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Dennis A. Johnson - One of the best experts on this subject based on the ideXlab platform.
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transmission of phytophthora infestans from infected potato Seed Tubers to emerged shoots
Plant Disease, 2010Co-Authors: Dennis A. JohnsonAbstract:Transmission of Phytophthora infestans from infected Seed Tubers to emerged potato sprouts, infectivity of sporangia deposited on whole Tubers before burial in soil, and infectivity of sporangia in a loamy fine sand to leaflets were investigated in the greenhouse under simulated spring planting conditions of the Columbia Basin. Incidence of late-blight-infected shoots from infected Seed Tubers was significantly greater when foliage was exposed to wet periods in mist chambers (mist for 45 s every 15 min) for either 24 or 48 h than when not exposed to a wet period. Proportion of infected shoots from infected Tubers was 0.210 to 0.261 in a moist environment versus 0.013 to 0.052 in a nonmist environment. Development of chlorosis, necrosis, and sporangia occurred on shoots that emerged from infected, symptomatic Tubers buried in soil. However, approximately 20% of the infected shoots produced sporangia before stems had visible discoloration of late-blight symptoms. Sporulation was sparse and formed near the soil line on some of the shoots after 24 h in the moist environment. The latent period or time from inoculation to sporulation on young stems of Russet Burbank was 5 to 6 days, which is too long to account for an infection from either sporangia or zoospores at the soil level of shoots during the wet period in this study. Sporangia were infective when placed directly on eyes of whole Tubers before planting. Leaflets touching a loamy fine sand infested with sporangia developed typical late-blight lesions beginning at the leaflet tip within 7 days after a 24-h wet period and the infested loamy fine sand was infective when splashed on leaflets.
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latent infection of potato Seed Tubers by phytophthora infestans during long term cold storage
Plant Disease, 2009Co-Authors: Dennis A. Johnson, Thomas F. CummingsAbstract:Johnson, D. A., and Cummings, T. F. 2009. Latent infection of potato Seed Tubers by Phytophthora infestans during long-term cold storage. Plant Dis. 93:940-946. Latent infection of potato Seed Tubers by Phytophthora infestans was determined following inoculation of Tubers and typical Seed tuber storage conditions in the Pacific Northwest. Severity of late blight increased over 182 to 209 days during two storage seasons at mean temperatures of 4.1 and 4.2°C. From 0 to 44% of inoculated Tubers sampled at given intervals were asymptomatic. However, P. infestans sporangia were observed on slices from these Tubers when incubated in a humidity chamber at 15°C or late blight symptoms developed in asymptomatic Tubers obtained following storage when incubated at 22 to 23°C for 3 weeks. Development of P. infestans sporangia and symptoms of late blight in asymptomatic Seed Tubers indicated latent infection of Tubers by P. infestans during long-term cold storage. Sporulation was observed after 21 to 24 h on symptomatic Tubers and 6 to 20 days on asymptomatic Tubers that were removed from storage and incubated in a humidity chamber at 15°C. Latent infection of Seed Tubers and production of viable sporangia of P. infestans were demonstrated after long-term cold storage of infected potato Tubers.
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relationship between silver scurf levels on Seed and progeny Tubers from successive generations of potato Seed
American Journal of Potato Research, 2006Co-Authors: Brad Geary, Dennis A. JohnsonAbstract:The level of silver scurf on potato Seed Tubers on successive generations of potato Seed Tubers and their progeny Tubers was investigated during 3 years in the field. The objective was to determine the importance of Seed-borne inoculum on silver scurf development on the subsequent progeny Tubers. Silver scurf incidence and severity increased with each generation. Coefficients of determination for disease levels among generations were significant and ranged from 0.89 to 0.97, indicating that Seed tuber source accounted for a large proportion of silver scurf on progeny Seed Tubers. Incidence and severity of silver scurf also increased with decreasing time periods between potato crops in the field. In a field near Paterson, WA, where potatoes had not been previously grown, the severity of silver scurf increased on progeny Tubers of cvs Russet Norkotah, Ranger Russet, and Shepody as disease severity increased on Seed Tubers of successive generations. Disease severity index significantly increased as disease incidence increased. The relationship between the two was best described using a curvilinear regression model.
