Cucurbit Genetics Cooperative Report 12:39-40 (article 16) 1989
M.S. Gomez-Guillamon and J.A. Tores
Estacion Experimental “La Mayora”, Algarrobo-Costa, 29750 Malaga, Spain
In 1987 and 1988 several cultivars of Spanish type melons were inoculated with Sphaerotheca fuliginea race 1 to determine possible sources of resistance to this pathogen. The cultivars chosen were those who in previous years were free of disease symptoms under natural conditions of infection.
Two methods of artificial inoculation were employed; both used a dry inoculum. In one, a small mass of spores was placed on the leaf surface with a scalpel (M. Pitrat, personal communication). This method allowed a visual check of the efficiency of inoculation success. In the other, the spores were applied by dusting the leaves (1). The inoculum was a strain of S. fuliginea race 1 isolated in the Estacion Experimental “La Mayora” (Malaga, Spain) (3).
Table 1. Response of different Spanish melon cultivars against S. fuliginea race 1.
Cultivars |
Artificial inoculation |
Natural inoculation |
Observations |
| AN-C-36 | R | + | Piel do Sapo type |
| C-C-3 | S | + | Type not ascribable |
| AN-C-57 | R | 0 | Yellow type |
| AN-C-39 | S | +++ | – |
| MU-C-44 | S | +++ | – |
| AN-C-7 | S | +++ | – |
| PI 1224112 B | R | 0 | Resistant races 1, 2, and 3 |
| PMR 6 | R | 0 | Resistant races 1 and 2 |
| AN-C-68 | R | 0 | Yellow type |
| PMR45 | R | 0 | Resistant race 1 |
| E-C-14 | S | +++ | – |
| AN-C-08 | S | +++ | – |
| AN-C-42 | R | 0 | Type not ascribable |
| J-22112-C | S | +++ | – |
R resistant; S sensitive.
+++ the symptoms appeared from the start of cultivation period.
+ mild symptoms appear at the end of the cultivation period.
0 no symptoms were observed.
The same cultivars were grown in a polyethylene greenhouse on a sandy soil with drip irrigation in a field with a previous history of powdery mildew. No fungicide applications against the fungus was carried out and the plants were left to be infected naturally. The sensitive genotypes acted as a source of inoculum throughout the cultivation period, and melon genotypes with known resistance to the three races of S. fuliginea were used as testers (2).
Crosses have been initiated between the resistant cultivars AN-C-42, AN-C-68 and AN-C-57, and the muskmelon varieties of commercial importance of the Yellow and Piel do Sapo types to study the genetic of this resistance and ways of introducing it.
Literature Cited
- Adeniji, A.A. and D.P. Coyne. 1983. Genetics and nature of resistance to powdery mildew in crosses of Butternut with Calabaza Squash and ‘Seminole Pumpkin’. J. Amer. Sci. Hort. Sci. 108:360-368.
- McCreight, J.D., M. Pitrat, C.E. Thomas, A.N. Kishaba and G.W. Bohn. 1987. Powdery mildew resistance genes in muskmelon. J. Amer. Soc. Hort. Sci. 112:156-160.
- Tores, J.A. 1987. Sphaerotheca fuliginea (Schlect. ex Fr.) Poll., Causal agent of cucurbit powdery mildew in southern Spain. 7th Congress of the Mediterranean Phytopathological Union. September 1877. Granada, Spain.