Assessing six Austrian potato cultivars for resistance toErwinia carotovora subsp.atroseptica

Summary The susceptibility of six new Austrian cultivars to soft rot, stem rot and blackleg caused byErwinia carotovora subsp.atroseptica was assessed over 2 years in two locations. Soft rot susceptibility was assessed by whole tuber and half tuber tests, stem rot by stem inoculation and blackleg by planting inoculated tubers in the glasshouse. The susceptibility of the cultivars tested with the tuber and blackleg test methods were in general agreement. The half tuber test was more precise in differentiating intermediate levels of susceptibility than the whole tuber test. The reaction of the cultivars to soft rot could be classified as susceptible (Gina and Romina), moderately susceptible (Ditta, Sonja and Bintje), or slightly susceptible (Treff, Komet and Désirée). Results from the stem rot test did not agree with this classification and also depended upon the physiological state of plants as influenced by growing season and glasshouse conditions.     

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.     

Preliminary selection of antagonists ofErwinia carotovora subsp.atroseptica (Van Hall) Dye for application during green crop lifting of seed potato tubers

Summary Green crop lifting (GCL) for haulm killing was developed in The Netherlands and offers ideal conditions for controlling the blackleg pathogenErwinia carotovora subsp.atroseptica (Eca) by antagonists. Based on the use of mini-tubers or young tubers from field crops, two bioassays for wound protection were developed. GCL was simulated by artificially skinning or wounding tubers, inoculating the damaged skin with Eca, treating with antagonists and incubating in either potting compost or outside in field soil. Mainly fluorescent pseudomonads, pre-screened for in vitro antagonistic activity on agar and high soft rot reducing ability on tuber slices, were tested in the mini-tuber bioassay. Strains giving the highest degree of wound protection were further tested individually and in combination under field conditions in the young tuber bioassay. One individual strain and two combinations, resulting in reduction of contamination levels on skinned surfaces of 85% and between 60% and 70%, respectively, show good potential for biological control of blackleg.     

Impact of Agronomic Strategies (Seed Tuber Pre-sprouting,Cultivar Choice) to Control Late Blight (<Emphasis Type="Italic">Phytophthora infestans</Emphasis>) on Tuber Growth and Yield in Organic Potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.) Crops

In order to optimize potato crop management in organic farming systems, knowledge of crop growth processes in relation to limitations and reductions by nitrogen (N) and disease is necessary. This paper examines the effect of different prevention measures (seed tuber pre-sprouting, choice of cultivars: resistance to Phytophthora infestans; earliness of tuber initiation) against disease-related constraints on yields, depending on the N-mediated growing conditions of organic potato crops. Under conditions of a relatively high N supply, accelerating the early development and tuber initiation of potato crops by seed tuber pre-sprouting (yield increase of c. 18–23%) or the selective choice of cultivars with an earlier tuber initiation (yield increase of c. 0–21%) are the most effective strategies in combating late blight. They bring forward the crop development c. 7–10 days, escaping the negative impact of the fungus on tuber growth. Under conditions of a relatively low N supply, these strategies do not affect final tuber yield. The reason for the differences of the effect depending on N supply of the crops is, that the lower the N supply, the shorter the period of time over which tuber growth takes place, independent of whether P. infestans becomes severe or not. Tuber growth of organic crops low in N has mostly ceased by the time late blight becomes potentially important for limiting yield, with the consequence that preventative measures against P. infestans are meaningless. Surprisingly, the level of cultivar haulm resistance to late blight did not affect tuber yields in years with an early and strong late blight development. Probably, the positive effect of a longer resistance to the fungus (c. 1 week) was counterbalanced by a later tuber initiation (also c. 1 week). In years with a moderate late blight incidence, less susceptible cultivars were able to produce higher tuber yields on fields with a lower N availability (c. 17–20%), probably due to higher N use efficiency and a better match of N mineralization and N uptake. Under conditions of a relatively high N supply, the tested cultivars with a higher haulm resistance to late blight were not able to improve tuber yields.     

