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Archive for the ‘Fungi’ Category

Nigeria losing over 1m tonnes of onions to purple blotch annually – FG

From Olanrewaju Lawal, Birnin Kebbi

The Federal Government has asserted that the annual purple blotch fungal disease affecting onions in the country has created a demand deficit of 1.1million metric tonnes of the product, even as Nigeria is supposed to be harvesting 2.4 million metric tonnes to meet up demands.

Permanent Secretary, Federal Ministry of Agriculture and Rural Development, Mr Ernest Umakhihe, stated this at a two-day workshop on management of Onion Purple Blotch ‘ Dan- Zazzalau’ Fungal Disease’ organised by the ministry under Horticulture Programmes in Birnin Kebbi

Umakhime, who was represented by an Acting Deputy Director in the ministry, Mrs Agbani Omotosho, explained that “it is however sad to note that though Nigeria, rated as a major producer of onions in Africa, contributes little to the export market largely due to produce quality resulting from poor management of pests and diseases, and use of pesticides causing food- borne illnesses.

“The national output as at 2018/2019 was 1.4 million metric tones, while national demand is 2.5 million metric tones, with demand gap of 1.1 million metric tones to be bridged by importation of onion and other products estimated at N3 million metric tone between 2015 and 2018. This is twice the country’s annual production; exerting enormous pressure on our foreign exchange earnings.”

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“Our lettuce varieties have resistance against new downy mildew race BI:37EU”

Downy mildew is a major threat in lettuce. The fungus can damage the lettuce leaves in both protected and open-field crops, resulting in a loss of yield. Last year the European Commission of the International Bremia Evaluation Board (IBEB-EU) identified a widely occurring new variant of downy mildew in lettuce. As of 1 June 2021, it has officially been named Bl:37EU. The large majority of Rijk Zwaan’s current lettuce varieties are resistant to the new race of downy mildew.

New official denominated race
On 1 June 2021, the European Commission of the International Bremia Evaluation Board (IBEB-EU) officially denominated the new race BI:37EU. This variant of downy mildew (Bremia lactucae, Bl) has been found in multiple regions in France in the past years and more recently also in Spain, Portugal, and Italy. IBEB-EU expects this race to spread further in the summer and autumn of this year, although it is currently difficult to predict which areas will actually be affected.

Resistances in lettuce
The development of resistances against downy mildew is one of the pillars of vegetable breeding company Rijk Zwaan’s lettuce breeding program. “Downy mildew is evolving genetically all the time and a large number of isolates of the plant fungus are already known worldwide. In our breeding program, we are continuously working on improving the traits of our lettuce varieties, including resistances to new downy mildew variants. The large majority of Rijk Zwaan’s current lettuce varieties are resistant to the new BI:37EU race of downy mildew,” comments Johan Schut, Breeding Manager Lettuce.

Sustainable solution
Rijk Zwaan is a strong advocate of an integral approach to combating plant diseases in order to reduce the use of chemicals. Although resistant varieties play an important role in this, the company also advises crop protection agents and hygiene measures to prevent new downy mildew variants from developing. Good hygiene practices such as burying crop residues and promptly removing diseased plants help to limit the spread of downy mildew in lettuce.

International Bremia Evaluation Board
The International Bremia Evaluation Board (IBEB) is a joint initiative of lettuce breeding companies in the USA, France and the Netherlands, the University of California-Davis, the Netherlands Inspection Service for Horticulture (Naktuinbouw) and the French National Seed Station (GEVES). IBEB’s mission is to identify new races of Bremia lactucae that pose a significant threat to the North American or European lettuce market and to promote the use of standardized race names in communication with growers.

Races are identified and nominated by regional IBEB committees specifically for each continent. For more information, visit the International Seed Federation’s website. For more information:
Rijk Zwaan
info@rijkzwaan.com
www.rijkzwaan.com

Publication date: Tue 1 Jun 2021

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FOL race 1 is a critical issue for lettuce production in Norway

Lettuce is produced in Norway both in field and greenhouses. In Norway, greenhouse lettuce is one of the most important vegetables grown year-round. In winter 2018, wilting symptoms were observed on soil-grown lettuce of the cultivar Frillice in a greenhouse in southeast Norway (Buskerud county). Affected plants showed stunted growth, wilting of outer leaves, and brownish discoloration of vascular tissues of taproots and crowns. According to the growers, the disease caused an estimated 10% of yield losses.

