The xylophagous leafhopper Homalodisca coagulata Say is an important vector of diseases caused by the bacterium, Xylella fastidiosa (e.g., Pierce's disease, phony peach disease, plum leaf scald, etc.). Neither leafhoppers or X. fastidiosa can be controlled by chemical sprays. For many plant species there is no resistant germplasm. H. coagulata is highly polyphagous, and within Prunus spp. host preference ranges from moderate (plum) to low (peach). The abundance, feeding and performance of H. coagulata on many unrelated plant species have been previously correlated with the amino acid profile, and particularly the amides in xylem fluid. We tested Prunus scion/rootstock combinations, which provided for a range of xylem fluid chemistry, on the behavior (abundance, feeding) and performance (survivorship, fecundity, body weight and body composition) of H. coagulata. Leafhopper abundance on various rootstock/scion combinations was determined seasonally. During the period of peak abundance (June 14 to 30) feeding rates and performance indices were determined. Leafhopper abundance and feeding increased with an increased concentration of amino acids. Abundance and feeding rate were most highly correlated with the amides in xylem fluid; performance indices were influenced by the amides and certain essential amino acids. Lower consumption rates decreased survivorship, reduced body dry weight and the carbon concentration of surviving insects.
Forty eight cultivars, species, and their progeny including Prunus americana P. angustifolia, P. cerasifera P. munsoniona, P. salicina, P. simoni, and P. triflora were evaluated for resistance to Xylella fastidiosa based on percent of scalded leaves and tree longevity. Observations indicate that resistance is heritable and controlled by recessive genes. Further, X. fastidiosa transmission was evaluated in plum and peach by chip and slip budding. Transmission as measured by enzyme-linked immunoabsorbant assay indicated that chip budding resulted in a higher level of transmission over slip budding in plum but not in peach. Neither Lovell nor Nemaguard rootstock had an effect on transmission.
Effects of scion inclination on root growth and distribution were studied on INRA GF 677 (Prunus persica × Prunus amygdalus) and apple/M.9 trees. At planting, central leaders were positioned vertically (0°) or inclined 45° or 60° to the north and south. Three years after planting, root total dry weight of inclined trees was lower than that of the control (0°, vertical central leader). Five years after planting, the isotropic distribution of the normal root systems was distorted by inclination in both species. Roots were more numerous and more elongated in the direction of inclination. Statistical analysis of root density data, using a polar coordinate system, confirmed that the trunk inclination reduced root development and redirected root distribution. The major effect was induced on GF 677 by 60° inclinations. Tree orientation did not seem to influence root distribution.
strong indication that Unknown 7 from Goldridge is a cultivar of P. rivularis . Sister to the previous monophyletic group is ‘Chalco’ (DPRU.431) (WEO), which is listed as Prunus spp. in the USDA-ARS-NCGR GRIN Global database ( Figs. 2 , 4 , and 5
Armillaria spp. associated with root disease in peach orchards in the State of Mexico, Mexico For. Pathol. 43 390 401 Guillaumin, J.J. Pierson, J. Grassely, C. 1989 The susceptibility of different Prunus species used as stone fruit rootstocks to
. 1994 Graft establishment between compatible and incompatible Prunus spp J. Expt. Bot. 272 393 401 Errea, P. Garay, L. Marín, J.A. 2001 Early detection of graft incompatibility in apricot ( Prunus
by a number of soilborne pests, including pathogens such as Pythium spp. and Verticillium dahlia ; nematodes such as lesion nematode ( Pratylenchus spp.), root-knot nematode, and dagger nematode ( Xiphinema spp.); and competition from a wide
Abstract
Ethanol treatment broke dormancy in Gladiolus spp., Freesia spp., Lilium longiflorum Thunb., Zingiber myoga Rose., Platycodon grandiflorum A. DC., Paeonia suffruticosa Andr., and Prunus persica (L.) Batsch. Effectiveness of ethanol depended on species and stage of dormancy.
Abstract
‘Velvaglo’ is a very attractive apricot (Prunus armeniaca L.) ripening in the last week of July with ‘Goldcot’. It has moderate resistance to bacterial spot (Xanthomonas pruni (E. F. Smith) Dowson), brown rot (Monilinia fructi-cola (Wint.) Honey) and perennial canker (Leucostoma spp). It was introduced in 1978 as a later-ripening cultivar than ‘Harcot’, adapted to conditions of southern Ontario, Canada.
Abstract
Volatiles from garlic and horseradish paste broke corm dormancy of springflowering gladiolus (Gladiolus × Tubergenii Hort. Effective substances in garlic were allyl sulfide, methyl disulfide, n-propyl disulfide, and those in horseradish were allyl sulfide, allyl isothiocyanate, and n-propyl sulfide. Monosulfide extracted from garlic paste, allyl sulfide, and allyl disulfide were effective in breaking corm dormancy of summer-flowering gladiolus (Gladiolus spp.). Methyl disulfide promoted sprouting and flowering of tree peony (Paeonia suffruticosa Andr.) and flowering of ornamental cherry (Prunus spp.) without phytotoxic symptoms.