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Incidence of Colletotrichum coccodes in certified potato Seed Tubers planted in Washington State
Plant disease, 1997Co-Authors: Dennis A. Johnson, Randall C. Rowe, Thomas F. CummingsAbstract:Incidence of Colletotrichum coccodes in lots of certified Seed Tubers planted in Washington state, originating from nine western and midwestern states in the United State and two provinces in Canada, ranged from 0 to 90% in 1994 and 0 to 53% in 1995. In 1994, significant interactions between state/province and cultivar, and between Seed grower and cultivar, were evident. In 1995, incidence of C. coccodes in Seed lots did not vary significantly among states and cultivars. C. coccodes was not isolated from nuclear Seed Tubers and incidence of infected Tubers was higher with higher Seed generations. The fungus was isolated from the tuber periderm and outer medulla tissues and isolation frequency was greater from tuber stem ends than from either bud ends or lateral sections. Significantly greater stem infections developed in plants grown from Seed Tubers in which C. coccodes had been detected than in plants grown from Seed Tubers from which C. coccodes had not been isolated. This study confirms that C. coccodes is distributed among potato-production areas within Seed Tubers, and that Seed tuber infection increases the incidence of early-season plant infection.
Richard N Knowles - One of the best experts on this subject based on the ideXlab platform.
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correlative changes in proteases and protease inhibitors during mobilisation of protein from potato solanum tuberosum Seed Tubers
Functional Plant Biology, 2010Co-Authors: Sarah M Weeda, G Mohan N Kumar, Richard N KnowlesAbstract:Potato Tubers (Solanum tuberosum L.) contain protease inhibitors that function in plant defence and as storage proteins. A multi-domain cysteine protease inhibitor, potato multicystatin (PMC), has also been implicated in regulating protein accumulation in developing Tubers by inhibiting proteases. Unlike developing Tubers, sprouting Tubers mobilise protein reserves to support growth of developing plants and, therefore, show an increase in protease activity. Using single-eye containing cores (Seedcores) from Seed Tubers, we characterised the relative changes in patatin, PMC, proteases and serine (Ser) protease inhibitors, as a prerequisite to further research on their potential roles in protein mobilisation from Tubers during plant establishment. Approximately 63% of Seedcore dry matter was mobilised over a 29-day period of plant establishment (1.7 mg Seedcore dry matter mobilised for every mg increase in plant dry matter). The gelatinolytic protease isoforms induced in Seedcores during plant establishment differed from those characterised previously in developing Tubers. Total protease activity increased progressively in Seedcores and reached a maximum 23 days after planting. Conversely, Seedcore soluble protein content declined, with patatin accounting for the greatest decrease in the soluble protein fraction during plant establishment. PMC also decreased 44% and Ser (trypsin) protease inhibitors decreased to levels barely detectable in Seedcores over the 29-day growth interval. Moreover, the temporal changes in PMC, protease activity and patatin content were highly correlated. As PMC decreased from 6 to 4 ng core–1, protease activity increased 9-fold, patatin decreased 2.6-fold and total soluble protein decreased by 58%. These results suggest that catabolism of protease inhibitors may facilitate protein mobilisation from Seed Tubers. Further work to define unequivocally the role of protease inhibitors in modulating the activity of proteases during protein mobilisation from Tubers is warranted.
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changes in lipid molecular species and sterols of microsomal membranes during aging of potato solanum tuberosum l Seed Tubers
Lipids, 2002Co-Authors: Vladimir Zabrouskov, Richard N KnowlesAbstract:Changes in sterols and the molecular species composition of polar lipids from microsomal membranes were characterized as a prerequisite to determining how lipid chemistry affects membrane susceptibility to peroxidation during aging of potato Tubers. Polar lipid content of the microsomal fraction fell 17% (protein basis) as Tubers aged from 2 to 38 mon at 4°C. In younger Seed-Tubers, PC concentration (protein basis) was the highest, followed by digalactosyldiacylglycerol (DGDG), PE, monogalactosyldiacylglycerol (MGDG), and PI. PC and PE increased 14 and 27%, respectively, whereas glycolipids fell 64 and PI 43% with advancing age. These changes resulted in PC and PE dominating the microsomal membrane lipids of 38-mon-old Tubers. Nonpositional analysis of lipid molecular species across lipid pools showed an increase in 16∶0/18∶3, 18∶3/18∶3, and 18∶2/18∶3 (PC and PE only), and a decline in 18∶2/18∶2 and 16∶0/18∶2 (except for MGDG) with advancing tuber age. The increase in 18∶3-bearing species effected a linear increase in double-bond index (DBI) of PC and PE during aging. The DBI of DGDG did not change with age; however, it fell 65% for MGDG, resulting in an overall decrease in average microsomal DBI. In addition, Δ5-avenasterol and stigmasterol concentrations increased 1.6- and 3.3-fold, respectively, effecting a significant increase in the sterol/phospholipid ratio with advancing tuber age. The increase in sterol/phospholipid ratio and the possibility that the increased unsaturation of microsomal membranes reflects a compensatory response to maintain optimal membrane function in light of the age-induced loss of galactolipid and PI are discussed.