Symptoms of fusarium wilt of lettuce caused by Fusarium oxysporum f. sp. lactucae

Scientists at the Norwegian Institute of Bioeconomy Research (NIBIO) isolated fungal pathogen from crowns and roots of diseased plants collected from the greenhouse in 2018 and 2019. Morphological and DNA sequences analyses indicated that the pathogen was Fusarium oxysporum f.sp. lactucae (FOL) race 1. The same results were showed by Koch’postulate.

Pathogenicity test 12 days after inoculation: d) plant inoculated with isolate; e) control plants

“Race identity was confirmed using the differential lettuce cultivars Costa Rica No.4 (resistant to FOL race 1), Banchu Red Fire (resistant to FOL races 2 and 4) and Romana Romabella (resistant to FOL races 1 and 2) provided by the breeding company Rijk Zwaan (De Lier, the Netherlands). Roots of six 2 weeks old seedlings per cultivar were inoculated by dipping in a spore suspension for 1 min, while controls were dipped in distilled water. Seedlings were planted in 250 ml pots containing fertilized potting substrate and were placed in a greenhouse with temperature ranging from 15 to 35 ⁰C and an average of 23 ⁰C. After 10 days reduced growth was observed in cultivars Frillice and Banchu Red Fire for fungal isolates. After 25 days wilting was observed in both cultivars. Affected plants presented discoloration of vascular tissue. No difference in growth was observed between cultivars Romana Romabella and Costa Rica No. 4 and their respective controls,” the scientists explained.

FOL was re-isolated from all inoculated cultivars but not from controls. The colony patterns of the recovered isolates confirmed that the isolate belongs to race 1. Greenhouse lettuce in Norway is mainly produced in hydroponics. FOL is here reported to cause damages in soil-grown lettuce. Nevertheless FOL in hydroponic systems has been reported in Japan in 2003 and Thailand in 2017. Thus, the possibility of infections in hydroponics remain a big concern for lettuce production in Norway.

Source: Maria Luz Herrero, Nina Elisabeth Nagy, Halvor Solheim, ‘First Report of Fusarium oxysporum f. sp. lactucae Race 1 Causing Fusarium Wilt of Lettuce in Norway’, April 2021, Plant Disease.

Publication date: Mon 10 May 2021
Author: Emanuela Fontana
© FreshPlaza.com

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Septoria warning as high levels of latent disease found

11 May 2021 | by FarmingUK Team | ArableFarm ProductsNewsA robust T2 fungicide programme is advised to tackle the hidden threat, Corteva Agriscience saysA robust T2 fungicide programme is advised to tackle the hidden threat, Corteva Agriscience says    

A septoria warning has been issued to UK growers as high levels of latent disease has been found in plant samples.

Septoria pressure in wheat crops is expected to build in the coming weeks as warmer temperatures are set to follow early May rainfall.

Laboratory analysis of plant samples has shown high levels of latent septoria, which indicates disease pressure could be greater than expected following a cold dry April.

Corteva Agriscience warns that the conditions could be favourable for septoria to spread through crops ahead of key flag-leaf fungicide applications which take place from mid-May.

Sally Egerton, technical manager said: “In general cereal crops have looked reasonably clean and free from disease which led to T0 fungicides either being skipped, or rates being cut back.

“T1 fungicides are going on following very little rain so, again, programmes will have been adjusted according to the perceived level of disease prevalence.

“Now we are seeing reports of high levels of latent septoria infection which will spread with further rain events and the warmer temperature expected in the next 10-12 days.”

Microgenetics’ rapid test for septoria, SwiftDetect, indicates the level of infection using a traffic light system and log genome equivalents.

This helps farmers to understand their position before making a decision on the appropriate product and rate for a T2 fungicide spray.

Microgenetics said it had not been surprised by the number of positive samples sent in from fields across England and Wales, highlighting the importance of testing.

