Verticillium Wilt on Resistant Tomato Cultivars in California: Virulence of Isolates from Plants and Soil and Relationship of Inoculum Density to Disease Incidence

Grogan, R. G.; Ioannou, N.; Schneider, R. W.; Sall, M. A.; Kimble, K. A.

doi:10.1094/phyto-69-1176

Cited by 87 publications

(79 citation statements)

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“…Similar variation previously has been observed for isolates of V. dahliae pathogenic on tomato, potato, and cotton (3,10,14,24). Grogan et al (10) found that isolates of V. dahliae obtained from commercial tomato fields varied in virulence for both races, with race 1 isolates typically exhibiting greater virulence compared with race 2 on a tomato cultivar lacking the Ve genes. Although it appears that similar variation for virulence exists among race 2 isolates on lettuce based on three tested isolates, the race 2 isolate VdLs17 was as virulent on susceptible lettuce cultivars as several race 1 isolates.…”

Section: Discussionsupporting

confidence: 73%

“…It was speculated that their appearance was due to the spread of a new recombinant or mutant isolate or to the selection of endemic race 2 isolates, because of the widespread use of the Ve resistance genes in tomato production (10,17,24). Regardless of the race, a continuum of virulence exists among isolates of V. dahliae pathogenic on tomato, suggesting that considerable genetic variation at loci other than those critical to the specificity of Ve genes also exists (10,17,24). Similar findings regarding the existence of a continuum of virulence among isolates of V. dahliae also were made in crops like cotton (3) and potato (14).…”

Section: This Article Is From the December 2006 Issue Of Published Bymentioning

confidence: 99%

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Characterization of Race-Specific Interactions Among Isolates ofVerticillium dahliaePathogenic on Lettuce

Vallad¹,

Qin²,

Grube³

et al. 2006

Phytopathology®

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Verticillium wilt, caused by Verticillium dahliae, poses a major threat to lettuce (Lactuca sativa) production in California. Incorporation of resistance into commercial lettuce cultivars offers the least expensive technique of sustaining production in infested areas. To test the breadth of the resistance identified in field experiments, a pair of susceptible (‘Salinas’ and ‘Sniper’) and resistant (‘La Brillante’ and ‘Little Gem’) lettuce cultivars were used as differentials and individually inoculated with 29 isolates of V. dahliae and two isolates of V. albo-atrum from several hosts, including lettuce, in replicated greenhouse experiments. The reactions of the four cultivars were determined based on the disease severity at maturity. None of the V. albo-atrum isolates or V. dahliae isolates from cruciferous hosts caused significant disease on lettuce. Both Salinas and Sniper were susceptible to many isolates of V. dahliae (21 of 23) from noncruciferous hosts, and the isolates varied in their overall virulence. However, of these, only three isolates caused significant disease on the resistant cvs. La Brillante and Little Gem. These three isolates also were distinct from the other V. dahliae isolates based on sequence data from the intergenic spacer (IGS) region of the nuclear ribosomal RNA gene, suggesting that they form a phylogenetically distinct subgroup that differs in virulence toward specific lettuce genotypes. Accordingly, isolates of V. dahliae virulent on all tested cultivars, including the resistant La Brillante and Little Gem, were designated as race 2, whereas those virulent only on the susceptible Salinas and Sniper were designated as race 1. Although a range of virulence among isolates has been described in other hosts, this is the first description of distinct virulence phenotypes in V. dahliae since a similar race structure was described in tomato in the 1960s.

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Section: Discussionsupporting

confidence: 73%

Section: This Article Is From the December 2006 Issue Of Published Bymentioning

confidence: 99%

Characterization of Race-Specific Interactions Among Isolates ofVerticillium dahliaePathogenic on Lettuce

Vallad¹,

Qin²,

Grube³

et al. 2006

Phytopathology®

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“…It is possible that race 1 isolates may be more fit than race 2 isolates and, thus, would become more prevalent in the field with subsequent lettuce crops (strawberry was the crop grown immediately prior to the 2004 experiment). Grogan et al (8) found differences in virulence between race 1 and race 2 tomato isolates of V. dahliae on susceptible cultivars, with race 1 being the more virulent. However, such differences in virulence were not apparent between the race 1 and race 2 lettuce isolates used in the experiments described here (24).…”

Section: Discussionmentioning

confidence: 99%

Variation for Resistance to Verticillium Wilt in Lettuce (Lactuca sativaL.)

