Cucurbit Genetics Cooperative Report 17:106-110 (article 32) 1994
G.E. Boylan, J.D. Norton and B.R. Abrahams
Department of Horticulture, Alabama Agricultural Experiment Station, Auburn University, AL 36849
Over the past six years Auburn University has increased watermelon germplasm for the USDA-ARS. This germplasm has been routinely screened for resistance to gummy stem blight, root knot nematodes and race 2 anthracnose. To date 138 watermelon accessions have been screened for resistance to these diseases (Table 1).
Each accession evaluated for gummy stem blight resistance was arranged in a completely randomized block design with three replications and eight seed planted for each accession within a replication. Plants were grown in 28 x 53 cm flats in Metromix 300 (Cambridge, MA).
Gummy stem blight (Didymella bryoniae (Auersw.) Rehm,) inoculum was prepared from culture number BJH 602-5 obtained from Dr. M. J. Havey, University of Wisconsin. The fungal cultures were maintained on PDA and grown for inoculation purposes on sterile green beans. Spore suspensions in sterile water were adjusted to 100,000 spores per ml. using a hemocytometer (3). This spore suspension was sprayed to runoff on two week old seedlings which were then incubated at 100% relative humidity and 25 ˚ C for 48 hours. After incubation seedlings were placed in a greenhouse (20-35 ˚ C) for two weeks at which time the I-9 scale with 1 indicating resistance and 9, susceptibility.
Resistance to anthracnose (Colletorichum orbiculare (Pass.) Ell. & Halst.) race 2 was handled in a similar fashion to gummy stem blight. The culture used was CP3 from Dr. J.C. Correll of the University of Arkansas. The spore suspension was adjusted to 50,000 spores per ml (5).
Root knot nematode (Meloidogyne incognita) (Kofoid and White) Chitwood) races 3 and 4 were used by continual cropping of susceptible tomato and cotton plants (4) in a root knot nematode infested soil. These plants were greenhouse grown in rotation in a sandy-loam soil obtained from the E.V. Smith Plant Breeding Unit, Shorter, AL. Nematode eggs were obtained from these tomato or cotton roots by placing roots in a closed contained containing a 10% clorox solution which was shaken for four minutes. This solution containing the nematode eggs was passed through an 80, 200, and 500 mesh screen with the eggs collected on the 500 mesh screen and adjusted, using a hemocytometer, in a sterile water solution to 2,500-3,000 eggs per ml (1). One ml. of this solution was placed in a 7.5 cm pot containing a nematode free sandy-loam soil. Two seed of each accession was planted in each pot so inoculated. The experimental design was a completely randomized block design of three replications with three pots for each accession within a replication. Plants were lifted and the roots carefully washed and evaluated one month after planting on a 1-9 scale with 1 indicating resistance and 9, susceptibility.
As seed increases for accessions were completed, they were evaluated for resistance. Thus, these accessions were not evaluated all at the same time for the three diseases, therefore caution should be exercised in interpreting these results, due to the subjective nature of rating scales and changes in test conditions. The top five accessions for gummy stem blight (GSB) resistance were PIs 500335, 505590, 512373, 164247, and 500334 with ratings of 1.8, 1.9, 1.9, 2.1 and 2.2 respectively. The top 5 PIs for root-knot nematode resistance are 512369, 164247, 494815, 532811, and 500329 with ratings of 2, 2.8, 3.3, 3,3, and 3.4 respectively. Finally, the top 5 performers with respect to race 2 anthracnose are PIs 502318, 505592, 500329, 505593, and 500315 with ratings of 1.4, 1.7, 1.8, 1.9 and 1.9 respectively.
Resistance to GSB and anthracnose race 2 have been found in several PIS and have been successfully incorporated into watermelon varieties (2). The PIs listed here may be additional sources of resistance, however, additional testing is required to confirm this. It should be noted that there is no widely accepted source of resistance to root-knot nematode in watermelon. Our testing method used a lower concentration of nematodes (2,500-3,000 eggs/ml.) compared to the standard method of 8,000 eggs/ml. The relatively low ratings of these accessions may be due to the lower egg counts; however, these results warrant further investigation and selection.
