Promising new mango cultivars through natural open-pollinated crosses using polycross nurseries in mango breeding
Although the classical breeding of mango cultivars is a time-consuming process, most of the current mango cultivars were derived from classical breeding or random selection. The mango industry in South Africa is mainly based on five or six commercial cultivars with numerous negative characteristics; therefore, the mango breeding programme of the Agricultural Research Council's Institute for Tropical and Subtropical Crops (ARC-ITSC) was started in 1990. Natural crosses (open pollination) are mainly used in the ARC-ITSC breeding programme, although artificial crosses (hand pollination) and caging of top-worked cultivars were also used. Due to the low success rate of hand pollinations, open-pollinated crosses from polycross nurseries are mainly used as seed source. Polycross nurseries involve planting selected parent clones in an isolated area with the plants positioned in a manner that facilitates all possible combinations. A second-phase statistical trial with 11 promising selections compared with four commercial cultivars also doubles up as the polycross nursery. Crossing is by way of natural pollinators and, while the female plant is known, the pollen source is not. The progeny is evaluated in different orchards to determine their commercial potential. Phase I, or the open-pollinated seedlings programme, consists of 2696 seedlings spread over 6 ha. Two of these orchards consist of 330 open-pollinated seedlings from the polycross nursery, of which a large portion did not yet produce fruit. The evaluators identified 62 selections with potential during the 2014 season and 29 promising selections during the 2013 season, totalling 91 selections from the polycross nursery, which were promoted to the second phase of evaluation. This high percentage of promising selections can be attributed to the collection of seed from the polycross nursery.
Human, C.F., Willemse, S. and Sippel, A.D. (2017). Promising new mango cultivars through natural open-pollinated crosses using polycross nurseries in mango breeding. Acta Hortic. 1183, 69-72
Mangifera indica L., polycross nursery, cultivar, selection, evaluation