Peas For Processing

Press, Volume CVIII, Issue 31866, 19 December 1968, Page 20

Peas For Processing

New varieties of peas tailored to fit the requirements of the processing industry may result from a breeding programme that is being conducted by the Crop Research Division of the Department of Scientific and Industrial Research.

The division's aim is to combine good processing characteristics with resistance to virus diseases which affect the yield or quality of varieties now grown for the industry.

If this could be done, the industry’s costs would be reduced, and the scope for export of peas, whether processed or as seed, would be increased. The division’s pea breeder, Mr M. J. Crampton, has made mapy crosses between good processing varieties which are susceptible to viruses, and resistant varieties which are of good quality but not ideal for processing. Some crosses have resulted in promising disease-resistant lines, and the most advanced of these have already reached the stage where quality testing has been undertaken with the co-operation of processors at Hastings and Christchurch. Major Crop Peas are a major crop in New Zealand. Last year, about 16,000 acres of them were grown for processing, mainly in the Hawke’s Bay, Gisborne, Nelson, Marlborough and Canterbury districts. Large acreages are also sown for seed production, mainly in Canterbury and Marlborough. Frozen peas have become an important export product, increasing quantities being sold to Australia and Britain. Producing varieties specially suitable for the processing industry is something of a tall order for the plant breeder. The vines must not grow higher than two feet. The pegs must mature as nearly as possible all at the same time, and slowly enough to

ensure that they can be harvested before passing their peak of quality. The pods must be easily threshed, and the peas must Ije thin-skinned but able to stand mechanical harvesting without damage. They must be fairly even in size, no fewer than seven to the pod, and of a deep green colour that does not change much in processing. They must be sweet in flavour and not mealy in texture. The variety regarded as coming closest to these requirements in New Zealand is Victory Freezer, and this is the pea that is now mainly grown for processing, except in Canterbury, where Greenfeast is the most popular variety. The most important diseases affecting pea crops in New Zealand are mosaic and top yellows, both of which are caused by aphis-borne viruses. They are not controlled by systemic insecticides or sprays because the aphids transmit the viruses from other plant species, and have already infected the pea vines before being killed by the insecticide. Mosaic is a serious problem in Hawke's Bay and Marlborough. Peas from infected vines are hard and discoloured, and are unsatisfactory for processing. Incidence of the disease tends to be patchy in the field, but mechanical harvesters make no distinction between healthy and diseased, so an otherwise good quality crop can be spoiled by a percentage of diseased peas.

Top yellow occurs in all growing districts. It causes yellowing of the vine tops, and kills many plants. It affects the quantity rather than the quality of the chop, because infected plants do not produce seed, and peas from the healthy vines are normal. Heavy infections reduce yields by 20 to 30 per cent. The Victory Freezer variety is resistant to top yellows but susceptible to mosaic. At Crop Research, Mr Crampton has crossed it with William Massey and Greenfeast 68, both of which are good quality peas and resistant to mosaic. The resultant lines appear to yield well and resist virus diseases, but it has yet to be

proven that their other qualities will be suitable. A number of other crosses of different -parentage, not all including Victory Freezer, are at earlier stages of development. As seed becomes available, the hybrids produced are being tested in various parts of New Zealand, and also, with an eye on export possibilities, in Tasmania and Britain. However, it will take some years of further testing before the merits of any of these crosses can be fully assessed and decisions made on whether to develop and release new varieties based on them.