Annona Species Monograph.pdf - Crops for the Future

Chapter 10. Agronomy
Annona species
Time of
Storage
(days)
Time of
Germination
(days)
Germination
(%)
Age for
Transplant
(days)
Age for
Grafting
(days)
(A. squamosa)
Source: Hernandez (1983).
Irregular germination is due to different levels and types of dormancy (Pinto,
1975 a, b; Ferreira et al., 1997; de Smet et al., 1999; Ferreira et al., 1999;
Hernández et al., 1999; Moreno Andrade, 1999). Nevertheless, there still
exists disagreement about the presence of dormancy in Annona seeds and the
correct treatments to overcome it. Sanewski (1991) claimed that no
dormancy exists, whereas other authors claim the presence of dormancy
(Hayat, 1963; Purohit, 1995; Ferreira et al., 1999; Hernández et al., 1999). A
possible hypothesis to explain this disagreement among authors is the degree
of seed maturity when tested and the fact that dormancy can be induced by
environmental factors rather than being innate. Many of the comparisons
below do not give data on how the seed was handled and what conditions it
was kept in before testing; hence measures of viability and/or germination
results may not be truly comparable.
Pre-treatment of Annona seeds is very important and can be physical, such as
seed scarification and water immersion to reduce or eliminate the
impermeability of the seed coat, or chemical, such as gibberellic acid (GA) to
counteract endogenous germination inhibitors (Campbell and Popenoe, 1968;
Hartmann et al., 1990; de Smet et al., 1999). Duarte et al. (1974) found that
dry cherimoya seeds treated with GA at 10,000 ppm significantly increased
the seed germination to around 70%, compared with 57% for untreated seed,
while hot water showed an adverse effect on seed germination (28%).
Pittman (1956) suggested that cherimoya seeds must be soaked in water for 3
to 4 days and then sown in warm soil, after which they will start to germinate
in 4 to 5 weeks.
Castillo Alcopar et al. (1997) found that germination capacity of cherimoya
seed varied from 66 to 94% and period of germination varied between 58 and
69 days after planting. They found that seed scarification had only a slight
influence on germination. Significantly, all physiological responses were
genotype dependent. De Smet et al. (1999) evaluated germination percentage
and rate in cherimoya using different pre-treatments, such as soaking in
different concentrations of GA (extreme values of 500 and 10,000 ppm),
soaking for different periods (12-72 hours) in distilled water, and chemical
scarification with sulphuric acid. They found that GA showed a positive
effect on both physiological parameters.
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