Estimation of narrow-sense heritability for specific gravity in diploid potatoes (Solanum tuberosum subsp.phureja andstenotomum)

Narrow-sense heritability was estimated for specific gravity in diploid potatoes grown at two locations in North Carolina. Three methods used to estimate narrow-sense heritability were realized heritability, parent-offspring regression, and half-sib family analysis. Nine narrow-sense heritability estimates obtained ranged from 0.276 to 0.739. The three estimates least biased by genotype × environment interaction provided an average estimate of 0.428. The selected population was significantly different from the unselected population in specific gravity. Comparable genetic variances in selected and unselected populations suggest that further selection cycles should be effective in increasing specific gravity.     

Effect of nitrogen,phosphorus, and potassium fertilizers on yield components and specific gravity of potatoes

Netted Gem potatoes were grown at four levels of N, three of P, and two of K fertilizer in metal lysimeters protected from rain by an automatic shelter. The first two increments of N fertilizer, 200 and 400lb/acre (224 and 448 kg/ha), successively increased yields by increasing the number of tubers produced. The first increment also increased the average tuber weight. With 800 lb N/acre (896 kg N/ha), tuber yield and grade of potatoes were reduced from those of the 400-lb/acre (448-kg/ha) treatment becuase the average weight per tuber was reduced. P fertilizer increased yield by increasing the average tuber weight. The increased yield due to N and P fertilizers was almost entirely in the form of Canada No. 1 potatoes. K fertilizer did not affect number or weight of tubers in this high-K soil.     

Resistance toErwinia carotovora subsp.atroseptica in second backcross populations of somatic hybrids betweenSolanum tuberosum andS. brevidens

Summary Eleven clones obtained from a cross between cv. Katahdin and fusion products betweenSolanum tuberosum and the non tuber-bearing speciesS. brevidens, were backcrossed again withS. tuberosum (clone AR80-127-5). Small tubers harvested from 583 seedlings of these second backcross (BC2) populations were screened for tuber tissue resistance toErwinia carotovora subsp.atroseptica under aerobic conditions. After multiplication in the field. BC2 clones again were screened for soft rot resistance under aerobic as well as anaerobic conditions. In general, the resistance of the BC2 populations was reduced in comparison with the BC1. Variation for resistance was found within the BC2 populations, but there was no correlation between the results of the three tests performed. Four BC2 populations were also screenned for resistance to blackleg in the field. Significant differences were found between populations for mean percentage of diseased plants, but these differences could not be explained by the resistance of the parental clones.     

Correlation of yield and specific gravity in a tetraploid potato tuberling population

In the fall of 1987 and 1988 true seed from 128 and 83 potato crosses, respectively, were sown in flats in the greenhouses at Beltsville, MD, and approximately 350 seedlings from each cross were transplanted into 7.6 cm pots. The largest tuber from each pot was saved for the field experiment. Tubers from the same family were bulked and shipped to Presque Isle, ME, for spring planting in 50-hill plots. Individual hills of one 50-hill plot from each of 24 randomly selected families were harvested. Within each 50-hill plot, five hills were selected based on horticultural characteristics, such as shape, size, smoothness, and freedom from defects to form the population selected for horticultural characteristics (HC). Specific gravity and yield were recorded for all hills harvested. From the remaining 45 hills, the five highest specific gravity hills were selected to form the population selected for specific gravity (SG). Those hills not selected for either horticultural characteristics or specific gravity formed the unselected population (UP). The average specific gravity for the HC was significandy (P < 0.05) greater than the UP. There was a significant (P < 0.05) negative correlation between yield and specific gravity in the HC and SG. There was no correlation between yield and specific gravity in UP. Selection among this plant material on the basis of horticultural characteristics resulted in a population of significantly (P < 0.05) higher yielding plants whose average specific gravity was significantly (P < 0.05) greater than the UP.     

Effect ofErwinia carotovora subsp.atroseptica on yield of potatoes from cut and uncut seed tubers in Valencia

Summary The effect on the development of blackleg symptoms and on yield of inoculating seed tubers of 15 cultivars withErwinia carotovora subsp.atroseptica (Eca) was investigated. Tubers were planted either whole or as pieces. Eca inoculation reduced the mean yield per plant by 8% for whole tubers and by 12% for cut tubers. There was no correlation between blackleg symptoms and yield loss.     

