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Fusarium basal rot (FBR) caused by Fusarium oxysporum f. sp. cepae (FOC) is a major threat to onion (Allium cepa L.) production and marketing worldwide. Finding new sources of FBR-resistance to develop synthetic cultivars is a priority for onion breeders. As there are no FBR-resistant short-day onion cultivars, 85 U.S. National Plant Germplasm System plant introduction onion accessions that originated from 23 different countries were screened for their FBR susceptibility. To compare FBR susceptibility of these accessions at their seedling and mature bulb stages, a susceptible check cultivar, NuMex Crimson, a partially resistant check cultivar, Serrana and its selected population, Serrana-sel, were included in the study. The seedling screening was performed after inoculating silica-sand media with a virulent FOC isolate ‘CSC-515’ at 1.0 × 104 macroconidia g−1 of sand. Each entry was evaluated twice in growth chambers, and percent survival was adjusted to the number of seedlings that germinated in the uninoculated trays. Mature bulbs produced in the field were screened by inoculating transversely cut basal plates with potato dextrose agar plugs containing spores of the same isolate at 3.0 × 104 macroconidia mL−1. FBR severity and incidence were then calculated after 20 days of incubation. Significant variation was found among the accessions for FBR-susceptibility (p< 0.001) at both the seedling and the mature bulb stages. Two sets of 18 accessions were identified either for their higher seedling survival or higher mature bulb FBR-resistance compared to the checks. Among them, PI 256326 (‘Baia Periforme’, the originator cultivar of ‘Serrana’) had a higher seedling survival than both the checks, and a lower mature bulb severity than the susceptible check. Another accession, PI 656956 (‘S015’), exhibited higher seedling survival than the susceptible check and a low FBR severity (4.3 on a 1 to 9 scale) and incidence (41.7%). These two accessions, which were known previously for their high intra-population heterogeneity and root or bulb resistance for FBR, respectively, show promise for incorporating FBR-resistance into short-day onion cultivars. The cultivar rankings could vary in future studies with a range of FOC isolates due to a high cultivar × isolate interaction as observed in past studies.
Subhankar Mandal; Christopher Cramer. Screening of USDA Onion Germplasm for Fusarium Basal Rot Resistance. Horticulturae 2021, 7, 174 .
AMA StyleSubhankar Mandal, Christopher Cramer. Screening of USDA Onion Germplasm for Fusarium Basal Rot Resistance. Horticulturae. 2021; 7 (7):174.
Chicago/Turabian StyleSubhankar Mandal; Christopher Cramer. 2021. "Screening of USDA Onion Germplasm for Fusarium Basal Rot Resistance." Horticulturae 7, no. 7: 174.
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.
Subhankar Mandal; Christopher Cramer. Improving Fusarium Basal Rot Resistance of Onion Cultivars through Artificial Inoculation and Selection of Mature Bulbs. Horticulturae 2021, 7, 168 .
AMA StyleSubhankar Mandal, Christopher Cramer. Improving Fusarium Basal Rot Resistance of Onion Cultivars through Artificial Inoculation and Selection of Mature Bulbs. Horticulturae. 2021; 7 (7):168.
Chicago/Turabian StyleSubhankar Mandal; Christopher Cramer. 2021. "Improving Fusarium Basal Rot Resistance of Onion Cultivars through Artificial Inoculation and Selection of Mature Bulbs." Horticulturae 7, no. 7: 168.
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.
Subhankar Mandal; Christopher Cramer. Comparing Visual and Image Analysis Techniques to Quantify Fusarium Basal Rot Severity in Mature Onion Bulbs. Horticulturae 2021, 7, 156 .
AMA StyleSubhankar Mandal, Christopher Cramer. Comparing Visual and Image Analysis Techniques to Quantify Fusarium Basal Rot Severity in Mature Onion Bulbs. Horticulturae. 2021; 7 (6):156.
Chicago/Turabian StyleSubhankar Mandal; Christopher Cramer. 2021. "Comparing Visual and Image Analysis Techniques to Quantify Fusarium Basal Rot Severity in Mature Onion Bulbs." Horticulturae 7, no. 6: 156.
