associated with raspberry, Pratylenchus penetrans , the root lesion nematode, is the most economically important ( McElroy, 1991 ). Feeding on roots by Pratylenchus penetrans (Cobb) Filipjev and Schuurmans Stekhoven can reduce the capacity of the plant to
Methods to screen for resistance to root-lesion nematode Pratylenchus penetrans in Rosa were modified to screen-rooted materials. Sixty days after rooting, plants were transplanted into 50-mL pots filled with river sand and each inoculated with 500 P. penetrans in 400 μL water 10 days later. The inoculated plants were fertilized weekly and incubated in a growth chamber or a greenhouse for 5 months when nematodes were extracted from the sand and root system and enumerated. When used for screening of the 131 Rosa accessions, this approach allowed the observation of a large variation in host suitability. While a majority of the accessions supported the multiplication of P. penetrans, previously reported resistance of R. multiflora `K1' and R. virginiana to P. penetrans was confirmed. Rosa laevigata anemoides allowed a significantly lower nematode multiplication than the currently prevalent rootstock R. corymbifera `Laxa'.
Abstract
Eight rose rootstocks were tested in pot experiments for their suitability as host to Meloidogyne hapla Chitwood, Pratylenchus penetrans Cobb, and P. vulnus Allen & Jensen. Most rootstocks were host for both Pratylenchus spp. but great difference in host efficiency occurred. Rosa indica ‘Major’ and R. multiflora‘ 60-5’ proved to be the most efficient hosts for P. vulnus and P. penetrans, respectively. M. hapla reproduced well on R. indica‘ Major’ but not on R. ‘Manetti’. R.‘ Manetti’ shows outstanding resistance, if not complete immunity to M. hapla. Other rootstocks showed infection varying from slight to severe.
Abstract
Field samplings in 3 peach orchards with 4 seedling rootstocks showed that Siberian C seedlings had significantly higher levels of Pratylenchus penetrans [(Cobb) Filip, and Stek.] populations in both root tissues and surrounding soil than 3 other seedling rootstocks tested. Little difference in nematode populations could be shown between seedlings of Veteran, Harrow Blood and Rutgers Red Leaf. Greenhouse studies of infected and nematode-free seedlings of these rootstocks confirmed field results. Significant reduction in growth occurred in all the rootstocks tested, with Siberian C seedlings being the most severely affected. Nematode control and plant breeding implications are discussed.
Abstract
Sixteen nonbearing new and replanted ‘McIntosh’ apple (Malus domestica Borkh.) orchards were surveyed in August of 1983. Rootstock and soil type influenced the number of nematodes [Pratylenchus penetrans (Cobb 1917) Sher and Allen] found in feeder roots of the 12 two-year-old orchards (P = 0.007). Mailing Merton (MM) 111 roots in clay had fewer P. penetrans (12.4/g) than MM 106 roots in clay (42.2/g) or roots of MM 111 in loam (93.2/g). Nematode populations in feeder roots increased with soil depth down to 24 cm. P. penetrans populations were not influenced by soil pH, organic matter, drainage, root conditions, tree vigor, herbicide management, or replant status.
Root lesion nematodes (Pratylenchus penetrans Cobb) are well-adapted to sandy soils and have a host range including most agronomic, horticultural, and wild species grown in Ontario. As native climax sand-prairie species have coexisted with the nematode for millennia, resistance or tolerance may have developed. We have screened using the Baermann pan technique, soil samples taken from a private collection of sand-prairie species collected from local prairie remnants. Several species [Liatris cylindracea Michx., Monarda punctata L., Pycnanthemum virginianum L., Echinacea purpurea (L.) Moench] proved to be excellent hosts (>500/kg of soil) of root lesion nematode, confirming the presence of this nematode in the soil. Over two seasons, we determined that 10 plant species belonging to the families Asclepiadaceae, Compositae, Graminae, and Leguminosae to support very low numbers of P. penetrans. Brown-eyed susan (Rudbeckia hirta L.) had no root lesion nematodes throughout both seasons, Butterfly weed (Asclepias tuberosa L.) very low counts, while Switch grass (Panicum virgatum L.) and Indian grass [Sorghastrum nutans (L.) Nash] had detectable root lesion nematodes on only one sampling date each year. Big Bluestem (Andropogon gerardii Vitman), Little Bluestem [Schizachyrium scoparium (Michx) Nash], Sand Dropseed [Sporobolus cryptandrus (Torr.) Gray], Side-oats Grama [Bouteloua curtipendula (Michx.)) Torr], Broomsedge (Andropogon virginicus L.), Bush clover [Lespedeza capitata (Michx] also are poor hosts. These species have potential as cover or rotation crops useful for nematode management.
