Characterization of tuber blight‐suppressive soils from four provinces of the Ecuadorean Andes

Late blight, caused by the oomycete Phytophthora infestans, is a threat to potato‐cropping systems worldwide. In the Ecuadorian Andes, despite a high late blight incidence in foliage, tuber blight is rare. In this work, the hypothesis that Ecuadorian Andean soils are naturally suppressive to P. infestans tuber infection was evaluated. Soils from four potato‐growing regions were assessed for disease suppressiveness by determining the effects of soil heat treatment on P. infestans sporangia and their ability to infect potato slices after 1, 8, 15 and 30 days of exposure to soils. Tuber infection after inoculation with P. infestans‐infested soils was consistently lower during the evaluation period compared with heat‐treated soils. Fresh, untreated soils affected germination and viability of P. infestans sporangia in a site‐dependent manner. In addition, the effect of heat treatment on soil bacterial communities was assessed through terminal restriction fragment length polymorphism analysis of the 16S rDNA gene region. Heat treatment disrupted bacterial community composition, and a subset of terminal restriction fragments (TRF) was either positively or negatively correlated with tuber infection. Bacterial TRF negatively correlated with tuber infection corresponded in fragment size to taxa with known ability to inhibit pathogens and promote plant growth. Finally, bacterial isolates obtained from untreated soils, which inhibited P. infestans growth in vitro, represented 22–47% of isolates recovered, and matched classes predicted by the TRFs. This work represents a first step in understanding the mechanisms behind the low incidence of tuber blight in Andean potato‐cropping systems.     

Temporal association of potato tuber development with susceptibility to common scab and Streptomyces scabiei‐induced responses in the potato periderm

Using hydroponics and novel non‐destructive pot culture systems which enable inoculation at specific tuber development stages, the dynamics of common scab infection patterns in potato were studied in order to provide more precise identification of tuber physiological factors associated with susceptibility. At the whole‐tuber level, infection percentages were greatest when Streptomyces scabiei inoculation occurred early; at 2 weeks after tuberization (WAT) 68% of tubers became infected, contrasting with late inoculation (8 WAT), when only 4% infection occurred. The first‐formed internodes were most susceptible to infection, whilst later‐forming and slower‐expanding internodes were less susceptible. Detailed tuber physiological examination of internode 2 showed that pathogen‐induced changes, including increased phellem (periderm) thickness, cell layers and phellem suberization (key physiological features believed critical to S. scabiei infection) were promoted through S. scabiei inoculation. Sequential harvesting showed enhanced phellem suberization (28% greater than the control) within 7 days of pathogen exposure, while phellem thickness and layer responses were also initiated early in the infection process (10–14 days after pathogen exposure) and these responses were independent of symptom expression. Differences in cultivar response were observed, with greater phellem suberization observed 10 days after tuberization (DAT) in the common‐scab‐tolerant cv. Russet Burbank than in the susceptible cv. Desiree. Likewise, Russet Burbank had thicker and more numerous cell layers in the phellem (up to eight cell layers) during early tuber growth (20–30 DAT) than Desiree (up to six cell layers).     

Purple nutsedge tuber sprouting

Purple nutsedge ( Cyperus rotundus L.) tubers remain viable for several years and serve as its principal means of survival. The maintenance of high moisture content is essential to tuber survival. Apical dominance influences bud dormancy within a tuber and in a chain of tubers, and dormancy increases with tuber age. Several growth inhibitors were identified in tubers, but their role in tuber dormancy has not been established. Moisture levels in soil must increase to a critical level before sprouting occurs, but excess soil moisture deters sprouting. Oxygen may be a limiting factor for tuber sprouting in waterlogged soils. Although light is not a requirement for sprouting, it has promoted sprouting. Temperature regulates sprouting; no sprouting occured below 10°C and above 45°C. Optimum sprouting occurred between 25 and 35°C when provided with constant temperatures. However, daily alternating temperatures greatly stimulated sprouting. A daily short duration (0.5 h) of high temperature increased sprouting to nearly 100%, whereas less than 50% sprouting occurred without the daily high temperature pulse. Bud break occurred readily for most tubers at 20°C and in nearly 100% of the tubers with a single 0.5 h exposure to a high temperature (35°C) pulse. However, most buds did not elongate if the tuber remained at 20°C. Bud elongation occurred at higher temperatures, and daily alternating temperatures stimulated shoot elongation up to eightfold greater than at the respective mean constant temperatures. Daily soil temperature fluctuation may be a major signal for purple nutsedge emergence, such as when the plant canopy is removed, or when soils are solarized. Future research is needed to determine tuber sprouting for different ecotypes, and on the role of the rhizome chain. Systems to manipulate sprouting may provide new strategies for purple nutsedge management.     

