Tree crops

Each tree crop should be considered on it own merits. Usually, the biggest problem is a long breeding cycle. Coffee, for example, has a minimum breeding cycle of three years. The stone and pome fruits, and citrus, are rather difficult to breed, and are not generally recommended for breeding clubs. Palms, such as date palm, and oil palm, are very difficult indeed. However, the production of hybrid coconut palms (i.e., hybrids between dwarf and tall palms), for resistance to lethal yellowing in the New World, or to Cadang-Cadang disease in the Philippines, is within the capacity of plant breeding clubs. So too is the selection of fast growing Eucalyptus trees for firewood in countries that have no cheap source of fuel. Many plantation forest species are amenable to selection within existing populations (see 7.14). The important tropical tree crops, other than palms, are tea, coffee, cocoa, rubber, avocado, cashew, cloves, nutmeg, and mango.

Many tree crops can be propagated vegetatively and selection within existing, genetically diverse populations can produce improved new clones very quickly. In this context, it should be noted that the techniques of vegetative propagation have improved very considerably during the past few decades. This includes use of a mist propagator with a rooting medium that is both biologically and nutritionally inert, while retaining the maximum leaf area of single node cuttings exposed to full sunlight. Rooting hormones may also help.

0 0

Post a comment