Reduced Tuber Weight Research Articles

Genetic manipulation of protein phosphatase 2A affects multiple agronomic traits and physiological parameters in potato (Solanum tuberosum).

In this study, agronomic and functional characteristics of potato (Solanum tuberosum ) plants constitutively overexpressing the protein phosphatase 2A (PP2A) catalytic subunit StPP2Ac2b (StPP2Ac2b-OE) were evaluated. StPP2Ac2b-OE plants display reduced vegetative growth, tuber yield and tuber weight under well-watered and drought conditions. Leaves of StPP2Ac2b-OE plants show an increased rate of water loss, associated with an impaired ability to close stomata in response to abscisic acid. StPP2Ac2b-OE lines exhibit larger stomatal size and reduced stomatal density. These altered stomatal characteristics might be responsible for the impaired stomatal closure and the elevated transpiration rates, ultimately leading to increased sensitivity to water-deficit stress and greater yield loss under drought conditions. Overexpression of StPP2Ac2b accelerates senescence in response to water-deficit stress, which could also contribute to the increased sensitivity to drought. Actively photosynthesising leaves of StPP2Ac2b-OE plants exhibit elevated levels of carbohydrates and a down-regulation of the sucrose transporter StSWEET11 , suggesting a reduced sucrose export from leaves to developing tubers. This effect, combined with the hindered vegetative development, may contribute to the reduced tuber weight and yield in StPP2Ac2b-OE plants. These findings offer novel insights into the physiological functions of PP2A in potato plants and provide valuable information for enhancing potato productivity by modulating the expression of StPP2Ac2b .

The GpIA7 effector from the potato cyst nematode Globodera pallida targets potato EBP1 and interferes with the plant cell cycle programme.

The potato cyst nematode Globodera pallida acquires all of its nutrients from an elaborate feeding site that it establishes in a host plant root. Normal development of the root cells is re-programmed in a process coordinated by secreted nematode effector proteins. The biological function of the G. pallida GpIA7 effector was investigated in this study. GpIA7 is specifically expressed in the subventral pharyngeal glands of pre-parasitic stage nematodes. Ectopic expression of GpIA7 in potato plants affected plant growth and development, suggesting a potential role for this effector in feeding site establishment. Potato plants overexpressing GpIA7 were shorter, with reduced tuber weight and delayed flowering. We provide evidence that GpIA7 associates with the plant growth regulator StEBP1 (ErbB-3 epidermal growth factor receptor-binding protein 1). GpIA7 modulates the regulatory function of StEBP1, altering the expression level of downstream target genes, including ribonucleotide reductase 2, cyclin D3;1, and retinoblastoma related 1, which are down-regulated in plants overexpressing GpIA7. We provide an insight into the molecular mechanism used by the nematode to manipulate the host cell cycle and demonstrate that this may rely, at least in part, on hindering the function of host EBP1.

Effects of Foliar and Tuber Sprout Suppressants on Storage of Ware Potatoes under Tropical Conditions

Potato (Solanum tuberosum L.) is an important source of dietary carbohydrate and cash income generation for farmers in the tropical highlands of Kenya. The feasibility for cold storage at the farm level is limited due to the high costs of maintaining such a facility and there is limited data on the long-term post-harvest storage and quality of tubers of tropical-adapted cultivars. Application of sprout suppressants to control premature sprouting of ware potato is an attractive proposition. The objectives of this study were to evaluate the efficacy of pre-harvest foliar applications of paclobutrazol (PBZ) and ethephon for sprout suppression on ware potato tubers in storage. Post-harvest spray applications of Isopropyl N-(3-chlorophenyl carbamate) chloropropham (CIPC) and 1,4-dimethylnaphthalene (DMN) on tubers as fog was also evaluated. Potato cultivars had varying levels of tuber dormancy. The tubers were stored at ambient temperature (23 C) and evaluated weekly for 24 weeks for percent of tubers sprouting, length of longest sprouts, tuber weight loss and assessed for dormancy for 24 weeks. Paclobutrazol prolonged tuber dormancy by 21–31 days and reduced tuber weight loss. Ethephon treatment had no effect on dormancy and tuber weight loss. Potato tubers treated with CIPC had greater sprout control than the other treatments in storage. Tuber response to DMN treatment varied among the three potato cultivars evaluated. The findings from this study imply that PBZ is effective in prolonging potato tuber dormancy for short-term basis at 23 C, while CIPC applied on tubers was effective for long term storage. Optimization of post-harvest potato storage can improve food security in the highland tropics.