The role of the seed tuber in determining partial resistance to potato blackleg caused byErwinia spp.

In 1991 and 1992, 12 potato cultivars were screened at two locations for resistance to blackleg, after vacuum infiltration of the seed withErwinia carotovora subsp.atroseptica orE. chrysanthemi. Cultivar differences for resistance toE.c. subsp.Atroseptica andE. chrysanthemi were found which were consistent over locations and years. Seed tubers of the same cultivars were also screened for resistance to bothErwinia spp. by using a tuber slice inoculation method. Correlation coefficients for comparisons between resistance to blackleg in the field and tuber tissue resistance under aerobic or anaerobic conditions were not significant. This could partly be explained by drastic changes in relative tuber tissue resistance of the cultivars within a 5 weeks period after planting in the field. Presprouting of seed tubers in diffuse daylight had a less pronounced effect on relative tuber tissue resistance than planting in the field. Monitoring the process of mother tuber decay during the growing season of 1993 after vacuum infiltration withE.c. subsp.atroseptica andE. chrysanthemi revealed that cultivars differed in the extent to which these bacteria enhanced the process of mother tuber decay. These differences partly explained the cultivar differences for resistance to blackleg in the field.Abbreviations Eca Erwinia carotovora subsp.atroseptica - Ech Erwinia chrysanthemi - NOP Noordoostpolder - Wag Wageningen     

Effect of plant genotype, virus isolate and temperature on the expression of the potato tuber necrotic ringspot disease (PTNRD)

The present study shows that a large range of potato cultivars (29/33 tested), widely grown in the world, are susceptible to potato tuber necrotic ringspot disease caused by potato virus Y. The three factors studied in this work, which proved to influence the level of tuber necrosis reaction, were, first, the plant genotype, since varietal behaviour exhibited large differences; second, the virus genotype, since variations of virulence occurred between the four isolates tested; and third, the environmental conditions, as shown by the different rates of tuber necrosis obtained under contrasting conditions of temperature as much during the growing period as during storage. Three of the cultivars tested, Spunta, Maris Piper and Thalassa, failed to produce necrotic tubers, although infected with a virulent tuber-necrosing isolate. This result, following observations on the inheritance of the tuber necrosis trait, suggests that at least a major dominant gene controls this reaction in non-sensitive cultivars. On the other hand, the extreme resistance genes ( Ry ) provide a good resistance to virus infection, thus, preventing tuber necrosis under field conditions.     

Shading effects on spatial growth and biomass partitioning of Cynodon dactylon

Cynodon dactylon is a low-growing C4 weed that is highly sensitive to shading. This species shows severe biomass reductions and highly plastic morphological changes in response to resource availability. The objective of this study was to analyse the effect of shading on the spatial and biomass growth of C. dactylon . Two experiments were carried out exploring different environmental conditions. Six treatments were applied on C. dactylon patches. Daylight and 18%, 41%, 48%, 69% and 85% shading of daylight photosynthetic active radiation (PAR) were imposed in Expt 1 and 0%, 22%, 44%, 50%, 74% and 87% shading of daylight PAR in Expt 2. Patches were slightly elliptical in shape and grew 3.2 and 1.5 cm d⁻¹ with 0% shading, on average, during the whole studied periods in Expts 1 and 2 respectively. Biomass was significantly reduced from 41% shading onwards in Expt 1 and from 50% shading in Expt 2. However, patch extension rate was only significantly reduced from 85% and 74% shading in Expts 1 and 2 respectively. Biomass partitioning was modified by shading in both experiments. A functional analysis of C. dactylon patches showed that the patch extension rate diminished linearly when patch biomass growth rate was lower than 1.66 g d⁻¹; above this value, the extension rate remained constant.     