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nature of enhanced respiration during sprouting of aged potato Seed Tubers
Physiologia Plantarum, 1996Co-Authors: G Mohan N Kumar, Richard N KnowlesAbstract:Respiration of 18-month-old Solarium tuberosum L. Tubers was about 53% greater than that of 6-month-old Tubers during sprouting at 23°C; yet, a significant loss of sprout vigor in the older Tubers was apparent. Involvement of alternative oxidase (AO) in the age-induced difference in tuber respiration was assessed. AO was only detected in immunoblots if tissue disks from Tubers were pre-incubated for 24 h prior to isolation of submitochondrial membrane particles (SMPs). No AO1 was detected in SMPs from nonincubated tuber tissue of either age, indicating that it was not contributing to tuber respiration during sprouting as previously thought. Respiratory control and ADP/O ratios indicated that oxidative phosphorylation was fully coupled to electron transport in mitochondria isolated from 6- and 18-month-old Tubers. Cytochrome c oxidase (EC 1.9.3.1) activities of intact mitochondria were also not affected by tuber age. The difference in respiration during sprouting was unique to whole Tubers, as oxygen consumption by mitochondria from young and oid Tubers was equal on a milligram protein basis. Sprouting 18-month-old Tubers had 15% more mitochondrial protein per gram fresh weight than did 6-month-old Tubers. Older Tubers also produced more ATP than younger Tubers prior to and during sprouting, through a fully coupled, Cyt-mediated respiratory pathway, reduced sprout vigor notwithstanding. From 5 to 10 days of sprouting, coinciding with development of the age-induced difference in whole-tuber respiration, ATP concentration in 18-month-old Tubers increased to become 52% higher than that in 6-month-old Tubers. ATP synthase (EC 3.6.1.34), assessed by SDS-PAGE and immunoblots of β- and oligomycin-sensitivity conferring protein-subunits, also increased as a proportion of SMP protein in older Tubers during this period. Relative to 6-month-old Tubers, the increased respiration and associated oxidative phosphorylation of 18-rnonth-old Tubers during sprouting were probably in response to a lower adenylate energy charge (AEC) prior to sprouting (from 0 fo 5 days). From 5 to 10 days of sprouting, AEC of 18-rnonth-old Tubers increased to equal that of 6-month-old Tubers and the two tuber ages maintained the same AEC for the remainder of the 20-day sprouting interval. Higher respiration and lower AEC of older Tubers in storage at 4°C, along with the fact that older Tubers respired at a higher rate to achieve the same AEC as younger Tubers during sprouting, indicate greater utilization of ATP by older Tubers.
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age of potato Seed Tubers influences protein synthesis during sprouting
Physiologia Plantarum, 1993Co-Authors: G Mohan N Kumar, Richard N KnowlesAbstract:The effect of Seed-tuber age on the ability of tuber tissue to synthesize protein during sprouting was examined. As Seed-tuber age advanced from 4 to 32 months (at 4°C, 95% relative humidity), soluble protein concentration of Tubers decreased linearly, with a concomitant increase in free amino acid concentration. The age-induced loss of tuber protein may thus be due to increased proteolysis, decreased protein synthesis, or both. Five- and 17-month-old Seed-Tubers were compared for their ability to incorporate radiolabeled amino acids into soluble protein at equivalent stages of sprout development. Tuber respiration was profiled through each sprouting stage to characterize the physiological status of the Seed-Tubers prior to incorporation studies. Five-month-old Seed-Tubers maintained a constant rate of respiration during sprouting. In contrast, respiration of 17-month-old Tubers increased as sprout dry matter increased, resulting in a 2- to 3-fold greater respiratory rate from the older Tubers, relative to the younger Tubers, at similar stages of sprout development. Prior to sprouting, the rate of incorporation of amino acids into trichloroacetic acid-precipitable protein of tissue from 5-month-old Tubers was 2. 9-fold higher than that from 17-month-old Tubers. More importantly, protein-synthetic capacity of tissue from younger Tubers increased about 1. 7-fold during sprout development. Despite the higher respiratory activity and faster total sprout dry matter accumulation from older Seed-Tubers, protein synthesis remained at a low and constant level through all stages of sprouting. Protein-synthetic capacity thus declines with advancing tuber age, and this may contribute to reduced growth potential during the latter stages of establishment by affecting the ability of Seed-Tubers to synthesize enzymes involved in mobilization and translocation of tuber reserves to developing plants.
