Germplasm enhancement of maize: a look into haploid induction and chromosomal doubling of haploids from temperate‐adapted tropical sources

Abstract

The allelic diversity (AD) project of the Germplasm Enhancement of Maize (GEM) programme utilized the double haploid (DH) breeding method to expedite development and release of lines derived from 300 exotic maize races. Using 18 races in this study, differential effects on haploid induction rates (HIRs) and doubling rates (DRs) by the recurrent parents PHB47 and PHZ51, the elevation that the race is traditionally grown at, and by the race itself were addressed in this study. Races from the AD project were grouped by elevation of their origin, high, middle or low altitude. Six races per elevation were randomly selected and backcrossed using both recurrent parents to generate 36 populations. Ten replications were randomized in a complete randomized design for two growing seasons. The recurrent parent effect was significant, with PHB47 having a higher HIR than PHZ51. Effect of elevation was significant with higher HIR associated with low‐elevation origin, and race also proved to be significant. Effects of elevation, recurrent parent and race were not significant for DR.

Major locus for spontaneous haploid genome doubling detected by a case–control GWAS in exotic maize germplasm

“…While tools and methods for induction and identification of haploids have improved over time, haploid genome doubling remains a challenge for successful application of DH technology at a large-scale (Boerman et al 2020). Genome doubling in haploids derived from exotic germplasm is even more challenging due to the presence of deleterious recessive alleles that are expressed in haploids (Smelser et al 2016). Hence, direct application of DH technology for exotic germplasm is not as effective as in temperate and elite germplasm (Prigge et al 2011).…”

Classification approaches for sorting maize (Zea mays subsp. mays) haploids using single‐kernel near‐infrared spectroscopy

“…The female donor parents were backcross generation 3 (BC3) plants from introgressions of BGEM inbred lines into the expired PVP lines, PHB47 and PHZ51, as recurrent parents. BGEM inbred lines contain introgressions of various tropical accessions into PHB47 and PHZ51 (Brenner et al, 2012; Sanchez, Liu, Ibrahim, Blanco, & Lübberstedt, 2018; Smelser, Gardner, Blanco, Lübberstedt, & Frei, 2016; Vanous et al, 2018; Vanous et al, 2019). PHB47 is from the stiff stalk (SS) heterotic group, while PHZ51 is a non‐stiff stalk (NSS).…”

Usefulness of Adapted Exotic Maize Lines Developed By Doubled Haploid and Single Seed Descent Methods

“…technology has been used in connection with exotic germplasm to effectively purge landraces of genetic load (Smelser et al 2016). Only the more vigorous haploids survive the stressful steps of genome doubling by colchicine treatment and transplanting of the seedlings.…”