Cucurbit Genetics Cooperative Report 23:37-40 (article110) 2000
J. Jain and V.K. Verma
Division of Vegetable Crops, IARI, New Delhi, 110012, India
Muskmelon, Cucumis melo L. is an important cucurbitaceous crop, being grown extensively in the garden land and riverbeds. Most important limiting factors in the production of muskmelon are devastating diseases like Fusarium wilt, GCMMV and mildews. Therefore, emphasis has been given to utilize available genotypes/accessions to identify and incorporate genes for disease resistance (Fusarium wilt, CGMMV and powdery mildew etc.), fruit quality attributes (fruit weight, fruit shape, flesh color, flesh thickness, bitterness/sweetness etc.) and vegetative characters (e.g. seedling marker, plant habit).
Several multiple-disease resistant genotypes and accessions have been identified and screened as a step towards variety improvement. Efforts are underway to combine multiple-disease resistance and superior quality attributes.
Materials and Methods. Seventeen genotypes were selected based on available descriptions in the Cucumis melo L.gene list (4) and information obtained through correspondence. These lines were characterized for vegetative and fruit traits. Seed viability was tested under controlled greenhouse conditions. Major disease screening (Fusarium wilt, powdery mildew, virus [e.g., CGMMV].) was conducted under field conditions at various stages of development up to fruit harvest. Several fruit characters were evaluated (See Table 2) and nutritional traits (total soluble solids [TSS], ascorbic acid) were also collected (Table 3). Standardized cropping practice was in the field during three years.
Total soluble solids (TSS) was measured using a hand refractioner and ascorbic acid content (mg/l 100 gm sample) was calculated based on a 2,6-dichlorophenol-indophenol visual titration method (6).
Results. Eight accessions (Table 1) obtained from INRA, Montfavet, France, were identified based on their field resistance (PDI < 25%) to Fusarium wilt, powdery mildew, and native viruses. Flesh color and plant habit were also characterized. ‘MR-1’ is a multiple disease resistant genotype (Table 1), known to possess genes for Fusarium wilt resistance (Fom-1, Fom-2) and powdery mildew resistance (Pm-H), PI 414723 (Pm-x), ‘PMR 5’ (Pm-2, Pm-E) and ‘WMR 29’ (Pm-w). Flesh color was found to be white, green and salmon in eight secessions with compact plant habit known to be contributed by si-1 gene in ‘Top Mark Bush’.
Seed viability based on percent germination was found to be greater than 33% under controlled greenhouse conditions. In the field, maximum fruit settling occurred in WMR-29 (38.08 + 7.12 percent).
Fruit characters of eight identified resistant genotypes given in Table 2 reveal small fruit size (Ogon-9), medium (Honey-dew, MR-1, Top Mark Bush and WMR-29), medium to large sized (PI 414723) and large (Nantais-oblong, PMR-5) with fruit weight in direct proportion to fruit size. Fruits differ widely in shape (round, oval, flattish round, oblong, pear-shaped and elliptically long), flesh color (white, green and orange), rind (netted, smooth and ribbed), and flesh-to-cavity ratio (1:1.54 [Nantais-oblong] to 1:2.83 [Top Mark Bush]).
TSS varied between 3.82 to 8.16, and ascorbic acid content was equal or greater than 20l0 mg/100 gm sample in five of the eight genotypes (Table 3).
Discussion. Eight genotypes with resistance to three major diseases and diversity in fruit quality traits can be utilized as parents in melon resistance breeding through conventional and non-conventional techniques. Artificial screening studies will further highlight the feasibility of incorporation of these lines in the improvement of existing cultivars.
A number of resistant accessions (‘WMR-29’ (2), PI 414723 (5), ‘Casaba’ (3) ) have been reported and are being utilized further for multiple disease resistance and under other economically important attributes.
TSS and ascorbic acid differ with accession. Low TSS and high ascorbic acid content may be associated with field resistance to major virus and fungal diseases.
Molecular mapping of these identified genetic markers would facilitate the rapid marker assisted selection and cloning of the resistant genes. For example, markers have been identified for the Fom-2 and can be utilized in marker assisted selection (7,9).
