Photoperiod sensitivity after flowering and seed number determination in indeterminate soybean cultivars

Seed and pod numbers are the main yield components in soybean (Glycine max (L.) Merrill). They are related to canopy photosynthesis during a critical period, occurring between the R1 (beginning of flowering) and R6 (full seed) stages. We investigated the relationship between the duration of the critical period and the number of seeds produced. Response to photoperiod during post-flowering stages was evaluated in indeterminate soybean cultivars from maturity groups (MG) IV and V. The study was conducted under field conditions with two sowing dates (normal and late). Plants were grown under natural photoperiod throughout the experiment or exposed, from the R3 stage (beginning pod) onwards, to artificially extended regimes of 2 h longer than natural daylength. Duration of the R3–R6 period increased in response to the extension of photoperiod, and cultivars of MG V exhibited a stronger sensitivity to photoperiod than those of MG IV. Exposure to long photoperiods promoted node production, mainly in branches, and increased node fertility. Within each sowing date, the increased duration of R3–R6 under longer photoperiods was corresponded with increments in pod and seed number. Seed number was related to the duration of R3–R6, particularly when the length of the period was corrected for temperature differences between treatments. Seed number was also related to the integral of solar radiation during R3–R6. The possibility of using sensitivity to photoperiod after flowering as a criterion for increasing yields through increasing seed number are discussed.     

Evolutionary aspects of the trade-off between seed size and number in crops

Whereas the concept that availability of resources drives seed production is sound in principle, it is incomplete as there are many solutions to the allocation of resources that derive from the trade-off between number and size. This paper examines evolutionary aspects of this trade-off in annual grain crops. The analysis is centred on the working hypotheses that, for a given species and environment, allocation of resources to reproduction involves (H1) high plasticity in seed number, which allows for variable resource availability, and (H2) a relatively narrow range of seed size that results from evolutionary and agronomic selection. Comparisons between crops and fish are used to highlight common evolutionary elements in taxa where parents provide little or no care to their offspring, with the consequence that both number and early survival of offspring, hence fitness of parents, are partially related to embryo size and reserves.

The plasticity of seed number in relation to availability of resources is analysed against the established relationship between offspring number and parent growth rate during critical stages. The notion that seed size is under stabilising selection is analysed against three conditions: (1) mean seed size is conservative for a given species and environment, (2) seed size affects fitness, and (3) seed size is heritable. Databases from published papers were compiled to analyse the relative variability of seed size and number, and the heritability of seed size. Evidence for and against the link between seed size and parental fitness is revised using the Smith–Fretwell model as framework (Am. Nat., 108, 499–506).

The proposal of high plasticity of seed number and narrow variability of seed size resulting from stabilising natural selection is generally consistent with evolutionary and genetic considerations. Agronomic selection may have reinforced natural selection leading to relatively narrow seed size in species such as wheat and soybean, where cultivated types retained high plasticity for seed number. In contrast, selection for one or few inflorescences in crops like sunflower and maize may have morphologically reduced seed number plasticity and increased variability of seed size and its responsiveness to resource availability in relation to their wild ancestors.     

Performance of true potato seed families. 1. Effect of level of inbreeding

Summary Successive generations of open pollinated (OP) true potato seed (TPS) families represent a low-cost planting material. This study was conducted to determine whether inbreeding occurred during two successive OP generations and, if so, whether it adversely affected the performance of transplant families from true seed. Potato seedling transplants from 4x×2x hybrid, OP₁, OP₂, S₁ and S₂ families were compared for plant vigour, flowering, pollen stainability, OP fruit set, tuber yield and specific gravity. Hybrids were consistently superior, while S₂ families were inferior. The performance of OP₁, OP₂ and S₁ families did not differ significantly for most traits. The accumulation of inbreeding in successive OP generations was limited by reduced OP seed production on selfed plants; thus, a synthetic TPS variety propagated by open pollination may be feasible. Paper no. 3162 from the Department of Genetics, University of Madison.     

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.     

Identification of a candidate QTG for seed number per silique by integrating QTL mapping and RNA-seq in Brassica napus L.

Seed number per silique(SNPS) is one of seed yield components in rapeseed, but its genetic mechanism remains elusive. Here a double haploid(DH) population derived from a hybrid between female 6Q006with 35–40 SNPS and male 6W26 with 10–15 SNPS was investigated for SNPS in the year 2017, 2018,2019 and 2021, and genotyped with Brassica 60K Illumina Infinium SNP array. An overlapping major QTL(qSNPS.C09) explaining 51.50% of phenotypic variance on average was narrowed to a 0.90 Mb region from 44.87 ...     

