‘Mountain Regina’ is a large-fruited, fresh-market hybrid tomato ( Solanum lycopersicum L.) adapted to vine-ripe production. It is resistant to verticillium wilt ( Verticillium dahliae Kleb) race 1 ( Ve gene); fusarium wilt [ Fusarium oxysporum
‘Mountain Merit’ is a large-fruited, determinate, fresh-market F 1 hybrid tomato ( Solanum lycopersicum L.) resistant to late blight [ Phytophthora infestans (Montagne, Bary)]; verticillium wilt ( Verticillium dahliae ); fusarium wilt
, designated RH14-1156, RH14-1157, and RH14-1158, are the first to combine resistance to the soilborne diseases corky root and verticillium wilt race 1. The populations are genetically fixed for disease resistance, and all progeny descending from these
Runner plants from strawberry (Fragaria ×ananassa Duch.) genotypes previously identified as relatively susceptible, intermediate, and resistant to wilt caused by Verticillium dahliae Kreb. were inoculated with a conidial suspension containing a mixture of five isolates of V. dahliae at 104, 105, and 106 conidia/mL. Disease symptoms were scored as the number of dead or severely stunted plants per plot, or on the basis of a subjective phenotypic resistance score assigned to each plot on eight dates during the spring after planting. Overall disease symptoms increased with inoculum concentration; resistance scores for all genotypes were 4.8, 3.7, and 3.2, and the percentages of plants stunted or dead were 6.8, 32.6, and 44.9 for the three conidial concentrations, respectively. The relative resistance categories were separable at concentrations of 106 and 105, whereas no separation was obtained at 104 conidia/mL. Genotypes originally classified as intermediate in resistance performed more like susceptible types at the highest conidial concentration. Significant resistance category × conidial concentration level interactions were detected for resistance score but not for the number of dead or severely stunted plants per plot. Regression coefficients for resistance score and percentage of stunting on conidial concentrations were statistically significant only for susceptible and intermediate genotypes. Some stunting was detected within all resistance categories at the highest conidial concentration, and the practical value of the resistance developed to date will depend ultimately on realistic field inoculum levels.
Verticillium albo-atrum, a cosmopolitan pathogen that causes wilt of strawberry, can cause economic losses for growers and increased prices for consumers. This study was conducted in 1998 to assess the impact of organically and inorganically supplied N on fruit yield and quality. `Allstar' (resistant) and `Raritan' (susceptible) varieties of strawberry were planted in V. albo-atrum-infested soil that was amended with poultry compost (organic N) or ammonium nitrate (inorganic N). Fruit quality was assessed as titratable acidity (TA), soluble solids content (SSC) using a refractometer, and reducing sugars concentration using a gas chromatography. Disease incidence was below threshold level and did not affect the results of this study. Plants grown in compost amended plots produced an average of 41 fruit, weighing 354 g, compared to the 34.5 fruit weighing 487 g that were harvested from the inorganically amended plots. TA was not affected by the treatments. Overall, yield of `Raritan' was 40% greater than that of `Allstar'. The SSC of `Allstar' was highest in fruit that were produced in compost-amended soil in contrast to that of `Raritan', which was greatest for plants that were grown in the inorganically amended plots. Fruit grown in the inorganically amended plots generally had a higher concentration of glucose and fructose, but sucrose was found only in fruit from the control plots. Poultry compost may be an alternative source of N for producing strawberries but this needs to be further evaluated because of the slower release of nutrients over time.
Strawberry genotypes were retained from biparental progenies previously identified as either relatively susceptible or resistant to wilt caused by Verticillium dahliae based on a phenotypic resistance score. Runner plants from these selected genotypes were inoculated with a conidial suspension containing a mixture of five isolates obtained from symptomatic strawberry plants at 106 conidia/mL, then scored for disease symptoms. Genotypes from resistant progenies had significantly higher phenotypic resistance scores (1 = severe symptoms, 5 = no detectable symptoms) than those from susceptible progenies (4.15 vs. 2.23), and there also was a correlated selection response for the percent plants severely stunted or dead (26.4 and 69.1 for resistant and susceptible selections, respectively). Comparisons of the resistance scores for selected groups with those for the original parents (2.76) indicated that selection had changed relative resistance significantly in both directions and that realized response had been 24% to 43% larger than predicted for selection in both directions. Although several of the selections from resistant progenies were highly susceptible, five of the 21 resistant selections had resistance scores outside the range of the original parents, representing possible transgressive segregants. This comparison is limited by the precision with which individual resistance scores are estimated and by the scope of the disease symptoms in this trial. Detecting genotypes with sufficient resistance ultimately will depend on development of screening methods with greater sensitivity than those used here.
. This breeding line, however, can be used in breeding programs because it combines high level resistances to downy mildew, bacterial leaf spot, Verticillium wilt race 1, and lettuce dieback. Two (SM13-R2, SM13-R3) of the four romaine breeding lines are
Verticillium wilt of olive (VWO), incited by Verticillium dahliae Kleb., has become the most destructive disease of olive throughout the Mediterranean basin ( Al-Ahamad and Mosli, 1993 ; Blanco-López et al., 1984 ; Hiemstra and Harris, 1998
Pistachio (Pistacia vera) was successfully introduced into California and initially touted as a tree nut crop with no disease or insect pests. Unfortunately, these expectations were dashed as a number of diseases and pests followed commercial plantings, making plant protection practices integral to production. Verticillium wilt (Verticillium dahliae) devastated early plantings but is now controlled with the use of resistant rootstocks. Botryosphaeria blight (Botryosphaeria dothidea) and alternaria late blight (Alternaria alternata) are recently arrived foliar fungal diseases that blight fruit clusters and defoliate trees, respectively, and multiple fungicide applications are needed for control. The conversion to low volume irrigation systems, specifically to drip or buried drip, has reduced disease. Pruning out botryosphaeria blight infections has reduced overwintering inoculum and disease, while current research aims at accurately predicting infection events to increase fungicide efficacy. A number of hemipteran insect pests have been associated with epicarp lesion: spring treatments have been replaced with dormant carbaryl and oil applications which are less toxic to beneficial insects while controlling phytocoris (Phytocoris californicus and P. relativus) and soft scale pests. Early season insect damage can be tolerated because trees compensate by maturing a higher percentage of remaining fruit kernels. Some mirid (Calocoris spp.) pests can be effectively reduced by eliminating alternate hosts in an effective weed control program. If lygus (Lygus hesperus) populations are present, weeds should not be disturbed from bloom until shell hardening to prevent movement by insects into the trees where feeding can result in epicarp lesion. Stink bugs (Pentatomidae) and leaffooted bugs (Leptoglossus clypealis and L. occidentalis) can penetrate the hardened shell and cause internal nut necrosis along with epicarp lesion. Trap crops are used to monitor pest populations in order to develop treatment thresholds. Degree-day based timing of treatments increase insecticide efficacy for the control of navel orangeworm (Amyelois transitella) and obliquebanded leafroller (Choristonuera rosaceana), but navel orangeworm populations are more effectively managed by destroying unharvested over wintering fruit. Bacillus thuriengiensis sprays, liquid-lime-sulfur, and biological control show promise in controlling obliquebanded leafroller.
Verticillium dahliae (Kleb.) is a destructive soilborne pathogen that infects many economically important agricultural crops worldwide. Wilt caused by V. dahliae is difficult to control because the fungus can survive in the soil as