Analytical breeding

Ploidy manipulations consist on scaling up and down chromosome numbers of a species within a polyploid series. Chromosome sets are manipulated with haploids, 2n gametes, and through interspecific-interploidy crosses. Analytical breeding schemes rely mainly on ploidy manipulations to “capture” diversity from exotic (wild or non-adapted germplasm) and use 2n gametes to incorporate this genetic diversity through unilateral (USP; n x 2n or 2n x n) or bilateral (BSP; 2n x 2n) polyploidization. Most interesting examples of analytical breeding in crop improvement are in vegetatively propagated species such as potato, sweetpotato, cassava, among roots and tubers, and plantain/banana among fruit crops. This breeding approach appears promising in blackberry, blueberry, strawberry and other fruits. An evolutionary crop breeding method was developed for further improvement of the plantain genome. This method ensued from the genetic knowledge accumulated during the analytical breeding of this triploid (3x) crop. Heterozygous 3x landraces are crossed with diploid (2x) wild or cultivated accessions showing the desired characteristic(s). Primary tetraploid (4x) hybrids are recovered after USP, i.e., 2n eggs from 3x x n pollen from 2x. Secondary triploids result by crossing selected 4x with selected 2x stocks, both producing n gametes. Triploid Musa hybrids may also occur due to USP among 2x, i.e., one 2x producing 2n gametes. Hybrids may result from artificial hand-pollination or through polycrosses among selected 4x and 2x parents according to their specific combining ability. Synthetic populations derived from the polycrosses may be tested in other locations to identify promising offspring for cultivar selection. Local selections may lead to dynamic conservation of genetic resources because farmers will preserve distinct locally adapted, improved genotypes across environments. Analytical breeding, coupled with this evolutionary breeding approach, offers an option for broadening the genetic base of fruit crops, enhancing their adaptation, and sustaining breeding gains in respective gene pools.