Erwinia carotovora subsp.atroseptica infection promotes verticillium wilt development in potato in Israel

Summary The interaction betweenErwinia carotovora subsp.atroseptica (Eca) andVerticillium dahliae and its effect on symptom development in potato cultivars showing different degrees of resistance to them was examined over two seasons in irrigated fields in a hot, dry climate. Four cultivars were used: Cara, highly resistant to blackleg and tolerant to Verticillium wilt; Pentland Crown also resistant to blackleg but susceptible to Verticillium wilt; Désirée, moderately susceptible to blackleg but tolerant to Verticillium wilt; and Maris Bard, susceptible to both diseases. Seed tubers were inoculated with Eca immediately after harvest in Scotland, to simulate natural infection, and then planted in Israel in soil naturally infested byV. dahliae. In Verticillium tolerant cultivars, Eca infection increased the rate of colonization byV. dahliae and significantly enhanced symptom development, as assessed by suppression of plant height and wilt symptoms. This report is a portion of the Ph.D. thesis of the senior author in Ben-Gurion University of the Negev.     

The Effect of Nitrogen Rate on Vine Kill,Tuber Skinning Injury,Tuber Yield and Size Distribution,and Tuber Nutrients and Phytonutrients in Two Potato Cultivars Grown for Early Potato Production

Early potatoes are typically produced using less nitrogen than a full season potato crop as high rates of nitrogen may delay tuber set and lead to excessive vine growth that is difficult to terminate prior to harvest. Bintje and Ciklamen potato cultivars were grown with preplant soil nitrogen levels of 34 to 38, 67, and 101 kg N ha^-1 in 2013 and 2014 near Paterson, Washington. Nitrogen rate had little impact on the number of tubers and stems per plant of both cultivars, but increasing nitrogen rate tended to increase leaf area of both cultivars. Vine desiccation of Bintje with diquat was less complete as nitrogen rate increased, while Ciklamen vine kill was reduced by higher nitrogen in 1 of 2 years. Tuber skinning injury, tuber weight loss, and tuber size distribution were not affected by nitrogen rate. Tuber skinning injury and tuber weight loss were reduced in both cultivars by harvesting at 4 weeks after initial vine kill compared to harvesting at 2 weeks after vine kill. Total tuber yield was lower for both Bintje and Ciklamen in 1 of 2 years at the 34 to 38 kg N ha^-1 rate. Tuber nitrogen and zinc levels tended to increase with increasing nitrogen rates, while most other nutrients, vitamin C, total phenolics, and antioxidant capacity showed little response. It appears that 67 kg N ha^-1 provides adequate nitrogen to produce a good tuber set and yield of small tubers while not producing excessive vine growth that may be more difficult to kill.     

Aspects of nitrogen fertilizer rate on tuber dry-matter content of potato cv. Record

Summary Effects of three rates of fertilizer nitrogen, viz. 80, 160 and 240 kg N/ha, on tuber yield and dry-matter percentage in potato cv. Record were compared in two experiments. Crop nitrogen uptake increased with application rate but total uptake differed between experiments. Tuber yield was highest following application of 160 or 240 kg N/ha but differences between these two rates were not significant. Tuber dry-matter percentage was reduced in one experiment with increasing nitrogen rate, but in the second experiment final dry- matter percentage was highest following application of 240 kg N/ha. In all treatments, positive linear relationships were found between dry matter percentage and mean fresh weight of tubers >30 mm, but within experiments, the regression coefficients were generally reduced by increased crop nitrogen uptake.     

Variation in tuber pathogenicity ofPhytophthora infestans in the Netherlands

Summary Variation in aggressiveness to tubers among isolates ofPhytophthora infestans sampled from three potato growing regions in the Netherlands was compared. Variation in the ability to infect tubers of cv. Bintje was found between isolates of each of the three regional populations. The most aggressive isolate of the old population matched the average level of the new population in its ability to infect tubers. As a consequence, the commonly used reference isolate VK 6C can no longer be considered to be representative of the present population ofP. infestans. Therefore it is recommended that testing tuber resistance for the official list of potato cultivars with this isolate should be discontinued. Tuber infection and subsequent spread of the fungus in the tuber tissues were not found to be correlated. The components of tuber pathogenicity studied were not correlated to pathogenicity factors in the foliage, as measured under growth chamber conditions.     