Chris Steele, the firm’s product manager, said they had detected latent septoria in over 400 samples sent to their laboratory since T1 applications took place.

“Many of the positive samples come from varieties which do not have a strong disease profile, and where growers might expect to find septoria present, even if it was not visible,” he said.

“We have also had positive samples from varieties which have excellent septoria ratings, which demonstrates the importance of testing before deciding on product choice and dose rate.

“Once temperatures get to 15 degrees and above, septoria can really get going,” Mr Steele said.

Corteva Agriscience has advised growers to use a robust product which will deliver lasting protection during a key growth stage of the crop.

Univoq fungicide, containing Inatreq active, was approved for sale and use in the UK last month and offers protectant control on all septoria strains.

The product is the first new target site for septoria control registered in the UK for 15 years.

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LSU student identifies fungus causing soybean taproot decline

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TAGS: CROP DISEASELSUGarciaArocajpg.jpgTeddy Garcia-Aroca, an LSU Ph.D. student, holds a sample of a fungus he found and named that causes the disease soybean taproot decline.Discovery just “tip of the iceberg” as scientists strive to learn more about this devastating soybean disease.

Bruce Shultz, Louisiana State University | Apr 13, 2021

An LSU graduate student has identified and named a new species of fungus that causes a devastating soybean disease. 

LSU doctoral student Teddy Garcia-Aroca identified and named the fungus Xylaria necrophora, the pathogen that causes soybean taproot decline. He chose the species name necrophora after the Latin form of the Greek word “nekros,” meaning “dead tissue,” and “-phorum,” a Greek suffix referring to a plant’s stalk. 

“It’s certainly a great opportunity for a graduate student to work on describing a new species,” said Vinson Doyle, LSU AgCenter plant pathologist and co-advisor on the research project. “It opens up a ton of questions for us. This is just the tip of the iceberg.” 

Taproot decline

The fungus infects soybean roots, causing them to become blackened while causing leaves to turn yellow or orange with chlorosis. The disease has the potential to kill the plant. 

“It’s a big problem in the northeast part of the state,” said Trey Price, LSU AgCenter plant pathologist who is Garcia-Aroca’s major professor and co-advisor with Doyle. 

“I’ve seen fields that suffered a 25% yield loss, and that’s a conservative estimate,” Price said. Heather Kellytaproot decline in soybeans

Yellowing leaves are early symptoms of taproot decline in soybeans.

Louisiana soybean losses from the disease total more than one million bushels per year. 

Price said the disease has been a problem for many years as pathologists struggled to identify it. Some incorrectly attributed it to related soybean diseases such as black-root rot. 

“People called it the mystery disease because we didn’t know what caused it.” 

Price said while Garcia-Aroca was working on the cause of taproot decline, so were labs at the University of Arkansas and Mississippi State University. 

Price said the project is significant. “It’s exciting to work on something that is new. Not many have the opportunity to work on something unique.” 

Research 

Garcia-Aroca compared samples of the fungus that he collected from infected soybeans in Louisiana, Arkansas, Tennessee, Mississippi and Alabama with samples from the LSU Herbarium and 28 samples from the U.S. National Fungus Collections that were collected as far back as the 1920s. 

Some of these historical samples were collected in Louisiana sugarcane fields, but were not documented as pathogenic to sugarcane. In addition, non-pathogenic samples from Martinique and Hawaii were also used in the comparison, along with the genetic sequence of a sample from China. 

Garcia-Aroca said these historical specimens were selected because scientists who made the earlier collections had classified many of the samples as the fungus Xylaria arbuscula that causes diseases on macadamia and apple trees, along with sugarcane in Indonesia. But could genetic testing of samples almost 100 years old be conducted? “It turns out it was quite possible,” he said. 

DNA sequencing showed a match for Xylaria necrophora for five of these historical, non-pathogenic samples — two from Louisiana, two from Florida, and one from the island of Martinique in the Caribbean — as well as DNA sequences from the non-pathogenic specimen from China. All of these were consistently placed within the same group as the specimens causing taproot decline on soybeans. 

Why now? 