Table 1. Description of eight resistant accessions obtained from INRA, Montfavet, France.
| Accession | Description |
| Honeydew | Green flesh color, recessive to salmon. |
| MR-I | Monoecious, (a+ _g+<_) , fusarium oxysporum melonis resistance (Fom-1, Fom-2), powdery mildew resistance (Pm-3, Pm-6), white seeds, white flesh |
| Nantais oblong | Powdery mildew resistance (Pm-H) |
| Ogon 9 | Yellow epicarp of mature fruit (y), white flesh, (wf epistatic to gf) |
| PI 414723 | Powdery mildew resistance (Pm-x) |
| PMR 5 | Powdery mildew resistance (Pm-2, Pm-E) |
| Topmark Bush | Compact plant habit (si-1) |
| WMR 29 | Powdery mildew resistance (Pm-w), Papaya ringspot resistance (Prv1) |
Table 2. Fruit traits of eight disease resistant accessions.
| Accession | Fruit weight (g) | Size and shape of fruit | Rind Color | No. of ribs | Fruit dia. (cm) | Flesh color | Flesh thickness | Cavity dia. (cm) | Fresh seed weight (g) | Nature and thickness of skin (cm) |
| Honeydew | 725 + 177 | medium, round to oval | pale yellow | 10 | 9.95 + 2.18 | diffused green-orange | 2.32 + 0.44 | 5.88 + 1.24 | 125 + 35 | smooth,
0.25 + 0.07 |
| MR-1 | 610 + 65 | medium, flat-round to oval (splits on maturity) | pale orange | 10 | 10/85 + 0.31 | orange-cream | 2.68 + 0.21 | 6.61 + 1.05 | 121 + 65 | smooth,
0.21 + 0.0 |
| Nantais oblong | 2063 + 439 | large, elliptically oblong (25.25 + 2.10 cm long) | orange | absent | 13.35 + 2.25 | orange | 3.88 + 0.31 | 6.0 + 1.04 | 200 + 58 | smooth,
0.1 + 0.0 |
| Ogon 9 | 75.0 | small, pear-shaped | yellow | 10 | 3.97 | green-white | 0.9 | 2.23 | – | 0.1 |
| PMR 5 | 2250 + 707 | large elliptically long (29.00 + 7/07 cm long) | wild greenish orange | absent | 13.18 + 8.45 | orange | 3.40 + 0.18 | 7.3 + 0.23 | 225 +106 | rough,
0.2 + 0.0 |
| WMR 29 | 522 + 40 | medium, round | yellow | green, 10 | 10.20 + 0.49 | dark orange | 2.61 + 0.21 | 5.98 + 0.52 | 88 + 18 | netted,
0.38 + 0.2 |
| PI 414723 | 650 + 283 | cylindrically long (15.5 + 3.59 cm long) | green | absent | 9.54 + 0.05 | cream-green (juicy fresh) | 2.14 + 0.67 | 5.75 + 0.56 | 750 + 35 | smooth,
0.1 + 0.00 |
| Topmark Bush | 783 + 532 | flat-round (3 sided) fruit | yellow | 10 | 12.12 + 1.09 | cream-green (dry, crisp fresh) | 2.88 + 0.58 | 8.17 + 0.83 | 154 + 33 | smooth,
0.15 + 0.00 |
Literature Cited
- Jain, J. and T.A. More, 1996. Identification and selection of genetic marker donor lines for incorporation of disease resistance in cultivars of Cucumis melo L. Cucurbit Genetics Coop Report 19: 53-56.
- Nandpuri, K.S., Lal Tarsem and J.S. Dhiman, 1995. Muskmelon ‘Punjab Rasila’. Ind. Hort 40 (3): 4,9.
- Norton, J.D. 1981. Multiple disease resistant ‘Casaba’. Cucurbit Genetics Coop. Report 4:24.
- Pitrat, Michel, 1994. Gene list for Cucumis melo L. Cucurbit Genetics Coop. Report 17:135-142.
- Guitton, L., L. Hagen, and M. Pitrat. 1999. genetic Control and linkages of some fruit characters in melon. Cucurbit Genetics Coop. Report 22:16-18.
- Ranganna, S. Vitamins, In: Handbook of analysis and quality control for fruit and vegetable products. 2nd edition, pp. 105-106.
- Wolff, D.W. and Z. Jianling. 1996. Potential utility of RAPD markers linked to Fom-2 gene in melon (Cucumis melo L.) – Cucurbit Genetics Coop. Report 19:61-62.
- Zheng, X.Y., D.W. Wolff, S. Baudracco-Arnas and M. Pitrat. 1999. Development and utility of cleaved amplified polymorphic sequences (CAPS) and restriction fragment length polymorphisms (RFLPs) linked to Fom-2 Fusarium wilt resistance gene in melon (Cucumis melo L.) Theor. Appl. Genet. 99:453-463.