Pioneer agronomy manager Dr Rowland Tsimba gave an insight at this year’s rural professionals conference to the gains breeders are making in improving the crop’s yield while facing the challenge of global warming, tight water supplies and a need to reduce nitrogen losses.
“We have managed to continuously increase maize yield over the past 60 years but we also have the issue that only 50% of the nitrogen applied is actually taken up by a crop.
“How do we introduce crops capable of picking up more nitrogen from the soil, requiring less to be applied, or have less nitrogen in the soil, post-harvest?”
Earlier boosts in maize yield were driven partly by good breeding but also by increased nitrogen application, particularly from 1965-1980 when the amount applied doubled.
“But since 1980 that level has remained almost exactly the same but yields have continued to increase by about 125kg a hectare a year.”
Breeding has resulted in hybrids that now use more of the available nitrogen and in a different pattern, with 28-40% more of the nitrate used at the critical silking (flowering) period.
Breeders are now looking to genomic DNA analysis to better identify hybrids using Marker Assisted Selection (MAS).
The process identifies traits in possible hybrid seeds without having to go through traditional breeding-crossing routines to identify hybrid candidates.
“It means we are not waiting seven years to identify hybrids that work.
“You go in knowing exactly what traits you are working with. You identify the plants you are going to grow to give you the traits you require.”
That includes plants with genes that make them more efficient at nitrogen use.
The science is also helping agronomists identify traits in plants that might help with specific agricultural challenges, such as drought tolerance.
That trait has enabled them to develop a super maize and breeders can now tailor hybrids that have the ability to cope with moisture stress and perform in premium growing situations.
“Generally, those that perform under stress will not perform as well in premium situations but we are working to a hybrid that is consistent under all conditions, along with having a reduced environmental footprint in terms of nitrogen efficiency.”
He cited the 2012 United States drought where despite tough conditions there was no statistically significant decline in crop yields.
The same breeding tools have meant water efficiency has increased dramatically in the modern hybrids, requiring only 60% of the water older hybrids needed in the 30s and 40s, with significantly greater yields.
New Zealand legislators are considering revisiting the definition of genetic modification as new technology like CRISPR gene editing gains traction and overseas the maize industry has already used the technology to develop a new variety.
DuPont Pioneer has used the technology to develop an improved waxy corn variety with a higher starch content for industrial uses.
The US government has told the company it will not be regulated as a GM product, setting the stage for future crop developments.
Tsimba said it remains to be seen what position NZ will take on CRISPR’s being defined as genetic modification but it is a space Pioneer will remain active in overseas.