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.
Christopher Cramer; Subhankar Mandal; Suman Sharma; Seyed Nourbakhsh; Irwin Goldman; Ivette Guzman. Recent Advances in Onion Genetic Improvement. Agronomy 2021, 11, 482 .
AMA StyleChristopher Cramer, Subhankar Mandal, Suman Sharma, Seyed Nourbakhsh, Irwin Goldman, Ivette Guzman. Recent Advances in Onion Genetic Improvement. Agronomy. 2021; 11 (3):482.
Chicago/Turabian StyleChristopher Cramer; Subhankar Mandal; Suman Sharma; Seyed Nourbakhsh; Irwin Goldman; Ivette Guzman. 2021. "Recent Advances in Onion Genetic Improvement." Agronomy 11, no. 3: 482.
Iris yellow spot (IYS) disease in onion (Allium cepa L.) is caused by onion thrips (Thrips tabaci L.) vectored Iris yellow spot virus (IYSV). The absence of cultivars that are resistant/tolerant to thrips and/or IYS is a challenge for onion bulb and seed production worldwide. To measure selection progress for reduced/delayed IYS symptom expression in onion breeding lines after two selection cycles, selections were performed in 2011 on previously evaluated lines that exhibited a reduced symptom expression after one selection cycle. Selected plants from each line were massed in a cage and the resulted progenies were evaluated in 2013 and 2014 along with their original populations and a susceptible check—’Rumba’. In some comparisons, the selection progress for delayed/reduced IYS symptom expression was observed for some breeding lines. Plants of most selected breeding lines exhibited less disease expression than plants of ‘Rumba’. For some selections, a low disease severity was observed even with a relatively high number of thrips per plant. These results suggest that further improvement might be achievable with additional cycles of selection.
Neel Kamal; Seyed Nourbakhsh; Christopher Cramer. Reduced Iris Yellow Spot Symptoms through Selection within Onion Breeding Lines. Horticulturae 2021, 7, 12 .
AMA StyleNeel Kamal, Seyed Nourbakhsh, Christopher Cramer. Reduced Iris Yellow Spot Symptoms through Selection within Onion Breeding Lines. Horticulturae. 2021; 7 (2):12.
Chicago/Turabian StyleNeel Kamal; Seyed Nourbakhsh; Christopher Cramer. 2021. "Reduced Iris Yellow Spot Symptoms through Selection within Onion Breeding Lines." Horticulturae 7, no. 2: 12.
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.
Subhankar Mandal; Ashish Saxena; Christopher Cramer; Robert Steiner. Comparing Efficiencies of Two Selection Approaches for Improving Fusarium Basal Rot Resistance in Short-Day Onion after a Single Cycle of Selection. Horticulturae 2020, 6, 26 .
AMA StyleSubhankar Mandal, Ashish Saxena, Christopher Cramer, Robert Steiner. Comparing Efficiencies of Two Selection Approaches for Improving Fusarium Basal Rot Resistance in Short-Day Onion after a Single Cycle of Selection. Horticulturae. 2020; 6 (2):26.
Chicago/Turabian StyleSubhankar Mandal; Ashish Saxena; Christopher Cramer; Robert Steiner. 2020. "Comparing Efficiencies of Two Selection Approaches for Improving Fusarium Basal Rot Resistance in Short-Day Onion after a Single Cycle of Selection." Horticulturae 6, no. 2: 26.