Table 1. Plant introduction means, standard erros and numbers of entries for resistance to gummy stem blight (GSB), nematodes, and anthracnose (race 2).
GSB |
Nematodes |
Anthracnose |
|||||||
Plant Introduction |
Ratingz |
+SE |
No. of entries |
Ratingz |
+SE |
No. of entries |
Ratingz |
+SE |
No. of entries |
| 164247 | 2.1 | 0.3 | 3 | 2.8 | 0.4 | 3 | 8.4 | 0.4 | 3 |
| 167126 | 3.5 | 0.6 | 3 | 6.2 | 1.3 | 3 | 7.2 | 1.2 | 3 |
| 487458 | 5.9 | 0.7 | 3 | 6.7 | 1.2 | 3 | 3.0 | 0.6 | 3 |
| 187459 | 2.7 | 0.6 | 3 | 5.8 | 0.7 | 3 | 3.5 | 2.3 | 3 |
| 487476 | 5.4 | 0.3 | 3 | 5.3 | 1 | 3 | 3.2 | 0.5 | 3 |
| 494815 | 6.1 | 0.3 | 2 | 3.3 | 0.2 | 3 | 2.8 | 0.3 | 3 |
| 494816 | 4.4 | 0.7 | 3 | 5.1 | 1.1 | 3 | 2.3 | 0.1 | 3 |
| 494817 | 2.3 | 0.5 | 3 | 4.7 | 0.9 | 3 | 2.3 | 0.5 | 3 |
| 494818 | 7.7 | 1.3 | 2 | 3.7 | – | 1 | – | – | – |
| 494819 | 4.5 | 1 | 3 | 4.4 | 1.3 | 3 | 3.7 | 1.7 | 3 |
| 494820 | 3.4 | 0.7 | 3 | 5.6 | 1.7 | 3 | 4.6 | 2.2 | 3 |
| 494821 | 5.3 | 0.2 | 3 | 5.3 | 1.5 | 3 | 5.3 | 1.9 | 3 |
| 500306 | 3.9 | 0.4 | 3 | 5.8 | 1.5 | 3 | 4.1 | 1.8 | 3 |
| 500309 | 2.4 | 0.8 | 3 | 4.8 | 0.2 | 3 | 2.7 | 0.6 | 3 |
| 500310 | 3.9 | 0.3 | 3 | 6.4 | 1.3 | 3 | 4.0 | 1.0 | 3 |
| 500312 | 3.5 | 0.8 | 3 | 5.4 | 0.9 | 3 | 3.8 | 0.6 | 3 |
| 500315 | 4.8 | 1.3 | 6 | 4.6 | 0.8 | 3 | 1.9 | 0.3 | 3 |
| 500317 | 4.5 | 0.5 | 3 | 6.1 | 0.6 | 3 | 2.6 | 0.1 | 3 |
| 500327 | 3.3 | 0.7 | 3 | 4.3 | 1.1 | 3 | 2.1 | 0.1 | 3 |
| 500329 | 2.7 | 0.9 | 3 | 3.4 | 0.1 | 3 | 1.8 | 0.2 | 3 |
| 500331 | 3.1 | 0.9 | 3 | 3.7 | 0.7 | 3 | 3.9 | 0.3 | 2 |
| 500332 | 2.9 | 0.3 | 3 | 6 | 1.5 | 3 | 3.5 | 0.9 | 3 |
| 500334 | 2.2 | 0.2 | 6 | 7 | 0.7 | 3 | 2.0 | 0.1 | 3 |
| 500335 | 1.8 | 0.3 | 3 | 4 | – | 1 | 3.2 | 0.7 | 3 |
| 500337 | – | – | – | – | – | – | 2.2 | – | 1 |
| 500345 | – | – | – | 8 | 0.6 | 3 | 2.4 | 0.3 | 6 |
| 500353 | 4.3 | 1.1 | 3 | 6 | 1.3 | 3 | 2.9 | 0.7 | 3 |