Spring defoliation of white clover seed crops. 1. Inflorescence production of contrasting white clover cultivars

Three white clover cultivars, S184 (small-leaved), Menna (medium-leaved) and Olwen (large-leaved), were sown at a seed rate of 3 kg ha^-1 under spring wheat cv. Tonic. In the spring of the two following years, there were three pre-bud emergence mechanical defoliation treatments on which were superimposed four post-bud emergence treatments giving a total of twelve cutting treatments. Pre-bud emergence, plots were either cut twice (at approximately two weeks before bud emergence and at bud emergence), cut once at bud emergence or not cut. To each treatment were applied four post-bud emergence treatments: plots were not cut or cut once (one, two or three weeks after bud emergence). Counts of the total number of inflorescences and of the proportions in various ripeness categories were made throughout the period of seed crop development to determine the pattern of inflorescence development and optimum harvest date. Overall, inflorescence numbers were greatest in cv. S184and least in cv. Olwen. Defoliation before bud emergence had no effect on inflorescence production; however, it was significantly influenced by defoliation after bud emergence. Although delaying the initial development of the crop, inflorescence numbers of all cultivars were highest in both years following cuts two and three weeks after bud emergence. Optimum harvest date was not affected by defoliation or cultivar, numbers of ripe inflorescences in both years reaching a peak at the end of August. The number of brown inflorescences, which may also contribute to seed yield, reached a peak in both years in late July. Seasonal differences in inflorescence production were again observed, emphasizing the difference between first and second year crops and importance of climate in while clover seed production. The implications of these differences in numbers and proportions of inflorescences in various ripeness categories under different defoliation regimes are discussed in relation to seed crop management in the UK.     

The dormancy of seed potatoes. 1. The effect of time of haulm destruction and harvesting

Summary The effect of seven dates of haulm destruction and three intervals to harvesting on the physiological ageing of seed potatoes was studied. Tubers were placed in sprouting boxes in a store at 15 C immediately after each harvest and the number of days from planting the parent crop to sprouting was recorded. Earlier haulm destruction resulted in earlier sprouting in two of the three years. Sprout growth started 14 or 16 days earlier on tubers from plots defoliated in July compared with tubers from plots defoliated 6 weeks later. A short interval from haulm destruction to harvesting tended to result in earlier sprouting but the response was small in two of the three years. The results suggest that United Kingdom seed for export to countries where planting takes place in January should be produced from cropsin which haulm destruction and harvesting has taken place as early as possible.

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Zusammenfassung Von 1974 bis 1976 wurde der Einfluss von sieben Daten der Krautvernichtung und drei zeitlichen Intervallen bis zur Ernte auf die physiologische Alterung von Pflanzkartoffeln der Sorten Arran Banner und Alpha untersucht. In Tabelle 1 sind die Einzelheiten der Verfahren für jedes Jahr angegeben. Sofortnach der Ernte wurden ausjeder Versuchsparzelle 40 Knollen in Pflanzgutgr?sse in Vorkeimkisten bei 15 C aufgestellt, und der Zeitpunkt des Beginns des Keimwachstums wurde notiert. Frühere Krautvernichtung verkürzte in den Jahren 1974 und 1975 signifikant den Zeitraum bis zum Beginn des Keimwachstums (Tabelle 2). Bei Knollen von im Juli entlaubten Best?nden begann das Keimwachstum 14 oder 16 Tage früher im Vergleich zu Knollen aus Best?nden, die sechs Wochen sp?terentlaubt wurden. Im dritten Jahrzeigte sich keine signifikante Tendenz. Bei einem kurzen Zeitabstand zwischen der Krautvernichtung und der Ernte bestand eine Neigung zu früherem Austreiben (Tabelle 3). Die Unterschiede waren 1975 gross und 1976 klein, aber immer noch signifikant, 1974 zeigte sich kein signifikanter Unterschied. Die w?chentliche Regenmenge und die Bodentemperatur in 10 cm Tiefe für jede Vegetationsperiode ist in den Abb. 1,2 und 3 dargestellt. Die Wachstumsbedingungen waren in jedem Jahr verschieden. Die Kartoffeln litten 1976 unter der Trockenheit. Dies mag die fehlende Reaktion auf den Zeitpunkt der Krautvernichtung in diesem Jahr erkl?ren. Diese Ergebnisse legen nahe, dass Pflanzgut aus dem Vereinigten K?nigreich früh krautgezogen und so früh wie m?glich geerntet werden soll, wenn es für den Export in L?nder bestimmt ist, wo das Auspflanzen im Januar vorgenommen wird.