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involvement of auxin in the loss of apical dominance and plant growth potential accompanying aging of potato Seed Tubers
Botany, 1993Co-Authors: G N M Kumar, Richard N KnowlesAbstract:potential accompanying aging of potato Seed Tubers. Can. J. Bot. 71: 541 -550. Studies were conducted to further characterize a role for auxin in the loss of apical dominance and plant growth potential that occurs during long-term storage of potato (Solanum tuberosurn L.) Seed Tubers. Treatment of single-eye Seed cores from 18-month-old Seed Tubers with l-naphthaleneacetic acid (NAA) restored apical dominance and increased dry matter partitioning to roots, stems, and leaves, thus partially mitigating the deleterious effects of advanced Seed-tuber age on growth potential. Conversely, NAA treatment of Seed cores from 6-month-old Tubers substantially inhibited plant growth. In contrast to NAA, IAA was totally ineffective at counteracting the deleterious effects of advanced tuber age on plant growth, whereas the effect of IAA on overall growth of plants from 6-month-old Seed cores remained slightly inhibitory. The difference in efficacy of these two auxins appears to be related to age-induced differences in ability of tissues to transport and catabolize IAA. The specific activity of IAA oxidase (IAAox) was 4 times higher in tissue from 20-month-old Seed Tubers at planting and increased at a faster rate during sprouting compared with that from 8-month-old Tubers. Hence, the higher potential for oxidation of IAA in tissue from older Seed cores is well correlated with the inability of this auxin to alter growth. In translocation studies, etiolated sprouts from aged Seed Tubers showed a reduced ability to translocate [l-'"IIAA basipetally compared with those from younger Tubers. Moreover, intact etiolated sprouts growing from older Seed cores decarboxylated the radiolabeled IAA at a much faster rate on a dry weight basis than those from younger Seed cores. The specific activities of IAAox and peroxidase in the sprout apex, sprout base, and tuber tissue from 18-month-old Seed cores were substantially higher than in similar tissues from 6-month-old Seed cores, and tissue concentration of the radiolabel was negatively correlated with IAAox activity. Hence, aging of potato Seed Tubers not only reduces the ability of sprouts to transport auxin basipetally, but it also increases the capacity for auxin catabolism during sprouting. The physiological consequence of this may be the release of lateral meristems from correlative inhibition, and in effect, reduced apical dominance and shoot growth potential during plant establishment from aged Seed Tubers.
P.c. Struik - One of the best experts on this subject based on the ideXlab platform.