| 502315 | 5.4 | 0.9 | 6 | 7.1 | 0.6 | 6 | 3.3 | 1.0 | 6 |
| 502316 | – | – | – | 4.3 | – | 1 | – | – | – |
| 502317 | 4.8 | 0.6 | 2 | 7 | 0.9 | 4 | 3.1 | 1.2 | 3 |
| 502318 | 6 | 1.1 | 3 | 7 | – | 1 | 1.4 | 0.1 | 3 |
| 502319 | 8.5 | 0.5 | 3 | 7.3 | 1.3 | 2 | 2.2 | 0.2 | 3 |
| 504519 | 5 | 1.3 | 2 | 5 | 1.5 | 3 | 1.9 | 0.6 | 3 |
| 505584 | 4.3 | 1.4 | 3 | 6.6 | 0.8 | 3 | 2.4 | 0.5 | 3 |
| 505585 | 4.1 | 0.6 | 4 | 6.1 | 1.2 | 2 | 2.9 | 0.6 | 3 |
| 505586 | 2.5 | 0.5 | 3 | 8.5 | 0.5 | 3 | 4.2 | 0.9 | 3 |
| 505587 | 4.3 | 0.5 | 2 | 5.2 | 0.8 | 3 | 2.3 | 0.4 | 3 |
| 505588 | 5.1 | 0.9 | 3 | 6.4 | 1.5 | 3 | 3.8 | 1.3 | 3 |
| 505589 | 3.3 | 0.9 | 3 | 5 | 0.7 | 2 | 2.3 | 0.2 | 3 |
| 505590 | 1.9 | 0.3 | 3 | 6.5 | 0.5 | 2 | 2.0 | 0.1 | 3 |
| 505591 | 4.1 | 1 | 3 | 6 | 1.2 | 3 | 1.9 | 0.3 | 3 |
| 505592 | 2.9 | 1 | 4 | 5.3 | 1.4 | 3 | 1.7 | 0.3 | 3 |
| 505593 | 2.9 | 0.5 | 4 | 4.9 | 0.9 | 3 | 1.9 | 0.4 | 3 |
| 505594 | 3.6 | 0.8 | 3 | 6.4 | 1.4 | 3 | 2.4 | 0.4 | 3 |
| 505595 | 3.6 | 0.7 | 2 | 4.6 | 0.2 | 3 | 3.0 | 0.6 | 3 |
| 505935 | 4.4 | 0.7 | 6 | 5 | 0.6 | 6 | 8.4 | 0.3 | 3 |
| 506439 | 4.8 | 0.7 | 3 | 4.3 | 1.3 | 2 | 2.7 | 0.4 | 3 |
| 507858 | 5.1 | 1 | 3 | 5.8 | 0.9 | 3 | 3.3 | 0.5 | 3 |
| 507859 | 8.6 | 0.4 | 3 | 7.4 | 0.4 | 3 | 2.7 | 0.7 | 3 |
| 507860 | 3.8 | 1.3 | 2 | 6.7 | 0.9 | 3 | 6.1 | 1.5 | 3 |
| 507861 | 5.2 | 1.1 | 3 | 6.3 | 1 | 3 | 2.0 | 0.1 | 3 |
| 507863 | 6 | 0.2 | 3 | 8.5 | 0.5 | 2 | 4.3 | 1.5 | 3 |
| 507864 | 6.8 | 1.1 | 3 | 7.8 | 0.7 | 3 | 2.1 | 08 | 3 |
| 507865 | 9 | 0 | 3 | 7.7 | 0.7 | 3 | 8.9 | 0.1 | 3 |
| 507866 | 7.7 | 0.7 | 3 | 8.1 | 0.9 | 3 | 7.6 | 1.3 | 3 |
| 507867 | 4.9 | 1.4 | 3 | 7.9 | 0.3 | 3 | 3.1 | 0.9 | 3 |
| 507868 | 7.8 | 0.4 | 3 | 8.8 | 0.2 | 3 | 3.5 | 1.1 | 3 |
| 507869 | 8.6 | 3 | 8.7 | 0.1 | 3 | 5.8 | 1.3 | 1.3 | 3 |
| 508441 | 5.8 | 3 | 8.1 | 0.2 | 3 | 4.4 | 1.0 | 1.0 | 33 |
