Abstract
6-Furfuxylamino purine (kinetin) at 0.1% plus indoleacetic acid (IAA) at 0.005 to 0.025% in lanolin, applied directly to the lateral buds at nodes on the basal portion of stems induced aerial crown formation with shoot growth.
Media and nutrient variables were investigated to develop methods of reducing the incidence and severity of fusarium crown rot incited by Fusarium oxysporum Schlecht. f. sp. radicis-lycopersici Jarvis & Shoemaker (FORL), a disease problem of current importance with tomato Lycopersicon esculentum Mill. Root-dip inoculated seedlings were transplanted into trays of a 1 Canadian peat: 1 vermiculite medium that had been prepared with factorial combinations of CaCO, (0.75 or 3.0 kg·m), Ca(NO) or (NH) SO (each at 225 mg N/liter), and NaCl at 0 or 2000 mg Na/liter as the experimental treatments. Crown rot was more severe with the lower CaCO rate, with (NH) SO, and supplemental NaCI. Data on fresh weight of seedlings expressed as percentage values relative to the noninoculated controls supported observations on disease severity.
Fusarium crown and root rot (crown rot) develops on tomato from the fungus Fusarium oxysporum f.sp. radicis-lycopersici (FORL). Genetic resistance to crown rot was previously introduced into the cultivated tomato from the wild species Lycopersicon peruvianum and found to be a single dominant gene, Frl, on the long arm near the centromere of chromosome 9 of the tomato genome. In an effort to identify molecular markers tightly linked to the gene, Ohio 89-1 Fla 7226, Fla 7464, `Mocis', and `Mopèrou', lines homozygous for Frl (resistant), were screened with restriction fragment length polymorphism (RFLP) markers in comparison to Fla 7482B and `Monalbo', lines homozygous for Frl + (susceptible). Frl was determined to be between the RFLP markers CT208 and CD8. These two markers are separated by a genetic map distance of 0.9 cM according to Pillen et al. (1996). In addition, we screened a pool of eight resistant plants against a pool of nine susceptibles from a BC1 population segregating for Frl for amplified fragment length polymorphism (AFLP) markers. Fazio et al. (1998) previously determined that crossover events occurred in these 17 plants between Frl and a rapid amplified polymorphic DNA (RAPD) marker, UBC194. Our research has indicated that UBC194 is also between CT208 and CD8 on the centromeric side of Frl. Of the 62 AFLP primer combinations tested, 34 showed more than 63 strong polymorphisms in linkage to resistant phenotypes.
Agrobacterium radiobacter (Beijerinc and van Delden) Conn strain K-84 failed to control raspberry (Rubus idaeus L.) crown gall caused by A. tumefaciens (E.F. Smith and Townsend) Conn. Agrobacterium tumefaciens strains isolated from galls on plants that had been treated with K-84 were not sensitive to agrocin 84 in vitro. These strains were isolated from `Titan' and `Hilton' raspberry in New York state and from `Himbo Queen' and `Schönemann' raspberry in Italy. Almost all strains were identified as A. tumefaciens biovar 2. Raspberry crown gall was not controlled by K-84 in three field experiments in New York state. In two of the experiments, plants were produced by micropropagation and were known to be pathogen-free. The other plant source was shown to be contaminated with the pathogen before treatment with K-84. Crown gall was not controlled either on raspberry in a greenhouse experiment or on Kalanchoe diagremintiana (Hamet. and Perrier) plants that were coinoculated with K-84 and strains of A. tumefaciens isolated from galls on raspberry.
Larvae of several insects injure and kill strawberry (Fragaria ×ananassa Duchesne) plants by burrowing into and hollowing out plant crowns. Occasionally, these infestations are serious enough to cause heavy economic losses to fruit producers and nursery plant growers. In 1997 in Beltsville, Md., we observed wilting and dying mature plants and unrooted runner plants in two experimental strawberry plantings. Injury by larvae was extensive; large cavities occurred in crowns, and the central pith tissues were removed from stolons and leaf petioles. Often, insect frass was seen at entrance holes. Larvae removed from hollowed-out parts of injured plants were identified as the European corn borer (Ostrinia nubilalis Hübner) in their fifth instar stage. Their presence in this instance also was associated with a cover crop of millet [Setaria italica (L.) P. Beauv., `German Strain R'] planted between the strawberry rows for weed suppression. This is the first published report of the European corn borer attacking strawberry. Although this insect may occur only sporadically in strawberry plantings, it may become important in the future. Growers and other professionals should become aware of this new strawberry pest and recognize that its management in strawberry will be different from management of other crown-boring insects.