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the canon of potato science 40 physiological age of Seed Tubers
Potato Research, 2007Co-Authors: P.c. StruikAbstract:What is it? The physiological quality of Seed Tubers is determined by dormancy and – after the dormancy has been broken – by physiological age. Physiological age is the developmental stage of a potatoSeedtuber but itcan alsobedefined as the physiological state of the Seed tuber which influences its production capacity. Physiological age determines the behaviour of each bud of the Seed tuber thus affecting the number of sprouts per eye and their vigour. Moreover, it also influences the physiological behaviour of the resulting stem, even well after emergence. Physiological age advances progressively by increasing chronological age, but also depends on: a. the size of the individual tuber; b. the growth history of the Seed crop from which the Seed tuber has been obtained; c. possible treatments applied to the Seed crop (e.g., hormonal sprays on the canopy); d. the timing and method of haulm killing; e. the conditions between haulm killing of the Seed crop and the harvesting of the Seed tuber; f. the conditions during storage and from storage until planting; g. possible treatments during harvesting or storage; h. possible treatments between storage and planting. The temperature sum after the end of dormancy during storage of is the most dominant factor affecting physiological ageing, although its effect is moderated by light conditions and by genotypic characteristics. While the physiological age progresses, the Seed tuber goes through different stages, including dormancy (no sprout), apical dominance (only one sprout), normal
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response of stored potato Seed Tubers from contrasting cultivars to accumulated day degrees
Crop Science, 2006Co-Authors: P.c. Struik, D. O. Caldiz, P E L Van Der Putten, K ScholteAbstract:In potato (Solanum tuberosum L.), the accumulated day-degrees (temperature sum, calculated by accumulating the daily temperatures) from dormancy break until Seed tuber use has been suggested as an indicator of the physiological status of the Seed. We tested whether similar temperature sums differing in timing of a short period of high temperatures gave similar Seed performance. Four field experiments were performed in which Seed was used that had been exposed to different storage temperature regimes, differing in total temperature sum or in timing or duration of a warm period. Emergence, number of stems, number of Tubers, and early and mature tuber yield were assessed. During the storage period, the onset of sprouting was recorded. Cultivars with a high rate of physiological degeneration ("ageing") were usually sensitive to warm storage during the second part of the storage period, especially if the first 12 to 18 wk of storage had also been warm. This was reflected in reduced emergence (10%), low densities of stems (0.5 stems m?2) and Tubers (5 Tubers m?2), and low yields, especially with early harvesting (20 g m?2). Specific phasing of the warm period could reduce yields to levels even below the yield of the Seed Tubers exposed to the highest accumulated temperature sum. A higher temperature sum after the end of dormancy advanced and accelerated the process of ageing of Seed Tubers. Cultivars with a high rate of ageing showed much greater difference between the same temperature sums built up over time in different ways than cultivars with a low rate of ageing. The resulting maximum differences in final fresh tuber yield between Seed lots exposed to the same temperature sum could be 65 Mg ha?1 for Astarte (a cultivar with a high rate of ageing) compared with nil for Desiree (a cultivar with a low rate of ageing).
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sprouting of Seed Tubers during cold storage and its influence on tuber formation flowering and the duration of the life cycle in a diploid population of potato
Potato Research, 2003Co-Authors: Carolina Celisgamboa, P.c. Struik, E Jacobsen, Richard G F VisserAbstract:The influence of a short tuber dormancy and the subsequent sprout growth of the Seed Tubers during storage at 4 °C on the processes related to plant development and tuber formation was investigated in a diploid population with 238 genotypes, its crossing parents and seven tetraploid varieties. Sprout growth during storage at 4 °C was positively correlated to the duration of the dormancy period at 18–22 °C, the low temperature prolonging the dormancy period. Results show that the duration of the dormancy period and the sprouting of Seed Tubers during storage at low temperature did not have a determinant influence on plant development, tuber formation or the duration of the plant cycle in this large and highly diverse population of potato.
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physiological age index a new simple and reliable index to assess the physiological age of Seed potato Tubers based on haulm killing date and length of the incubation period
Field Crops Research, 2001Co-Authors: D. O. Caldiz, Laura V Fernandez, P.c. StruikAbstract:Chronological and physiological age of Seed Tubers have major impacts on potato yields. This paper presents a new, simple and reliable physiological age index (PAI) that considers and reconciles the effects of chronological and physiological age. PAI calculation is based on the haulm killing date of the Seed crop (T0) and the end of the incubation period of Seed Tubers, measured under standardized conditions. The PAI formula is T1/T2, where T1 is the time from haulm killing date (T0 )t o possible planting date and T2 the time from T0 to the end of the incubation period. The PAI expresses physiological ageing of Seed potato Tubers within a range from 0 (for physiologically young) to 1 (old) Tubers. To test the PAI existing data were reevaluated and re-elaborated and specific experiments regarding Seed origin and storage conditions for different cultivars were performed during 1994‐1999. The PAI proved useful in assessing differences due to differences in growing conditions, cultivar, haulm killing, Seed origin and storage system, and pre-planting treatments. For example, for cv. Spunta 6 days after haulm killing the PAI was 0.025 and after 100-storage days the PAI was 0.56, 0.52 and 0.49 for Seed Tubers stored in heaps in the field, at relatively high temperatures, natural diffuse light and a cold (48C) and ventilated store, respectively. The PAI is related to ground cover duration and yield of the future crop. For a PAI of 0.55 tuber yield was 55 t ha ˇ1 , while for a PAI of 0.80 tuber yield was 40 t ha ˇ1 . The PAI is easy to measure, non-invasive, objective, reproducible and reliable and could be used for modelling purposes to describe performance of Seed Tubers. # 2001 Elsevier Science B.V. All rights reserved.
