appeared to have substantial tolerance to HLB when trees were exposed to the disease after maturity ( Stover and McCollum, 2011 ; Stover et al., 2015 ). If tolerance is verified, through sustained growth and economic fruit production when newly planted
performance, pest resistance, disease resistance, and drought tolerance that possessed desirable ornamental characteristics in north central Texas [U.S. Department of Agriculture (USDA) Plant Hardiness Zone 8a] using low-input Earth-Kind ® rose trialing
provide growers and gardeners with regionally specific information on morphometrics, phenology, and disease tolerance ( Coombs 2016 ; Hawke 1998 ). The Mt. Cuba trials further identify wildlife observed on Monarda flowers within the trial garden
Solanum lycopersicoides is a valuable genetic resource for tomato (Lycopersicon esculentum) genetic improvement. However, there are few reports on its agronomic traits such as disease resistance and cold tolerance. In this paper, the resistance to cucumber mosaic virus (CMV) and leaf mold (Cladosporium fulvum Cooke) and cold tolerance of five lines of S. lycopersicoides were studied through investigation of disease inoculation and electrolyte leakage analysis. The results showed that S. lycopersicoides was highly resistant or immune to CMV and leaf mold and more tolerant to low temperature than L. esculentum. This study is helpful for the genetic improvement of tomato by using S. lycopersicoides as breeding materials.
Abstract
Rickettsia-like bacteria, implicated as the casual agent of Pierce’s disease, were easily observed by electron microscopy in the xylem of muscadine grape (Vitis rotundifolia Michx.) with symptoms of Pierce’s disease. The symptoms included severe stunt, marginal leaf burn, and dieback. The bacterium was observed only in the tracheary elements of the xylem.
Differences in levels of tolerance to Pierce’s disease were found in muscadine cultivars and breeding selections. Muscadine cultivars and selections developed at Experiment, GA were generally more tolerant to the disease than those developed at Meridian, MS or Raleigh, NC, however, there were some highly tolerant cultivars from all 3 locations. Cultivars from MS were much more tolerant to the disease than were selections from that location which were never considered acceptable for release to commercial growers.
We tested 40 seedling lots and 17 clonal accessions—representing 941 genotypes and 19 species or interspecific hybrids of Malus—for their resistance or tolerance to apple replant disease (ARD) in a mixture of five New York soils with known replant problems. Total plant biomass, root necrosis, root-infesting fungi, and root-lesion nematode (RLN; Pratylenchus penetrans Cobb) or dagger nematode (DN; Xiphinema americanum Cobb) populations were evaluated in apple seedlings and clones grown for ≈60 days in the composite soil. In addition to phytophagous nematodes, various Pythium, Cylindrocarpon, Fusarium, Rhizoctonia and Phytophthora species were isolated from roots grown in the test soil. Plant growth response was categorized by a relative biomass index (RBI), calculated as total plant dry weight in the pasteurized field soil (PS) minus that in an unpasteurized field soil (FS), divided by PS. Nematode reproduction on each genotype was defined by a relative reproduction index (RRI), calculated as final nematode populations in roots and soil (Pf) minus initial soil populations (Pi), divided by Pi. The RBI, RRI, and other responses of accessions to ARD soil were used to rate their resistance, tolerance, or susceptibility to apple replant disease. None of the accessions was completely resistant to ARD pathogens in our test soil. Seedling accessions of M. sieversii Roem. and M. kirghisorum Ponom. appeared to have some tolerance to ARD, based upon their low RRIs and RBIs. Three clonal rootstock accessions (G.65, CG.6210, and G.30), and four other clones (M. baccata Borkh.—1883.h, M. xanthocarpa Langenf.—Xan, M. spectabilis Borkh.— PI589404, and M. mandshurica Schneid.—364.s) were categorized as tolerant to ARD. The disease response of other accessions was rated as susceptible or too variable to classify. We concluded that sources of genetic tolerance to ARD exist in Malus germplasm collections and could be used in breeding and selecting clonal rootstocks for improved control of orchard replant pathogens.
the mechanisms of disease tolerance in mycorrhizal plants. In pathogen stress conditions, production of a higher concentration of reactive oxygen species (ROS) such as H 2 O 2 , superoxide anion (O 2 – ), and hydroxyl radical has been shown to create
plants of PIs 546188 and PI 546192 ( Table 1 ). Another mechanism besides thrips feeding tolerance or thrips feeding nonpreference must be causing a reduction in disease severity as compared with other accessions. Plants of PI 239633 exhibited dark green
. Previously, we reported tolerance to fusarium root rot in mycorrhizal asparagus (cv. Mary Washington 500W) plants ( Matsubara et al., 2003 ); however, many points remain unclear about the mechanisms of disease tolerance in mycorrhizal asparagus plants. As for
Grafting vegetable crops is a common practice in Asia and parts of Europe. It was initially introduced to control fusarium wilt in watermelon ( Murata and Ohara, 1936 ), but its use has expanded to include a variety of diseases on cucurbit and