Potato Research

The importance of the potato tuber disease powdery scab, caused by the zoosporic pathogen Spongospora subterranea f. sp. subterranea, has increased worldwide, and the disease is one of the most important problems facing potato production in some regions. This soilborne pathogen produces many resting spores which can remain dormant for long periods, are highly resistant to environmental stresses and can spread the disease on seed potatoes and in contaminated soil. The enigmatic nature of this organism exacerbates the development of effective powdery scab control methods. Substantial knowledge has been gained in the last decade on the biology of the pathogen and the epidemiology of the disease, but no single effective control measure is, or is likely to be, available. An integrated approach to powdery scab management is the aim, with host resistance as a substantial and sustainable component. Further research on the epidemiology of powdery scab and population genetics of the pathogen is urgently required. All stakeholders involved in the potato industry must become aware that solution of the powdery scab problem is likely to be a long-term goal. When resistant cultivars with all the other characteristics demanded for marketing high-quality potatoes are available, and when disease risk from the pathogen on seed and/or in soil can be accurately determined, then the mission to develop effective powdery scab control will become achievable.

Two culture systems for propagating first generation potatoes were compared; the traditional system used a peat/sand mixture with mineral fertilizer, and hydroponic culture used perlite and nutrient solution. Total production and the number of tubers obtained using the hydroponic system were significantly higher than using the traditional culture system. Tuber yields from in vitro plants and minitubers depended upon time of year. During the autumn/winter cycle yield from minitubers was double that from in vitro plants, whereas the reverse was true during the spring/summer cycle. Four hydroponic test cultures were carried out to study the influence of seed density. The number of tubers obtained increased significantly with seed density but there was no decrease in the number of large-diameter tubers.

Haploid plants (2n=12) were produced by anther culture from the tuber-bearing wild speciesS. verrucosum.

Plant water status information of potato (Solanum tuberosum L. cv. Russet Burbank) is needed at the farm level for irrigation scheduling. This research investigated the feasibility of using a 5-megapixel digital camera to determine the leaf water potential (ΨL) of potato plants by capturing red, green, blue (RGB) digital images in the visible region of the electromagnetic spectrum. A greenhouse experiment was conducted in containerized cv. Russet Burbank potato plants subjected to five soil nitrate-nitrogen (N) levels and four soil water content levels. An artificial neural network (ANN) model, built with RGB images, RGB image transformations, RGB vegetation indices, and principal components analysis, found that for the validation data set, the measured ΨL and predicted ΨL results were from common populations. Other results showed: (1) a linear trend between soil nitrate-N levels and leaf reflectance in the G image band, (2) that the RG image bands were more suitable than the B image band for classifying leaf pigment from leaf shadow and leaf damage, (3) soil nitrate-N interacted with leaf greenness, affecting ΨL prediction, and (4) some image variables were more important than others in the ANN model. Although this greenhouse research shows promise, further field-based research is required to validate the selection of input neurons used and also validate the use of ANN modelling to determine ΨL at the plant canopy level with cv. Russet Burbank and other cultivars. In addition, an image acquisition method needs to be developed to obtain periodic representative sample coverage over a field.

Potato stem cuttings, cv. Désitrée, were treated with a powder formulation of 4-indol-3-ylbutyric acid (IBA), a gel formulation of 1-naphthylacetic acid (NAA), or a powder formulation of NAA. Both the IBA powder and the NAA gel stimulated significantly more roots per rooted cutting than were produced by the untreated controls but the NAA gel also significantly reduced the number of root branches per rooted cutting (Table 1). Untreated cuttings of cvs. Désirée and Recond were more likely to form only roots when the basal internode was long and more likely to form only tubers when the basal internode was short (Table 2). We suggest that the number of stem cuttings forming roots would be increased if, where necessary, the cuttings were trimmed to leave a long basal internode.

The weight in water (m u ) of 100 g air-free potatoes multiplied by the dry matter factor (K) equals the percentage dry matter (m t ) in the tubers. The weight in water is unaffected by the water in the potatoes but is reduced by air in the intercellular spaces and must be corrected for this by a constantk. From the specific gravity of the dry matter the factorK is estimated as 2.50. From the weight in water and the percentage of dry matter estimated by oven-drying of 5.413 samples between 1937 and 1964.K is also estimated as 2.50. The amount of air in potatoes varies. In 1.911 samples examined between 1937 and 1948 air reducedM u on average by 0.8g, therefore,m t (m u +0.8)·2.5 orm t ·m u 2.5–2.00., In 2,732 samples examined between 1952 and 1964 the reduction was 0.6 g therefore,m t —(m u —0.6) 2.5 orm t ·m u ·2.5+1.5. The percentage dry matter can be calculated more exactly from the weight in water of potatoes from which the air has been evacuated by immersing the tubers in water in a closed container and subjecting to vacuum (50–20 mm Hg) for about 30 minutes.

The association of ground cover and ground cover duration with fresh- and dry-weight potato tuber yields in a semi-arid Mediterranean climate, was investigated. Cultivars of different maturity classes were tested under the contrasting climatological conditions of the spring and autumn seasons. The correlation coefficients of ground cover (GC) and ground cover duration (GCD) with fresh- and dry-weight tuber yields were lower for the autumn than for the spring season. In both seasons, high yields were positively correlated with high GCD. However, variation in tuber yields was evident in cultivars with similar GCD, indicating the involvement of factors other than ground cover and light interception in tuber yield.