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

Mandal, Subhankar; Saxena, Amita; Cramer, Christopher S.; Steiner, Robert L.

doi:10.3390/horticulturae6020026

Cited by 5 publications

(28 citation statements)

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“…2. Harvested bulbs were stored for 4 weeks to discard any naturally infected bulbs (Mandal et al, 2020). Then, the remaining dormant bulbs were artificially inoculated using the mycelial inoculation method described previously, and the inoculated bulbs were placed in a greenhouse (temperature, 25 to 30°C; relative humidity, 70%) (Saxena, 2009).…”

Section: Methodsmentioning

confidence: 99%

“…These inoculation and selection methods were conducted again for the remaining bulbs. After two rounds of selection, disease-free bulbs were bulked and planted inside insect-proof cages to obtain seeds (Mandal et al, 2020). The production of seeds concluded one cycle of selection in 2008 to produce the FBR1 generation from the FBR0 generation.…”

Section: Methodsmentioning

confidence: 99%

“…The most commonly practiced method of screening for FBR-resistant onion cultivars is seedling screening using a virulent FOC isolate or isolates (Caligiore-Gei et al, 2020;Esfahani et al, 2013;Galv an et al, 2008;Kalman et al, 2020;Lopez and Cramer, 2004;Mandal et al, 2020;€ Ozer et al, 2004;Rout et al, 2016;Taylor et al, 2013), followed by field screening that uses natural FOC isolates ( € Ozer et al, 2004). Even though these two methods were used extensively to develop highly FBR-resistant commercial intermediate-day and long-day hybrids (Cramer, 2000;Goldman, 1996;Retig et al, 1970), limited success has been realized for short-day cultivars (Gutierrez and Cramer, 2005;Gutierrez et al, 2006;Lopez and Cramer, 2004).…”

mentioning

confidence: 99%

“…Even though these two methods were used extensively to develop highly FBR-resistant commercial intermediate-day and long-day hybrids (Cramer, 2000;Goldman, 1996;Retig et al, 1970), limited success has been realized for short-day cultivars (Gutierrez and Cramer, 2005;Gutierrez et al, 2006;Lopez and Cramer, 2004). The main reasons for this lack of success are due to the random chance of host-pathogen interactions during field inoculation (Mandal et al, 2020), a complicated cultivar-isolate relationship (Saxena and Cramer, 2009), and isolate virulence differences among geographical regions (Caligiore-Gei et al, 2020;Sasaki et al, 2015). Even though FBR resistance at the seedling stage could be translated into the later growing stages (Taylor et al, 2019), the seedling resistance may not be useful during storage of a dormant bulb (Mandal et al, 2020) for which environmental conditions are more favorable for FOC damage (Cramer, 2000).…”

mentioning

confidence: 99%

“…The main reasons for this lack of success are due to the random chance of host-pathogen interactions during field inoculation (Mandal et al, 2020), a complicated cultivar-isolate relationship (Saxena and Cramer, 2009), and isolate virulence differences among geographical regions (Caligiore-Gei et al, 2020;Sasaki et al, 2015). Even though FBR resistance at the seedling stage could be translated into the later growing stages (Taylor et al, 2019), the seedling resistance may not be useful during storage of a dormant bulb (Mandal et al, 2020) for which environmental conditions are more favorable for FOC damage (Cramer, 2000). A resistance response against FOC in the mature bulb is characterized by slowing of disease progression (Cramer, 2000) due to lower pectic enzyme production Knox-Davies, 1985a, 1985b) and/or the production of antifungal compounds ( € Ozer et al, 2003( € Ozer et al, , 2004.…”

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

Mandal¹,

Cramer²

2020

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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.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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

Mandal¹,

Cramer²

2020

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Recent Advances in Onion Genetic Improvement

et al. 2021

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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.

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

Mandal

Cramer

2021

Horticulturae

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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.

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

Cited by 5 publications

References 31 publications

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

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

Recent Advances in Onion Genetic Improvement

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

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