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Cucurbit Genetics Cooperative Report 14:19-21 (article 8) 1991

Correlation of Shoot Weight with Root Galling in Cucumis spp. Inoculated with Root-knot Nematodes

Todd C. Wehner, S. Alan Walters and Kenneth R. Barker

Department of Horticultural Science (first and second authors) and Department of Plant Pathology (third author), North Carolina State University, Raleigh, NC 27695-7609

Root-knot nematodes (Meloidogyne spp.) are the most important pathogen of cucumbers (Cucumis sativus L.) in North Carolina. Root-knot nematodes destroy approximately 12% of the crop in the state annually (4). Root-knot nematodes reduce fresh weight of plants (i.e. plant stunting) as well as reducing plant yields (i.e. fruit production).

Methods. A greenhouse study was conducted to determine whether shoot weight and root galling were correlated in six Cucumis cultigens (C. sativus L. cv. Sumter and C. metuliferus Naud. PI 482448, PI 482450, PI 482452, PI 482454 and PI 482461). Root Galling was induced by inoculation of seedlings with one of four different species of root knot nematodes, M. hapla, M. arenaria race 1, M. incognita race 1, and M. javanica. The experiment was a factorial treatment arrangement in a randomized complete block design with four replications. Each treatment combinations consisted of one Cucumis cultigen and one root knot nematode species in a 100-mm diameter (1450 cm3 volume) pot. Pots contained sterilized sand and soil in a 1:1 ratio. Plants were grown from seed, with one plant per pot.

Inoculum was prepared using the technique developed by Hussey and Barker (3). Each pot was inoculated two weeks after planting with 5000 root-knot nematode eggs of the appropriate root-knot nematode species or race. Plants were rated after 10 weeks after planting for root-knot nematode damage (0 to 100% of roots galled), and shoot fresh weight.

Results. 'Sumter' had the lowest overall shoot weight and the highest percentage of galled roots, which indicated that it was the most susceptible cultigen tested (Table 1). However, 'Sumter' did not differ significantly from the other cultigens tested with respect to mean shoot weight. 'Sumter' was the most susceptible cultigen to M. incognita race 1, significantly different from the four plant introduction accessions of C. metuliferus (PI 482450, PI482452, PI482454 and PI 482461). With respect to mean percentage root galls, 'Sumter' was significantly different from the accessions of C. metuliferus tested. An accession of C. metuliferus, PI 482452, was the least susceptible cultigen tested, having a mean shoot weight of 514 g, and 35% of the roots galled.

Table 1. Shoot fresh weight (ShWt) and percentage of roots galled (%G) of 'Sumter' (C. sativus) and 5 accessions of C. metuliferus inoculated with 4 species of root-knot nematodes.z

 

Mean

Mh

Ma1

Mi1

Mj

Cultigen

ShWt

%G

ShWt

%G

ShWt

%G

ShWt

%G

ShWt

%G

PI 482452

514

35

529

6

448

36

484

50

596

46

PI 482454

499

42

552

6

588

40

420

60

434

60

PI 482450

469

43

552

6

367

60

448

66

510

41

PI 482461

478

50

546

16

493

56

417

80

456

46

PI 482448

413

56

398

20

445

50

381

86

428

66

Sumter

389

80

423

30

434

96

258

96

442

96

Mean

460

51

501

14

462

56

400

73

479

59

LSD (5%) for row-column comparisons of means

135

22

 

 

 

 

z Data are means of replications of 1 plant each. Shoot weight is in grams. Mh = M. hapla, Ma1 = M. arenaria race 1, Mi1= M. incognita race 1, and Mj = M. javanica.

Root galling was negatively correlated (-0.38) with shoot fresh weight (Table 2), as expected. Thus, susceptible plants with many root galls had a lower shoot weight than a resistant ones. Correlations were largest for plants inoculated with M. hapla or M incognita race 1, whereas plants inoculated with M. arenaria race 1 or M. javanica had only small negative correlations. The most pathogenic species tested was M. incognita race 1, indicated by the lowest shoot fresh weight and the highest percentage root galling (Table 1). The least pathogenic species tested was M. hapla.

Table 2. Correlations of fresh shoot weights and gall indices for each species of root-knot nematodes tested.z

Correlation

Overall

Mh

Ma1

Mi1

Mj

Shoot wt. vs. gall index

-0.38

-0.64

-0.08

-0.58

-0.01

z Mh = M. hapla, Ma1 = M. arenaria race 1, Mi1= M. incognita race 1 and Mj = M. javanica.

These results confirm previous work showing that species of Cucumis are resistant to M. hapla (5, 6) and 'Sumter' (C. sativus) is more susceptible to root-knot nematodes than are accessions of C. metuliferus (1, 2). In addition, shoot fresh weight might be a useful trait to aid in the selection for nematode resistance.

Literature Cited

  1. Boukema, I. W., G. T. M. Reuling and K. Hofman. 1984. The reliability of a seedling test for resistance to root know nematode in cucurbits. Cucurbit Genetics Coop. Rpt. 7:92-93.
  2. Fassuliotis, G. 1967. Species of Cucumis resistant to the root-knot nematode, Meloidogyne incognita acrita. Plant Dis. Rptr. 51 (9):720-723.
  3. Hussey, R. S. and K. R. Barker. 1973. A comparison of methods of collecting inocula of Meloidogyne spp., including a new technique. Plant Dis. Rptr. 12: 1025-1028.
  4. Main, C. E. and S. K. Gurtz (eds.). 1989. 1988 estimates of crop losses in North Carolina due to plant diseases and nematodes. Dept. of Plant Path. Spec. Publ. No. 8, North Carolina State Univ., Raleigh, NC.
  5. Walters, S. A., T. C. Wehner and K. R. Barker. 1990. Resistance of the cucumber to the root-knot nematode, Meloidogyne hapla. Cucurbit Genetics Coop. Rpt. 13: 10-11.
  6. Winstead, N. N. and J. N. Sasser. 1956. Reaction of cucumber varieties to five root-knot nematodes (Meloidogyne spp.). Plant Dis. Rptr. 40(4): 272-275.
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Page citation: Wehner, T.C., Cucurbit Genetics Cooperative;
Created by T.C. Wehner and T. Ng, 1 June 2005; design by C.T. Glenn;
send questions to T.C. Wehner; last revised on 9 November, 2009