scholarly journals Improving Fusarium Basal Rot Resistance of Onion Cultivars through Artificial Inoculation and Selection of Mature Bulbs

Horticulturae ◽  
2021 ◽  
Vol 7 (7) ◽  
pp. 168
Author(s):  
Subhankar Mandal ◽  
Christopher S. Cramer
Keyword(s):  
Recurrent Selection ◽  
Quantitative Resistance ◽  
Field Trials ◽  
Basal Plate ◽  
Screening Methods ◽  
Short Day ◽  
Basal Rot ◽  
Fusarium Basal Rot ◽  
Maximum Improvement ◽  
Multiple Cycles

Fusarium basal rot (FBR) of onion, caused by the soil-borne fungus Fusarium oxysporum f.sp. cepae (FOC), results in a substantial storage loss of marketable bulbs. Seedling and field screening methods, which were used to generate FBR resistant long-day and intermediate-day onion cultivars, were found to be ineffective at increasing FBR resistance in short-day onion cultivars. This study attempted to improve the FBR resistance of seven commercial short-day onion cultivars and two check cultivars when evaluated at their mature bulb stage. Mature bulbs were artificially inoculated with 1 cm diameter potato dextrose agar plugs containing conidia of a virulent FOC isolate, CSC-515, at a concentration of 3 × 104 spore mL−1, after transversely cutting the basal plate tissue. Incubated bulbs, which had few or no FBR symptoms, were selected after 20 d using visual scoring, from 1 (no disease) to 9 (>70% basal plate is infected), and combined in seed production cages to produce the selected generation of a cultivar. Multiple cycles of phenotypic recurrent selection were conducted, and the resultant populations were compared with their respective original populations for FBR severity and incidence, from 2016 to 2019, using the same conidial inoculation method. A variable amount of progress was achieved in reducing FBR severity and incidence in the seven cultivars, with maximum improvement in the most advanced selected populations. FBR development in the advanced selected populations differed between mature bulbs of each entry and was influenced by yearly environmental variation. The progress of FOC infections was slower in resistant bulbs when compared to susceptible bulbs. These results indicated a partial or quantitative resistance against FBR. The partial FBR resistant cultivar populations could be used to develop synthetic short-day FBR resistant cultivars after multi-locational and multi-seasonal field trials. These populations could also be used to study the mechanism(s) of FBR resistance in onion, which has yet to be determined.

scholarly journals An Artificial Inoculation Method to Select Mature Onion Bulbs Resistant to Fusarium Basal Rot

HortScience ◽  
2020 ◽  
Vol 55 (11) ◽  
pp. 1840-1847
Author(s):  
Subhankar Mandal ◽  
Christopher S. Cramer
Keyword(s):  
Basal Plate ◽  
Artificial Inoculation ◽  
Economic Damage ◽  
Screening Methods ◽  
Field Inoculation ◽  
Inoculation Method ◽  
Short Day ◽  
Onion Bulbs ◽  
Basal Rot ◽  
Fusarium Basal Rot

Fusarium basal rot (FBR) of onion, which is caused by Fusarium oxysporum f.sp. cepae (Hanzawa) Snyder & Hansen (FOC) results in a substantial loss of marketable bulbs worldwide. One of the main reasons for the lack of FBR-resistant short-day cultivars is the unreliable screening methods available for the mature bulb stage when significant economic damage occurs. The objective of this study was to develop an artificial inoculation method with better quantification of inoculum for an effective selection of FBR-resistant mature onion bulbs. Mature bulbs of seven New Mexican short-day onion cultivars, along with susceptible and tolerant controls, were selected and evaluated for FBR resistance using mycelial and conidial inoculation methods, respectively. Transversely cut basal plates of mature bulbs were inoculated artificially with mycelia or conidia (12 × 105 spores/mL in 2014 and 3 × 105 spores/mL in 2015 embedded in potato dextrose agar plug) of a virulent FOC isolate ‘CSC-515’. Mature bulb evaluation using a visual rating scale (1 = no disease; 9 = >70% basal plate infected) revealed a high degree of FBR severity and incidence irrespective of the genetic background of the cultivars, minimizing the chance of disease escape, which is a significant problem in field inoculation. An attempt to inoculate intact basal plates postharvest resulted in minimal disease development, suggesting that mechanical resistance was conferred by the dry outer layer of the basal plate. The high selection pressure conferred by the conidial inoculation method developed in this study can effectively screen FBR-resistant onion bulbs to replace an unreliable field screening. Concentrations of the conidia lower than 3 × 105 spores/mL are recommended to detect subtle genetic differences in FBR resistance among the onion cultivars and their selected population.