Assessment of the impact of mid-season late blight infection on disease development and yield of potato variety Russet Norkotah in Maine

Development of late blight of potatoes caused by Phytophthora infestans (US 8 fungal genotype, A2 mating type) was monitored in two Russet Norkotah commercial fields at Fort Fairfield in 1996 and Duncan Farm in 1997. Experimental plots representing various disease treatments (low, moderate, high and random late blight severity levels) were established in two fields in 1996. In 1997, only low and high disease treatments were established. The application of fungicides for late blight control was conducted in both years. Late blight incidence and severity were assessed in each plot of each treatment. Components of late blight disease development, tuber blight incidence and tuber yields were determined from each plot. Progress of late blight disease was rapid in 1996 but not in 1997. During the 1996 cropping season, mean disease incidence and severity in the random disease treatment plots were 84 and 21% respectively within 10 days of disease detection. In 1997, low levels of late blight severity were detected in the field plots. Average numbers of late blight leaf and stem lesions on infected plant and fungal sporangia on the diseased leaf were not significantly affected by disease treatment. Late blight foliar severity significantly affected potato tuber yields. Lowest tuber yield was obtained in plots with high disease levels and highest yields were recorded in plots with low late blight severity in 1996. Late blight severity was significantly correlated with tuber yield but not with per cent tuber blight.     

生殖生长期光富集和遮阴对大豆干物质分配及产量品质的影响

大豆冠层截获的太阳辐射强度是决定大豆生长发育和产量的重要环境因素.通过对蛋白质、脂肪含量不同的三个大豆品种在生殖生长期进行光处理,研究田间条件下,群体光富集和遮阴对大豆干物质分配、产量及品质的影响.结果表明:与自然光照相比,光富集后大豆积累的光合产物更多地分配到库;而遮阴后大豆积累的光合产物更多地分配给了源.光富集显著增加大豆单株产量、荚数和粒数,不同品种(系)单株产量增加幅度为27.7%～71.7%、单株荚数增加幅度为33.3%～71.1%、单株粒数增加幅度为35.5%～85.7%;遮阴显著减少大豆单株产量、荚数和粒数,不同品种(系)单株产量降低幅度为34.4%～49.7%、单株荚数降低幅度为43.0%～47.7%、单株粒数降低幅度为33.4%～52.6%.生殖生长期光富集有增加籽粒蛋白质含量和降低籽粒脂肪含量的趋势,而遮阴有降低籽粒内蛋白质含量和增加籽粒脂肪含量的趋势,品种间有一定差异.     

Growth of Elymus repens (L.) Gould and Agrostis gigantea Roth. at different light intensities

Elymus repens (L.) Gould and Agrostis gigantea Roth. raised from rhizomes both responded to reduced light intensity by increased stem length, while the number of aerial shoots was reduced. The weight of the aerial parts was not influenced by a 50% reduction of the daylight intensity, but a further reduction of light caused a significant decrease in weight. The production of new rhizomes was more influenced by shading than were the aerial shoots. The consequence was an increase in the shoot/rhizome ratio. The food reserve per bud measured as inter-node weight in E. repens and A. gigantea was reduced only with intensive shading, and the vitality of the rhizomes appeared independent of light intensity. Intensive shading in early as compared to late summer caused a reduction in the number and weight of aerial shoots, but not in the weight of new rhizomes. Light intensities equal to those found in a spring wheat crop allowed more E. repens growth than light intensities equal to those in a spring oat crop. E. repens raised from seeds and grown at light intensities equal to those found in a cereal crop, showed insignificant rhizome production.     

