The Tropical Fruit Forum

In the past, growers preferred plants that supplied abundant basal slips for planting, not recognizing the fact that such plants gave smaller fruits than those without slips or suckers. Also, breeders aim toward elimination of slips to facilitate harvesting. Because of the increased demand for planting material, a new method of mass propagation received wide attention in 1960. During the harvest, plants that have borne single-crowned, superior fruits without basal slips are selected and marked. Following harvest, these plants are cut close to the ground, the leaves are stripped off and the stems—usually 1 to 2 ft (30-60 cm) long and 3 to 4 in (7.5-10 cm) thick—are sliced lengthwise into 4 triangular strips. The strips are disinfected and placed 4 in (10 cm) apart, with exterior side upward, in beds of sterilized soil, semi-shaded and sprinkler-irrigated. Shoots emerge in 3 to 5 weeks and are large enough to transplant to the nursery in 6 to 8 weeks. 'Smooth Cayenne' yields an average of 3 shoots per slice. 'Red Spanish' and 'Natal Queen', 4 per slice.

This use of the stem is a major improvement over the former practice of allowing it to develop suckers high up after the fruit is harvested. If such suckers bear fruit in situ they are not strong enough to support it and collapse. They are better removed for planting, but repeated removal of suckers weakens the mother plant.

In Sri Lanka, the shortage of planting material inspired experiments at first utilizing stem cross-sections 1 in (2.5 cm) thick—15 to 24 from each stem. These sprouted in 4 weeks but plant growth was slow and fruiting was delayed for 30 months. Most of the cuttings developed a single sprout, some as many as 5, others, none at all. Accordingly, this technique was abandoned in favor of a system developed for purposes of reproducing a selected strain in Hawaii. Stems are cut into segments bearing 3 to 5 whorls of leaves. The leaves are trimmed to 4 to 5 in (10-12.5 cm) and the disinfected cuttings set upright in beds until each gives rise to one strong plantlet which is then transferred to the nursery.

The butts, or bases, of mother plants, with leaves intact, are laid end to end in furrows in nurseries and covered with 2 to 3 in (5-7.5 cm) of soil. Sprouting occurs in 6 to 8 weeks. The butts give an average of 6 suckers each, though some have put forth up to 25. A one-acre (0.4 ha) nursery of 25,000 butts, therefore, yields between 100,000 and 200,000 suckers.

In India, double-grafting has been found to dwarf mango trees and induce early fruiting.