scholarly journals Comparing Efficiencies of Two Selection Approaches for Improving Fusarium Basal Rot Resistance in Short-Day Onion after a Single Cycle of Selection

Horticulturae ◽  
2020 ◽  
Vol 6 (2) ◽  
pp. 26
Author(s):  
Subhankar Mandal ◽  
Ashish Saxena ◽  
Christopher S. Cramer ◽  
Robert L. Steiner
Keyword(s):  
Environmental Factors ◽  
Random Distribution ◽  
Single Cycle ◽  
Field Screening ◽  
Selection Cycle ◽  
Short Day ◽  
Basal Rot ◽  
Fusarium Basal Rot ◽  
Consistent Method ◽  
Screening Approaches

The development of Fusarium Basal Rot (FBR)-resistant onion cultivars through field and seedling screening approaches faces tremendous challenges due to non-uniform distribution of the disease pathogen and possible multiple mechanisms of host–plant resistance. This study compared the efficiencies of these two methods for increasing FBR resistance of short-day onion after a single selection cycle. Asymptomatic plants or bulbs of seven onion cultivars were selected using a seedling screen performed in a growth chamber or a field screening of mature bulbs. Original and selected populations were evaluated for their responses to FBR stress thereafter employing the same two methods used for screening. The field screening of mature bulbs was found unreliable in both selection and evaluation, likely due to a non-random distribution of the FBR pathogen and variable environmental factors present in the field. The seedling screening successfully increased FBR resistance in the selected cultivar populations revealed by a seedling evaluation. From the results, it is recommended to use a consistent method for both screening and evaluation to make the most selection progress.

scholarly journals Comparing Visual and Image Analysis Techniques to Quantify Fusarium Basal Rot Severity in Mature Onion Bulbs

Horticulturae ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 156
Author(s):  
Subhankar Mandal ◽  
Christopher S. Cramer
Keyword(s):  
Image Analysis ◽  
Digital Image ◽  
Basal Plate ◽  
United States Department ◽  
Symptom Development ◽  
Breeding Programs ◽  
Resistant Cultivars ◽  
Visual Scoring ◽  
Basal Rot ◽  
Fusarium Basal Rot

Development of resistant cultivars for Fusarium basal rot (FBR), a fungal disease caused by the soil-borne fungus Fusarium oxysporum f.sp. cepae (FOC), is a major breeding goal for onion breeding programs around the world. Currently, the selection of FBR-resistant bulbs is based on a visual interval or category scale, which is an entirely subjective method. This study aimed to develop an objective approach using digital image analysis to quantify symptom development in the basal plate of dormant bulbs. Digital image analyses were performed after artificially inoculating dormant bulbs of eighty-five United States Department of Agriculture (USDA) Allium cepa accessions with a virulent FOC isolate, ‘CSC-515’. An analysis with confocal microscopy identified bright blue–green autofluorescence from FOC-infected tissue, effectively differentiating diseased from healthy tissue. Visual scoring of the FBR symptom was aided by stereo fluorescence microscopic images captured using a green fluorescence protein dual filter to quantify accurately FBR severity in the basal plate tissue. An automatic stepwise image segmentation method was developed that was relatively more accurate than a visual estimation. This method exhibited comparable reliability and precision to visual scoring, but it tended to underestimate FOC infection. To our best knowledge, this is the first comprehensive study to investigate the potential use of image analysis as a viable alternative to conventional visual scoring for FBR symptom development. This method could be used for developing resistant cultivars for onion breeding programs in the near future.

scholarly journals Recent Advances in Onion Genetic Improvement

Agronomy ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 482
Author(s):  
Christopher S. Cramer ◽  
Subhankar Mandal ◽  
Suman Sharma ◽  
Seyed Shahabedddin Nourbakhsh ◽  
Irwin Goldman ◽  
...  
Keyword(s):  
Genetic Improvement ◽  
Genetic Manipulation ◽  
Insect Pest ◽  
Yellow Spot ◽  
Screening Methods ◽  
Vegetable Crops ◽  
Onion Thrips ◽  
Basal Rot ◽  
Fusarium Basal Rot ◽  
Lachrymatory Factor

Onions are one of the most important vegetable crops worldwide. However, their production faces many challenges. Genetic improvement is one mechanism to address those challenges. In this review, we discuss recent research pertaining to the diseases Fusarium basal rot and Iris yellow spot, the insect pest onion thrips, onion pungency, and dormancy. Recent research for screening onion bulbs for Fusarium basal rot resistance has resulted in improved screening techniques and germplasm exhibiting less disease when inoculated with the disease-causing pathogen. Improved screening methods have resulted in germplasm exhibiting fewer and less severe Iris yellow spot symptoms when onion thrips and conducive environmental conditions are present. Onion germplasm with less and differing compositions of epicuticular wax on their leaves have shown a nonpreference for thrips feeding and have the potential for developing thrips tolerant cultivars. Conventional breeding efforts and genetic manipulation of the genes producing alliinase and lachrymatory factor synthase has resulted in low pungency, tearless onions. In long-day onions, an annual generation time has been achieved by artificially breaking bulb dormancy early while ensuring proper vernalization has been completed. Genetic improvement of these and many other onion traits will continue and result in better production in the future.

