Annona Species Monograph.pdf - Crops for the Future

Chapter 9. Genetic Improvement
and mass selected local types. Plant behaviour was observed with respect to
age, origin, farming practices, pest and disease resistance, organoleptic
parameters and so on. At the same time, genetic material was introduced
from other countries, especially the USA and Spain, increasing variability
and allowing comparison of adaptability, productivity and quality with the
local materials. Finally, clonal selection produced four improved cultivars:
Madeira, Mateus I, Perry Vidal, and Funchal (Nunes, 1997).
Soursop is still largely propagated by seed, and the progenies can be selected
and separated into groups based on acidity and sweetness. Morada, an
ecotype introduced into Brazil from Colombia, produces large fruits with an
average weight of 3.8 kg, but its fruits have very acid pulp, which is a
constraint for the fresh fruit market. A local soursop selection from Bahia
State named "ecotype A" produces very small fruits (< 1.8 kg), but has sweet
pulp, appropriate for the fresh market. Crossing between these two might
produce a medium weight fruit with a commercially acceptable taste. Several
genotypes and some related species are used in the soursop breeding work of
Embrapa Cerrados, Brazil, from which a clone based on Morada has been
released as a reliable option for tolerance to trunk borer (Pinto and Ramos,
1997). At the same time, A. glabra, which has dwarf characteristics and good
adaptation to damp areas, is being used in a breeding programme for
rootstock improvement, since there is acceptable rootstock/scion
compatibility between these two species.
Wild soursop has been used for insect control in Africa, since it has
significant amounts of secondary metabolites with insecticidal activity (see
Chapter 7). However, there is no specific breeding programme to improve
this characteristic, although Abubakar and Abdurahman (1998) mentioned a
project to prospect, collect and chemically identify wild soursop variation
with insect growth-regulating activity in Kaduma State, Nigeria (work at the
Department of Biological Sciences, Ahmadu Bello University, Zaria).
9.4.4 Selection and cultivar development
Like any other fruit tree, the type of selection or cultivar development of
annonas is strongly influenced by commercial use. Also, the feasibility of
using a particular type of selection or cultivar may depend on the nature of
the organisations that produce and distribute grafted plants for commercial
use, these being much better established in more developed countries. This
explains why annona cultivar development concentrates on cherimoya and
soursop (and atemoya), and has been carried out only by public institutions.
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