Cucurbit Genetics Cooperative Report 21:63-64 (article 23) 1998
Humberto Rios Labrada
Instituto Nacional de Ciencias Agricolas (INCA). GP no1 San Jose de las Lajas, La Habana, Cuba CP 32700
Introduction. Environment plays an important role in cucurbit production. In Cuba, prior to the current economic crisis, pumpkin (Cucurbita moschata) yields were highest with winter sowings (September-February), with moderate temperatures and artificial irrigation theoretically favoring fruit set. In contrast, spring and summer sowings (March-July) were usually characterized by high temperatures, and fruit set was lower despite the occurrence of rainfall during these months.
Recently, with the declining availability of chemical fertilizer, pesticides and irrigation in Cuba, some of the observed pumpkin yields have not corresponded to previous results. Thus, it has been essential to re-investigate the influence of the environment., particularly to determine what factors are limiting pumpkin production under low income conditions, and what breeding strategies should bemused given the current limitations.
Materials and Methods. In order to classify different environmental responses, a data set consisting of yield, number fruit per plant, and weight of fruit of 10 genotypes (Rios, 1997) grown in eight different environments (E1 through E8) of Havana province, was analysed by cluster multivariate technique. Six of the environments had a spring-summer growing season (E1, E2, E5, E6, E7, E8) and two had a winter growing season (E3, E4).
The selected environments for cluster analysis application did not use chemical fertilizers )organic fertilization according to Rios, 1997) or pesticides. A light artificial irrigation was only used for germination and during flowering and female flowering times, regardless of whether rainfall had occurred during these periods.
Results and Discussion. In principle, the cluster analysis permitted classification of the environmental response into two large groups based upon yield (Table 1): moderate (2.90-7.29 t.ha-1) and poor (0.15-1.68 t.ha-1). The first group could be subdivided into two subgroups. Environments E1 and E2 were characterized by satisfactory rainfall during the shrub and male flowering periods, even though temperatures were over 25 C. E3 and E4 experienced less rainfall and yielded less, even though their temperatures were near the 22.2 C considered optimum for pumpkins (Hernandez, 1995). These results indicated that the amount of rainfall during the shrub and male flowering periods may be a limiting factor when moderate yield temperature conditions are experienced under low income regimens.
With regard to the poor yield responses experienced in environments E5, E6, E7 and E8, these were generally associated with high temperatures and drought stress conditions during shrub and male flowering.
Based upon these results, a breeding strategy for growing pumpkins under scarce water periods during spring and summer would have to be accompanied by practicing intercropping and non-conventional irrigation, as well as introducing genes from other species of Cucurbita. In fact, it has become a real necessity to avoid the dangerous yield-reducing effects of drought stress and high temperatures when growing pumpkins under low income conditions.
Table 1. Pumpkin yields under different environmental conditions.
Yield category |
Environment |
Yield
|
Average temperature (°C) |
Rainfall regime |
| Moderate | E1: spring-summer |
7.29
|
25.9 + 0.1
|
wet
|
| E2: spring-summer |
4.89
|
25.1 + 0.3
|
wet
|
|
| E3: winter |
3.41
|
21.7 + 0.6
|
dry
|
|
| E4: winter |
2.90
|
22.2 + 10.4
|
dry
|
|
| Poor | E5: spring-summer |
1.68
|
26.2 + 0.6
|
dry
|
| E6: spring-summer |
0.41
|
25.7 + 0.4
|
dry
|
|
| E7: spring-summer |
0.19
|
25.3 + 0.4
|
dry
|
|
| E8: spring-summer |
0.15
|
26.5 + 0.4
|
dry
|
Literature Cited
- Hernandez, A. 1995. Fases fenologicas de dos genotipos de calabaza en cuatro fechas di siembra. Cultivos tropicales 16(3):16-68
- Rios Labrada, H., A.F. Almirall and E.C. Galarraga. 1997. Response of Cuban pumpkin Cucurbita moschata Duch.) to abiotic and biotic stress interactions. Cucurbit Genetics Cooperative Rept. 20:50-52.
- Rios Labrada H., A.F. Almirall and E.C. Galarraga. 1998. Tropical pumpkin (Cucurbita moschata Duch,) for marginal conditions: breeding for stress interactions. Plant Genetic Resource Newsletter, 1998, No. 113:1-4.