Garcia-Aroca said a hypothesis that could explain the appearance of the pathogen in the region is that the fungus could have been in the soil before soybeans were grown, feeding on decaying wild plant material, and it eventually made the jump to live soybeans. 

Arcoa’s study poses the question of why the fungus, after living off dead woody plant tissue, started infecting live soybeans in recent years. “Events underlying the emergence of X. necrophora as a soybean pathogen remain a mystery,” the study concludes. 

But he suggests that changes in the environment, new soybean genetics and changes in the fungal population may have resulted in the shift. 

The lifespan of the fungus is not known, Garcia-Aroca said, but it thrives in warmer weather of at least 80 degrees. Freezing weather may kill off some of the population, he said, but the fungus survives during the winter by living on buried soybean plant debris left over from harvest. It is likely that soybean seeds become infected with the fungus after coming in contact with infected soybean debris from previous crops. These hypotheses remain to be tested. 

Many of the fungal samples were collected long before soybeans were a major U.S. crop, Doyle said. “The people who collected them probably thought they weren’t of much importance.” 

Garcia-Aroca said this illustrates the importance of conducting scientific exploration and research as well as collecting samples from the wild. “You never know what effect these wild species have on the environment later on.” 

What’s next? Now that the pathogen has been identified, Price said, management strategies need to be refined. Crop rotation and tillage can be used to reduce incidence as well as tolerant varieties. 

“We’ve installed an annual field screening location at the Macon Ridge Research Station where we provide taproot decline rating information for soybean varieties,” Price said. “In-furrow and fungicide seed treatments may be a management option, and we have some promising data on some materials. However, some of the fungicides aren’t labeled, and we need more field data before we can recommend any.” 

He said LSU, Mississippi State and University of Arkansas researchers are collaborating on this front. 

Doyle said Garcia-Aroca proved his work ethic on this project. “It’s tedious work and just takes time. Teddy has turned out to be very meticulous and detailed.” 

The final chapter in Garcia-Aroca’s study, Doyle said, will be further research into the origins of this fungus and how it got to Louisiana. Source: Louisiana State University, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.  

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GarciaArocajpg.jpg

Teddy Garcia-Aroca, an LSU Ph.D. student, holds a sample of a fungus he found and named that causes the disease soybean taproot decline.Discovery just “tip of the iceberg” as scientists strive to learn more about this devastating soybean disease.

Bruce Shultz, Louisiana State University | Apr 13, 2021

An LSU graduate student has identified and named a new species of fungus that causes a devastating soybean disease. 

LSU doctoral student Teddy Garcia-Aroca identified and named the fungus Xylaria necrophora, the pathogen that causes soybean taproot decline. He chose the species name necrophora after the Latin form of the Greek word “nekros,” meaning “dead tissue,” and “-phorum,” a Greek suffix referring to a plant’s stalk. https://f51f4f44a38d9cb02edf74f97f4f06e6.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html

“It’s certainly a great opportunity for a graduate student to work on describing a new species,” said Vinson Doyle, LSU AgCenter plant pathologist and co-advisor on the research project. “It opens up a ton of questions for us. This is just the tip of the iceberg.” 

Taproot decline

The fungus infects soybean roots, causing them to become blackened while causing leaves to turn yellow or orange with chlorosis. The disease has the potential to kill the plant. 

“It’s a big problem in the northeast part of the state,” said Trey Price, LSU AgCenter plant pathologist who is Garcia-Aroca’s major professor and co-advisor with Doyle. 

“I’ve seen fields that suffered a 25% yield loss, and that’s a conservative estimate,” Price said. Heather Kellytaproot decline in soybeans

Yellowing leaves are early symptoms of taproot decline in soybeans.

Louisiana soybean losses from the disease total more than one million bushels per year. 

Price said the disease has been a problem for many years as pathologists struggled to identify it. Some incorrectly attributed it to related soybean diseases such as black-root rot. 

“People called it the mystery disease because we didn’t know what caused it.” 

Price said while Garcia-Aroca was working on the cause of taproot decline, so were labs at the University of Arkansas and Mississippi State University. 

Price said the project is significant. “It’s exciting to work on something that is new. Not many have the opportunity to work on something unique.” 