Iris yellow spot (IYS), a disease caused by Iris yellow spot virus (IYSV) and spread by onion thrips, is a devastating disease of onion bulb and seed production. The development of onion germplasm resistant to IYS and/or thrips is crucial to onion production, since host plant resistance is unknown for both pests. During the summer of 2010 and 2012, plants with fewer IYS disease symptoms were selected from a screening of plant introduction accessions (PIs) and first-generation selections, respectively. The resulting progeny from these selected plants were evaluated during the summers of 2013 and 2014 for thrips numbers and IYS symptom expression, and compared with their respective original PIs and a susceptible check, ‘Rumba’. The field experiment was designed such that every plant in the field screening had an equal chance of being infected with IYSV. This study shows that variation for thrips and IYS existed among PIs and first- and second-generation selections. Even though not enough progress towards minimizing IYS severity was evident from this study, we did identify several lines with improved tolerance to onion thrips in first- and second-generation selections. The majority of the selected lines exhibited lower thrips and IYS severity compared to ‘Rumba’, which suggests that the progress towards developing insect- and ultimately disease-resistant germplasm can be achieved.
Narinder Singh; Christopher Cramer. Improved Tolerance for Onion Thrips and Iris Yellow Spot in Onion Plant Introductions after Two Selection Cycles. Horticulturae 2019, 5, 18 .
AMA StyleNarinder Singh, Christopher Cramer. Improved Tolerance for Onion Thrips and Iris Yellow Spot in Onion Plant Introductions after Two Selection Cycles. Horticulturae. 2019; 5 (1):18.
Chicago/Turabian StyleNarinder Singh; Christopher Cramer. 2019. "Improved Tolerance for Onion Thrips and Iris Yellow Spot in Onion Plant Introductions after Two Selection Cycles." Horticulturae 5, no. 1: 18.
Christopher S. Cramer. ‘NuMex Silhouette’ Onion. HortScience 2019, 54, 377 -379.
AMA StyleChristopher S. Cramer. ‘NuMex Silhouette’ Onion. HortScience. 2019; 54 (2):377-379.
Chicago/Turabian StyleChristopher S. Cramer. 2019. "‘NuMex Silhouette’ Onion." HortScience 54, no. 2: 377-379.
Iris yellow spot (IYS) disease, caused by Iris yellow spot virus (IYSV), results in irregular and diamond-shaped, chlorotic, and necrotic lesions on the leaves and seedstalks of onions (Allium cepa L.). These lesions reduce leaf photosynthetic area and ultimately reduce onion bulb size and yield from larger bulb classes. IYSV is vectored by onion thrips (Thrips tabaci L.) that are difficult to control under certain environmental conditions. Currently, no onion cultivar is resistant to the disease symptoms, virus, and/or thrips. Twenty-one cultivars and 17 germplasm lines were evaluated in the field for IYS disease severity and thrips densities at multiple times during the season as well as leaf color, waxiness, and axil openness of these entries. Plants were grown under conditions that favored thrips populations (high temperatures, low moisture, and no insecticidal spray applications), IYSV presence and distribution, and IYS development. Plants of New Mexico State University (NMSU) 07-10-1 had fewer thrips than several entries later in the season in both 2009 and 2010. Several entries exhibited a lower number of thrips per plant early or later in the season; however, these results were not consistent across years and were not associated with a particular foliage characteristic. Lighter leaf color and/or a lesser amount of epicuticular wax did not always result in the fewest number of thrips per plant as has been reported in the literature. Plants of NMSU 09-58 tended to exhibit fewer and less severe IYS symptoms early in the season as compared with plants of other entries.
Christopher S. Cramer; Neel Kamal; Narinder Singh. Evaluating Iris Yellow Spot Disease Incidence and Severity in Onion Germplasm of Varying Leaf Characteristics. HortScience 2017, 52, 527 -532.
AMA StyleChristopher S. Cramer, Neel Kamal, Narinder Singh. Evaluating Iris Yellow Spot Disease Incidence and Severity in Onion Germplasm of Varying Leaf Characteristics. HortScience. 2017; 52 (4):527-532.
Chicago/Turabian StyleChristopher S. Cramer; Neel Kamal; Narinder Singh. 2017. "Evaluating Iris Yellow Spot Disease Incidence and Severity in Onion Germplasm of Varying Leaf Characteristics." HortScience 52, no. 4: 527-532.
Christopher S. Cramer. ‘NuMex Allure’ Onion. HortScience 2015, 50, 1735 -1738.
