Stability of eight potato genotypes for sugar content and French fry quality at harvest and after storage

Affleck, I., Sullivan, J. A., Tarn, R. and Yada, R. 2012. Stability of eight potato genotypes for sugar content and French fry quality at harvest and after storage. Can. J. Plant Sci. 92: 87–96. Processing quality of potatoes for French fries is partially determined by reducing sugar content of the tuber. Much of the potato crop is processed after a storage period when sugar content can change and affect processing quality. In this study, the stability of sugar levels in eight potato genotypes was studied over four environments (i.e., two locations over 2 yr). The GGE biplot analysis was used to measure the stability of, and the association between, quality traits and sugar content. Quality and sugar content were measured 105 and 120 d after planting and 60 and 120 d after storage. The biplots indicated a change in French fry colour scores and stability between the 105 and 120 d after planting harvest dates. Genotypic differences were noted for French fry colour scores and glucose content. Genotypes were identified that were stable for French fry colour during the two storage periods indicating low genotype by environment interaction. The GGE biplot identified mega-environments that encompassed a group of environments with similar attributes. Based on this finding potatoes from only one environment within the mega-environment would need to be stored for quality evaluations.

Genotype by environment interaction effect on yield and quality of potatoes

Colour is an important character in the processing of potatoes for French fries. French fry colour is closely associated with sugar content in the tuber. This study examines the stability of yield, sugar content and French fry colour for eight potato cultivars and advanced selections in four environments. Stability was determined using three approaches based on the Eberhart-Russell, Tai and GGE Biplot analyses. The GGE Biplot analysis provided a better characterization of stability than the other two analyses. The most stable and best performing genotypes for both French fry colour and total sugars were Russet Burbank and Umatilla Russet. Cal White had high yield and yield stability but had average stability for poor (dark) French fry colour. The GGE biplot analysis was able to identify mega-environments and those environments which optimized differentiation between genotypes. Both factors are important for the optimization of resources for testing new genotypes. Stability for quality factors in potato can be as important or more important than yield for some processing uses. In this study, genotypes with stability for sugar content and French fry colour were identified and these may be used as parents in breeding for stability. Key words: Potato, yield stability, quality, French fry

Rate and timing of nitrogen fertilization of Russet Burbank potato: Yield and processing quality

Split fertilizer N application is thought to improve fertilizer N use efficiency of potato, primarily by reducing NO3 leaching losses. This study evaluated the effects of the rate and timing of N fertilization on yield and processing quality of Russet Burbank potato under rain-fed production. Trials conducted in 1999–2001 included different fertilizer N rates (0–160 kg N ha-1 in 1999 and 0–200 kg N ha-1 in 2000 and 2001) applied either at planting according to normal grower practice, or at hilling, the latest time that granular fertilizer can practically be applied. Tuber total and marketable yield, size distribution, specific gravity, fry colour and tuber concentrations of NO3, sucrose and glucose were measured. Increasing rates of N fertilization increased tuber yield and tuber size, increased tuber NO3 concentration and decreased tuber specific gravity, but had little effect on tuber sugar concentrations or fry colour. Season-to-season variations in total tuber yield responses to N fertilization rate were attributed primarily to variation in soil N supply. Timing of N application had little effect on tuber yield, size distribution or processing quality under adequate soil moisture conditions. However, under dry soil conditions, split N application reduced tuber yield and tuber size. Key words: Solanum tuberosum, tuber specific gravity, tuber nitrate concentration, fry colour

Effects of field treatments on processing quality of Record and Pentland Dell potatoes during storage

SUMMARYPrevious research has suggested that fry colour of processed potatoes is inversely correlated with tuber reducing sugar content, and agronomic practice should therefore be tailored to minimize amounts of tuber sugars at harvest and during storage as a means of maximizing processing quality. A total of 30 experiments from three sites in England from 1985 to 1988 examined this hypothesis for two cultivars using a wider range of husbandry than that used in practice and long periods of storage. No tuber sugar value was sufficiently well correlated with fry colour for the relationship to be interpreted as causal and of use predictively, irrespective of whether it was measured early in growth, at harvest or at the time of processing. Fry colour at harvest was not correlated with fry colour after storage. No agronomic practice (variables used were physiological age, date of planting, irrigation or date of harvest) consistently caused fry colours to be darker than the acceptable colour limit, whether at harvest or after long term storage. Crops producing unacceptable fry colours early in storage generally improved to produce acceptable fry colours after long term storage. Agronomic practices within the range normally found in commercial production are therefore considered to have little effect on long-term processing quality, although harvesting, handling and transport operations were not investigated.