Impact of potato psyllid density and timing of infestation on Zebra chip disease expression in potato plants

The impact of vector density and timing of infestation on potato were investigated. Healthy potato plants at different growth stages (4, 5, and 7 weeks after germination) were exposed separately to four different B. cockerelli densities (0, 5, 20, and 40 psyllids per cage) in field cages and Zebra chip (ZC) symptoms, leaf photosynthetic rates, tuber yield, and total nonstructural carbohydrate accumulation in leaves and tubers of healthy and B. cockerelli-infested plants were monitored. Potato psyllid nymph and egg populations reached a seasonal peak at 6 weeks after the exposure to insect. Younger plants at 4-week growth stage after germination were more susceptible to B. cockerelli infestation and ZC expression than older plants. As few as five B. cockerelli adults were enough to transmit the ZC pathogen and cause ZC expression both in foliage and tuber. At the density of 20 psyllids per cage, more than 50% of plants showed ZC symptoms in tubers. Furthermore, B. cockerelli infestation reduced leaf photosynthesis rates (P<sub>n</sub>), resulting in less starch and more reducing sugars in tubers, and hence reduced tuber weight and yield, especially when psyllid infestation occurred at the early growth stages. The results indicate that early B. cockerelli infestation of younger plants was associated with more severe ZC expression in both foliage and tubers, leading to earlier dead plants. The data suggest that strategies for controlling B. cockerelli during early potato crop development could thus lessen the severity of ZC development.

Promotion of shoot development and tuberisation in potato by expression of a chimaeric cytokinin synthesis gene at normal and elevated CO2 levels

The bacterial cytokinin biosynthesis gene ipt under control of a chalcone synthase promoter (PCHS) was introduced into potato (Solanum tuberosum L.). Two transgenic lines were selected for detailed study, because in these, root development was reduced only moderately, thus, enabling the plants to be grown in pots. Expression of the PCHS-ipt gene elevated the level of zeatin cytokinins markedly in the apical bud, subapical stems and leaves. The transgenic (IPT) plants exhibited a lower and denser leaf canopy relative to wild-type (WT) plants owing to reduction in main stem length, increase in node number per stem and promotion of lateral shoot development. Main stem diameter was increased markedly due to promotion of cell division associated with activation of cyclin-dependent kinase in the subapical stem. Expression of the PCHS-ipt gene induced aerial stolons, promoted growth of underground stolons and increased tuber number but reduced tuber weight and nitrogen content. The gene expression also increased pinnae and pinnule number per leaf, increased thickness of pinnae and promoted transpiration, photosynthesis and stomatal conductance – effects monitored by gas exchange and 18O and 13C analysis. The elevation of [CO2] to 900 μmol mol–1 promoted growth of both WT and IPT plants, ameliorated the negative effect of high cytokinin on tuber weight and interacted additively with ipt gene expression to promote stem growth.

Variability in Morphology and Aggressiveness Among North American Vegetative Compatibility Groups of Colletotrichum coccodes

North American isolates of Colletotrichum coccodes, representing six vegetative compatibility groups (NA-VCG), were used to study morphological and pathogenic variability. The objective was to determine if variability in conidial and microsclerotial size was related to pathogenicity. Significant differences were detected in length, width, and length/width ratios of conidia as well as in the length and width of microsclerotia among the NA-VCGs. The longest and widest conidia were produced by isolates belonging to NA-VCG1 and the largest microsclerotia were produced by isolates of NA-VCG2. Conidial and microsclerotial lengths and widths also were affected significantly by type of growth medium. There was no relationship between the size of conidia and the size of microsclerotia among the NA-VCGs studied. Conidial and microsclerotial size may affect inoculum potential and survival as isolates of NA-VCG2 have been demonstrated to occur more frequently than other NA-VCGs. Aggressiveness of 17 isolates of C. coccodes representing six NA-VCG's was studied on three potato cultivars using foliar and root inoculation methods. C. coccodes infection reduced tuber weight in all cultivars with both inoculation methods although tuber weight reductions were significantly higher following root inoculations than foliar inoculations. Pathogenic aggressiveness varied among NA-VCGs. Isolates belonging to NA-VCG2 and 3 were the least aggressive on potato foliage and isolates of NA-VCG1, 2, 3, 4, and 5 produced higher microsclerotial density on all three cultivars compared with isolates of NA-VCG6. Across inoculation methods, isolates of C. coccodes belonging to NA-VCG2 and 6 were the most aggressive based on reductions in tuber weight. Umatilla Russet was the most susceptible cultivar to C. coccodes compared to other cultivars regardless of inoculation method. These results demonstrate variability in morphology and pathogenic aggressiveness among the NA-VCGs of C. coccodes but these traits are not related.