The influence of cyst nematodes and drought on potato growth. 1. Effects on plant growth under semi-controlled conditions

Potatoes were grown under a permanent rain shelter in mobile containers in soil with or without potato cyst nematodes (Globodera pallida). The plants were subjected to an early drought stress period starting at planting until 43 days after planting, to a late drought stress period starting at 43 days until senescence at 92 days and to a drought control. Dry matter weight and characteristics of leaves, stems, stolons and roots were determined at periodic harvests. The early drought stress and nematode infection affected many plant organ characteristics in similar ways. Numbers of leaves, specific leaf area, plant height, specific stem weight, leaf area ratio, mean tuber weight and harvest index were reduced by both stress factors at early stages of growth.Later on, interactions between both stress factors which influence the development rate of the plants led to more diverse plant reactions. Plants of all treatments rapidly senesced at about 90 days after planting. Uninfected plants had then depleted the soil nutrient supply whereas the plants grown in the inoculated soil senesced as a result of the potato cyst nematode infection.     

Unrestricted growth, tuber formation and spread of Cyperus esculentus L. in Zimbabwe

The unrestricted growth and clonal spread from individual tubers of Cyperus esculentus L. were studied in Zimbabwe. Clonal material, collected from the Trelawney area, was grown in a square arrangement in the field with a 5 m spacing between original tubers. Growth was recorded at approximately monthly intervals for 2 years. The natural logarithm of clonal spread (m per month) was positively correlated to temperature and rainfall. Most growth occurred from November to March, a period of optimal moisture and temperature conditions. There was little growth during the remainder of the year. The changes in clonal spread during the year are expressed mathematically and incorporate two parameters of growth; one describes the rate of growth and the other predicts the radius once growth ceases Tuber numbers increased exponentially from December-April, the rate of tuber production being greater in the first than in the second year of growth. Tuber production was greatest during March, April and December, 1980. Dormancy of the tubers decreased during the cooler months from May to August. The value of describing unrestricted clonal growth, and conditions favouring tuber production, are discussed.     

不同氮水平对旱地覆膜马铃薯干物质积累与分配的影响

针对马铃薯生产中存在的氮肥施用过量问题,通过田间试验,研究了不同氮肥水平(0、50、100、150、200、250 kg·hm~(-2),分别对应T1、T2、T3、T4、T5、T6处理)对旱地覆膜马铃薯"陇薯3号"的生育进程及其干物质积累与分配的影响。结果表明:施用氮肥显著推迟了马铃薯的生育进程,随施氮量的增加,马铃薯的生育期延后,各施氮处理的干重平衡期比不施氮肥的对照处理(T1)推迟了2~16 d;施用氮肥显著增加了马铃薯全株和块茎干物质快速积累的持续时间(Δt),随施氮量的增加,与T1相比,全株Δt增加了2~14 d,块茎Δt增加2~10 d;马铃薯整株和块茎干物质积累均表现出明显的"S"曲线特征。不同氮水平对成熟期马铃薯干物质在不同器官中的分配比例也有显著影响,随施氮量的增加,成熟期茎和叶所占干物质比例明显增加,块茎所占干物质比例呈单峰趋势变化;不同氮水平也显著影响马铃薯块茎产量,与对照处理(T1)相比,T2处理增产17.86%,T3、T4、T5和T6分别减产6.88%、21.06%、27.05%和38.63%,说明过量施用氮肥会导致马铃薯减产,其本质是马铃薯库源关系的失调(施氮量超过50 kg·hm~(-2)时)。在本试验条件下,当目标产量为1.65 t·667m-2时,50 kg·hm~(-2)为经济最佳施肥量。     

不同增施微肥方式对马铃薯块茎产量和Zn、Fe含量的影响

本研究的目的在于揭示土施和喷施两种增施微肥方式对马铃薯块茎产量和Zn、Fe含量的影响。试验选取定薯1号为试材,进行田间试验,设13个处理,依次为:硫酸锌、硫酸亚铁、硫酸锰分别作基肥施入(D1、D2、D3),在现蕾期、开花期和块茎膨大期喷施0.2%水溶液(A1、A2、A3、B1、B2、B3、C1、C2、C3),不喷施为对照(CK)。结果表明:增施微肥能使株高降低0.9~3.9 cm,茎粗增粗0.02~0.13 cm,单株结薯数增加0.13~0.86个,也能使单株产量增加0.002~0.18 kg,平均单薯重增加7.48~12.04 g,使生育期延长1~8 d,在现蕾期、开花期、块茎膨大期喷施硫酸锌和现蕾期喷施硫酸锰能使产量增加18.4%~25.7%;现蕾期喷施硫酸锌可提高块茎Zn含量(提高2.2 mg·kg~(-1)),而在现蕾期喷施硫酸锌、硫酸亚铁、硫酸锰,开花期喷施硫酸亚铁,硫酸锰作基肥施入可提高块茎Fe含量(提高2.0~9.0 mg·kg~(-1))。     