Relation between growth conditions and dormancy of seed potatoes. 1. Effects of nitrogen

Summary The duration of dormancy of seed potatoes varies between years and between origins. Therefore, the effects of conditions during crop growth on dormancy of progeny tubers were studied. The effect of nitrogen during tuber bulking on the duration of dormancy was investigated in three field experiments with two cultivars. In addition to an application of 125 kg N/ha at planting, top dressings of 0–150 kg N/ha were given about 2 weeks after tuber initiation. Haulm was pulled about 4 weeks later. The effect of nitrogen rate at planting was also examined in one experiment. Nitrogen top dressings shortened dormancy in all experiments by 5–8 days. An increased nitrogen rate at planting resulted in a shorter dormancy when the duration of dormancy was expressed in days after tuber initiation, but not when it was expressed in days after haulm pulling, probably because extra nitrogen also delayed tuber initiation.     

实时定量荧光PCR法检测马铃薯黑胫病菌

马铃薯黑胫病是国内外马铃薯产区发生比较普遍的一种细菌性病害,严重地影响了马铃薯的产量和质量。本研究根据Potato Black Leg序列,设计出马铃薯黑胫病菌特异性的引物,对10种供试菌株进行了实时荧光PCR检测。结果表明,该方法的特异性好,可以将马铃薯黑胫病菌和其它马铃薯常见病害相区分;灵敏度较高,可检测出最低的黑胫病菌浓度为3.6~3.9 cfu.mL-1;而且检测时间仅用4 h,大大缩短了检测周期。该方法可有效地应用于马铃薯黑胫病菌的检测和监控。     

Potato planter performance and effects of non-uniform spacing

A survey of potato (Solanum tuberosum L.) plant stands in upstate New York over a three-year period showed that the average distance between plants was 4 cm wider than intended. Plant stands averaged 83%. The failure to plant seed pieces was the major reason for missing hills. Seed rot was not generally a problem, although one field in the survey was severely affected. Speed of planting up to 6.7 km/h had no consistent effect on average spacing or uniformity of seed piece distribution. Seed type (whole or cut) and mechanical condition of planter influenced spacing. Experiments conducted over four years indicated that the non-uniform seed piece distribution delivered by commercial picker-arm planters does not adversely affect crop yield or tuber size. Non-uniform seed distribution with extremely high coefficients of variation (greater than 100%), however, affected yield, tuber size and tuber number. Tuber numbers and yields were decreased by reducing the number of seed pieces planted per unit area whether or not the pieces were uniformly spaced.     

Effect of seed piece population on the yield and processing quality of Russet Burbank potatoes

The effect of seed piece population on tuber yield, size distribution and processing quality of Russet Burbank potatoes grown under nonirrigated conditions in southern Manitoba from 1983 to 1987 was determined. Seed pieces were planted at 21.7, 26.3, 33.3 and 45.5 thousand seed pieces per hectare, and plant emergence generally exceeded 90% of the seed piece population. Marketable tuber (greater than 5 cm in diameter) yields were not affected by seed piece population. As population increased, however, the number of harvested tubers increased and average tuber size decreased, which resulted in a decreased yield of premium tubers (greater than 284 g) and an increased yield of small tubers (less than 5.0 cm in diameter). Specific gravity, the incidence of hollow heart in maingrade (5 cm in diameter to 284 g in weight) and premium tubers, and fry color were not significantly affected by seed piece population. In the one trial tested, sucrose content decreased as population increased, however, this was not reflected in improved fry color after storage.     

Soft rot and blackleg reactions in diploid potato hybrids inoculated withErwinia spp.