Research 

Garcia-Aroca compared samples of the fungus that he collected from infected soybeans in Louisiana, Arkansas, Tennessee, Mississippi and Alabama with samples from the LSU Herbarium and 28 samples from the U.S. National Fungus Collections that were collected as far back as the 1920s. 

Some of these historical samples were collected in Louisiana sugarcane fields, but were not documented as pathogenic to sugarcane. In addition, non-pathogenic samples from Martinique and Hawaii were also used in the comparison, along with the genetic sequence of a sample from China. 

Garcia-Aroca said these historical specimens were selected because scientists who made the earlier collections had classified many of the samples as the fungus Xylaria arbuscula that causes diseases on macadamia and apple trees, along with sugarcane in Indonesia. But could genetic testing of samples almost 100 years old be conducted? “It turns out it was quite possible,” he said. 

DNA sequencing showed a match for Xylaria necrophora for five of these historical, non-pathogenic samples — two from Louisiana, two from Florida, and one from the island of Martinique in the Caribbean — as well as DNA sequences from the non-pathogenic specimen from China. All of these were consistently placed within the same group as the specimens causing taproot decline on soybeans. 

Why now? 

Garcia-Aroca said a hypothesis that could explain the appearance of the pathogen in the region is that the fungus could have been in the soil before soybeans were grown, feeding on decaying wild plant material, and it eventually made the jump to live soybeans. 

Arcoa’s study poses the question of why the fungus, after living off dead woody plant tissue, started infecting live soybeans in recent years. “Events underlying the emergence of X. necrophora as a soybean pathogen remain a mystery,” the study concludes. 

But he suggests that changes in the environment, new soybean genetics and changes in the fungal population may have resulted in the shift. 

The lifespan of the fungus is not known, Garcia-Aroca said, but it thrives in warmer weather of at least 80 degrees. Freezing weather may kill off some of the population, he said, but the fungus survives during the winter by living on buried soybean plant debris left over from harvest. It is likely that soybean seeds become infected with the fungus after coming in contact with infected soybean debris from previous crops. These hypotheses remain to be tested. 

Many of the fungal samples were collected long before soybeans were a major U.S. crop, Doyle said. “The people who collected them probably thought they weren’t of much importance.” 

Garcia-Aroca said this illustrates the importance of conducting scientific exploration and research as well as collecting samples from the wild. “You never know what effect these wild species have on the environment later on.” 

What’s next? 

Now that the pathogen has been identified, Price said, management strategies need to be refined. Crop rotation and tillage can be used to reduce incidence as well as tolerant varieties. 

“We’ve installed an annual field screening location at the Macon Ridge Research Station where we provide taproot decline rating information for soybean varieties,” Price said. “In-furrow and fungicide seed treatments may be a management option, and we have some promising data on some materials. However, some of the fungicides aren’t labeled, and we need more field data before we can recommend any.” 

He said LSU, Mississippi State and University of Arkansas researchers are collaborating on this front. 

Doyle said Garcia-Aroca proved his work ethic on this project. “It’s tedious work and just takes time. Teddy has turned out to be very meticulous and detailed.” 

The final chapter in Garcia-Aroca’s study, Doyle said, will be further research into the origins of this fungus and how it got to Louisiana. Source: Louisiana State University, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.  

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DMI resistance in wheat powdery mildew confirmed for the first time

Date: 17 Mar 2021

image of powdery mildew
Powdery mildew in a head of wheat. Photo: CCDM

New South Wales and Victorian grain growers are urged to be on alert following confirmation that difficulties experienced in 2020 controlling wheat powdery mildew are linked to resistance of the pathogen to demethylase inhibitor (DMI, Group 3) fungicides.

Fungicide resistance was detected at frequencies ranging from 50 to 100 per cent in samples collected from paddocks around Albury, Rennie, Balldale, Deniliquin and Jerilderie in NSW, and Cobram and Katamatite in Victoria.

Further sampling revealed a wider NSW distribution, from around Hillston and Yenda in south-west NSW, as well as Edgeroi and Wee Waa in northern NSW, in similar frequencies. This marks the first time that resistance in wheat powdery mildew to DMIs has been detected in Australia.

