World search for hybrid maize in Canterbury

Press, 28 April 1989, Page 16

World search for hybrid maize in Canterbury

By

DAVID LUCAS

A small Greenpark farmlet, south of Christchurch, has become a vital cog in the search by a Northern Hemisphere plant breeding company for new maize hybrids. For 10 years, Mr Paul Hadfield has grown and crossed thousands of different lines of maize for a major Dutch maize breeder on his smallholding.

By having a Southern Hemisphere base to grow, trial and cross different lines out of season, plant breeders can speed up their breeding programmes. It allows them to grow two generations in one year. Mr Hadfield is this season growing 3700 different lines of maize on 3ha. Most lines consist of only 10 to 15 seeds. Many hours of painstaking work in hand crossing, preventing cross-pollina-tion and recording are involved. Paul Hadfield said maize was the most common cereal crop in the world and the breeding work was highly competitive because of the opportunity to make big profits if an outstanding hydrid was bred. All modern maize crops were hybrids which meant fresh seed had to be specially produced each season.

Maize breeding companies were, therefore, secretive about their activities and went to a lot of effort to keep ahead of their competitors. Mr Hadfield formerly worked for the Crop Research Division of the D.S.I.R. at Lincoln, in charge of seed production marketing and commercialisation of G.R.D. varieties.

At that stage, before user-pays, the D.S.I.R. did not handle private breeding work. The Dutch com-

pany was seeking a private breeder with no commercial ties to other breeders to handle its Southern Hemisphere operations, and eventually contracted the operation to Mr Hadfield. The Dutch company had been impressed by the excellent seed quality of the maize grown at the site which was now its main maize breeding farm (outside the Netherlands) and is believed to be the biggest maize nursery in the Southern Hemisphere. The dry climate and low humidity of Canterbury were highly suitable to seed production.

The nursery’s main breeding section is divided into four blocks containing 800 different lines in each and surrounded by buffer rows of maize about 2.5 m high for protection. Plant breeders from the Netherlands visit the farm each season to monitor the progress of the crop. Some lines are cross-polli-nated, selfpollinated or pollinated by other plants within the same line (siblings). Last season, 56,000 pollinations were done by hand and this season there were probably even more. A team of 16 parttime workers — housewives and students — is employed during the busy season. Where pollen from certain plants is wanted for cross-pollination, a bag is secured over the male tassels at the top of the plant to catch the ripe pollen. The female silks at the top of the cob are covered with a bag to prevent unwanted fertilisation.

For breeding work, only the top (or primary) cob is selected because it is better quality than the lower cobs. The ripe cobs are harvested by hand during mid-March to mid-April. The complete cobs are dried, then air-freighted to the Netherlands for the seed to be stripped and planted during the Northern Hemisphere’s growing season, although Mr Hadfield has a small thrasher for measuring grain yields and keeping particular seed lines. Seed from the following season in Europe is sent to Greenpark for continuing trials and more crossing. The more promising lines identified by the breeders are openpollinated in isolation blocks situated well away from the main breeding block. Eight isolation blocks which contain an average of 300 different lines, are located in the Greenpark district and seven are in Blenheim.

Hand-pollination to produce these hybrid lines would be far too expensive so they are openpollinated. The isolation blocks are encircled by a buffer zone of maize and are criss-crossed with a single pollinating variety planted at staggering dates to ensure a good spread of pollen over as long a period as possible. To prevent unwanted cross-pollination, the pol-len-producing male tassels from the buffer maize and from the lines being crossed by a male pollinator, must be removed every day. This work is done in the mornings before the rising temperature allows the pollen to start flowing. The silks on the cobs remain receptive to pollination for about 10

days although this depends on the temperature. The third section of the nursery is devoted to yield trials of desirable lines. Many of these are three-way hybrids. There are three trials plots — two for forage maize and one for grain each containing 25 hybrids. Each trial is replicated three times. The seed is sown in 5m rows with plants at spacings of about 140 mm, giving a sowing rate per hectare of 85,000. The trials allow the dry matter and grain yield to be measured.

Identical trials . were held in the Netherlands which were giving very similar results to those recorded at Greenpark. Working so closely with maize breeding has made Mr Hadfield conscious of the crop’s value and reputation throughout the world as an animal feed. He has recently promoted crop as ideal for making silage for cattle and deer, a suggestion which has become popular among dairy farmers.

Within about an Bkm radius of his home, 150 ha of maize is growing this season for silage and in Mid-Canterbury the growth in dairying has seen at least 300 ha put into maize. The crop was ideal on the Mid-Canter-bury border-dyked land, said Mr Hadfield. He has formed a small company to market maize seed and estimates he has supplied enough this season to sow nearly IOOOha between Nelson and Millers Flat. The extensive breeding and trialling done on behalf of the Dutch company has given him the opportunity to look for hybrids which might ideally suit NeuZealand’s climate.

Most of the maize hybrids used by New Zealand farmers suited North Island conditions, but he is confident a line has been identified which will suit the shorter growing season in the South. Trials have shown that it is about 20 days earlier at harvest than commercial hybrids available at present and it has given good grain yields.