Abstract
Single applications of ancymidol at 0.03, 0.12, 0.50, or 1.0 mg/plant were soil applied to asparagus seedlings (Asparagus officinalis L.) 3.5, 5.5, or 7.5 weeks after seeding. Increasing ancymidol rates from 0.03 to 1.0 mg/plant decreased bud number, fern dry weight, but not shoot number at all application times. When ancymidol was applied at 1.0 mg/plant at 3.5 weeks it reduced fleshy root production, but in plants treated at 5.5 to 7.5 weeks, it did not reduce fleshy root production. Increasing ancymidol rates from 0.03 to 1.0 mg/plant reduced the crown dry weight of plants 5.5 weeks and younger. Ancymidol from 0.03 to 1.0 mg/plant applied to 3.5-week-old plants increased the partitioning of dry matter into fern rather than crowns, but delaying application to 7.5 weeks after seeding reversed this relationship suggesting increased carbohydrate storage. Application of ancymidol from 0.03 to 1.0 mg/plant to plants 5.5-weeks-old or younger was considered detrimental to plant growth. Ancymidol at 0.50 mg/plant or less applied to 7.5-week-old plants enhanced the production of a stocky, compact transplant. Chemicals used. Ancymidol: α-cycloprophyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol.
Phytoplasma PoiBI is responsible for free branching in poinsettia (Euphorbia pulcherrima Wild. ex. Klotzsch). In this study, PoiBI was transmitted by dodder from poinsettia to crown-of-thorns (E. milii Des Moulins) in one out of ≈100 attempts, whereas grafting transmission was unsuccessful. PoiBI was shown to be viable in E. milii, as it was detected in the recipient plant and in its cuttings over 1.5 years by polymerase chain reaction. It was shown that PoiBI induces free branching in E. milii as well as in poinsettia. Smaller leaves, reduced growth rates, and delayed flowering were other effects of PoiBI infection.
Asparagus officinalis L. cv. Centennial established with transplants in 1983 was maintained with tillage or a no-till (NT) system to evaluate effects of tillage on yield and plant growth in a mature asparagus planting. Metribuzin or metribuzin + napropamide at 1.12 and 1.68 kg a.i./ha, respectively, were used for weed control in both tillage regimes. Marketable yields were assessed for 5 years. In 1989, in addition to yield data, destructive harvests of entire plants were made every 3 weeks from March to November to evaluate the effect of tillage on fern, crown, and bud growth, and carbohydrate status. Yields were reduced by tillage from 12% to 50% from 1985 to 1989. There were no herbicide effects nor was there an effect on yield due to an interaction between herbicides and tillage. All indices of growth measured for NT exceeded those in tilled plots, although seasonal patterns of growth were similar in both. Crown and fern weight, bud cluster, and bud and fern counts were higher by 178%, 175%, 152%, 161%, and 195%, respectively, in NT than in tilled plots. The metribuzin + napropamide combination did not reduce fern fresh weight or yield, but significantly reduced the number of bud clusters, buds, and ferns when compared to metribuzin alone. Chemical names used: 4-amino-(1,1-dimethylethyl)-3-(methylthio)-l (metribuzin); 2,4-triazin-5(4H) -one, N,N-diethyl-2-(naphthalenyloxy)-propanamide (napropamide).
Fusarium crown and stem rot, caused by Fusarium avenaceum, is a serious disease of lisianthus, Eustoma grandiflorum Raf. (Shinn.). While more than 80 new cultivars of lisianthus have been released for sale in the United States in the past decade, there is a lack of information on their susceptibility to this pathogen. Forty-six cultivars of lisianthus were evaluated for resistance to F. avenaceum. Cultivars were grouped according to blue/purple, pink, or white colors and evaluated within their color class. Although all cultivars evaluated were susceptible to F. avenaceum, partial resistance was observed as indicated by differences in the length of time to symptom expression and in the frequency of diseased plants. `Ventura Deep Blue' and `Hallelujah Purple' (25%) in the blue group, `Bridal Pink' (23%) in the pink group, and `Heidi Pure White' (53%) in the white group had the lowest frequency of diseased plants at 55 days after inoculation. In 21 of the 46 cultivars, 80% to 100% of the plants expressed symptoms at 55 days after inoculation. Screening cultivars for resistance to F. avenaceum is the first step to breeding and developing resistant cultivars. These results also can be useful to growers who could select cultivars that express some level of resistance as an aid in management of this disease until more resistant cultivars are released.
Fusarium crown and stem rot, caused by Fusarium avenaceum (Fr.: Fr.) Sacc., is a serious disease of lisianthus [Eustoma grandiflorum Raf. (Shinn.)]. While more than 80 new cultivars of lisianthus have been released for sale in the United States in the last decade, there is a lack of information on their susceptibility to this pathogen. Forty-six cultivars of lisianthus were evaluated for their response to infection by F. avenaceum. Cultivars were grouped according to blue/purple, pink, or white flower colors and evaluated within their color class. Although some plants of all cultivars were susceptible to F. avenaceum, partial resistance was observed as indicated by differences in the length of time to symptom expression and in the frequency of diseased plants within each color group. In 21 of the 46 cultivars, 80 to 100% of the plants expressed symptoms within 55 days after inoculation. The lowest frequencies of diseased plants 55 days after inoculation were found in `Ventura Deep Blue' and `Hallelujah Purple' (25%), `Bridal Pink' (23%), and `Heidi Pure White' (53%) for the blue/purple, pink, and white flower color groups, respectively. Screening cultivars for resistance to F. avenaceum is the first step in breeding resistant cultivars. The methods we developed for these studies should be useful in screening for resistance. These results also may help growers select cultivars that are less susceptible to F. avenaceum, which should aid in the management of this disease.