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physiological age index a new simple and reliable index to assess the physiological age of Seed potato Tubers based on haulm killing date and length of the incubation period
Field Crops Research, 2001Co-Authors: D. O. Caldiz, Laura V Fernandez, P.c. StruikAbstract:Abstract Chronological and physiological age of Seed Tubers have major impacts on potato yields. This paper presents a new, simple and reliable physiological age index (PAI) that considers and reconciles the effects of chronological and physiological age. PAI calculation is based on the haulm killing date of the Seed crop (T0) and the end of the incubation period of Seed Tubers, measured under standardized conditions. The PAI formula is T1/T2, where T1 is the time from haulm killing date (T0) to possible planting date and T2 the time from T0 to the end of the incubation period. The PAI expresses physiological ageing of Seed potato Tubers within a range from 0 (for physiologically young) to 1 (old) Tubers. To test the PAI existing data were re-evaluated and re-elaborated and specific experiments regarding Seed origin and storage conditions for different cultivars were performed during 1994–1999. The PAI proved useful in assessing differences due to differences in growing conditions, cultivar, haulm killing, Seed origin and storage system, and pre-planting treatments. For example, for cv. Spunta 6 days after haulm killing the PAI was 0.025 and after 100-storage days the PAI was 0.56, 0.52 and 0.49 for Seed Tubers stored in heaps in the field, at relatively high temperatures, natural diffuse light and a cold (4°C) and ventilated store, respectively. The PAI is related to ground cover duration and yield of the future crop. For a PAI of 0.55 tuber yield was 55 t ha−1, while for a PAI of 0.80 tuber yield was 40 t ha−1. The PAI is easy to measure, non-invasive, objective, reproducible and reliable and could be used for modelling purposes to describe performance of Seed Tubers.
D. O. Caldiz - One of the best experts on this subject based on the ideXlab platform.
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Phosphite compounds reduce disease severity in potato Seed Tubers and foliage
European Journal of Plant Pathology, 2008Co-Authors: M. C. Lobato, F. P. Olivieri, E. A. González Altamiranda, E. A. Wolski, G. R. Daleo, D. O. Caldiz, A. B. AndreuAbstract:Phosphites (Phi) are alkali metal salts of phosphorous acid, with the ability to protect plants against different pathogens. In this research, the effect of Phi applied to potato plants on severity of three important potato diseases in Argentina was assessed. Seed Tubers and foliage of potato cvs Shepody and Kennebec were treated with Phi to assess effects on resistance against Phytophthora infestans , Fusarium solani and Rhizoctonia solani . Protection resulting from Phi treatment in Seed Tubers was high against P. infestans , intermediate against F. solani , and low against R. solani . In addition, Seed Tubers treated with calcium or potassium phosphites (CaPhi and KPhi, respectively) at 1% of commercial product emerged earlier than untreated ones. When Phi were foliarly applied two or four times at different doses, high levels of protection against P. infestans were achieved in both cultivars. Higher protection was observed in Kennebec when CaPhi was applied, while in Shepody this was true for KPhi. Expression of β-1,3-glucanases was induced at different times after treatment but no correlation between β-1,3-glucanases expression and foliar protection level was found. On the other hand, Phi positive protection effects did not produce negative effects in plant growth. Leaves from CaPhi-treated plants showed a darker green colour than leaves from control plants; also an increase in Rubisco protein and a delay in crop senescence was observed.