AMA StyleChristopher S. Cramer. ‘NuMex Allure’ Onion. HortScience. 2015; 50 (11):1735-1738.
Chicago/Turabian StyleChristopher S. Cramer. 2015. "‘NuMex Allure’ Onion." HortScience 50, no. 11: 1735-1738.
Iris yellow spot is an economically important disease of onion that reduces bulb size and yield and is difficult to control. The disease is spread by Thrips tabaci (onion thrips) and disease symptoms are exacerbated by hot, dry climatic conditions that also favor rapid thrips multiplication and make control programs less effective. Currently, no onion cultivar is resistant to the disease and/or thrips. Certain onion foliar characteristics have shown nonpreferential feeding activity by thrips and may be the first step in developing Iris yellow spot (IYS)-tolerant onion cultivars. Seventy-five onion PI accessions from the U.S. germplasm collection were evaluated for leaf color, waxiness (bloom), and axil pattern; thrips number per plant; and IYS disease severity under conditions that favored thrips and disease buildup. Plants of PI 289689 were less attractive to thrips and had a lower number of thrips per plant than plants of most other accessions. These plants were rated as having light green to green-colored foliage and a relatively low amount of epicuticular leaf wax. Plants of PIs 239633 and 546192 generally exhibited less severe IYS disease symptoms than those of other accessions. Individual plants, that exhibited less leaf area exhibiting IYS disease symptoms, were selected at bulb maturity from 22 different accessions with PI 546140 producing the largest number of selected bulbs. Physiological plant development, environmental conditions, and tolerance to plant stress may influence the degree of disease symptom expression. Further work that examines the role of plant maturity and host plant tolerance to stress with respect to disease expression is needed.
Christopher S. Cramer; Narinder Singh; Neel Kamal; Hanu R. Pappu. Screening Onion Plant Introduction Accessions for Tolerance to Onion Thrips and Iris Yellow Spot. HortScience 2014, 49, 1253 -1261.
AMA StyleChristopher S. Cramer, Narinder Singh, Neel Kamal, Hanu R. Pappu. Screening Onion Plant Introduction Accessions for Tolerance to Onion Thrips and Iris Yellow Spot. HortScience. 2014; 49 (10):1253-1261.
Chicago/Turabian StyleChristopher S. Cramer; Narinder Singh; Neel Kamal; Hanu R. Pappu. 2014. "Screening Onion Plant Introduction Accessions for Tolerance to Onion Thrips and Iris Yellow Spot." HortScience 49, no. 10: 1253-1261.
Christopher S. Cramer. ‘NuMex Whisper’ Onion. HortScience 2014, 49, 971 -976.
AMA StyleChristopher S. Cramer. ‘NuMex Whisper’ Onion. HortScience. 2014; 49 (7):971-976.
Chicago/Turabian StyleChristopher S. Cramer. 2014. "‘NuMex Whisper’ Onion." HortScience 49, no. 7: 971-976.
Christopher S. Cramer. ‘NuMex Grandeur’ Onion. HortScience 2014, 49, 350 -353.
AMA StyleChristopher S. Cramer. ‘NuMex Grandeur’ Onion. HortScience. 2014; 49 (3):350-353.
Chicago/Turabian StyleChristopher S. Cramer. 2014. "‘NuMex Grandeur’ Onion." HortScience 49, no. 3: 350-353.
Black mold, caused by the fungus Aspergillus niger, is one of the major postharvest onion (Allium cepa) diseases causing qualitative and quantitative losses. To screen autumn-sown onion cultivars for black mold resistance, 12 cultivars were sown in 2004 and 2005 in Las Cruces, NM. Percent sporulated area, disease severity, and disease incidence were recorded after 2 and 4 weeks of storage. ‘Texas Early White’ exhibited less disease symptoms than other cultivars tested. For all cultivars, disease symptoms in terms of severity and incidence increased as bulbs were stored for longer periods of time.