From 1993 to 1996 three groups of potato genotypes were evaluated for resistance toErwinia spp.: (1) 31 interspecific diploid hybrids (28 resistant and three susceptible), (2) five hexaploid or pentaploid somatic hybrids ofSolanum tuberosum (tbr) ×S. brevidens (brd), and (3) eight cultivars. Two evaluation methods were applied: tuber point inoculation with eitherErwinia carotovora ssp.atroseptica (Eca) orE. chrysanthemi (Ech) to test tuber soft rot resistance and stem base inoculation with Eca to test blackleg resistance. Some resistant diploid hybrids and somatic hybrids oftbr × brd were superior to cultivars for both tuber and stem resistance. Tuber and stem resistance toErwinia spp. in the most resistant diploid hybrids were equal to the highly resistant somatic hybrids oftbr xbrd. Tuber resistance to Eca was highly correlated to tuber resistance to Ech (r=0.815***). In two years of evaluation for stem resistance, three diploid hybrids and a derivative of one of the somatic hybrids (USA M 264) failed to develop symptoms of blackleg following inoculation with Eca, Analyses of variance for tuber and stem resistance indicated significant effects of genotype, year and genotype × year interaction. A positive relationship between tuber and stem resistance toErwinia spp. has been found, however the genetic control of resistance in tuber and stem is partially independent. In the case of Eca the correlation coefficient was r = 0.725***. Therefore it should be possible to obtain resistant genotypes to both blackleg and tuber soft rot. Several resistant diploid hybrids were selected from among those tested, which also have several other characters desirable for potato breeders.     

The effect of chloride fertilization on blackspot susceptibility and other quality characteristics and on yield of potato

Summary Trials were carried out in two years on a sandy loam and on a heavy clay soil with two cultivars to examine the potential of chloride fertilization as a tool to reduce blackspot susceptibility of potatoes and to investigate other effects on yield and quality. Blackspot susceptibility was significantly reduced in cv. Marijke, but not in cv. Bintje as a result of increasing doses of applied chloride from 0 to 400 kg ha1. Dry matter concentration, assessed as under-water weight, was reduced by chloride in both cultivars at the two locations. Fry colour of French fries was improved by chloride. Applying 400 kg ha⁻¹ Cl⁻ to both soil types decreased net tuber yield >35 mm of cv. Bintje but not of cv. Marijke. Chloride caused slower emergence, retarded crop development and less stems per plant on the sandy loam soil but not on the heavy clay soil.     

The effect of green crop lifting on the contamination of seed potato tubers by pathogenicErwinia spp.

Summary In the Netherlands seed potato crops are harvested when still green, the haulm being destroyed before harvest. We compared the effect on the contamination of seed potatoes byErwinia carotovora subsp.atroseptica (Eca) andE. chrysanthemi (Ech) of the common method of haulm destruction by flailing and chemically destroying remaining stems, with the recently developed green crop lifting method. After chenical haulm destruction the levels of contamination with both Eca and Ech surviving cold storage were found not to differ significantly from those after green crop lifting. Losses due to watery wound rot (Pythium ultimum) were considerable in the warm and humid conditions during 1991, especially after green crop lifting.     

Yield-enhancing and tuber-downsizing effects of transplantation cultivation method of case-held tuber seedlings in the sweet potato cultivar Beniharuka

