R. A. Genet

Field performance of transgenic potatoes

Abstract Field performance was assessed in 13 transgenic potato (Solanum tuberosum L.) lines from three cultivars expressing a selectable marker gene conferring kanamycin resistance. All lines developed unexpected changes in the phenotypic appearance of shoots, and/or poor tuber yield generally involving a reduced number of small tubers. Each independently selected transgenic line showed distinctly different changes in phenotypic appearance or yield performance. The observed changes were very uniform within each clonally propagated transgenic line, and were consistent in appearance over two seasons in the field. These changes were attributed to either epigenetic or genetic events occurring during the tissue culture phase of transformation. Efficient systems for the rapid selection and regeneration of transformed plant cells are therefore required to minimise the frequency of tissue culture induced variation in plant performance.

Assessment of seed tuber, in‐furrow, and foliar chemical treatments for control of powdery scab (Spongospora subterranea f.sp. subterranea) of potato

Abstract Two field trials were carried out (at different sites at Lincoln, Canterbury, New Zealand) to test the efficacy of chemicals for control of powdery scab (caused by Spongospora subterranea (Wallr.) Lagerh. f. sp. subterranea Tomlinson) of potato (Solanum tuberosum L.). In Trial 1, at a site where potatoes had not been previously grown, 17 seed tuber treatments and eight in‐furrow treatments were applied just prior to, or at, planting, to seed tubers of ‘Agria’ infected with powdery scab, and six foliar treatments were later applied to plants grown from infected tubers. In Trial 2, seven in‐furrow treatments were appl ied at the time of planting healthy seed tubers of ‘Rua’ or ‘Agria’ into a field site heavily infested with S. subterranea, and one foliar treatment was later applied to plants of ‘Rua’. Both trials were irrigated to provide soil conditions likely to encourage development of powdery scab. The trials were harvested at crop maturity, when all tubers were assessed for powdery scab infect...

Control of powdery scab of potatoes with chemical seed tuber treatments

Abstract Powdery scab, caused by Spongospora subterranea (Wallr.) Lagerh. f. sp. subterranea Tomlinson, has become an increasingly important problem on potatoes grown in New Zealand in recent seasons. During the 1992/93 season, the efficacy of 25 chemical seed tuber treatments against tuber‐borne inoculum of S. subterranea was tested in a field trial. Four treatments (stored treatments) were applied 6 weeks before planting whereas 21 were applied within 24 h of planting. Treatments were applied to tubers of cultivars ‘Agria’ (which had severe powdery scab infection) and ‘Rua’ (light infection). Plant emergence was assessed and tubers from the subsequent crop were harvested and scored for powdery scab infection. Yield parameters were also determined. Mancozeb, formaldehyde solution, fluazinam, propineb, dichlorophen‐Na, and mixtures of maneb + zinc oxide, mancozeb + zinc oxide, propineb + zinc oxide, fluazinam + zinc oxide, and tolclofos‐methyl + cupric hydroxide, applied to ‘Agria’ tubers just before plan...

‘Karaka’: A new fresh market potato with high resistance to Globodera pallida and G. rostochiensis

Abstract ‘Karaka’ is a new potato cultivar with high resistance to all populations of potato cyst nematode (Globodera pallida and G. rostochiensis) that occur in New Zealand. Its main market niche is as an early to early maincrop fresh market potato, and it has some potential for french fry production.

‘Gladiator’: A new potato cultivar with high resistance to potato cyst nematode and powdery scab suitable for french fries and fresh market

Abstract ‘Gladiator’ is a new maincrop potato (Solanum tuberosum L.) cultivar with resistance to both potato cyst nematode species (Globodera rostochiensis and G. pallida) and powdery scab (Spongospora subterranea). It has long oval, block‐shaped tubers suitable for french fry manufacture when mature and for fresh market when still immature.

Screening the New Zealand potato germplasm collection for resistance to sugar accumulation during low temperature storage

Abstract The ability of potato (Solanum tuberosum) cultivars to withstand cool storage without accumulating reducing sugars would allow manufacturers of fried potato products to process potatoes year‐round without the development of undesirable Maillard browning compounds. More than 600 potato cultivars and selections held by the New Zealand Institute for Crop & Food Research Limited were screened over three seasons ( 1991–93) to identify material with resistance to cold‐induced sweetening. Potato lines were tested 1–2 weeks after harvest using diabetic glucose test tape, and those with glucose levels below 0.1% (1 g/litre) in the potato juices were stored at 4°C for 2 and 4 months. The effect of any changes in sugar levels on chip colour was then reassessed by frying thin slices in oil and measuring the development of Maillard browning in individual crisps by image analysis. Tubers which failed to produce crisps of an acceptable colour were reconditioned at 18–20°C for up to 4 weeks and retested. Lines w...

‘Moonlight’: A new dual‐purpose main crop potato (Solanum tuberosum) cultivar

Abstract ‘Moonlight’ is a new early‐main to main crop potato (Solanum tuberosum) cultivar with high yield potential that has been developed for both the fresh market and French fry production. Tubers are oval and have white flesh. ‘Moonlight’ has moderate resistance to the cream potato cyst nematode (Globodera pallida) and has the H1 gene for resistance to G. rostochiensis. It also has moderately high resistance to powdery scab (Spongospora subterranea) and bacterial soft rot (Erwinia sp.)

‘Dawn'—a new early‐maincrop fresh market/crisping potato cultivar

Abstract ‘Dawn’ is a new, high‐yielding, early‐maincrop potato (Solanum tuberosum L.) cultivar suited to the fresh market and crisp manufacture. Tubers are round‐oval in shape and have white flesh. This variety has moderate resistance to late blight (Phytophthora infestans) and to powdery scab (Spongospora subterranea).

‘White Delight’: A new maincrop fresh market potato cultivar

Abstract ‘White Delight’ is a new, high yielding, maincrop potato (Solarium tuberosum L.) cultivar suitable for the fresh market and crisp manufacture. Tubers are round—oval in shape and have white flesh. This variety has moderate resistance to late blight (Phytophthora infestans) and to bacterial soft rot (Erwinia sp.).

‘Pacific’: A new fresh market and crisping potato cultivar

Abstract ‘Pacific’ is a new mid‐season to main‐crop potato (Solanum tuberosum L.) cultivar suitable for both crisping and the fresh market. Tubers are round to round‐oval with light yellow flesh. ‘Pacific’ has partial resistance to the cream potato cyst nematode (Globodera pallida).