Search Results

You are looking at 61 - 70 of 151 items for :

  • "nematode resistance" x
  • Refine by Access: All x
Clear All
Free access

J.C. Cervantes, D.L. Davis, and G.C. Yencho

This study was conducted to determine whether the type of pot used for the evaluation affected the resistance response of the sweetpotato plants, and to assess the resistance response to different root-knot nematode species. Five sweetpotato [Ipomoea batatas (L.) Lam] cultivars, `Beauregard', `Exce'l, `Jewel', `Hernandez', and `Porto Rico', were screened for M. incognita (race 3), Meloidogyne arenaria (race 2), and M. javanica, in both 10-cm-side, square pots and 4-cm-diameter, cone pots. Gall index, necrosis index, and number of nematode eggs per gram of root were used to estimate nematode-resistance reaction. Mean of all indices between the 2 pot types were not significantly different (α = 0.05). Gall and necrosis indices were not correlated in any of the cultivars. Resistance response depended on cultivars and nematode species for all variables analyzed. `Beauregard' was the most susceptible to Meloidogyne. `Hernandez' and `Excel' were found to be the most resistant cultivars to the Meloidogyne species.

Free access

F.A. Hammerschlag and R.N. Huettel

Five in vitro propagated peach scion cultivars (Suncrest, Rio Oso Gem, Compact Redhaven, Redhaven, Jerseyqueen) and two rootstock (Nemaguard and Lovell) were screened in vitro and in microplots for their susceptibility to the root-knot nematode, Meloidogyne incognita. Evaluations in tissue culture for galling were conducted at 5 wk. Trees in microplots were evaluated for 3 years for nematode populations, trunk diameter, and yield. Comparative results indicated that the number and size of galls observed at 5 wk in vitro is indicative of the response of peaches to nematodes under field conditions after three years. Cultivar Compact Redhaven was significantly more tolerant to root-knot than `Lovell' the most widely used peach rootstock. These results suggest that Compact Redhaven might be potentially useful as a rootstock in the Southeast where Nemaguard is used sparingly because of its lack of cold tolerance. In addition, these results indicate that in vitro screening holds promise as a rapid technique for evaluating root-knot nematode resistance.

Free access

R.L. Fery and P.D. Dukes

The USDA has released a new cream-type southernpea [Vigna unguiculata (L.) Walp.] cultivar that is well adapted for productionthroughout the southern United States. The new cultivar, named `Tender Cream', is the product of a backcross breeding procedure to transfer the dominant Rk gene for root-knot nematode resistance from `Floricream' into `Carolina Cream'. `Tender Cream' is resistant to cowpea curculio, root-knot nematodes, southern bean mosaic virus, cercospora leaf spot, southern blight, rust, and powdery mildew. `Tender Cream' outyielded the cream control in the 1992, 1993, and 1994 Regional Southernpea Cooperative Trials by 5.4%, 11.0%, and 18.8%, respectively. It outyielded its root-knot-nematode-susceptible `Carolina Cream' isoline by 22.3% in a replicated 1994 test conducted in a field infested with a natural population of the southern root-knot nematode. Canned samples of fresh `Tender Cream' peas scored well during 3 years of testing at the Univ. of Arkansas.

Free access

John W. Potter and Adam Dale

Intraspecific crossing of `Guardian' and `Midway' cultivated strawberry (Fragaria ×ananassa Duch.) produced a family of genotypes, some of which suppressed root-lesion nematode [Pratylenchus penetrans (Cobb)] population counts and produced large berries and high yield. Unlike `Midway', `Guardian' also suppressed P. penetrans. Among several beach strawberry [Fragaria chiloensis (L.) Duch.] and woodland strawberry (Fragaria virginiana Duch.) genotypes, variation was found in resistance and tolerance to root-lesion nematodes. Three F. chiloensis genotypes showed tolerance, and at least two genotypes may be somewhat resistant. Three F. virginiana genotypes also were tolerant, and three were resistant. Also, one (`Little Cataraqui 4') combined root growth vigor with nematode resistance. We concluded that exploitable genetic diversity in vigor and reaction to root-lesion nematodes exists in wild Fragaria and in F. ×ananassa.

Free access

G.B. Cap, P.A. Roberts, I.J. Thomason, and T. Murashige

Genotypes of Lycopersicon peruvianum (L.) Mill. and L. peruvianum var. glandulosum (Rick), selected from accessions that possess resistance to Meloidogyne incognita [(Kofoid and White) Chitwood] at high soil temperature (30C), were used as male parents in crosses with L. esculentum (Mill.) susceptible cultivars UC82, Lukullus, Tropic, and male-sterile line ms-31, respectively. The incongruity barrier between the two plant species was overcome by embryo callus and embryo cloning techniques. Hybridity of the F, progeny obtained from each cross was confirmed by differences in leaf and flower morphology, plant growth habits, and by acid phosphatase isozyme phenotypes using polyacrylamide gel electrophoresis. In greenhouse inoculation experiments, F1 plants were highly resistant to M. incognita in soil at 25 and 30C. These results confirmed the successful transfer and expression of heat-stable resistance to M. incognita from L. peruvianum to hybrids with L. esculentum as a preliminary step to introgressing additional root-knot nematode resistance into tomato.