Neel Kamal; Ashish Saxena; Robert L. Steiner; Christopher S. Cramer. Screening of New Mexico Autumn-sown Onions for Black Mold Disease. HortTechnology 2012, 22, 719 -723.
AMA StyleNeel Kamal, Ashish Saxena, Robert L. Steiner, Christopher S. Cramer. Screening of New Mexico Autumn-sown Onions for Black Mold Disease. HortTechnology. 2012; 22 (5):719-723.
Chicago/Turabian StyleNeel Kamal; Ashish Saxena; Robert L. Steiner; Christopher S. Cramer. 2012. "Screening of New Mexico Autumn-sown Onions for Black Mold Disease." HortTechnology 22, no. 5: 719-723.
Christopher S. Cramer; Joe N. Corgan. ‘NuMex Fabian Garcia’ Onion. HortScience 2012, 47, 1369 -1371.
AMA StyleChristopher S. Cramer, Joe N. Corgan. ‘NuMex Fabian Garcia’ Onion. HortScience. 2012; 47 (9):1369-1371.
Chicago/Turabian StyleChristopher S. Cramer; Joe N. Corgan. 2012. "‘NuMex Fabian Garcia’ Onion." HortScience 47, no. 9: 1369-1371.
Iris yellow spot virus (IYSV) causes a foliar disease in onion (Allium cepa L.) that results in a reduction in bulb size. Currently, no IYSV-tolerant or -resistant cultivar exists and a genetic source for tolerance or resistance has not been identified. Because other disease control methods are limited, host plant resistance offers the best hope to combat this disease. In this study, 13 winter-sown onion entries were screened for iris yellow spot (IYS) symptoms during the 2007 and 2008 cropping seasons. Twenty plants from each plot were observed and rated weekly during the growing seasons for straw-colored, necrotic lesions, typical of IYSV infection. Collected plant samples were assayed for IYSV by enzyme-linked immunosorbent assay (ELISA) and reverse-transcription polymerase chain reaction (RT-PCR). Visual rating was done using a scale of 1 to 9 with 1 representing no symptomatic tissue and 9 representing more than 50% tissue damage. Two different plant sampling methods were used in disease rating to determine their effect on mean severity and to correlate disease severity with absorbance values. Of the entries tested, plants of NMSU 05-33-1 exhibited a delay in symptom expression and lower IYSV levels relative to plants of other entries. Plants of ‘Denali’ and ‘Gelma’ appeared to be more susceptible to IYSV than plants of other entries. Plant selection within the plot over time did not influence disease rating values. When the same plants were rated and sampled for IYSV using ELISA, there was a strong, positive correlation between rating and absorbance values.
Mohsen Mohseni-Moghadam; Christopher S. Cramer; Robert L. Steiner; Rebecca Creamer. Evaluating Winter-sown Onion Entries for Iris yellow spot virus Susceptibility. HortScience 2011, 46, 1224 -1229.
AMA StyleMohsen Mohseni-Moghadam, Christopher S. Cramer, Robert L. Steiner, Rebecca Creamer. Evaluating Winter-sown Onion Entries for Iris yellow spot virus Susceptibility. HortScience. 2011; 46 (9):1224-1229.
Chicago/Turabian StyleMohsen Mohseni-Moghadam; Christopher S. Cramer; Robert L. Steiner; Rebecca Creamer. 2011. "Evaluating Winter-sown Onion Entries for Iris yellow spot virus Susceptibility." HortScience 46, no. 9: 1224-1229.
Christopher S. Cramer; Joe N. Corgan. ‘NuMex Serenade’ Onion. HortScience 2010, 45, 1889 -1892.
AMA StyleChristopher S. Cramer, Joe N. Corgan. ‘NuMex Serenade’ Onion. HortScience. 2010; 45 (12):1889-1892.
Chicago/Turabian StyleChristopher S. Cramer; Joe N. Corgan. 2010. "‘NuMex Serenade’ Onion." HortScience 45, no. 12: 1889-1892.