Abstract
‘Rogers Red McIntosh’ (Malus domestica Borkh.) on Mailing Merton (MM)111, MM 106, Mailing (M) 26 and M 7a were planted within an old apple orchard site. The trees were trickle-irrigated and the sandy soil was treated with the nematicides Telone (C-17), Vorlex, or Nemacur 3. In 1984, data were collected from trees excavated at 50, 100, and 156 days after planting and from permanent trees in 1985 from plots treated with nematicides prior to planting. The numbers of Pratylenchus penetrans [(Cobb) Filipjev & Schuurmans-Stekhoven] in soil and rootstocks from nematicide treatments and controls were well below reported damage levels and not considered a problem on this test site. M 111 and MM 106 roots and ‘McIntosh’ scion growth were superior to M 26 and M 7a counterparts regardless of soil treatment in 1984, while only the scions on MM 111 were larger than those on M 26 in 1985. ‘McIntosh’ scions grew 36% larger on Telone C-17-treated soil and 19% larger on Vorlex-treated soil than on untreated soil. Leaf and soil analyses showed no interaction with rootstocks and minor differences between soil treatments in both years. A soil replant bioassay revealed disease factor(s), including P. penetrans, present in untreated soil.
Because of the need to find plants that suppress root lesion nematodes for use in rotation or cover-crops, 16 native sand-prairie species were evaluated for host status for 6 years. Plants were grown on a Fox sand soil at a local prairie plant nursery. Soil cores were taken in the spring, summer, and fall and assayed for plant parasitic nematodes. Five species supported very low numbers (less than 100/kg soil) of root lesion nematodes. Brown-eyed Susan (Rudbeckia hirta) had no detectable nematodes for the duration. Switchgrass (Panicum virgatum L.) and Indiangrass (Sorghastrum nutans L., Nash) samples produced detectable nematodes on only two sampling dates over the 6 years and were statistically not different from brown-eyed Susan. Butterfly weed (Asclepias tuberosa L.) also had very low detectable nematodes as did sand dropseed [Sporobolus cryptandrus (Torr.) Gray.]. New Jersey tea (Ceanothus americanus L.), little bluestem [Schizachyrium scoparium (Michx.) Nash], and big bluestem (Andropogon gerardi Vitman) were poor hosts with <200 nematodes/kg soil. Mountain mint (Pycnanthemum virginianum L), wild bergamont (Monarda fistulosa L), horsemint (Monarda punctata L), and dwarf blazing star (Liatris cylindracea L) all had root lesion populations over 3000/kg soil. Horsemint and wild bergamont plants died out, possibly as a result of nematode infestation. Root lesion nematodes have an extremely wide host range in current agronomic and horticultural crops, and weeds and are difficult to manage using nonchemical means. Indiangrass, switchgrass, big bluestem, and little bluestem have all been used agriculturally for pastures and consequently have potential as beneficial long-term rotation crops for nematode management and soil building.
The effects of temperature and root-lesion nematodes [Pratylenchus penetrans (Cobb)] on the growth of newly germinated `Bartlett' pear seedlings (Pyrus communis L.) were examined. At five temperatures from 10 to 30C, P. penetrans (five per gram of soil) did not purple the leaves. After 8 weeks, leaf number, trunk height, and top and root weights were reduced only at 25C. The number of P. penetrans in the roots were greatest at 15 and 20C. At 20C, P. penetrans (16 per gram of soil) caused the leaves of seedlings to turn purple, and, by 6 weeks after treatment, the nematodes had reduced leaf production, trunk elongation, and top and root growth.
The inheritance of resistance to the root lesion nematode [Pratylenchus penetrans (Cobb) Filip. and Stek.] in red raspberry (Rubus idaeus L.) was studied in a four-member half diallel, involving two resistant genotypes and two susceptible genotypes. Estimates of general and specific combining abilities (GCA and SCA, respectively) were determined for nematode densities in roots alone and soil alone, nematode densities per plant, and plant root and foliage biomass. GCA were significant for nematodes in soil and for root and foliage biomass; SCA were significant for nematodes in the soil and for root biomass. Neither GCA nor SCA was significant for number of nematodes in the roots or per plant.