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Résumé Les effets de sept dates de destruction de fanes et de trois dates de récolte sur l’age physiologique des plants d’Arran-Banner et d’Alpha ont été étudiés de 1974 à 1976. Le détail des traitements, chaque année, est donné dans le tableau 1. Immédiatement après l’arrachage, 40 tubercules de calibre plant de chaque parcelle ont été placés en germoir à 15 C et la date de départ de la germination a été notée. La destruction des fanes la plus précoce a rapproché significativement la date de départ de la germination en 1974 et 1975 (tableau 2). La germination des tubercules défanés en juillet commence 14 à 16 jours plus t?t que ceux défanés six semaines plus tard. Iln’y a pas eu de tendance significative la troisième année. Un défanage peu de temps a vant la récolte tend à provoquer une germination plus précoce (tableau 3). Les différences étaient importantes en 1975 et faibles mais encore significatives en 1976. Iln’y a pas eu de différences significatives en 1977. La pluviométrie hebdomadaire et la température du sol à 10 cm sont présentées pour chaque mois dans les figures 1,2 et 3. Les conditions de culture étaient différentes chaque année. Les pommes de terre ont souffert de la sécheresse en 1976 et ceci peut expliquer l’absence d’effet de la date de défanage cette année-là. Les résultats suggèrent que les plants du Royaume-Uni, destinés à l’exportation vers les pays où la plantation a lieu en janvier, devraient être issus de récoltes défanées et récoltées le plus t?t possible.

     

Spring defoliation of white clover seed crops. 2. Potential harvestable seed yield and seed yield components of contrasting white clover cultivars

The effects of different spring defoliation managements on potential harvestable seed yield and seed yield components of three contrasting white clover cultivars were assessed. The small-leaved cv. S184 produced more but smaller inflorescences than the large-leaved cv. Olwen and Menna, a medium-leaved cultivar. Cultivar Olwen, however, produced more ripe and brown (nearly ripe) inflorescences with more florets, seeds per floret and a higher seed yield per ten inflorescences than the other cultivars. Potential harvestable seed yield and individual seed yield components were only influenced by defoliation after bud emergence, as defoliation before bud emergence had no effect on seed yield components. Defoliation after bud emergence had a similar effect on all cultivars: the number of ripe inflorescences was unaffected by defoliation but the number of brown and therefore harvestable (ripe + brown) inflorescences was highest following defoliation three weeks after bud emergence. Florets per inflorescence, seed per floret, 1000 seed weight, seed yield per ten inflorescences and potential harvestable seed yield were not influenced by defoliation after bud emergence. Season had a significant effect on seed yield components and influenced the effect of defoliation treatments, emphasizing the importance of climate in white clover seed production. The results are discussed in relation to the spring defoliation of white clover seed crops, harvesting techniques and the provision of guidelines for optimizing seed yield.     

湘杂油1号制种父母本不同行比与产量的关系

为了明确湘杂油1号制种时父母本适宜行比，为大面积制种提供技术方案，于2002年在张家界进行了父母本不同行比制种的比较试验。试验共设1：1，1：2，1：3，1：4，1：5等5个父母本行比，结果表明：(1)行比小的单株产量高，而群体产量低，行比大的单株产量低，而群体产量高，其中以1：4的群体产量居第1位，为912．4kg／hm^2；(2)距父本距离近的母本行全株有效角果数多，距离父本行远的母本行全株有效角果数减少，每角实粒数减少，千粒重升高。采用1:4的行比，可保证制种产量。     

Effect of seed crop management on the potential seed yield of contrasting white clover varieties.