Harvest of onions in New Mexico is becoming cost prohibitive due to labor shortages and increased labor costs. Mechanical harvest will need to be adopted in order for growers to remain competitive. Onion cultivars, currently grown in New Mexico, need to be evaluated for their suitability to be harvested by mechanical methods. Bulb firmness is one trait that may correlate to mechanical harvest ability of a cultivar. Observations of genetic variation for bulb firmness were taken with an objective to develop cultivars suitable for mechanical harvest. Sixteen short- and intermediate-day onion entries were grown for 2 years and evaluated for bulb firmness and other possible correlated variables. Seedstalks, maturity date, pink root, Fusarium basal rot, percentage marketable yield, average bulb weight, bulb firmness, and single-centeredness were recorded during 2003 and 2004. An instrument, called a durometer, was found to be a reliable tool to measure firmness based upon strong correlation between subjective and objective methods. Single-centeredness and average bulb weight were found to be important factors correlated with bulb firmness.
T. Larsen; A. Saxena; C. S. Cramer. Relatedness of Bulb Firmness to Other Attributes of New Mexico Onion Entries. International Journal of Vegetable Science 2009, 15, 206 -217.
AMA StyleT. Larsen, A. Saxena, C. S. Cramer. Relatedness of Bulb Firmness to Other Attributes of New Mexico Onion Entries. International Journal of Vegetable Science. 2009; 15 (3):206-217.
Chicago/Turabian StyleT. Larsen; A. Saxena; C. S. Cramer. 2009. "Relatedness of Bulb Firmness to Other Attributes of New Mexico Onion Entries." International Journal of Vegetable Science 15, no. 3: 206-217.
Christopher S. Cramer; Joe N. Corgan. ‘NuMex Radiance’ Onion. HortScience 2009, 44, 820 -823.
AMA StyleChristopher S. Cramer, Joe N. Corgan. ‘NuMex Radiance’ Onion. HortScience. 2009; 44 (3):820-823.
Chicago/Turabian StyleChristopher S. Cramer; Joe N. Corgan. 2009. "‘NuMex Radiance’ Onion." HortScience 44, no. 3: 820-823.
Identification of resistant or tolerant onion (Allium cepa L.) cultivars is crucial for the development of integrated management strategies for Iris yellow spot virus (IYSV). Exclusively vectored by onion thrips (Thrips tabaci), IYSV is a potentially devastating tospovirus of onion that has been confirmed to be present in 15 countries all over the world. In this study, 18 winter-sown onion entries were screened for IYSV symptom expression over two seasons. Over the growing season, straw-colored, necrotic lesions typical of IYSV infection were observed and rated for disease severity. Entries, NMSU 03-52-1, NMSU 04-41, NMSU 04-44-1, and ‘NuMex Jose Fernandez’, exhibited fewer symptoms than many other entries tested. ‘Caballero’, NMSU 04-57-1, NMSU 04-78-1, and ‘Cimarron’ exhibited more symptoms. Disease progression over time was rapid for entries exhibiting more symptoms and slow for entries exhibiting fewer symptoms. Enzyme-linked immunosorbent assay (ELISA) optical densities correlated poorly with the severity of disease symptoms. Trends in the disease progression over time emphasize the importance of rating IYSV symptoms late in the crop's development and to search for delayed disease progression rather than early symptom expression to determine IYSV susceptibility.
Parminder S. Multani; Christopher S. Cramer; Robert L. Steiner; Rebecca Creamer. Screening Winter-sown Onion Entries for Iris Yellow Spot Virus Tolerance. HortScience 2009, 44, 627 -632.
AMA StyleParminder S. Multani, Christopher S. Cramer, Robert L. Steiner, Rebecca Creamer. Screening Winter-sown Onion Entries for Iris Yellow Spot Virus Tolerance. HortScience. 2009; 44 (3):627-632.
Chicago/Turabian StyleParminder S. Multani; Christopher S. Cramer; Robert L. Steiner; Rebecca Creamer. 2009. "Screening Winter-sown Onion Entries for Iris Yellow Spot Virus Tolerance." HortScience 44, no. 3: 627-632.