Effect of Inoculation with Myrothecium roridum Tode ex Fries on Seed Germination and Early Seedling Growth of 12 Cultivars of Muskmelon (Cucumis melo)

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Cucurbit Genetics Cooperative Report 8:44-45 (Article 17) 1985

Kuti, J., T. J. Ng, and G. A. Bean
University of Maryland, College Park, MD 20742 U.S.A.

Myrothecium roridum Tode ex Fries, a common soil fungus that produces mycotoxins, has been reported to be pathogenic to several plant species. McLean and Sleeth (4) reported that symptoms of pathogenicity of M. roridum on muskmelon included leaf spots, stem decline and postharvest rind decay of fruits. Recently Bruton (1) reported the devastating economic effect of the pathogen in Texas, where fruit losses occurred up to 30%. As soilborne pathogens are also known-to affect seed germination (2,3), this study was initiated to ascertain the influence of the pathogen on seed germination and seedling growth of muskmelon.

Myrothecium roridum (ATCC#52485) was isolated from a diseased melon fruit in Texas and maintained on potato dextrose agar (PDA). Twelve muskmelon cultivars were used: ‘Amarelo’ (AMR), ‘Big Daddy’ (BDY), ‘Don Juan’ (DJN), ‘Early Dawn’ (EDN), ‘Hale’s Best’ (HBT), ‘Harmony’ (HAR), ‘Hearts of Gold’ (HOG), ‘Iroquois’ (IRQ), ‘Jumbo Hale’s Best’ (JHB), “PMR 45′ (PMR), ‘Schoon’s Hardshell’ (SHS), and ‘Summet’ (SUM).

Seed Treatment: A 14-day culture of M. roridum on a PDA slant was washed twice in sterile water and a spore suspension containing 106 spores/ml prepared. Seeds were soaked for 8 hrs in either the spore suspension or sterile water.

Soil Treatment: 125 gm of sterilized oat grains were inoculated with 10 ml of a 106 spores/ml solution of M. roridum in 250 ml flasks. The cultures were grown for 25-30 days with daily agitation of the flasks for uniform fungal growth. The oat grain mixture containing the spores was then mixed with sterile sand at a ratio of 1:10 (oats/sand, w/w) in a cement mixer for 30 min.

Each treatment was sown in a randomized complete block design with 4 replications of 10 seeds each. Seeds were considered germinated when cotyledons were visible. A germination index (5) was calculated for each experiment, and seedling growth was evaluated by recording shoot dry weight after 8 weeks of growth in the greenhouse.

Analyses of variance of the results revealed significant differences among cultivars for both germination and seedling growth (Table 1). The pathogen effect was more pronounced in the seed treatment study, and cultivar responses were similar to our results with leaf tissue inoculation using M. roridum.

Table 1. Effect of Myrothecium roridum on seed germination and seedling growth of muskmelon after seed and soil treatment.

 

zMean separation in columns by Duncan’s Multiple Range Test, 5% level.

Germination Index

Shoot Dry Weight (g)
Treatment
Cv.
Treatment
Control
% of
Control
Treatment
Control
% of
Control
Soil AMR 11.2z 14.Oa 80.0 0.308c 0.352c 87.5
Soil BDY 10.4b 13.4b 77.6 0.215h 0.289f 74.4
Soil DJN 10.0bc 11.3de 88.5 0.212h 0.233h 91.0
Soil EDN 11.5a 11.8d 97.5 0.386a 0.398a 97.0
Soil HBT 10.3b 11.7d 88.0 0.234g 0.242g 96.7
Soil HAR 11.6a 13.7ab 84.7 0.187i 0.233h 80.3
Soil HOG 6.6e 9.7g 68.0 0.278d 0.337d 82.5
Soil IRQ 9.5c 11.7d 81.2 0.246fg 0.311e 79.1
Soil JHB 8.3t 10.1f 82.2 0.366b 0.382b 95.8
Soil PMR 10.5b 11.1e 94.6 0.370b 0.389b 95.1
Soil SHS 4.1f 7.4h 55.4 0.105j 0.194i 54.1
Soil SUM 6.5e 12.5e 52.0 0.261e 0.337d 90.0
Seed AMR 7.5d 14.7a 51.0 0.283b 0.383a 73.9
Seed BDY 6.1e 10.8e 56.5 0.240f 0.367c 65.4
Seed DJN 7.9d 13.2bc 59.8 0.269cd 0.337e 79.8
Seed EDN 11.4a 12.6c 90.5 0.343a 0.368bc 93.2
Seed HBT 8.6c 12.7c 67.7 0.258d 0.295h 87.5
Seed HAR 3.8g 13.9b 27.3 0.159h 0.257i 61.9
Seed HOG 7.3d 10.4e 70.2 0.255d 0.362cd 70.4
Seed IRQ 5.8ef 11.6t 50.0 0.246ef 0.358d 68.7
Seed JHB 8.6c 13.8b 62.3 0.269c 0.331f 81.3
Seed PMR 10.6b 11.6d 91.4 0.345a 0.380ab 90.8
Seed SHS 3.2g 7.4f 43.2 0.121i 0.219j 55.3
Seed SUM 5.3f 14.3a 37.1 0.192g 0.319g 60.2

Literature Cited

  1. Bruton, B. D. 1982. Myrothecium roridum, a probable devastating pathogen of
    muskmelon in south Texas. Phytopath. 72:355 (Abstr.).
  2. Drake, G. N. 1980. Effect of Myrothecium roridum on the germination of cotton seeds. Indian Phytopath. 33:591-593.
  3. Harper, S. H. and J. M. Lynch. 1981. Effects of fungi on barley seed germination. J. Gen. Microbiol. 122:55-60.
  4. McLean, D. M. and B. Sleeth. 1961. Myrothecium rind rot of cantaloupes. Plant Dis. Reptr. 45:728-729.
  5. Ng, T. J. and E. C. Tigchelaar. 1973. Inheritance of low temperature seed sprouting in tomato. J. Amer. Soc. Hort. Sci. 98:314-316.