Correlations for yield and specific gravity between potato tuberling and second year field generations

Individual hills of one 50-hill plot from each of 24 randomly chosen tuberling families were harvested in 1988 and 1989. Within each 50-hill plot, five hills were selected based on horticultural characteristics, such as shape, size, smoothness, and freedom from defects to form the population selected for horticultural characteristics (HC). From the remaining 45 hills, the five highest specific gravity hills were selected to form the population selected for specific gravity (SG). The HC and SG populations from 1988 and 1989 were planted in a randomized complete block design with two replications of six hills in 1989 and 1990, respectively. There was a significant positive correlation for yield and for specific gravity between the tuberling generation and the second year field generation in both 1988–89 and 1989–90. There was no correlation between yield and specific gravity in the second year field generation in either the SG or HC populations for 1989 and 1990. In selecting within the second year field generation on the basis of horticultural characteristics, a clone from the HC population was 1.9 and 1.7 times more likely to be selected in 1989 and 1990, respectively, than a clone from the SG population.     

Evaluation of potato clones for severity of Verticillium wilt, yield and specific gravity in Maine

In 1994 and 1995, the effect of Verticillium wilt, caused byVerticillium dahliae andV. albo-atrum, on tuber yields, number and weight of U.S. No. 1 and B size tubers, and specific gravity was studied in northern Maine, an area with a short growing season. Seven clones (four resistant and three susceptible) were evaluated in a split-plot design with three replications. Clones were the whole-plot factor, and seed pieces in sub-plots were either uninoculated or inoculated with 50 ml of 4 × 10⁴ cfu/mlVerticillium spp. at planting. Individual plants were scored for Verticillium wilt symptoms before harvest on a 1= <3% wilt to 10= >97% wilt. Differences among clones for wilting and specific gravity were significant. The inoculation treatment had no effect on any of the tuber traits measured. However, there were significant clone x inoculation interactions for most tuber traits. Reductions in yield, weight and number of U.S. No. 1 potatoes, and specific gravity were greater in the Verticillium wilt susceptible clones than in the resistant clones. These results suggest that breeding clones with resistance toVerticillium spp. will reduce yield losses, while maintaining tuber size and specific gravity under disease pressure.     

The influence of rates of nitrogen and potassium application on the yield and specific gravity of four potato varieties

Summary The influence of four nitrogen and four potassium levels on tuber yield, specific gravity and dry matter yield was investigated with the varietiesAristo, Irene, Libertas andIJsselster grown on twelve trial fields on sandy soils. Potassium did not improve dry matter yields, since the improvement in tuber yield was cancelled by a corresponding linear decrease in dry matter content (measured as specific gravity). The same result was found with application of more than 80 kg N/ha, except in the varietyLibertas. Nitrogen caused a linear decrease in specific gravity except in the varietyLibertas which reacted weakly and with an optimum curve. Varieties showed different responses in their specific gravity to the various combinations of nitrogen and potassium. The influence of field on yields and specific gravity was considerable, but could not be explained by the known soil factors, such as moisture retention. pH, % organic matter, etc. This applied also for the variations between fields in their reaction to nitrogen, potassium or variety.