Three contrasting white clover varieties, Olwen (large-leaved), Menna (medium-leaved) and S184 (small-leaved) were sown with and without a grass companion in 30 cm drills. Two grazing and one mechanical spring defoliation managements were imposed. Counts of the total number of inflorescences and of the percentage in various ripeness categories were made throughout the period of seed crop development to determine the pattern of inflorescence development and optimum harvest date. Inflorescence numbers were greatest in cv. S184 and least in cv. Olwen and, in general, varieties produced both more inflorescences and a greater proportion of ripe inflorescences when grown under spring defoliation managements similar to those for which they were bred. Thus, cv. Olwen produced more ripe inflorescences, and a lower proportion of brown inflorescences (semi-ripe), after mechanical defoliation while cv. Menna produced more ripe inflorescences following mechanical defoliation and rotational grazing. However, cv. S184 produced more ripe inflorescences under both grazing managements than under mechanical defoliation. Optimum harvest date was not affected by management or variety, total inflorescence number and maximum ripe inflorescences having reached a peak on 11 September. However, varieties differed in the proportion of ripe and brown (semi-ripe) inflorescences on this date, with cv. Menna and cv. S184 containing a significantly higher proportion of brown inflorescences than cv. Olwen, The implications of these differences in inflorescence development, the proportions of inflorescences in the various ripeness categories and their contribution to seed yield are discussed in relation to the management of white clover seed crops and harvesting method under UK climatic conditions.     

A new model for the structure of lignosulphonates: Part 1. Behaviour in dilute solutions

Lignosulphonates are formed by the cleavages of the α-O-4 linkages of the “infinite” lignin network in wood, and a sulphonation of the α- and/or γ-positions of the side chains of the C₉ units. The resulting lignosulphonate molecule forms a randomly branched polyelectrolyte. The molecule coils in solution to make a more ball-shaped molecule with the sulphonate groups enriched on the surface. The scaling laws for this model of the lignosulphonate polymer as well as for other models of the lignosulphonate have been derived. The scaling laws for the randomly branched polyelectrolyte and microgel are the same for most properties except the polyelectrolyte expansion. The scaling laws are compared with literature experimental values for radii and polyelectrolyte expansion. The randomly branched polyelectrolyte model successfully accounts for the behaviour in solution. The dependence of the polyelectrolyte expansion on the molecular weight demonstrates that the lignosulphonate is not a microgel structure.     

The feasibility of predicting the number of stems per tuber produced by potato seed stocks from measurements made before planting

Summary The number of stems per seed tuber produced by 17 seed stocks of cv. Record was determined in glasshouse and field experiments to assess the feasibility of predicting the number of stems produced in the field. Multiple regression analysis showed that seed tuber weight alone gave the most satisfactory fit to stems produced in the field, which was not improved by adding terms involving the number of stems produced in the glasshouse. Quadratic relationships between the number of above-ground stems per tuber and tuber weight were most appropriate for each stock, with the fitted curves for individual stocks differing only in the constant term. However, there were significant rank correlation coefficients between the constant terms for relationships between field stems and tuber weight and glasshouse stems and tuber weight, suggesting that in other cultivars and seed stocks a predictive glasshouse test might still be useful.     

Storage of seed potatoes in pallet boxes. 1. The role of tuber surface moisture on the population of Erwinia bacteria

Summary Three stocks of seed potatoes contaminated with soft rot Erwinias were stored for 172 days in a commercial pallet box store. Three treatments were applied: naturally ventilated boxes, forced air ventilated boxes and single tubers on trays. Skin resistance values were 2.3, 9.4 and 19.3 megohm respectively. Rewetting events numbered 4, 7 and 15.Erwinia carotovora pv.carotovora (Ecc) andErwinia carotovora pv.atroseptica (Eca) declined in all stocks and treatments. Ecc declined significantly faster in the forced air ventilated treatment. The more frequent rewettings in the trays reverse the benefit of their drier skins. In the earliest sprouting stock, the naturally ventilated, but not the forced ventilated boxes, showed a decrease in skin resistance and corresponding increase in Ecc as spring approached. Forced ventilation in the first 14 days after harvest halved the level of silver scurf compared to the naturally ventilated treatment.     

Relationships between disease levels on seed tubers,on crops during growth and in stored potatoes. 1. Introduction and black scurf

Summary In the Introduction general methods are described to assess inocolum of several potato diseases on seed tubers; on the progeny tubers during growth, at harvest and after 4 different storage regimes. Assessments were made in up to 26 commercial King Edward crops in each of 5 years, and up to 13 crops from ‘healthier’ seed, derived from stem cuttings, in 4 years. Results are reported from the work on black scurf (Rhizoctonia solani). Stem canker incidence was more closely related to the incidence of sclerotia on seed tubers than was the frequency ofRhizoctonia hyphae on growing tuber surfaces. Incidence of sclerotia on stored tubers was better related to the amount of surface colonization during growth than that of stem canker. Assessments on harvested and stored progeny of ‘healthier’ seed were correlated with those on adjacent commercial crops, indicating spread or, more likely, a common source of inocolum.

