Potato Certification Trials Inspected

Press, Volume CII, Issue 30028, 12 January 1963, Page 6

Potato Certification Trials Inspected

Twenty-five acres of potatoes samples from each of the 2000 fines of potatoes entered for certification with the Department of Agriculture this year—were inspected this week by departmental officers where they were growing on the Kenytown property of Mr V. Wilson, near Temuka.

Each grower in New Zealand who had entered potatoes for certification submitted 150 tubers to be grown in the mass trial. They are planted in groups of 50 tubers and the inspection is be correlated with the field inspection made on the grower’s crop.

Potatoes in the trials are from growers as far north as Ohakune and as tar south as Southland. There are not many from the North Island as the certification scheme | requires, that the potatoes be grown there at an altitude of not less than 1000 feet About 25 advisory officers took part in the inspection, which also serves as a valuable training ground for younger officers and a refresher course for others. The inspection took about four days to complete.

The trials have been carried out on the Kerrytown property for a number of years, partly because of its central position in relation to the growing districts and also because of the need for a continuing uniformity of growing conditions from year to year.

Mr J. A. S. Miller, farm advisory officer (seed certification), of Palmerston North, who is responsible for the trials and the grouping of the certified seed, said that the potatoes were planted in groups according to variety, and the inspection was divided between officers who were experienced in particular varieties. They worked in pairs. For the other officers the inspection was valuable in broadening their experience and seeing all the entries growing together helped them when they made their field inspections in their local districts. The inspectors record their work in a special book which lists the grower’s name and the name of the grower from whom the seed potatoes were obtained. They record misses, or gaps in the rows, foreign varieties

or “rogues," leaf roll, severe and mild mosaic—the three main virus diseases of pota-toes-wilt disease which is caused by a fungus, blackleg bacterial disease and any subnormal factors such as latecomers and dwarfed plants. In one entry of Sebago potatoes the inspection found among the 150 plants six Up-to-Dates (which were last in the certification scheme in the early 1940’5), one Arran Banner, one Arran Chief and one Iron Duke. Iron Duke and Up-to-Date varieties are very similar in appearance to Sebago. “Rogue” Causes

These “rogues" can be caused by several factors. They may result from ground keepers or self-sown potatoes which have lasted in the pasture for up to six years since the previous crop. They could have remained in the ground from a previous trial some years before or from a farmer’s crop. If there are more than 2 per cent, “rogues" found in the field inspection of the farmer’s planting the line is eliminated from qualifying for grouping. The results of the trial inspection are transposed by Mr Miller to the field inspection report and separate variety sheets are prepared which then give a relation between the entries and the originating seed crop. The incidence of virus disease is averaged and a table is used to determine the grouping. Certified mother seed includes groups 1,2 and 3, and groups 4, 5 and 6 are designated commercial certified seed. Preliminary groupings are

adjusted to the locality in which they are being grown. Mr Miller said that from experience it was known that some areas were more prone to a breakdown through reinfection. These areas were those with higher aphid populations which carried the viruses. The better areas tended to be the foothills and the more southern latitudes. Isolation was also considered. If two adjoining crops were not separated by at least five yards a group 2 line could be downgraded to group 4. Foreign varieties to a degree of more than 1 per cent, would downgrade mother seed to commercial

The final stage before the groupings were announced was a discussion with local advisory officers to iron out any anomalies, Mr Miller said.

Group 1 is a fairly rare designation and to attain this a grower has to have had bis own line for at least five yearns and maintained it in a perfectly healthy condition and completely free from foreign varieties. Hie behaviour of progeny of the grower’s line is also taken into account.

The certification trials also provide for qualifying entries in wtrich a grower eubnrita 50 tubers and provided they measure up to standard and appear true to type and pro* periy named the Mne is permitted to be entered for certification in the normal way the next year. The trials also include

identification plots where samples which have been sent in to advisory officers can be grown and identified by their foliage. Growers aaao use the trials to try out new importations or introductions of known varieties from overseas The land for the trials is provided by the fanner who prepares the ground for planting. The Department provides the fertiliser—about

three to four hundredweight of 3:1 potato manure. This has three parts of superphosphate and one part of sulphate of ammonia. The potatoes are planted by band. After the inspection is made the crop becomes the property of the farmer to harvest and sell. The seed potatoes are of no commercial value as certified seed.

Cowgrasa Entries.—A revised figure for entries of cowgrass for certification this season in the CanterburyMarlborough area has been advised by the fields superintendent of the Department of Agriculture, Mr A. R. Dingwall. The acreage entered is 3359, which is only 540 acres less than last season.