Open access

Robert W. Jones

Abstract

Suitable parents for the production of F1 hybrid seed between almond and root-knot nematode resistant peach were selected. Three of 13 almond selections were found which, when pollinated by ‘Nemaguard’ pollen, produced good sets of seed. When germinated, their seedlings showed good root-knot nematode resistance, hybrid vigor, and exceptional compatibility with almond tops.

The self-incompatibility of almond was used to permit natural pollination between selection CP5-33 and a selected seedling of ‘Nemaguard’, 3-28. The F1 hybrids proved to be very compatible as rootstocks with almond and peach tops and imparted increased vigor to them.

Both ‘Nemaguard’ and a selected seedlings of ‘Nemaguard’ served as good pollen parents. ‘Okinawa’ peach, another rootknot nematode resistant peach type rootstock, was a less satisfactory pollen parent.

Open access

W. B. Nesbitt

Abstract

Introduction of the grape phylloxera (Phylloxera vitifoliae Fitch) into the vinifera grape growing areas of the world over 100 years ago forced viticulturalists to use resistant rootstocks from central North America. This aphid destroyed more than 2,500,000 acres of vineyards in France alone only 25 years after it was introduced. Control measures other than resistant rootstocks were inadequate for phylloxera. Extensive rootstock development programs have been underway for over 100 years. The North American species, which are generally the most resistant, were studied for their adaptability to soil climate, compatability with vinifera scions, and propagation characteristics. The presently-used rootstocks originated from these studies and breeding programs. The primary objectives of the earlier workers were phylloxera resistance, tolerance to lime induced chlorosis, ease of rooting and grafting, and desirable effect on the yield and quality of scion cultivars. More recently root knot nematode resistance was incorporated in rootstocks (19, 23, 24).

Open access

Richard W. Hartmann

Abstract

Although previous workers reported that root-knot nematode resistance was controlled by 2 pairs of genes, there were more than 1/16 resistant plants in an F2 population from ‘Alabama No. 1’ (resistant) crossed with ‘Hawaiian Wonder’ (susceptible). The evaluation of F3 families showed that the excess of resistant individuals was not due to escapes. The 2-gene hypothesis was insufficient to account for the segregation patterns in the F3 families, but they could be explained on a 3-gene basis. The simplest genetic explanation is that there are at least 3 pairs of genes which are equal in their action, but a certain minimum number of genes for susceptibility are necessary before all resistance is lost.

Free access

Min Wang and I.L. Goldman

The root-knot nematode (M. hapla Chitwood) poses a threat to carrot (Daucus carota L.) production in the United States. Little information is available concerning the genetic control of nematode resistance in carrot. Crosses between two inbreds, a resistant genotype (R1) and susceptible genotype (S1) identified in previous screening tests of carrot were studied in the F2 and BC1 generations to determine the heritability of resistance to the root-knot nematode. Seedlings of F2 (R1/S1), BC1S1, and BC1R1 generations were evaluated for their responses to infestation of M. hapla Chitwood based on gall number per root, gall rating per root, and root rating per root in a greenhouse experiment conducted during 1994. Narrow-sense heritabilities were calculated according to the method of Warner (1952). Narrow-sense heritability was 0.16 for resistance based on gall number, 0.88 for resistance based on gall rating, and 0.78 for resistance based on root rating. This information may be of importance to geneticists and carrot breeders for the development of nematode-resistant carrot cultivars.

Free access

Thomas G. Beckman, Philip A. Rollins, James Pitts, Dario J. Chavez, and Jose X. Chaparro

The primary focus of the stone fruit rootstock program at Byron, GA, has been the development of disease-resistant rootstocks for peach (Prunus persica L. Batsch). Historically peach tree short life (PTSL), aka bacterial canker complex, and Armillaria root rot (ARR) have been the two most important causes of premature mortality of commercial peach trees in the southeastern United States. Guardian®, a seedling peach rootstock, was cooperatively released in 1993 by the U.S. Department of Agriculture (USDA)-Agricultural Research Service (ARS) and Clemson University. It has since been widely adopted by the southeastern peach industry. As a result, trees losses to PTSL have declined sharply. However, Guardian, like most other peach seedling rootstocks, is susceptible to ARR. ARR has now moved to the forefront as the primary cause of premature peach tree death in the Southeast. In response to this threat, the USDA-ARS in cooperation with the University of Florida, released ‘Sharpe’, a plum hybrid rootstock in 2007. Despite its broad disease resistance, ‘Sharpe’ proved unsuited for widespread commercial utilization due to its relatively poor cropping performance. In 2011, ‘MP-29’, a semidwarf, clonal, plum × peach hybrid, was released for commercial trial. ‘MP-29’s broad disease and nematode resistance, in combination with its dwarfing ability and excellent productivity, offered great promise for use in this production area and in others suffering from similar issues. Since its release, testing of ‘MP-29’ has continued both in researcher and grower trials. To date, performance has exceeded all expectations.