Cucurbit Genetics Cooperative Report 20:48-49 (article 21) 1997
Cuban Pumpkin Genetic Variability under Low Input Conditions
Humberto Rios Labrada, Antonio Fernandez Almirall and Orlando Batista de la Carrera
Instituto Nacional de Cienncias Agricolas, INCA GP No 1, San Jose de Las Lajas, La Habana, Cuba, Cp 32700
Introduction. Genetic improvement of crop yields under marginal conditions suffers from many practical problems. One of them is to find varieties tolerant to the interactions among the different kinds of stresses resulting from temperature, drought, salinity, pests and diseases. Is it possible to select any varieties with these characteristics? How important are landraces in this process?
Cuban pumpkin (Cucurbita moschata Duch) is an interesting model. This crop is popular for culinary and medical properties, taste, -carotene content, and is also used in African religious ceremonies. Nonetheless, yields have proportionally declined in Cuba as crop input levels have decreased over the last 10 years. That is why pumpkin has disappeared from virtually every market (Rios et al., 1994, 1996). However, one genotype has been cultivated all over the island, even though it was developed under high-input conditions.
The aim of this paper is to show the role of landraces as an important genetic source for tolerance to marginal conditions.
Materials and Methods. Thirty four landraces of C. moschata from different Cuban sources were sown under low input conditions with neither chemical fertilizer nor chemical pest and disease control. Filter cake was used as organic fertilizer at the rate of 12 kg to a pair of plants. The experiment had 21 plants per genotype distributed in 3 replications, using plant spacing of 1m and 8m between rows. The plots were made up in a single row with 8m long and 8m wide.
In order to cluster the landrace collection according to qualitative and quantitative characters, factorial correspondence multivariate analyses were applied. Traits observed were yield and its components, and selected characteristics of fruits and leaves according to Esquinas and Gulick (1983). This experiment was carried out in the Research Institute of Fundamental Tropical Agriculture ( Havana).
Results and Discussion. Among the 34 landraces, 25 were able to produce fruit. It is important to note that the majority of these genotypes fruited between 80 and 110 days. Cuban germplasm can therefore be an important genetic source for earliness, since even in tropical areas it is common to find genotypes with a crop cycle longer than 160 days (Lyra, 1992). Such lengthening could be associated with genetically determined adaptative or escape mechanisms relative to marginal conditions (Ceccarelli, 1994).
Among the characters evaluated, primary skin color and yield had the most important contribution to genotype clustering, and six clusters were identified (Table 1).
Table 1. Clustering of 34 Cuban pumpkin landraces according to skin color and yield.
||High yield and green fruits
||High yield and yellow or brown fruits
||Medium yield and brown,yellow or gray fruits
||P-1461, P-1118, P-30
||Medium yield and green fruits
||P-1523, P-1411, P-1043, CRISOSTOMO, P-1029
||Low yield and yellow or brown fruits
||P-909, P-1175, P-900, RG*, P-826, P-1377
||Low yield and green fruits
||P-1188, P711, P-1974, P-1027, P-1189, P2002, P-1442, P-39
The predominant fruit types were the piriform and crookneck type. Elongate, globular and flat shapes were scarce. Yield per plant showed a large variability between landraces, ranging from 0.5 kg up to 18 ton/ha. The principal yielding varieties had medium-sized fruits (2.5-3 kg) as well as more than 4-5 fruits per plant.
In general terms, the genetic variability found was within the species’ boundary, because no deviation was observed even though C. moschata is cross compatible with other species of Cucurbita. It may be that other Cucurbita species do not tolerate the Cuban climate,, which is characterized by two periods: a high temperature period with some rainfall and a low temperature period with drought. The morphological variability under marginal conditions could be related to different low-input pumpkin genotypes brought to Cuba before Colombus (Perez Guzman, 1993). Probably, they were brought to Cuba by indigenous tribes through The Caribbean Sea from Central and South American, as has been theorized with other traditional crops such as beans (Castineira, 1992).
In summary, germplasm variability among landraces of Cuban pumpkin could be an essential resource for breeding plants for low-input environments.
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