Differential effect of nematicide treatments on tuber yields in early- and late-maturing potato cultivars

A 3-year field study examined the effects of 1,3-dichloropropene or oxamyl on tuber yields in four early- and five late-maturing potato cultivars. The nematicide treatments increased total tuber yield by ≈ 12% for early-maturing cultivars, but by less than 2% for the late-maturing cultivars. The treatments reduced the numbers of root lesion nematodes (primarily Pratylenchus penetrans ), which were the dominant plant parasitic nematodes at the site. Covariance analysis indicated that treatment effects on total tuber yield were no longer significant after adjusting for root lesion nematodes in soil at harvest, confirming that these nematodes had a direct effect on the host. As expected, there were significant inverse relationships ( P  = 0·05) between total tuber yields and numbers of root lesion nematodes in soil and in roots. However, the application of nematicides in late-maturing cultivars was found to be of no practical value. Crop production systems designed to reduce or optimize pesticide applications can form one criterion in the development of more environmentally sensitive management strategies. The merit of utilizing chemicals for root lesion nematode control are considered with regard to cultivar maturity.     

不同生育期土壤水分亏缺对双季超级稻产量及其构成的影响

通过盆栽试验研究了不同生育期土壤水分亏缺对双季稻生长发育及产量形成的影响。结果表明:双季超级稻生育前期土壤水分亏缺对株高存在较大影响,其中均以拔节孕穗期受土壤水分亏缺影响最重,早稻株高下降4.53%~11.1%,晚稻下降3.09%~10.04%,且水分亏缺程度越重,株高下降越多,而生育后期影响较小。双季超级稻不同生育期土壤水分亏缺处理的叶、穗、根及总的干物质积累量均低于浅水灌溉对照,且均表现为随土壤水分亏缺程度的加剧而积累量越少,根冠比也表现为相同规律。但土壤水分亏缺却一定程度上促进了茎鞘的发育,产生补偿作用,但作用较小。双季超级稻所有土壤水分亏缺处理的产量均低于对照浅水充分灌溉,早稻产量为对照的58.73%~99.42%,晚稻产量为对照的55.15%~96.74%。各生育期的双季稻产量均表现为随土壤水分亏缺的加剧而下降严重。双季超级稻产量受水分亏缺影响敏感程度排序:早稻为拔节孕穗期有效分蘖期抽穗开花期无效分蘖期乳熟期,晚稻为拔节孕穗期抽穗开花期有效分蘖期乳熟期无效分蘖期。水分亏缺对双季超级稻有效分蘖期的穗数和拔节孕穗期的穗粒数影响程度最大,可引起大幅减产。无效分蘖期和乳熟期受水分亏缺影响减产程度较小。     

大豆始粒期荚遮光对荚粒物质积累的影响

以黑河17等13份大豆品种(系)为材料,始粒期采用整株荚遮光法研究分析豆荚对粒重的相对光合贡献及荚遮光对荚、粒物质积累的影响。结果表明,荚对粒重的相对贡献因基因型而异,变幅为0.6%~16.6%;叶面积与荚面积比值较小的龙品90-055和石豆2,较比值较大的W1和垦18,荚对粒重的相对光合贡献率高;荚遮光对粒重与荚壳重的比值影响因基因型不同呈现降低、不变和升高三种类型,其中升高类型占大多数,表明荚遮光对荚壳物质积累的抑制大于籽粒的占多数。荚遮光处理降低成熟期籽粒及荚壳中蔗糖和还原糖含量,且籽粒的降低幅度明显大于荚壳,籽粒和荚壳的淀粉含量降低幅度相近;荚遮光处理降低成熟期荚壳的淀粉含量,其降幅明显大于蔗糖和还原糖。     

