Response of Muskmelon Cultivars to Bacterial Wilt (Erwinia tracheiphila [E.F. Smith] Holland)

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Cucurbit Genetics Cooperative Report 5:26-27 (article 13) 1982

K. W. Owens
Department of Horticulture, University of Wisconsin, Madison, WI 53706

C. E. Peterson
U.S. Department of Agriculture, Agricultural Research Service, University of Wisconsin, Madison, WI 53706

Bacterial wilt (BW) is a serious disease of muskmelon in the Midwest and Northeast U.S. The disease is caused by the bacteria Erwinia tracheiphila (E.F. Smith) Holland and overwinters in and is transmitted by cucumber beetles, Acalymma vittata, Diabrotica undecimpunctata Howardi and D. balteata Le Conte. Little work has been done on BW resistance in muskmelons (3, 4, 5) and no inheritance studies have reported to date. No high degree of resistance to BW has been found, so insecticides are the only control measure used.

In this study we adopted the screening methods developed by Abul-Hayja (1) and used by the USDA cucumber breeding program to screen for BW resistance in cucumbers. Briefly, the procedure consists of growing 40-60 seedlings of each of the 12 entries in fats of sterilized vermiculite in the greenhouse. The cotyledon or first true leaf is inoculated using a 2.25 cm2 flower frog dipped in a bacterial suspension prepared by grinding infected cucumber hypocotyl sections in a mortar and pestle. Symptoms in the seedling plants were allowed to develop in the greenhouse at approximately 25°C and 16 hr. photoperiod. Seedlings were inoculated three times at six day intervals and were evaluated 21 days after the first inoculation. A mean disease rating and a percent survival score were given to each entry. Controls were the resistant USDA cucumber breeding line W1589; the susceptible cucumber cultivar, Wis. SMR 18; and ‘Perlita’, a susceptible muskmelon. The controls were inoculated only once to determine the percentage of escapes.

There were major differences among the cultivars for mean disease rating and percent survival (Table 1). Both ‘Burrell Gem’ and ‘Super Market F1’ showed good growth 21 days after inoculation and 80-90% survival. In contrast, the ‘Honeydew’ and ‘Casaba’ melons were very susceptible to BW. There were approximately 2-15% escapes from the first inoculation.

BW resistance in cucumber is controlled by a single dominant gene (2). In muskmelons it appears that the nature of the resistance is more complex and is manifested by gradual necrosis and slow spread of the bacteria through the tissues. If resistance is quantitative, future tests should use a uniform, known inoculum concentration, as with a bacterial suspension in buffer, so that each plant is exposed to the same selection pressure to reduce escapes and avoid confounding disease ratings with differences in inoculum concentrations and the rate of symptom development. Once sources of partial resistance are identified in Cucumis melo, a recurrent selection procedure could be utilized to accumulate favorable genes for a high level of resistance.

Table 1. Mean disease rating and percent survival of muskmelon cultivars screened for bacterial wilt resistance.

Entry

Mean disease ratingz

% survival
Imperial 45 4.2 57
Burrell Gem 2.3 83
Super Market F1 2.2 88
Banana 3.6 63
HOney Dew-Morgan 4.9 6
Casaba – Golden Beauty 5.0 0
Far North 4.8 15
Honey Dew – Green Flesh 5.0 2
Iroquois 2.8 66
M986 5.0 0
Yellow Canary 4.6 16
Ananas 4.6 13
W1589y (resistant cucumber) – 100
Wis. SMR 18y (susceptible cucumber) – 2
Perlita y – 15

z Mean disease rating based on following scale: 0=No bacterial transmission, excellent plant growth; 1=Little bacterial transmission, excellent plant growth; 2=Transmission of bacterial, good growth of the plant; 3=Transmission of bacteria, some new growth of the plant; 4=Transmission of bacteria, severe wilting but the plant survives; 5=Plants are killed by BW.
y Control entries; inoculated only once.

Literature Cited

  1. Abul-Hayja, Z.M. 1975. Multiple disease screening and genetics of resistance in cucumber. University of Wisconsin-Madison, Ph.D. thesis.
  2. Nuttall, V.W. and J.J. Jasmin. 1958. The inheritance of resistance to bacterial wilt (Erwinia tracheiphila [E.F. Smith] Holland) in cucumber. Can. J. Plant Sci. 38:401-404
  3. Reed, G. 1981. Personal communication. USDA, ARS, Vincennes, IN 47591.
  4. Watterson, J.C. 1971. Cucurbit responses to Erwinia tracheiphila and the multiplication and movement of the bacterium in selected resistant and susceptible cucurbits. University of Wisconsin-Madison. M.S. thesis.
  5. Yu, T.F. 1933. Pathological and physiological effects of Bacillus tracheiphilus E.F. Smith on species of Cucurbitaceae. Nanking J. 3:47-128.