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Zusammenfassung In einer Studie wurde das Auftreten verschiedener Krankheiten im Erntegut der Sorte King Edward untersucht, die zwischen 1971 und 1975 in dem Fenland-Gebiet von Ostengland gewachsen war. Jedes Jahr wurden zwischen 15 und 26 Proben von Marktware untersucht und zwischen 1972 und 1975 wurde ‘gesünderes’ Pflanzgut (das von Stecklingen abstammte) auf dem selben Feld wie einige der Proben der Marktware gepflanzt (Tab. 1). Die Feststellung des Inokulums oder der Krankheit wurde an Pflanzgutproben, an Pflanzen w?hrend des Wachstums und an Knollen der Nachkommenschaft zum Erntezeitpunkt genommen. Geerntete Knollen wurden auch einheitlich verletzt und bei 3°C und 10°C gelagert, mit oder ohne zweiw?chige Wundheilperiode bei 15°C. Nach 3–4 Monaten erfolgte die Feststellung des Krankheitsbefalls. Die Auswertung der Ergebnisse wurde durch Regression zwischen allen m?glichen Paaren der Ergebnisse für jede Krankheit durchgeführt, wobei jedes Jahr sowohl getrennt als auch alle Jahre kombiniert genommen wurden. Die Regressionen wurden auch für das ‘gesündere’ Erntegut, das mit der entsprechenden Marktware übereinstimmte, durchgeführt. Rhizoctonia solani wurde auf dem Pflanzgut und auf dem nachfolgenden Erntegut als Prozentbefall mit Sklerotien angegeben, der Myzelbelag auf der Knollenoberfl?che rund um die Augen wurde durch mikroskopische Untersuchung von Augenstücken festgestellt und das Auftreten von Weisshosigkeit wurde w?hrend des Wachstums gesch?tzt. Das durchschnittliche Auftreten von Inokulum oder Krankheitsbefall auf Marktware (Tab. 2) zeigte, dass 1975 der Befall der Augen am h?ufigsten war und dass 1971 und 1975 der Krankheitsbefall im Lager am gr?ssten war. ‘Gesünderes’ Pflanzgut hatte gew?hnlich weniger Pocken als der Durchschnitt der Marktware aber der Befall der Augen der Tochterknollen w?hrend des Wachstums und zur Ernte war gr?sser und auf gelagerten Knollen wurden mehr Pocken gefunden (Tab. 3). Unter den nassen Erntebedingungen 1974 traten mehr Pocken auf den bei 10°C gelagerten Knollen auf als auf den bei 3°C, aber es ergaben sich keine Unterschiede in anderen Jahren. Die Signifikanz der Regressionen zwischen den Erhebungen, die nach verschiedenen Methoden oder zu verschiedenen Zeitpunkten (Tab. 4) gemacht wurden und Diagramme der signifikanten Regressionen in einzelnen Jahren (Abb. 1) zeigten, dass makroskopische und mikroskopische Bestimmungen auf dem Pflanzgut (Abb. la) und Befall der Schale rund um die Augen und Weisshosigkeit w?hrend des Wachstums (Abb. 1d) in allen Jahren miteinander verbunden waren. Die Weisshosigkeit stand h?ufiger in Beziehung zum Ausmass des Pockenbesatzes des Pflanzgutes (Abb. 1b) als der Befall der Augen (Abb. 1c). Dies führt zu der Annahme, dass die meisten Stengelinfektionen vom Inokulum des Pflanzgutes ausgingen w?hrend der Befall der Schale rund um die Augen auch durch andere Inokulumquellen (z.B. den Boden) beeinflusst wurden. Der Befall der Augen zur Ernte stand in jedem Jahr in Beziehung zum Befall w?hrend des Wachstums (Abb. 1e) und in 4 Jahren stand das Ausmass des Pockenbesatzes auf gelagerten Knollen in Beziehung zum Augenbefall w?hrend des Wachstums und zur Ernte (Abb. 1f und 1g). Die mikroskopische Untersuchung w?hrend des Wachstums gibt daher eine vernünftige Sch?tzung des Krankheitsbefalls im Lager. Wenn die Erhebungen des ‘gesünderen’ Pflanzgutes mit denen gleichartiger Marktware verglichen wurden (Abb. 2), ergaben sich signifikante Verbindungen für den Augenbefall w?hrend des Wachstums und zur Ernte, für den Pockenbesatz auf gelagerten Knollen, aber nicht für die Weisshosigkeit. Dies weist auf eine Verbreitung des Inokulums, auf die Bedeutung der allgemeinen Bodenbeschaffenheit oder, wahrscheinlicher, eine gemeinsame Quelle des Inokulums, vielleicht im Boden hin.