| 508442 | 7.7 | 3 | 7.9 | 0.9 | 3 | 2.6 | 0.6 | 0.6 | 2 |
| 508443 | 8.4 | 3 | 7.3 | 0.9 | 3 | 3.7 | 2.7 | 2.7 | 3 |
| 508444 | 8.5 | 3 | 8.8 | 0.1 | 3 | 2.6 | 0.5 | 0.5 | 3 |
| 508445 | 6.4 | 3 | 7.6 | 1.1 | 3 | 5.2 | 1.8 | 1.8 | 3 |
| 508446 | 7.4 | 3 | 7.8 | 0.3 | 3 | 4.2 | 1.3 | 1.3 | 3 |
| 512331 | 6.8 | 3 | 7.3 | 0.7 | 3 | 3.8 | 2.6 | 2.6 | 3 |
| 512332 | 8 | 3 | 8.6 | 0.2 | 3 | 3.6 | 1.9 | 1.9 | 3 |
| 512339 | 5.7 | 6 | 7.8 | 0.6 | 6 | 6.3 | 1.5 | 1.5 | 5 |
| 512340 | 3.2 | 3 | 5.5 | 3.5 | 2 | 7.9 | 0.1 | 0.1 | 3 |
| 512341 | 8.3 | 2 | 7 | 0.7 | 3 | 5.4 | 1.1 | 1.1 | 3 |
| 512342 | 8.4 | 0.4 | 3 | 8.2 | 0.3 | 3 | 8.3 | 0.4 | 3 |
| 512343 | 7.5 | 0.8 | 3 | 8.8 | 0.2 | 3 | 4.5 | 1.5 | 3 |
| 512344 | 7.1 | 1.3 | 3 | 7 | 2 | 3 | 5.7 | 1.4 | 3 |
| 512345 | 8.2 | 0.8 | 3 | 7.2 | 0.9 | 3 | 2.5 | 0.5 | 3 |
| 512346 | 3 | 0.1 | 3 | 8 | – | 1 | 9.0 | 0.0 | 3 |
| 512347 | 8.9 | 0.1 | 3 | 5 | 1.5 | 3 | 7.2 | 1.0 | 3 |
| 512348 | 8.9 | 0 | 3 | 6.6 | 1 | 3 | 4.6 | 0.6 | 3 |
| 512349 | 8.6 | 0.2 | 3 | 8.1 | 0.3 | 3 | 5.5 | 1.6 | 3 |
| 512350 | 5 | 1.6 | 5 | 4.3 | 1.4 | 4 | 7.7 | 1.0 | 3 |
| 512351 | 5.1 | 1.1 | 5 | 5.7 | 0.9 | 6 | 5.9 | 1.4 | 6 |
| 512352 | 4.3 | 0.7 | 6 | 6.5 | 0.8 | 6 | 6.4 | 1.4 | 6 |
| 512353 | 3.9 | 1.6 | 2 | 5.6 | 0.7 | 3 | 2.4 | 0.6 | 3 |
| 512354 | 6.3 | 0.8 | 3 | 7 | 1 | 3 | 8.6 | 0.3 | 3 |
| 512355 | 6.2 | 0.9 | 6 | 6.2 | 1.1 | 6 | 6.5 | 1.6 | 5 |
| 512356 | 5.5 | 1.2 | 6 | 5.5 | 1 | 6 | 5.8 | 1.3 | 6 |
| 512358 | 5.6 | 2.2 | 3 | 8.6 | 0.3 | 3 | 2.9 | 1.3 | 3 |
| 512359 | 4.3 | 0.9 | 6 | 7.5 | 0.7 | 6 | 5.9 | 1.3 | 6 |
| 512360 | 5 | 1.2 | 6 | 5 | 0.5 | 5 | 5.1 | 1.1 | 6 |
| 512361 | 4.4 | 1.6 | 4 | 6.5 | 0.7 | 5 | 8.9 | 0.1 | 5 |
| 512362 | 5.2 | 2.6 | 5 | 7.6 | 1 | 3 | 7.7 | 0.2 | 3 |
| 512363 | 1.1 | 0.2 | 3 | 6 | 1.2 | 3 | 8.8 | 0.2 | 3 |
| 512364 | 3.7 | 0.7 | 3 | 6.3 | 1.8 | 2 | 8.7 | 0.2 | 3 |