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response of stored potato Seed Tubers from contrasting cultivars to accumulated day degrees
Crop Science, 2006Co-Authors: P.c. Struik, D. O. Caldiz, P E L Van Der Putten, K ScholteAbstract:In potato (Solanum tuberosum L.), the accumulated day-degrees (temperature sum, calculated by accumulating the daily temperatures) from dormancy break until Seed tuber use has been suggested as an indicator of the physiological status of the Seed. We tested whether similar temperature sums differing in timing of a short period of high temperatures gave similar Seed performance. Four field experiments were performed in which Seed was used that had been exposed to different storage temperature regimes, differing in total temperature sum or in timing or duration of a warm period. Emergence, number of stems, number of Tubers, and early and mature tuber yield were assessed. During the storage period, the onset of sprouting was recorded. Cultivars with a high rate of physiological degeneration ("ageing") were usually sensitive to warm storage during the second part of the storage period, especially if the first 12 to 18 wk of storage had also been warm. This was reflected in reduced emergence (10%), low densities of stems (0.5 stems m?2) and Tubers (5 Tubers m?2), and low yields, especially with early harvesting (20 g m?2). Specific phasing of the warm period could reduce yields to levels even below the yield of the Seed Tubers exposed to the highest accumulated temperature sum. A higher temperature sum after the end of dormancy advanced and accelerated the process of ageing of Seed Tubers. Cultivars with a high rate of ageing showed much greater difference between the same temperature sums built up over time in different ways than cultivars with a low rate of ageing. The resulting maximum differences in final fresh tuber yield between Seed lots exposed to the same temperature sum could be 65 Mg ha?1 for Astarte (a cultivar with a high rate of ageing) compared with nil for Desiree (a cultivar with a low rate of ageing).
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early management of late blight phytophthora infestans by using systemic fungicides applied to Seed potato Tubers
Crop Protection, 2006Co-Authors: Adriana Balbina Andreu, D. O. CaldizAbstract:Abstract Planting of Seed Tubers infected with late blight has been reported as a major cause in initiating the disease at field level. Seed treatments with contact fungicides can protect healthy Tubers from infection during handling, grading and cutting before planting, but are not effective in protecting the young plant after emergence, when is more susceptible to the disease. Foliar fungicide applications are still required so crop protection early in the season, as a consequence of Seed treatments could be an advantage especially in environments conducive to late blight epidemics. The systemic fungicides iprovalicarb+propineb (Melody Duo) and propyl carbamate (Previcur N), from Bayer CropScience, were applied to Seed potato Tubers (40–50 g) immediately after cutting or at planting to the bottom of the furrow and Seed piece in cultivars Kennebec, Shepody, Ranger Russet, Russet Burbank and Spunta, at doses of 0.8 and 1.6 kg ton−1 and 0.4 and 0.8 l ton−1 of Seed, respectively. Treated and control Seed Tubers were planted in pots in a greenhouse. From the time plants had one fully expanded leaf up to 40 days after emergence each treatment was evaluated by the detached-leaf method to assess foliage protection by means of artificial late blight inoculation. For all cultivars a higher level of foliage protection was found in those plants from Seed Tubers treated with iprovalicarb+propineb, while no effects were observed when the chemical was applied at planting to the bottom of the furrow. Used as described, this fungicide provided a higher protection against late blight than propyl carbamate. Further pre-commercial field trials, carried out during two growing seasons, with iprovalicarb+propineb was effective in protecting the foliage of cultivars Spunta, Kennebec and Shepody up to 4–6 weeks after crop emergence. For the first 4 weeks protection was high and the following two weeks it was satisfactory. This innovative application of iprovalicarb+propineb was only effective when the chemical was applied to cut Seed Tubers immediately after cutting and before suberization. Due to its effectiveness in controlling late blight this type of treatment should be part of a strategy for integrated late blight management, particularly where late blight epidemics occur early in the season.
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physiological age index a new simple and reliable index to assess the physiological age of Seed potato Tubers based on haulm killing date and length of the incubation period
Field Crops Research, 2001Co-Authors: D. O. Caldiz, Laura V Fernandez, P.c. StruikAbstract:Chronological and physiological age of Seed Tubers have major impacts on potato yields. This paper presents a new, simple and reliable physiological age index (PAI) that considers and reconciles the effects of chronological and physiological age. PAI calculation is based on the haulm killing date of the Seed crop (T0) and the end of the incubation period of Seed Tubers, measured under standardized conditions. The PAI formula is T1/T2, where T1 is the time from haulm killing date (T0 )t o possible planting date and T2 the time from T0 to the end of the incubation period. The PAI expresses physiological ageing of Seed potato Tubers within a range from 0 (for physiologically young) to 1 (old) Tubers. To test the PAI existing data were reevaluated and re-elaborated and specific experiments regarding Seed origin and storage conditions for different cultivars were performed during 1994‐1999. The PAI proved useful in assessing differences due to differences in growing conditions, cultivar, haulm killing, Seed origin and storage system, and pre-planting treatments. For example, for cv. Spunta 6 days after haulm killing the PAI was 0.025 and after 100-storage days the PAI was 0.56, 0.52 and 0.49 for Seed Tubers stored in heaps in the field, at relatively high temperatures, natural diffuse light and a cold (48C) and ventilated store, respectively. The PAI is related to ground cover duration and yield of the future crop. For a PAI of 0.55 tuber yield was 55 t ha ˇ1 , while for a PAI of 0.80 tuber yield was 40 t ha ˇ1 . The PAI is easy to measure, non-invasive, objective, reproducible and reliable and could be used for modelling purposes to describe performance of Seed Tubers. # 2001 Elsevier Science B.V. All rights reserved.