scholarly journals Screening Short-day Onion Cultivars for Resistance to Fusarium Basal Rot

HortScience ◽  
2005 ◽  
Vol 40 (1) ◽  
pp. 157-160 ◽  
Author(s):  
Jessica A. Gutierrez ◽  
Christopher S. Cramer
Keyword(s):  
Fusarium Oxysporum ◽  
Disease Severity ◽  
First Year ◽  
Harvest Time ◽  
Breeding Lines ◽  
Short Day ◽  
Basal Rot ◽  
High Incidence ◽  
Fusarium Basal Rot ◽  
Second Year

Fusarium basal rot (FBR), caused by Fusarium oxysporum Schlechtend.:Fr. f. sp. cepae (H.N. Hans.) W.C. Snyder & H.N. Hans, is a soilborne fungal disease that affects bulb onions (Allium cepa L.) worldwide. Short-day onion cultivars that are resistant to FBR are lacking. The goal of this project was to screen fall-sown onion germplasm for FBR resistance using a mature bulb field screening at harvest and after 4 weeks in storage. The project was conducted for 2 years, and in each year, 26 fall-sown onion lines were grown in a field known to produce a high incidence of fusarium-basal-rot-infected bulbs. When all the bulbs in a plot were mature, the basal plates of 20 bulbs were cut transversely and each plate was rated for disease severity on a scale of one (no diseased tissue) to nine (70% or more diseased). Bulbs were stored and rerated at 2 and 4 weeks after harvest. Disease severity and incidence were higher in the first year than in the second year. Both severity and incidence increased as bulbs were stored for 4 weeks. NMSU 00-25 exhibited the lowest disease severity and incidence in both years at harvest time and after storage. `Buffalo' and `Cardinal' exhibited the highest severities and incidences across both years and at harvest time and after storage. Other entries exhibited high or low disease severity and incidence but not consistently across years and between harvest time and after storage. In the development of FBR resistant cultivars, breeding lines should be evaluated over multiple years and bulbs should be stored for 4 weeks before being screened.

scholarly journals Onion Trait Heritability and Response from Selection

2006 ◽  
Vol 131 (5) ◽  
pp. 646-650 ◽  
Author(s):  
Christopher S. Cramer
Keyword(s):  
Recurrent Selection ◽  
Disease Incidence ◽  
Heritability Estimate ◽  
Selection Response ◽  
Response Analysis ◽  
Realized Heritability ◽  
Basal Rot ◽  
Fusarium Basal Rot ◽  
Sib Families ◽  
Heritability Estimates

Realized heritability estimates of bolting percentage, pink root and fusarium basal rot severities and incidences, and percentage of single-centered bulbs were estimated for half-sib families of an intermediate-day, open-pollinated onion (Allium cepa L.) population using selection response analysis. Half-sib families were selected based upon an index that equally weighted bolting percentage, pink root and fusarium basal rot severities and incidences, percentage of single-centered bulbs, and bulb quality. Families were subjected to one cycle of half-sib family recurrent selection. Pink root and fusarium basal rot severity was reduced by 17% and 7%, respectively, with realized heritability estimates of 1.28 and 0.65, respectively. More progress for pink root severity was made than was selected. Disease incidence was reduced by 18% and 12%, respectively, with heritability estimates of 0.65 and 0.60, respectively. Very little progress was made for the percentage of single-centered bulbs and this was reflected in a heritability estimate of 0.17. Selection based upon multiple characters at the same time may reduce the effectiveness of making improvements in a single trait. However even with low to moderate heritability, improvements were made, and suggest that further improvements can be made through selection.

scholarly journals 057 Hybrid Performance of Male-sterile and Pollinator Inbred Onion Lines

HortScience ◽  
2000 ◽  
Vol 35 (3) ◽  
pp. 398B-398
Author(s):  
Christopher S. Cramer ◽  
Jose L. Mendoza ◽  
Joe N. Corgan
Keyword(s):  
Inbred Lines ◽  
Male Sterile ◽  
Marketable Yield ◽  
Breeding Programs ◽  
Short Day ◽  
Basal Rot ◽  
Fusarium Basal Rot ◽  
Hybrid Lines ◽  
Root Resistance ◽  
Current Emphasis