| 512365 | 8.8 | 0.2 | 3 | 7.7 | 1 | 3 | 3.6 | 1.5 | 3 |
| 512366 | 3.5 | 0.2 | 3 | 4.9 | 1.6 | 3 | 9.0 | 0.0 | 3 |
| 512367 | 3.5 | 0.2 | 3 | 5.5 | 2.5 | 2 | 9.0 | 0.0 | 3 |
| 512368 | 3.9 | 0.3 | 3 | 7.1 | 0.5 | 3 | 7.8 | 0.0 | 3 |
| 512369 | 4.5 | 0.1 | 3 | 2 | – | 1 | 7.0 | 0.9 | 3 |
| 512370 | 3.2 | 0.2 | 3 | 5.8 | 1.5 | 3 | 7.7 | 0.7 | 3 |
| 512373 | 1.9 | 0.1 | 3 | 7.5 | 0.3 | 3 | 8.9 | 0.1 | 3 |
| 512374 | 3.3 | 0.4 | 3 | 5.8 | 0.8 | 2 | 8.3 | 0.3 | 3 |
| 512375 | 2.7 | 0.2 | 3 | 7.4 | 0.6 | 3 | 8.5 | 0.3 | 3 |
| 512376 | 3.1 | 0.3 | 3 | 6.4 | 0.7 | 3 | 8.1 | 0.5 | 3 |
| 512377 | 2.5 | 0.5 | 3 | 7 | – | 1 | 8.6 | 0.3 | 3 |
| 512378 | 3.6 | 0.7 | 3 | 5.5 | 1.9 | 3 | 7.7 | 0.7 | 3 |
| 512379 | 3.5 | 0.4 | 3 | 6.8 | 0.8 | 2 | 7.8 | 0.2 | 3 |
| 512381 | 3.4 | 0.6 | 3 | 6.9 | 0.7 | 3 | 8.0 | 0.3 | 3 |
| 512382 | 3.1 | 0.2 | 3 | 8 | – | 1 | 8.9 | 0.1 | 2 |
| 512383 | 3.1 | 0.7 | 3 | 7.7 | 0.2 | 3 | 7.9 | 0.6 | 3 |
| 512384 | 3.2 | 0.2 | 3 | 6.3 | 0.7 | 3 | 8.7 | 0.3 | 3 |
| 512385 | 5.6 | 0.8 | 3 | 5.7 | 1.3 | 3 | 4.5 | 1.1 | 3 |
| 512386 | 4.2 | 0.8 | 3 | 5.9 | 0.8 | 3 | 8.6 | 0.4 | 3 |
| 512387 | 2.8 | 0.2 | 3 | 9 | – | 1 | 8.4 | 0.3 | 3 |
| 512388 | 4.3 | 1.1 | 3 | 7.8 | 0.2 | 3 | 8.1 | 0.5 | 3 |
| 512389 | 2.9 | 0.2 | 3 | 6.3 | 0.8 | 3 | 8.6 | 0.2 | 3 |
| 512390 | 3.1 | 0.6 | 3 | 5.1 | 1.2 | 3 | 8.2 | 0.5 | 3 |
| 512391 | 2.4 | 0.1 | 3 | 7.8 | 0.7 | 3 | 8 | 0.2 | 3 |
| 512392 | 2.6 | 0.3 | 3 | 7 | 1 | 2 | 7 | 0.0 | 3 |
| 512393 | 3.6 | 0.4 | 6 | 5.9 | 0.9 | 6 | 9.0 | 0.5 | 3 |
| 512394 | 2.9 | 0.2 | 3 | 7.2 | 1 | 3 | 8.1 | 0.5 | 3 |
| 512395 | 3.2 | 0.3 | 3 | 6.6 | 1.1 | 3 | 8.5 | 0.4 | 3 |
| 512396 | 3.3 | 0.5 | 3 | 8.3 | 0.3 | 2 | 8.3 | 0.1 | 3 |
| 512397 | 3.5 | 0.4 | 3 | 7.8 | 0.8 | 2 | 8.8 | 0.5 | 3 |
| 512398 | 3.3 | 0.4 | 3 | 4.6 | 1.2 | 3 | 8.3 | 0.4 | 3 |