We developed transplantation cultivation method of case-held tuber seedlings (CTS), which was derived from direct planting method of seed tubers, and applied this method to the sweet potato cultivar Beniharuka. A plastic case made of polypropylene was designed for cultivation of CTS. Seed tubers of cultivar Beniharuka in the range of 30–80 g were cut in half. The half-cut tubers were placed inside the plastic cases, and the cases were filled with a commercial soil mix. The case-held tubers were incubated under natural sunlight in a glass house. After 3–4 wk, the CTS were transplanted into a field. Mother tuber (seed tuber) enlargement was suppressed by the plastic confinement of the cases, and daughter tubers were formed above the case as vine-root-originated tubers. In the field experiments in 2012 and 2013, daughter tuber yields were increased 19% and 21% by case-held tuber seedling transplanting (CTST) over conventional vine-planting (VP), the number of daughter tubers per plant in CTST were 36 and 68% higher than in VP, and the mother tuber yields were limited to 2.1 and 4.3% of the total fresh yield of mother and daughter tubers, respectively in 2012 and 2013. Application of CTST method to cultivar Beniharuka enhanced tuber yield, increased the number of daughter tubers per plant, downsized daughter tubers compared to VP, and mother tuber enlargement was suppressed by case-holding. The CTST method is expected to produce more and smaller good in shape tubers of cultivar Beniharuka compared to VP.     

Position and date of seed tuber inoculation byErwinia carotovora ssp.atroseptica and appearance of potato blackleg

Summary The date of inoculation and the part of the potato seed tuber inoculated both influenced the number of blackleg plants appearing in June, July and August. In winter, inoculation of the heel end was more effective than inoculation of the rose end of seed tubers, but there were no significant differences following inoculation earlier, in autumn, or later, in spring.     

Comparison of the interactions ofErwinia carotovora ssp.atroseptica withPhytophthora infestans, Phoma foveata andFusarium coeruleum in rotting potato tubers

Summary An interaction betweenP. infestans andE. carotovora subsp.atroseptica (Eca) in rotting tubers was confirmed and the biochemical basis for its occurrence investigated. The pH of tissue infected withP. foveata became alkaline whereas tissue infected withP. infestans orF. coeruleum did not rise above neutrality, which could promote pathogenicity of Eca by maintaining pH closer to the optimum for polygalacturonase activity. Polygalacturonase, pectate lyase and galactanase were detected in cultures of all three fungi grown on media containing cell wall material or pectin from tubers. AsP. infestans produced more polygalacturonase than the other two fungal tuber rot pathogens the possibility was investigated that oligogalacturonide products of enzymatic degradation of pectin byP. infestans stimulates pathogenicity of Eca. However, while tubers soft-rotted after infiltration with supernatant from fungal cultures grown on tuber cell wall material, controls showed that rotting resulted from infiltration rather than the products contained in the infiltrated water.     

The effect of netted scab (Streptomyces spp.) andVerticillium dahliae on growth and yield of potato

Summary The effect ofStreptomyces spp. (netted scab) on the growth of potato was investigated in three pot experiments, in two of which the effect ofVerticillium dahliae was also assessed. The netted scab organisms attacked all underground plant parts of susceptible potato cultivars early in the growing season; the roots were especially seriously attacked, markedly reducing tuber yield and number but prolonging the duration of the growing season. The nematicide oxamyl had little effect on the incidence of netted scab. Repeated growing of the susceptible cv. Bintje greatly increased soil contamination with the netted scab pathogens. V. dahliae reduced haulm growth before wilt symptoms were evident and it reduced tuber yield but not number. Oxamyl delayed infection byV. dahliae by controlling parasiticPratylenchus nematodes (mainlyP. thornei).     

Effects of shoot,root and stolon temperature on the development of the potato (Solanum tuberosum L.) plant. III. Development of tubers

Summary The cultivars Bintje and Désirée were growth with their shoots, roots and stolons at different temperatures, to study the effects on tuber development. More tuber sites were initiated in ‘Bintje’ when the air, root or stolon temperature was increased but a combined increase of air and root temperature greatly reduced the number of sites. In contrast, each temperature increase reduced the number of tuber sites in ‘Désirée’ but an increase in temperature in one compartment usually increased the number of tubers set. The relative tuber set was enhanced by a combination of high stolon temperature and low root temperature. Especially an increase in air temperature reduced tuber yield and tuber dry-matter content, but increasing stolon temperature had the largest effects on the induction of second growth. Stolon and tuber development, dry-matter partitioning and initiation of second growth responded differently to variation in temperature around different plant parts suggesting that these processes are affected by different regulation mechanisms.