Breeding Open-Pollinated, Hybrid and Transgenic Outcrossing Species

Abstract

Outcrossing is the transfer of pollen grains from the anther of a flower to the stigma of another flower in a different plant of the same species in the angiosperms by the action of wind, insects, or other vectors, thereby enabling fertilization and reproduction. It allows for species diversity because it combines genetic information from different plants, and may lead to heterozygosity when involving two genetically distinct plants. About 50 % of crops show outcrossing and their reproductive systems include devices promoting it, for example, unisexuality, maturing time, self-incompatibility, and male sterility. Various outcrossing species may have a small amount (5-10 %) of selfing. Outcrossing species exhibit mild to severe inbreeding depression and significant heterosis. Maize, onion, and rye are among outcrossing species, while cotton shows up to 30 % of outcrossing. Composite, hybrid, and synthetic cultivars are the aim for breeding outcrossing species, when their seed production is feasible and profitable. A composite cultivar ensues from mixing seeds of outstanding lines (often up to 20) and encouraging open pollination among the mixed lines, while a synthetic cultivar results from crossing (6-8) lines that combine well with each other and are kept by open pollination in isolation. Pedigree, doubled haploids, and backcrossing are used for inbred line development, while recurrent selection methods accumulate favorable alleles in a breeding population. Plant genetic engineering and DNA marker-aided breeding are among the biotechnology tools for improving maize, cotton, cassava, and other outcrossing species. MaizeMaize (Zea mays) is the cereal with the largest global output and cash value. It is among the most important staple food crops, a source of feeding grains and silage for livestock, and used by the industry for ethanol, oil, and starch. Its average global per capita consumption is below that of wheat, rice, and potato because of the high