the publications on inoculation are concerned with testing at later stages when combining ability is tested. Inbreds differ in general and specific combining ability for ear rot resistance. The expression of resistance to disease severity and resistance to toxins is often used as synonyms, but in fact they are not. Higher resistance to visual disease severities mostly results in lower toxin contamination, and the resistance level seems to be the most important factor regulating the toxin content. The mode of inheritance of resistance appears to differ: additive, possibly non‐additive effects, digenic (dominant) and polygenic patterns have been identified. Improved phenotyping methods that take into account the influence of stalk rot and the use of several independent isolates are available. The QTLs mostly exhibit small effects and some are validated; however, marker‐assisted selection in breeding cannot yet be foreseen. As the severity of natural infections tends to correlate with the artificial inoculation results, the incorporation of artificial inoculation methods in breeding programmes is now the most important task. As genotypic resistance differences between hybrids are high, the registration of hybrids should consider the use of the inoculation tests to choose most resistant hybrids for commercial production. This is the most rapid way to increase feed safety.

Combination of Kluyveromyces marxianus and sodium bicarbonate for controlling green mold of citrus fruit

Biocontrol efficacy of an antagonistic yeast Kluyveromyces marxianus was evaluated individually or in combination with sodium bicarbonate (SBC) against green mold of citrus fruit caused by Penicillium digitatum. Their effects on postharvest quality of citrus fruit were also investigated. The results indicated that the antagonistic activity of K. marxianus at 1×10⁸ CFU/mL on green mold of citrus fruit was enhanced by 2% SBC treatment. In artificial inoculation trials, disease control after 3 and 6 days, respectively, with the mixture of K. marxianus and 2% SBC (18.33%, 58.33%) was significantly improved over that obtained with K. marxianus (41.67%, 70.00%) or SBC (43.33%, 81.67%) alone. The combination of K. marxianus with SBC was as effective as the imazalil treatment in natural infection trials, which gave about 90% control of green mold. Addition of 2% SBC significantly stimulated the growth of K. marxianus in citrus fruit wounds after 72 h. Moreover, K. marxianus, SBC and their combination did not impair quality parameters including weight loss, fruit firmness, total soluble solids, titratable acidity and ascorbic acid at 4 °C for 30 days followed by 20 °C for 15 days. These results suggested that the use of SBC is a useful approach to improve the efficacy of K. marxianus for the postharvest green mold of citrus fruit.

Influence of abiotic parameters on ochratoxin A production by a Penicillium nordicum strain in dry-cured meat model systems

OTA production from an ochratoxigenic Penicillium nordicum strain was studied in artificial inoculation trials managed both in a dry-cured pork-based medium (DCM) and in dry-cured pork cores. The experimental region defined by 7–23 °C temperature, 0.83–0.97 a w and 7–21 days of incubation was considered for DCM in the applied Central Composite Design (CCD). A w > 0.92, temperature > 18 °C and incubation time protracted to 21 days strongly enhanced OTA production. The conditions of CCD central point (a w = 0.90, temperature = 15 °C and days of incubation = 14) and those predicted as the most suitable for OTA production in DCM, were tested in dry-cured pork samples incubated up to 190 days. A ten-fold increase in OTA (0.04–0.41 μg/g) was achieved when the temperature rose from 15 °C up to 20 °C, an over twenty-fold (0.02–0.43 μg/g) when switching from 0.90 to 0.93 a w. The results can be useful as guidelines for critical control points (CCPs) detection in dry-curing processing to prevent OTA contamination of the products.

White pine blister rust resistance in North American, Asian and European species - results from artificial inoculation trials in Oregon

Dorena Genetic Resource Center (DGRC) has used artificial inoculation trials to evaluate progenies of thousands of Pinus monticola and P. lambertiana selections from Oregon and Washington for resistance to white pine blister rust caused by Cronartium ribicola. In addition, early results are now available for P. albicaulis and P. strobiformis. DGRC has also recently evaluated seed orchard progenies of P. strobus, as well as bulked seedlots from P. armandii and P. peuce. The majority of P. monticola, P. lambertiana, P. albicaulis, and P. strobus progenies are very susceptible to blister rust. However, resistance exists in all these species. P. strobiformis showed relatively high levels of resistance for the eight progenies tested. Resistance in P. armandii was mainly reflected in the very low percentage of cankered seedlings; for P. peuce, the high percentage of cankered seedlings alive three years after inoculation was notable. R-genes are present in some of the North American five-needle pine species, but partial resistance traits (e.g. bark reaction) will play a major role in breeding activities for P. monticola and P. lambertiana and will likely be the key to developing durable resistance.

Influence of host and pathogen factors on disease incidence resulting from artificial inoculation of kiwifruit by Botrytis cinema

The effects of various host and pathogen factors on disease incidence of Botrytis cinerea (Persoon: Fries) in kiwifruit (Actinidia deliciosa var. deliciosa ’Hayward’ (A.Chev.) C. F. Liang et A. R. Ferguson) were studied in artificial inoculation trials. High inoculum levels (≥25 000 spores/stem scar) and addition of yeast extract to spore suspensions significantly increased infection. There was no effect of fruit water potential on disease incidence, but total infection decreased when fruits were harvested later in the season or exposed to a curing treatment (6–24 h at 20°C).

Septoria Leaf Spot on Dogwoods

The fungus that frequently defoliates Siberian and yellow-twig dogwoods is identified as Septoria cornicola. Pathogenicity was confirmed in artificial inoculation trials, and environmental influences on fungal growth, sporulation, and spore germination were established.

Field evaluation of ecological differentiation of dwarf mistletoe on shore pine and western hemlock

Hemloclc dwarf mistletoe (Arcenthobiiuntsugense (Rosend.) G. N. Jones) principally infects western hemlock (Tsugaheteropliylla (Raf.) Sarg.), but it is also damaging to shore pine (Pinuscontorta Dougl. ex Loud.) growing in coastal British Columbia. Stands of varied composition were studied in the Home Lake area of Vancouver Island to compare the levels of infection in shore pine and western hemlock. Infection of shore pine occurred whether or not infected hemlock trees were present in the stand. Observations and measurements from these field studies support indications from earlier artificial inoculation trials that two ecological races of A. tsugense exist.

Bacterial Wilt Reaction and Survival of Alfalfa Varieties in Artificial Inoculation Trials1

Crop ScienceVolume 5, Issue 4 cropsci1965.0011183X000500040026x p. 368-369 Article Bacterial Wilt Reaction and Survival of Alfalfa Varieties in Artificial Inoculation Trials1 F. I. Frosheiser, F. I. FrosheiserSearch for more papers by this authorL. J. Elling, L. J. Elling Research Plant Pathologist, Crops Research Division, ARS, USDA, and Associate Professor, University of Minnesota, St. Paul, Minn.Search for more papers by this author F. I. Frosheiser, F. I. FrosheiserSearch for more papers by this authorL. J. Elling, L. J. Elling Research Plant Pathologist, Crops Research Division, ARS, USDA, and Associate Professor, University of Minnesota, St. Paul, Minn.Search for more papers by this author First published: 01 July 1965 https://doi.org/10.2135/cropsci1965.0011183X000500040026x 1 Contribution from the Crops Research Division, ARS, USDA, Department of Plant Pathology and Physiology, and Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, Minnesota. Paper No. 5421, Scientific Journal Series, Minnesota Agr. Exp. Sta. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume5, Issue4July–August 1965Pages 368-369 RelatedInformation