The movement of potato virus Y (PVY) in the vascular system of potato plants

Potato virus Y (PVY) is responsible for major viral diseases in most potato seed areas. It is transmitted by aphids in a non-persistent manner, and it is spread in potato fields by the winged aphids flying from an infected source plant to a healthy one. Six different PVY strains groups affect potato crops: PVY^C, PVY^N, PVY^O, PVY^N:O, PVY^NTN, and PVY^N-Wi. Nowadays, PVY^NTN and PVY^N-Wi are the predominant strains in Europe and the USA. After the infection of the leaf and accumulation of the virus, the virus is translocated to the progeny tubers. It is known that PVY^N is better translocated than PVY^O, but little is known about the translocation of the other PVY strains. The translocation of PVY occurs faster in young plants than in old plants; this mature plant resistance is generally explained by a restriction of the cell-to-cell movement of the virus in the leaves. The mother tuber may play an important role in explaining mature plant resistance. PVY is able to pass from one stem to the other stems of the same plant through the vascular system of the mother tuber, but it is unknown whether this vascular link between stems is permanent during the whole life of the plant. Two greenhouse trials were set up to study the spread of PVY in the vascular system of the potato plant. The PVY-susceptible cultivar Charlotte was used for both trials. It was demonstrated that all stems growing from a PVY-infected tuber will become infected sooner or later, and that PVY^N-Wi translocates more efficiently to progeny tubers than PVY^NTN. It was also demonstrated that the progressive decay of the mother tuber in the soil reduces the possibility for virus particles to infect healthy stems through the vascular system of the mother tuber. This new element contributes to a better understanding of the mechanism of mature plant resistance.     

Late blight (Phytophthora infestans (Mont) De Bary) development from potato seed-pieces treated with fungicides

Fungicides were applied as seed-piece treatments to control potato late blight, caused by Phytophthora infestans, US8, A2 biotype in controlled environment and field experiments. Efficacy of seed treatments for controlling late blight was examined under three disease development regimes simulated by artifical inoculation; (a) seed-borne infection, (b) transmission of infection resulting from spread during the seed-cutting operation, and (c) infection of foliage by aerial inoculation. Emergence of plants from the seed-borne infection was uniformly low (<40%) in controlled environment and field experiments. In controlled environment experiments some of the plants that emerged from fungicide-treated seed-pieces were infected with late blight. Following exposure of tuber surfaces to P infestans, emergence rates from seed-pieces treated with formulated products that included mancozeb in the formulation were comparable to the untreated and non-inoculated control in controlled environment and field experiments. Plants that emerged from non-inoculated seed-pieces treated with fungicides that contained active ingredients known to be effective against foliar late blight had lower percentage foliar infection after inoculation than the untreated control. Leaves close to the base of the stem had fewer infections than leaves attached at the mid region of the main stem, 14 days after inoculation, in some of the controlled environment studies. In contrast, field experiments conducted under conditions conducive to late blight development showed that none of the seed treatments applied to late blight-free seed-pieces delayed the onset and severity of late blight infection. In potato production areas at risk of early season late blight, seed treatments applied to healthy seed may confer limited protection against late blight between planting and the first scheduled applications of prophylactic foliar fungicides. © 1999 Society of Chemical Industry     

Potato plant response to seed tuber bacterization in the field in various rotations