et al. 2007

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Hayes, R. J., Vallad, G. E., Qin, Q.-M., Grube, R. C., and Subbarao, K. V. 2007. Variation for resistance to Verticillium wilt in lettuce (Lactuca sativa L.). Plant Dis. 91:439-445.Host resistance offers the most cost-effective method of Verticillium wilt control in lettuce (Lactuca sativa). In 2004 and 2005, 107 and 22 lettuce cultivars, respectively, were screened for resistance in a field infested with Verticillium dahliae, and disease progress on resistant and susceptible cultivars was determined. Greenhouse experiments were conducted to evaluate 16 cultivars for resistance to a race 1 and a race 2 isolate. Significant differences for resistance were observed within cultivated lettuce. In susceptible cultivars, disease levels increased through the season, whereas disease in resistant cultivars remained constant. Resistance in greenhouse tests was dependant upon the race used. Seven cultivars were resistant to race 1, whereas all were susceptible to race 2. Cultivar reactions to race 1 in greenhouse and field experiments were correlated, indicating the utility of greenhouse evaluations. The identification of resistance in diverse lettuce types is beneficial to the breeding process. However, because of the existence of resistance-breaking race 2 isolates, this resistance may not be durable. Alternatively, targeted releases of race-1-resistant cultivars to fields with only race 1 pathogen genotypes may extend the life of these cultivars.

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“…MS in soil are the primary source of inoculum for V. dahliae infections in host plants (21). Incidence of Verticillium wilt in herbaceous hosts is generally proportional to the number of MS in soil (11,12,19), but can vary considerably depending on the cultivar and crop (5,6,8,21). For example, in cauliflower, 4 MS g -1 of dry soil can cause 16% wilt incidence but 10 MS g -1 of soil causes 50% wilt (21).…”

mentioning

confidence: 99%

“…For example, in cauliflower, 4 MS g -1 of dry soil can cause 16% wilt incidence but 10 MS g -1 of soil causes 50% wilt (21). In tomato, 0.5 MS g -1 of soil causes 50% wilt incidence but 6 MS g -1 of soil causes 100% wilt (5). In strawberry, however, as little as 0.3 MS g -1 of soil causes 5% wilt and just 2 MS g -1 of soil can cause 100% wilt (6).…”

mentioning

confidence: 99%

Comparison of Media for Recovery of Verticillium dahliae from Soil

2004

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Polygalacturonic acid (PGA) is an important constituent of Sorensen's NP-10 medium (NP-10) for estimating the population density of Verticillium dahliae in soil. Different types of PGA are available, but not all of them favor the growth of V. dahliae. Unavailability of PGA sodium salt from orange (P-1879) has created an unprecedented problem for the quantification of microsclerotia (MS) of V. dahliae in soil. The PGA from orange (P-3889) that is now available does not support the growth of V. dahliae. Therefore, experiments were conducted to optimize the use of NP-10 prepared with P-3889 and various concentrations of NaOH. NP-10 with P-3889 amended with eight concentrations of NaOH were compared with NP-10 prepared from PGA sodium salt from orange (P-1879, now discontinued) and citrus (P-3850) along with cellophane and Napectate media for recovery of MS from soil and growth of V. dahliae on the media. Seven soils were assayed for MS, and eight isolates of V. dahliae were evaluated for growth and production of MS. Concentrations of NaOH >0.035N and <0.02N in NP-10 with P-3889 reduced mycelial growth, microsclerotial production, and recovery of MS from soils. Similarly, NP-10 with P-3850 alone, cellophane, and Na-pectate media had significantly reduced growth on media and recovery of V. dahliae from soils. The NP-10 with P-3889 and 0.025N NaOH consistently yielded numbers of V. dahliae MS from soil samples and supported the growth and production of MS similar to the NP-10 with P-1879. The medium developed in this study can serve as a direct replacement for the original NP-10 that was developed nearly three decades ago, an important component of which is no longer available.

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Verticillium Wilt on Resistant Tomato Cultivars in California: Virulence of Isolates from Plants and Soil and Relationship of Inoculum Density to Disease Incidence

Cited by 87 publications

References 0 publications

Characterization of Race-Specific Interactions Among Isolates ofVerticillium dahliaePathogenic on Lettuce

Characterization of Race-Specific Interactions Among Isolates ofVerticillium dahliaePathogenic on Lettuce

Variation for Resistance to Verticillium Wilt in Lettuce (Lactuca sativaL.)

Comparison of Media for Recovery of Verticillium dahliae from Soil

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