A common technique, called high performance liquid chromatography (HPLC), can assess the provitamin A content of individual plant lines. But screening a single sample costs $50 to $75, he said.
Thats really expensive, especially since plant breeders like to screen hundreds or more plants per cycle, twice a year, he said. The cost was just prohibitive.
The new approach uses much more affordable methods and gives a more detailed picture of the genetic endowment of individual lines. One technique the researchers employed, called quantitative trait loci (QTL) mapping, allowed them to identify regions of the maize chromosomes that influence production of the precursors of vitamin A. They also used association mapping, which involves studying variation in selected genes and tracking inheritance patterns to see which form of a gene coincides with the highest provitamin A content. Polymerase chain reaction (PCR) allowed them to amplify and sequence the different versions (alleles) of the genes of interest, to find the alleles that boosted levels of vitamin A precursors in the plant.
This approach led to an important discovery. The team found a mutant form of an enzyme vital to the cascade of chemical reactions that produce the precursors of vitamin A in the plant. This mutant is transcribed in lower quantities than the normal allele and steers the biochemistry toward producing higher levels of vitamin A precursors.
The study analyzed 300 genetic lines selected to represent the global diversity of maize, and identified some varieties that came close to the target amount of 15 micrograms of beta-carotene (a form of provitamin A) per gram. Current maize varieties consumed in Africa can have provitamin A content as low as 0.1 micrograms per gram.
The researchers can now i
|Contact: Diana Yates|
University of Illinois at Urbana-Champaign