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Résumé Une étude a été entreprise sur la variété King Edward, pour conna?tre l'incidence de différentes maladies. Cette étude s'est déroulée de 1971 à 1975 dans la région de Fenland en Angleterre Orientale. Chaque année, on a examiné entre 15 et 26 lots commerciaux; entre 1972 et 1975 des semences ‘plus saines’ (provenant de bouturage) ont été plantées dans le même champ que les lots commerciaux (tableau 1). Les estimations d'inoculum ou de maladie ont été faites sur des échantillons de tubercules de semence, sur des plantes en course de croissance, et sur les tubercules-fils à la récolte. Les tubercules-fils récoltés ont été également endommagés de manière uniforme et conservés à 3°C et 10°C, avec ou sans période initiale de cicatrisation des blessures de 2 semaines à 15°C. L'incidence de la maladie a été estimé après 3–4 mois. Les résultats ont été analysés par régressions entre toutes les paires possibles de données pour chaque maladie, en prenant séparément chaque année et toutes les années combinées. Les régressions ont aussi été faites à partir des estimations provenant des lots ‘plus sains’, et des estimations correspondantes provenant des lots commerciaux adjacents. L'estimation du rhizoctone a été faite par notation du pourcentage de sclérotes sur les tubercules de semence et sur les tubercules-fils en conservation. La colonisation de la peau, autour des yeux, par du mycelium deRhizoctonia solani a été déterminée par examen microscopique au niveau des yeux. L'incidence des nécroses sur tige a été estimée au cours de la croissance. L'incidence moyenne de l'inoculum ou de la maladie sur les lots commerciaux (tableau 2) a montré que la colonisation du tubercule au niveau des yeux a été plus fréquente en 1975, et que l'incidence de la maladie en cours de conservation a été plus forte en 1971 et 1975. Les tubercules de semence ‘plus saine’ ont eu moins de rhizoctone que la moyenne des lots commerciaux, mais la colonisation des tubercules-fils, au niveau des yeux pendant la période de croissance et à la récolte a été plus grande. On a également trouvé plus de sclérotes sur les tubercules conservés (tableau 3). En 1974, les conditions de récolte étant plus humides, il y avait plus de sclérotes sur les tubercules conservés à 10°C que sur ceux conservés à 3°C; mais, pour les autres années, il n'y avait aucune différence entre les traitements. La signification des régressions entre les estimations faites par différentes méthodes ou à différentes époques (tableau 4), et les graphiques relatifs aux régressions significatives pour chacune des années (Fig. 1) ont montré qu'il y avait toutes les années des relations entre les estimations macroscopiques et microscopiques sur la semence (Fig. 1 a), la colonisation de la peau autour des yeux et les nécroses des tiges en cours de végétation (Fig. 1d). Les nécroses sur tige étaient plus fréquemment en rapport avec les sclérotes portés par la semence (Fig. 1b) qu'ac la colonisation au niveau des yeux du tubercule (Fig. 1c). Les auteurs suggèrent donc que la plupart de la contamination de la tige provient de l'inoculum présent sur le tubercule de semence mais que la colonisation de la peau autour des yeux est également influencée par d'autres sources d'inoculum (par ex. le sol). Chaque année, la colonisation des yeux à la récolte était en relation avec celle en cours de croissance (Fig. 1c). Pour les 4 années, la quantité de sclérotes sur les tubercules conservés était en rapport avec l'incidence de la colonisation au niveau des yeux pendant la croissance et à la récolte (Figures 1f et 1g). Les estimations faites en cours de croissance donne donc une estimation correcte de l'incidence de la maladie en cours de conservation. Quand on compare les résultats des lots ‘plus sains’ et ceux des lots commerciaux adjacents, il y a des associations significatives pour la colonisation des yeux durant la croissance et à la récolte, pour les sclérotes sur les tubercules conservés, mais pas pour les nécroses sur tige. Ceci suggère la dispersion de l'inoculum, l'importance des conditions de sol ou plus vraisemblablement la présence d'une source commune d'inoculum au niveau du sol.