Current emphasis of onion breeding programs has been to develop male-sterile, maintainer, and pollinator inbred lines for the production of hybrid cultivars. Five short-day, male-sterile inbred lines from the New Mexico State Univ. Onion Breeding Program were crossed to four short-day, pollinator inbred lines in all possible combinations. In addition, six intermediate-day male-sterile inbred lines were crossed with seven intermediate-day, pollinator inbred lines in all possible combinations. The resulting hybrid lines from all crosses were evaluated for maturity, bolting resistance, pink root resistance, Fusarium basal rot resistance, percentage of marketable bulbs, marketable yield, average bulb weight, and percentage of bulbs with single centers. The average performance among male-sterile and among pollinator lines within each group was determined by averaging over hybrid lines that pertained to the respective male-sterile or pollinator line. Among the short-day inbred lines, NMSU 97-28-2 and NMSU 97-109-2 as female parents produced the best hybrid lines, while NMSU 96-17-1 and NMSU 96-51-1 as male parents produced the best hybrid lines. The best hybrid combinations among the short-day parents were NMSU 97-28-2 × 96-17-1 and 97-46-2 × 96-51-1. Among the intermediate-day inbred lines, NMSU 96-196-2 and 96-300-2 as female parents produced the best hybrid lines, while NMSU 96-280-1, NMSU 96-274-1 and 96-395-1 as male parents produced the best hybrid lines. Some of the best intermediate-day hybrid combinations included NMSU 96-300-2 × 96-335-1 and NMSU 96-300-2 × 96-274-1.

scholarly journals Fusarium basal rot: profile of an increasingly important disease in Allium spp.

2021 ◽  
Author(s):  
Dung Le ◽  
Kris Audenaert ◽  
Geert Haesaert
Keyword(s):  
Disease Management ◽  
Cultural Practices ◽  
Current Knowledge ◽  
Management Strategies ◽  
Future Directions ◽  
Basal Rot ◽  
Major Constraint ◽  
Fusarium Basal Rot ◽  
Chemical Pesticides ◽  
Important Disease

AbstractFusarium basal rot (FBR) is a soil-borne disease that affects Allium species worldwide. Although FBR has long been recognized as a major constraint to the production of economically important Allium species, information that could support disease management remains scattered. In this review, the current knowledge on the causal agents, symptomology and epidemiology, impact, and management strategies of FBR is synthesized. We highlight that FPR is associated with different complexes of several Fusarium species, of which Fusarium oxysporum and F. proliferatum are the most prevalent. These pathogenic complexes vary in composition and virulence, depending on sites and hosts, which can be challenging for disease management. Research to improve disease management using chemical pesticides, resistance cultivars, biocontrol agents, and cultural practices has achieved both promising results and limitations. Finally, research needs and future directions are proposed for the development of effective FBR management strategies.

scholarly journals Evaluation of Green Manure Amendments for the Management of Fusarium Basal Rot (Fusarium oxysporumf.sp.cepae) on Shallot

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Assefa Sintayehu ◽  
Seid Ahmed ◽  
Chemeda Fininsa ◽  
P. K. Sakhuja
Keyword(s):  
Green Manure ◽  
Agricultural Research ◽  
Disease Incidence ◽  
Limiting Factors ◽  
Lepidium Sativum ◽  
Ethiopian Mustard ◽  
Basal Rot ◽  
Fusarium Basal Rot ◽  
Manure Amendments

Shallot (Allium cepaL. var.ascalonicum) is the most traditional vegetable crop in Ethiopia. Shallot is susceptible to a number of diseases that reduce yield and quality, among which fusarium basal rot (FBR) caused byFusarium oxysporumf.sp.cepae (Foc)is one of the most important yield limiting factors in Ethiopia. The present study was designed to evaluate the effectiveness ofBrassicacrops for the management of shallot FBR on shallot. The experiments were carried out at Debre Zeit Agricultural Research Center using cabbage (Brassica oleracea), garden cress (Lepidium sativum), Ethiopia mustard (B. carinata), and rapeseed (B. napus). The evaluations were done underin vitroand greenhouse conditions. Underin vitrotest condition it was confirmed that extracts of Ethiopian mustard and rapeseed showed higher inhibition on the growth ofFocpathogen compared to control. Data on seedling emergence, plant height, plant stand, disease incidence, severity, cull bulbs, and bulb weight were collected in greenhouse experiment. The green manure amendments of rapeseed and Ethiopian mustard significantly reduced disease incidence by 21% and 30% and disease severity by 23% and 29%, respectively. However the plant emergency was not significantly different among treatments in greenhouse test. These results indicated that Ethiopian mustard and rapeseed crops have potential as green manure for the management of FBR disease of shallot crop.

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