A Genetic Map Of Melon (Cucumis Melo L.)

Theor Appl Genet (1997) 95 : 791 — 798

Springer-Verlag 1997

Y.-H. Wang · C. E. Thomas · R. A. Dean

A genetic map of melon (Cucumis melo L.)
based on amplified fragment length polymorphism (AFLP) markers

Received: 12 March 1997 / Accepted: 20 May 1997

Abstract Genetic maps facilitate the study of genome
structure and evolution, and the identification of
monogenic traits or Mendelian componentsof quantitative traits. We evaluated 228 RAPD, microsatellite
and AFLP markers for linkage analysis in melon
(Cucumis melo L.) varieties MR-1 (resistant to Fusarium
wilt, powdery and downy mildews) and Ananas
Yokneum (AY; susceptible to these diseases) and constructed a detailed genetic map. The mapping population consisted of 66 backcross progenies derived from
AY;(MR-1;AY). Despite a relativelylow level of
polymorphism in the species, AFLP markers were
found to be more efficient in mapping the melon
genome than RAPD or microsatellite markers. The
map contains 197 AFLPs, six RAPDs and one microsatellite marker assigned to 14 major and six minor
linkage groups, and covers 1942 cM with the average
distance between adjacent markers of approximately
10 cM. The maximum distance allowed betweenmarkers is 27.5 cM. About 11% of the intervals (20 out
of 173) are over 20 cM (but less than 27.5 cM). The map
has immediate utility for identifying markers linked to
disease resistance genes that are suitable for markerassisted breeding. The use of microsatellite markers for
integration with other maps is also discussed.
Key words Melon · Cucumis melo L. · Genetic
mapping · AFLP · RAPD ·Microsatellite ·
DNA markers

Communicated by M. A. Saghai Maroof
Y.-H. Wang · R. A. Dean ( )
Department of Plant Pathology and Physiology, 120 Long Hall,
Clemson University, Clemson, SC 29634-0377, USA
Fax:#
1-864-656-0274
e-mail: rdean@clemson.edu
C. E. Thomas
US Vegetable Laboratory, USDA-ARS, 2875 Savannah Highway,
Charleston, SC 29414, USA

Introduction
Melon (Cucumis melo L.) is a valuable cash cropgrown
throughout the world. It is a member of the genus
Cucumis, in the family Cucurbitaceae. C. melo includes
a diverse group of annual, trailing-vine plants. Despite
diversity in horticultural traits such as fruit shapes
[there are seven different horticultural groups of
melons (McCreight et al. 1993)] polymorphism at the
DNA level among the groups is relatively low (ShattuckEidens et al. 1990;Neuhausen 1992). The plant is diploid
with a base chromosome number of 12 (Dane 1991) and
a genome size of 4.5—5.0;10 bp (Arumuganathan and
Earle 1991). About 30% of the genome consists of repeated DNA sequences (Bendich and Anderson 1974).
Genetic maps with a relatively high-density of
markers are useful for a number of purposes. For
example, they serve to locate, or tag, gene(s) of interest
tofacilitate marker-assisted breeding and map-based
cloning; they also provide useful clues to understand
the biological basis of complex traits and phenomena
(Lee 1995). Genetic studies of melon have identified
over 90 genes (Pitrat 1994). However, before the advent
of molecular markers, linkage mapping was limited to
known genes or phenotypic markers. Pitrat (1991) analysed 28 phenotypic markers inan F population and

found that 23 of the markers fell into eight linkage
groups. Development of DNA markers has greatly
facilitated mapping. Baudracco-Arnas and Pitrat
(1994) developed a mapping strategy for melon using
RAPD and RFLP markers that resulted in assigning
77 DNA markers to 12 linkage groups with 2—12
markers in each group. The map was extended to 14
linkage groups covering 1390 cMwith 102 markers,
including five phenotypical markers (Baudracco-Arnas
and Pitrat 1996). Twenty three percent of the map
distance contained nine gaps larger than 30 cM. Microsatellite markers have also been developed for melon
(Katzir et al. 1996).

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Recently, amplified fragment length polymorphism
(AFLP2+ ) was developed (Vos et al. 1995) as a new
DNA marker system combining the features of...