Researchers from the Fungicide Resistance Group at the Centre for Crop and Disease Management (CCDM) – a co-investment by the Grains Research and Development Corporation (GRDC) and Curtin University – confirmed the presence of DMI resistance in a range of samples sent by agronomists who were concerned about disease levels in their clients’ wheat crops during the 2020 season.

The wheat samples from across NSW and into Victoria were from predominantly Vixen and Scepter bread wheat varieties, and a lower number of durum wheat varieties.

NSW Department of Primary Industries (DPI) cereal pathologist Steven Simpfendorfer says he is not entirely surprised some level of resistance was detected, but is surprised by the high frequency of the detections. He describes the detections as alarming and a wake-up call for industry.

“These detections have occurred predominantly in high-value, irrigated cropping regions, which create ideal conditions for wheat powdery mildew disease development,” Dr Simpfendorfer says.

He says that the reliance on DMI fungicides by many growers in the region over many years contributed to selecting for the fungicide resistance detected during this past season.

Strong collaborative networks were key to the rapid detection of this case of wheat powdery mildew DMI resistance.

Agronomists and growers collected 40 samples from 20 paddocks across NSW and Victoria and these were analysed by CCDM researchers in the laboratory.

image of Powdery mildew on leaves
Powdery mildew on leaves in a wheat crop. Photo: CCDM

Director of the CCDM, Mark Gibberd, praised his colleagues and collaborators for how quickly and effectively they worked together to detect this case of resistance.

“Recent case studies of fungicide resistance detections in WA, South Australia and now Victoria and New South Wales, demonstrate the importance of strong relationships and cross-institutional collaboration to deliver robust results that growers can act on,” Professor Gibberd says.

CCDM researcher Steven Chang says genetic and phenotypic analyses of the wheat powdery mildew pathogen isolated from the samples showed a combination of mutations in the DMI fungicide target gene that were associated with the resistance observed to some DMIs. Additionally, all samples tested had some level of strobilurin fungicide (Group 11) resistance.

CCDM’s fungicide resistance group leader Fran Lopez-Ruiz says CCDM researchers have run a monitoring program for fungicide resistance in wheat powdery mildew for many years. Thanks to this, they could determine that the mutations now found in NSW and Victoria were the same as those previously detected in Tasmania and SA.

The Australian grains crop protection market is dominated by only three major mode of action (MoA) groups to combat diseases of grain crops in Australia: the DMIs (Group 3), SDHIs (Group 7) and strobilurins (or quinone outside inhibitors, QoIs, Group 11). Having so few MoA groups available for use increases the risk of fungicide resistance developing, as growers have very few alternatives to rotate in order to reduce selection pressure for these fungicide groups.

With two of the three fungicide MoA groups now compromised in some paddocks in NSW and Victoria, all growers need to take care to implement fungicide resistance management strategies to maximise their chances of effective and long-term disease control.

The Australian Fungicide Resistance Extension Network (AFREN), a GRDC investment, suggests an integrated approach tailored to local growing conditions. AFREN has identified the following five key actions, ‘The Fungicide Resistance Five’, to help growers maintain control over fungicide resistance, regardless of their crop or growing region:

  1. Avoid susceptible crop varieties
  2. Rotate crops – use time and distance to reduce disease carry-over
  3. Use non-chemical control methods to reduce disease pressure
  4. Spray only if necessary and apply strategically
  5. Rotate and mix fungicides/MoA groups

Growers and agronomists who suspect DMI reduced sensitivity or resistance should contact the CCDM’s Fungicide Resistance Group at frg@curtin.edu.au. Alternatively, contact a local regional plant pathologist or fungicide resistance expert to discuss the situation. A list of contacts is on the AFREN website.

Further information on fungicide resistance and its management in Australian grains crops is also available via the AFREN website.