The effects of a seed tuber treatment with antagonistic isolates of fluorescentPseudomonas spp. were investigated on potato plants from 1981 to 1984. The experimental plots were located in fields in short and long rotations of potato. The short rotations are characterized by serious yield reductions which are caused by unknown microbial factors. The reductions varied from 30% in 1982 to only 3% in 1983 in the 3-year rotations. A statistically significant increase in yield (four to five months after planting) of ware potatoes varying from 9 to 20% was obtained in these plots through tuber bacterization, but only in 1981. In 1982 and 1983 initially significant improvements in shoot or tuber weight of seed potatoes were no longer detectable at ware potato harvest at the end of the growing period. Seed tuber bacterization had no effect on tuber yield in long rotations. Initial colonization of basal root parts by 53×10⁴ colony forming units (cfu) of antibiotic-resistant mutants per gram of root (fresh) dropped significantly to 20×10⁴ cfu per gram after three months. The bacterization effect on tuber yield depended on the development of harmful microbial activity and of introduced antagonists during the growing period. Seed tuber bacterization is more promising for seed potatoes than for ware potatoes in short rotations, the latter being harvested two months later.Samenvatting De invloed van pootgoedbehandeling met antagonistische isolaten van fluorescerendePseudomonas-soorten op de aardappelteelt, werd onderzocht in de periode van 1981 tot en met 1984. De proefvelden maakten deel uit van zowel ruime als nauwe rotaties met aardappelen. Kenmerkend voor de nauwe rotatie is, dat de opbrengst aanzienllijk gereduceerd wordt als gevolg van de aanwezigheid van nog onbekende microbiële factoren. Deze opbrengstverlaging varieerde van 30% in 1982 tot slechts 3% in 1983 in de 3-jarige rotaties. Pootgoedbacterisatie had in deze proefvelden een significante toename van de eindopbrengst (vier tot vijf maanden na pootdatum) van consumptieaardappelen tot gevolg, die varieerde van 9 tot 20%, echter allen in 1981. In 1982 en 1983 werd het effect van bacterisatie ook in de loop van de groeiperiode onderzocht. Aanvankelijk significante toenames van zowel spruit-als knolgewicht waren aan het einde van het groeiseizoen niet meer aantoonbaar. Pootgoedbacteristie bleek geen effect te hebben op aardappel in ruimte rotaties. Aanvankelijk werden de basale wortelgedeelten gekoloniseerd door antibioticum-resistente mutanten met 53×10⁴ kolonievormende eenheden (kve) per gram wortel(vers); dit aantal liep (drie maanden na pootdatum) echter significant terug tot 20×10⁴ kve per gram. Het effect van bacterisatie op de eindopbrengst werd bepaald door de ontwikkeling van de schadelijke microbiële activiteit en de ontwikkeling van de geïntroduceerde antagonisten tijdens het groeiseizoen. Pootgoedbacterisatie in nauwe rotaties biedt meer mogelijkheden voor de teelt van pootaardappelen dan die van consumptieaardappelen, die geruime tijd later geoogst worden.     

干旱与复水对马铃薯块茎膨大期碳氮转运的影响

为探讨干旱及复水对马铃薯块茎膨大期碳氮物质转运影响的生理机制，采用盆栽控水法研究了干旱胁迫、旱后复水过程中马铃薯叶片与块茎中碳水化合物、氮素同化物以及碳氮转运相关酶活性的变化规律。结果表明：干旱胁迫下马铃薯叶片蔗糖磷酸合成酶（SPS）活性显著增强，增幅为54.9%，可溶性糖与蔗糖含量显著增加，分别增加84%、25%；块茎蔗糖与淀粉含量显著下降，分别降低25%、11.8%。复水后叶片可溶性糖含量变化较小，叶片SPS活性仍保持较高水平；块茎中蔗糖合成酶（SS）活性下降6.25%(P＜0.05)，蔗糖与淀粉含量分别增加21.8%、29.8%。干旱胁迫下马铃薯叶片中硝酸还原酶（NR）活性下降49.3%，谷氨酰胺合成酶（GS）活性与对照差异不显著，叶片游离氨基酸与可溶性蛋白质含量分别降低29.4%、38.4%，全氮含量降低13%；块茎中游离氨基酸与可溶性蛋白质含量增加16.8%、270.9%。复水后叶片中NR与GS活性高出对照3.5%、12.1%，叶片游离氨基酸、可溶性蛋白质以及全氮含量仍保持较低水平；块茎游离氨基酸、可溶性蛋白含量较高，增幅分别为24.6%、178.4%，全氮含量增加，与对照差异不显著。说明干旱胁迫显著阻碍了马铃薯碳水化合物与氮素同化物的合成与转运，使马铃薯叶片碳水化合物积累，但干旱促进了氮素向块茎转运，块茎中的碳氮比下降；复水后马铃薯植株能够快速修复干旱胁迫造成的损伤，表现为块茎中淀粉含量增多，块茎碳氮比增加。