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Zusammenfassung Der Einfluss von 0, 80, 160 und 240 kg N/ha (je zur H?lfte als Salpeter und Ammoniak), je kombiniert mit 1, 100, 200 oder 300 kg K₂O/ha (als Sulfat), auf Knollenertrag, spezifisches Gewicht und Trockensubstanzertrag wurde an den SortenAristo, Irene, Libertas undIJsselster auf zw?lf Versuchsfeldern (sandiger Boden) untersucht. Obwohl die B?den ungenügend mit Kalium versehen waren, verbesserte eine Kaliumgabe die Trockensubstanzertr?ge nicht, da die Erh?hung des Knollenertrages durch eine entsprechende lineare Abnahme des Trockensubstanzgehaltes (Bestimmung des spezifischen Gewichtes) ausgeglichen wurde (Abb. 1). Eine Gabe von 80 kg N/ha bewirkte ein bedeutendes Ansteigen des Trockensubstanzertrages, aber eine weitere Gabe von 80 kg N/ha hatte keinen Einfluss, ausgenommen bei der SorteLibertas, die eine schwache Zunahme zeigte. Eine nochmalige Erh?hung der N-Gabe um 80 kg/ha verursachte bei allen Sorten ein Absinken des Trockensubstanzertrages (Abb. 1). Die Anwendung von Stickstoff verursachte bei den SortenAristo, Irene undIJsselster eine Abnahme des spezifischen Gewichtes, nurLibertas reagierte mit einer Zunahme, gefolgt von ciner Abhahme (Abb. 1). Die Sorten reagierten in ihrem spezifischen Gewicht unterschiedlich auf die verschiedenen Kombinationen der angewendeten Stickstoff-und Kaliummengen (Abb. 4). Nach Umrechnung des spezifischen Gewichtes in Trockensubstanzgehalte wurden die Gesamtmengen an Trockensubstanz und Wasser ermittelt. Bei h?heren Stickstoffgaben stieg die Wassermenge deutlich an, was die Transportkosten erh?hte, w?hrend der Trockensubstanzertrag keine Zunahme zeigte. Die einzige Wirkung der Kaliumdüngung bestand in der Zunahme der Wassermenge in den Knollen. Die sortenbedingten Unterschiede waren betr?chtlich (Abb. 5). Nach Errechnung des Ertrages an Chips auf der Grundlage des spezifischen Gewichtes dürfte die Ertragsabnahme infolge der Stickstoffgabe bei 0% (Libertas) bis 0,7% (Aristo) für die ersten 80 kg/ha, und bei 0% (Libertas) bis 0,8% (Aristo) für die zweiten 80 kg N/ha liegen. Die Kaliumgabe dürfte eine Ertragsabnahme von 0,3 bis 0.5% pro 100 kg K₂O/ha bewirken. Die Zunahme des Oelgehaltes der Chips dürfte sich im gleichen Rahmen bewegen.

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Résumé L'auteur a étudié l'influence de doses de 0, 80, 160 et 240 kg N/ha (moitié en nitrate, moitié en ammoniaque), chaque dose combinéc avec 0, 100, 200 et 300 kg K₂O/ha (en sulfate) sur la production de tubercules, le poids spécifique et la production en matière sèche, avec les variétésAristo, Irene, Libertas etIJsselster, cultivées dans douze champs d'essais sur sol sablonneux. Malgré une déficience des sols en potassium, celui-ci n'a pas amélioré les productions de matière sèche, l'augmentation de la production de tubercules étant neutralisée par une diminution linéaire correspondante de la teneur déterminée par le poids spécifique (Fig. 1). Une application de 80 kg N/ha a augmenté nettement la production de matière séche, mais une dose supplémentaire de 80 kg N/ha n'a eu aucune influence sauf chez la variétéLibertas où s'est marquée une légère augmentation. Une autre dose supplémentaire de 80 kg N/ha a amené une chute brusque des productions de matière sèche chez toutes les variétés (Fig. 1). L'application d'azote a causé une diminution du poids spécifique chezAristo, Irene etIJsselster, tandis queLibertas réagissait par une augmentation suivie d'une diminution (Fig. 1). Les variétés ont réagi différemment dans leur poids spécifique aux diverses combinaisons des quantités d'azote et de potassium appliquées (Fig. 4). On a calculé les quantités totales produites de matière sèche et d'eau après conversion des poids spécifiques en teneurs en matière sèche. Des doses élevées d'azote ont augmenté la quantité d'eau produite, accroissant ainsi les frais de transport, tandis que la production de matière sèche ne montre aucun accroissement. Le seul effet de la fertilisation potassique est d'accroitre la production d'eau. Les différences variétales sont considérables (Fig. 5). Après conversion du poids spécifique en production de pommes ‘chips’, la diminution de production causée par l'application d'azote pourrait être de l'ordre de 0% (Libertas) à 0,7% (Aristo) pour les premiers 80 kg N/ha, et de 0% (Libertas) à 0,8% (Aristo) pour les seconds 80 kg N/ha. L'effet du potassium pourrait être de diminuer la production de 0,3 à 0,5% par 100 kg K₂O/ha. L'augmentation de la teneur en huile des chips poura?t être du même ordre.

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Then stationed at the Provincial Research Centre for Agriculture in Drenthe, Assen, The Netherlands. Present address