Contact Details

For interviews

Steven Simpfendorfer, NSW DPI
0439 581 672
steven.simpfendorfer@dpi.nsw.gov.au

Kylie Ireland, Curtin University
(08) 9266 3541
ccdm@curtin.edu.au

Contact

Sharon Watt, GRDC
0409 675 100
sharon.watt@grdc.com.au

GRDC Project code: MSF2007-001SAX

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Fusarium fujikuroi may be an emerging problem for plum cultivation in China

Plums are commercially cultivated worldwide for the rich nutrient value of their fruit. In May 2019, plums with symptoms of fruit rot were collected from fields located in Liuma town, Guizhou Province, China. The incidence of the disease varied from 10 to 20%, which was observed in 15 plum orchards (18 hectares) surveyed. Estimated yield loss was from 5 to 10% for each field. Diseased fruits showed deformity, wilting and sunken lesions, and subsequently became melanized and rotted.

Scientists at Guizhou University have collected diseased tissues and conducted morphological analyses. Based on the cultural and conidial morphology, the isolates were identified as Fusarium fujikuroi. To confirm the morphological diagnosis, DNA sequencing and pathogenicity assay were performed.

“Fruit were artificially inoculated and maintained in a growth chamber with 90% relative humidity at 25°C, and a daily 12-h photoperiod. After 5 days, the artificially inoculated fruit showed blotches with sunken lesions similar to those observed in the orchards, whereas no symptoms were observed on the control fruit. The experiment was repeated twice with similar results. Fusarium fujikuroi was reisolated from infected tissues and confirmed by sequence analysis. To our knowledge, this is the first report of F. fujikuroi causing fruit blotch of plum in China. Considering the economic importance of plum in China and throughout the world, F. fujikuroi may be an emerging problem for plum cultivation. Thus, further study of fruit blotch of plums is warranted,” the scientists explain.

Source: Haijiang Long, Xianhui Yin, Zhibo Zhao, Youhua Long, Juan Fan, Ran Shu, Guifei Gu, ‘First Report of Fruit Blotch on Plum caused by Fusarium fujikuroi in China’, 2021, Plant Disease.

Publication date: Thu 11 Mar 2021
Author: Emanuela Fontana
© FreshPlaza.com

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FEBRUARY 25, 2021

Global change alters microbial life in soils—and thereby its ecological functions

by German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig

soil
Credit: CC0 Public Domain

Soil microorganisms play a critical role in the survival of life-sustaining ecosystems and, consequently, human well-being. Global assessments continue to provide strong evidence that humans are causing unprecedented biodiversity losses. However, existing information is strongly biased towards selected groups of vertebrates and plants, while much less is known about potential shifts in below ground communities.

Soil microbial communities are largely an unseen majority, even though, according to first author Dr. Carlos Guerra (iDiv, MLU), “they control a wide range of ecosystem functions that have implications for both human well-being and the sustainability of our ecosystems.” The published results provide evidence that climate change has a stronger influence on soil microbial communities than land-use change like deforestation and agricultural expansion.

The scientists focused especially on bacteria and fungi, which are the most diverse groups of soil-dwelling organisms across the globe. They studied a comprehensive database of soil microbial communities across six continents, whilst incorporating temperature, precipitation and vegetation cover data. Established climate and land-use projection datasets were used to compute various temporal change scenarios, based on a projection period from 1950 to 2090. To understand this complex system with multiple interdependent variables, four structural equation models were developed for bacterial richness, community dissimilarity, phosphate transport genes and ecological clusters. These models are particularly useful for distinguishing between the direct and indirect effects of external environmental variables (vegetation type, temperature, precipitation, etc.) on the aforementioned biodiversity variables.

The authors were able to show that local bacterial richness will increase in all scenarios of climate and land-use change considered. Although this increase will be followed by a generalized community homogenisation process affecting more than 85% of terrestrial ecosystems. Scientists also expect changes in the relative abundance of functional genes to accompany increases in bacterial richness. These could affect soil phosphorus uptake, which in turn could limit plant and microbial production. The results of the ecological cluster analysis suggest that certain bacteria and fungi known to include important human pathogens, major producers of antibiotic resistance genes, or potential fungal-transmitted plant pathogens will become more abundant.

While increases in local microbial diversity might seem positive at first glance, they hide strong reductions in community complexity in the majority of terrestrial systems, with implications for ecosystem functioning. Future ecosystems are therefore expected to have a greater number of bacterial lineage communities at the local scale, making several bacterial species groups potentially more abundant in soil communities under global change scenarios. Assuming the links between functionality and taxonomy remain constant through time, this suggests that similar bacterial groups with similar functional capabilities will live in soils across the globe, reducing specialization and potentially the adaptation capacity of ecosystems to new environmental realities.

