Cucurbit Genetics Cooperative Report 22:57-58 (article 21) 1999
Humberto Rios Labrada and Marta Alvarez
National Institute of Agriculture Science, INCA< GP 1, San Jose de Las Lajas, La Habana, Cuba, Cp 32700
The plant breeding approaches used by the informal seed sector has been little studied (1). However, in some crops such as pumpkin, this sector in cuba has maintained important genetic variability which has served to satisfy some farmer necessities after several years of low income conditions. In the framework of plant breeding, it is uncertain whether further genetic advances may be obtained through direct yield selection. Because yield is a complex trait influenced by many genes, some breeders use indirect selection of yield components in order to increase the principal aim of high yield.
At the same time, Cecarrelli (3) and Atlin and Frey (2) have reported how plant variability response under low income conditions may be different than the patterns obtained for crops growing favorably under artificial irrigation with chemical fertilizer and pesticide. Therefore, it seems to be advantageous to have an estimation of genetic parameters for selection with which to obtain better yield gains under low input conditions.
The present report intends to show the role of yield and its component selection on genetic response estimation under low income conditions.
Methods
Pumpkin seeds (Cucurbita moschata Duch.) from 10 fruits selected by farmers were each considered as a line (half sib families). These lines were sown two times: under low income conditions (5) during the sprig-summer (rainfall period) and the winter (dry period) seasons. Genetic response of fruit weight, number of fruits per plant and yield were determined according to Galvez (4) using 40% selection pressure.
Results
The estimation showed that the genetic response of yield and its components were superior in the winter season (Table 1), probably due to the environmental influence of weather conditions favorable to female flowering set. The response of number of fruits per plant was lower during the spring-summer season, High temperatures during this season may have resulted in flower and fruit abortion (Casanova, 1998, personal communication). The genetic response for this experimental series appeared to be negatively linked with yield, so a high genetic response occurred in the low-yield environment of the winter season while a low genetic response occurred in the high-yield summer season.
It is interesting to point out that yield has a superior or similar genetic response with regard to its components, suggesting that in half sib families some genetic advance could be made through direct selection ‘the favorable genetic response estimated for yield, and the fact that pumpkin seed management by farmers had been able to intro9duce, exchange and select conditions for a seed flow between and within communities, allows the assumption of the farmers’ capacity to make genetic advance in complex traits such as yield under low income conditions.
Table 1. Genetic response estimated for pumpkin under low income conditions.
| Yield (tons/ha) | Number of fruit per plant | Fruit weight (kg) | |
| Spring/Summer | |||
| Genetic Response | 0.62 | 0.252 | 0.7 |
| Average | 6.0845 | 2.6145 | 2.6121 |
| Winter | |||
| Genetic Response | 1.47 | 1.45 | 1.11 |
| Average | 3.1618 | 1.1967 | 2.2908 |
Literature Cited
- Almekinders, C. 1998. Por que fitomejoramiento participativo. In: Fitomejoramiento participativo Experiencias y Oportunidades in Meso-America. March 16-17, 1998. La Catalina. Costa Rica.
- Atlin. G.N. and K.J. Frey. 1989. Breeding crop varieties for low input agriculture. Amer. J. Alternative Agric. 4(2):53-58.
- Ceccarelli, S. 1994. Specific adaptation and breeding for marginal conditions. Euphytica 56(77):205-219.
- Galvez, G. 1985. Parametros y estadisticas en genetica cuantitativa. In: Genetica Vegetal y Fitomejoramiento. La Habana. Ciencia y Tecnica.
- Rios. H. Tropical pumpkin (Cucurbita moschata) for marginal conditions: breeding for stress interactions. Plant Genetic Resources Newsletter 113:1-4.