| 512399 | 2.9 | 0.4 | 3 | 7.5 | 0.3 | 3 | 8.2 | 0.3 | 3 |
| 512400 | 2.6 | 0.2 | 3 | 7.3 | 0.7 | 3 | 8.5 | 0.9 | 3 |
| 512401 | 3.6 | 0.1 | 3 | 6.8 | 0.8 | 3 | 7.6 | 0.2 | 3 |
| 512402 | 3.3 | 0.8 | 3 | 6.3 | 0.8 | 2 | 8.0 | 0.5 | 3 |
| 512403 | 3.5 | 0.4 | 3 | 5.6 | 0.3 | 3 | 8.8 | 0.1 | 3 |
| 512404 | 2.8 | 0.8 | 3 | 6.9 | 0.5 | 3 | 9.0 | 0.0 | 3 |
| 512405 | 3.5 | 0.3 | 3 | 7.2 | 0.4 | 3 | 8.6 | 0.3 | 3 |
| 512406 | 3.5 | 1.2 | 3 | 7 | 1 | 3 | 8.5 | 0.4 | 2 |
| 512407 | 3.1 | 0.1 | 3 | 7.3 | 0.5 | 3 | 6.5 | 0.3 | 3 |
| 532811 | 3.7 | 0.6 | 3 | 3.3 | 1.8 | 2 | 7.0 | 1.1 | 3 |
| 534593 | 4.3 | 0.6 | 4 | 4.9 | 0.9 | 6 | 8.7 | 0.3 | 3 |
| 537461 | 2.3 | 0.1 | 3 | 6.5 | 0.5 | 3 | 8.8 | 0.2 | 3 |
| 537465 | 3.1 | 0.4 | 5 | 5.6 | 0.4 | 3 | 8.3 | 0.0 | 3 |
| 537467 | 2.4 | 0.4 | 3 | 7.5 | 1 | 2 | 6.8 | 0.8 | 3 |
| 537468 | 3 | 0.7 | 3 | 4.7 | 1.4 | 3 | 7.9 | 0.8 | 3 |
| 537470 | 3.8 | 0.5 | 3 | 7.7 | 1.3 | 3 | 8.7 | 0.3 | 3 |
zRatings: 1-9 with 1-resistant and 9-susceptible.
Literature Cited
- Hussey, R.S. and K.R. Barker. 1973. A comparison of methods of collecting inocula of Meloidogyne spp., including a new technique. Plant Disease Reporter 57:1025-1028.
- Norton, J.D., Cosper, R.D., Smith, D.A. and K.S. Rymal. 1985. AU-Jubilant & AU-Producer quality, disease-resistant watermelon varieties for the south. Ala. Agr. Exp. Stat. Cir. 280.
- Norton, J.D. 1979. Inheritance of resistance to gummy stem blight in watermelon. HOrtScience. 14:630-632.
- Sasser, J.N. and C.C.Carter. 1982. Root-knot nematodes (Meloidogyne spp.): identification, morphological & physiological variation, host range, ecology, and control in: Nematology of the Southern Region of the United States. South. Coop. Bull. 276:21-32.
- Suvanprakorn, K. and J.D. Norton. 1980. Inheritance of resistance to race 2 anthracnose in watermelon. J. Amer. Soc. Hort. Sci. 105:862-865.