The published results are at odds with current global projections of aboveground biodiversity declines, but do not necessarily provide a more positive view of nature’s future. Major changes in microbial diversity driven by climate and land-use change have significant implications for ecosystem functioning. “The results also help to fill an important gap identified in current global assessments and agreements,” says group leader Prof Nico Eisenhauer (iDiv, UL). They also lay the groundwork for incorporating soil organisms into future assessments of ecosystem response to global change drivers. According to mathematician Dr. Eliana Duarte (MiS), “the application of mathematical and statistical methods to the study of the soil microbiome will play an increasingly important role as more data on soils becomes available.”


Explore further Research delineates the impacts of climate warming on microbial network interactions


More information: Carlos A. Guerra et al, Global projections of the soil microbiome in the Anthropocene, Global Ecology and Biogeography (2021). DOI: 10.1111/geb.13273Journal information:Global Ecology and BiogeographyProvided by German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig

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SunMedia

New app to detect plants at risk from myrtle rust

Capsules (also known as gumnuts) of Eucalyptus pilularis. Features like this can enable users of the NZ Myrtaceae Key to identify species of interest. Supplied photo.

People keen to support the fight against the fungal disease myrtle rust, which threatens many of Aotearoa-New Zealand’s native trees, shrubs and climbers, now have a new tool to help identify vulnerable plants in the myrtle family.

Manaaki Whenua – Landcare Research and Biosecurity New Zealand have partnered in the development of the NZ Myrtaceae Key – a free app that makes it easy for citizen biosecurity volunteers to identify susceptible plants and keep an eye out for the fungal disease myrtle rust.

Myrtle rust has already spread across the top half of the North Island and cases have been recorded as far south as Greymouth.

“We know how much damage plant pests and diseases are causing overseas, and science partnerships, like this, will help us stay ahead,” says Veronica Herrera, MPI’s diagnostics and surveillance services director.

The NZ Myrtaceae Key is a Lucid identification tool envisaged and funded by Biosecurity New Zealand and developed by botanists from Manaaki Whenua, the National Forestry Herbarium, Unitec, and other experts.

The app is easy-to-use, interactive and comprehensively illustrated with more than 1,600 fully captioned images built in and it is downloadable for both iPhone and Android smartphones.

“The key includes more than 100 of the most commonly found Myrtaceae species, subspecies, hybrids and cultivars in New Zealand. Of these, 27 species, such as the iconic pōhutukawa, mānuka and kānuka, are indigenous to New Zealand: others, such as feijoa and eucalyptus, are exotics of economic importance,” says Dr Herrera.

Manaaki Whenua – Landcare Research researcher, Murray Dawson says the arrival of the windborne myrtle rust in 2017 gave a new importance to being able to identify Myrtaceae as heavily infected plants inevitably die.

“The disease is a threat to the important and substantial mānuka and kānuka honey industry. Using the new app to accurately identify species of Myrtaceae in New Zealand will make it easier to monitor and report cases of myrtle rust.

“By using the key, anyone, from farmers and trampers to gardeners and park users, will be able to identify plants to check for and report the tell-tale yellow spores, and diseased leaves,” says Mr Dawson.

To use the app, the characteristics of the plant being identified are entered, the app then sorts plants possessing these features, and it rejects those that don’t match. By progressively choosing additional features, the key will eventually narrow the results to just one or a few matching species.

Once you’ve correctly identified a plant in the myrtle family and if you think you see signs of the disease on it, don’t touch it.

If you have a camera or mobile phone you can take a photo and submit it to the iNaturalist website. Experts can check to confirm whether it is myrtle rust.

Capturing this information makes it available to agencies and scientists to analyse the rate of spread and observed impacts.

The NZ Myrtaceae Key is available from the Google Play (Android) store and the iPhone app store as a mobile (smartphone) app suitable for undertaking identifications in the field, or through a web-based browser hosted by Manaaki Whenua.

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