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physiological age index a new simple and reliable index to assess the physiological age of Seed potato Tubers based on haulm killing date and length of the incubation period
Field Crops Research, 2001Co-Authors: D. O. Caldiz, Laura V Fernandez, P.c. StruikAbstract:Abstract Chronological and physiological age of Seed Tubers have major impacts on potato yields. This paper presents a new, simple and reliable physiological age index (PAI) that considers and reconciles the effects of chronological and physiological age. PAI calculation is based on the haulm killing date of the Seed crop (T0) and the end of the incubation period of Seed Tubers, measured under standardized conditions. The PAI formula is T1/T2, where T1 is the time from haulm killing date (T0) to possible planting date and T2 the time from T0 to the end of the incubation period. The PAI expresses physiological ageing of Seed potato Tubers within a range from 0 (for physiologically young) to 1 (old) Tubers. To test the PAI existing data were re-evaluated and re-elaborated and specific experiments regarding Seed origin and storage conditions for different cultivars were performed during 1994–1999. The PAI proved useful in assessing differences due to differences in growing conditions, cultivar, haulm killing, Seed origin and storage system, and pre-planting treatments. For example, for cv. Spunta 6 days after haulm killing the PAI was 0.025 and after 100-storage days the PAI was 0.56, 0.52 and 0.49 for Seed Tubers stored in heaps in the field, at relatively high temperatures, natural diffuse light and a cold (4°C) and ventilated store, respectively. The PAI is related to ground cover duration and yield of the future crop. For a PAI of 0.55 tuber yield was 55 t ha−1, while for a PAI of 0.80 tuber yield was 40 t ha−1. The PAI is easy to measure, non-invasive, objective, reproducible and reliable and could be used for modelling purposes to describe performance of Seed Tubers.
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Improved propagation methods to raise the productivity of yam (Dioscorea rotundata Poir.)
Food Security, 2015Co-Authors: B. A. Aighewi, R. Asiedu, N. Maroya, M. BalogunAbstract:White Guinea yam ( Dioscorea rotundata Poir.) is an important staple to millions of people in West Africa. Obtaining good quality planting material for yam cultivation is a major challenge. Multiplication ratios are low, and Seed Tubers are prone to contamination with pests and pathogens in the traditional systems of production. Some approaches to producing quality Seed of yam are as follows: farmers select small whole Tubers from a ware crop harvest; stimulate the production of Seed Tubers by ‘milking’ ware Tubers while the leaves of the plant are still green (double harvest system); cut ware Tubers into setts about the same sizes as regular Seed Tubers; or use the ‘Anambra’ system where smaller setts are cut and used to produce Seed Tubers. New methods that have been developed to address some of the challenges of quantity and quality of Seed Tubers are not yet widely applied, so farmers continue to use traditional methods and save Seed from a previous harvest to plant the ware crop. This document presents an overview of traditional and modern methods of Seed yam production and gives a perspective for the future. Among the modern methods of Seed yam production, only the minisett technique, which uses 25–100 g tuber pieces, is currently used at farmer level, although on a limited scale. While tissue and organ culture techniques are the most rapid methods of multiplying disease free propagules, their limitations include high costs, need for skilled personnel and specialized equipment. The aeroponics and temporary immersion bioreactor methods of producing Seed yam are relatively new, and still need more research. To build and sustain a viable Seed yam production system, a multiplication scheme is required that combines two or more methods including tissue culture for cleaning the Seed stock.