ASSESSMENT OF SIX STORAGE METHODS FOR SEED POTATO STORAGE IN NIGERIA

Studies were carried out in 1997 and 1998 at Kuru, Jos Plateau, Nigeria to assess six storage methods for the storage of seed potato. The methods were: Storage in jute bags, perforated polythene bags, baskets, racks, crates and floor. Potato varieties used were Nicola (medium to long dormancy) and B7716-2 (short dormancy). The seed tubers were stored for six months during which daily maximum and minimum temperatures of the storage environment, and the relative humidity were recorded. Tuber weight loss, loss due to rots, sprout number and length per tuber at the end of the storage were also recorded. Results showed that only polythene bag reduced tuber weight loss, but resulted in highest tuber rots due to soft rot disease of potato. Poor light condition in jute bags encouraged the development of long and etiolated sprouts of seed potato. Sprout number per tuber was not affected by the storage methods. Varietal differences in tuber weight loss, sprout number and tuber rots were significant (P≤ 0.05). Due to dehydration, tuber weight loss increased by 37 percent during the six months storage. Based on the results obtained, storage is recommended in crates, racks and on floor of well-ventilated stores for short-term (4 months) storage, since these methods provided good ventilation of stored seed and tuber rots are low. [Niger Agric. J. 34 (2003): 91-96]

A plant growth promoting rhizobacterium and temperature effects on performance of 18 clones of potato

A survey of genotypic responses to beneficial bacterium (Pseudomonas sp. strain PsJN) was conductedin vitro andex vitro, under two temperature conditions, using eighteen clones of potato of different heat stress tolerance: temperate adapted cultivars Kennebec and Russet Burbank; heat tolerant DTO-2, DTO-28, DTO-33, LT-1, LT-2, LT-5, LT-6, LT-7, LT-8, LT-9, Y84-02, NDD277-2, Desiree, and Maine-47; and heat sensitive abscissic acid (ABA)-deficient mutants 11401-01 and 9120-05. Nodal explants taken from 6-week-old bacterized and non-bacterized control plantlets were culturedin vitro on a hormone-free potato nodal cutting medium, and placed at either 20/15 C or 33/25 C day/night temperature, 12h photoperiod and 250 µE m−2 s−1 mixture of fluorescent and incandescent light, for six weeks. The tuberization response was studiedex vitro after two weeks acclimation of 2-week old plantlets at 33/25C. The acclimated plantlets were transplanted to 3L plastic nursery pots containing peat-based Pro-Mix growing medium and placed in growth chambers at either 20/15 or 33/25 C day/night temperature, 12 h photoperiod, 475 μE m−2 s−1 light and ≈80% RH, for 12 weeks. Compared to the non-bacterized controls, bacterization significantly increased stem length of 12, shoot biomass of 9, and root biomass of 2 clones at 20/15C; and stem length of 14, shoot biomass of 15, and root biomass of 13 clones at 33/25C. High temperature increased length of internodes and had either no effect or slightly decreased node number. Temperature increase had the most dramatic effect on root development. An average shoot to root ratio decreased from 3.7 at 20/15 C to 1.7 at 33/25 C for non-bacterized plantlets and, respectively, from 4.3 to 1.5 for bacterized. The beneficial effect of bacterization on root biomass was the most pronounced in LT-1 and Maine-47 at 20/15 C and LT-8, Maine 47, DTO-2, Kennebec, NDD277-2 and 11401-01 at 33/25C. The temperature elevation did not significantly affect root biomass of LT-6, DTO-28 and Desiree. Temperature stress caused severe reduction in tuber number and tuber fresh weight. ABA-deficient mutants did not produce any tubers and LT-8, LT-9, Y84-027 and DTO-28 tuberized very poorly at 33/25C. DTO-33, Desiree, LT-1 and Kennebec gave the highest number of tubers per pot and Kennebec, LT-1, Desiree and LT-7 the highest yields at this temperature. There was no significant effect of bacterization on tuberization at 20/15 C but at 33/25 C bacterization significantly enhanced tuber number and weight in LT-7 and reduced tuber weight in DTO-2. Although there was no clear link between thein vitro response of particular clones to bacterization and their heat stress tolerance, improvement ofex vitro performance of heat tolerant LT-7 indicates that rhizosphere bacteria may play a role in clonal adaptation of potato to heat stress.

Specific distribution of gibberellins, cytokinins, indole-3-acetic acid, and abscisic acid in radish plants closely correlates with photomorphogenetic responses to blue or red light

Summary Ontogenetic patterns of dry matter accumulation and contents of cytokinins, gibberellins, indole-3-acetic acid (IAA), and abscisic acid (ABA) in shoot and hypocotyl were studied in radish (Raphanus sativus L.) plants grown under blue (BL) or red (RL) light. BL promoted the development of storage organ (swollen hypocotyl), whereas RL favoured petiole and stem growth. RL did not prevent tuber formation, but delayed tuberization, which started on days 14 and 20 in BL- and RL-grown plants, respectively, and severalfold reduced tuber weight. About 10-times higher (as compared with BL-grown plants) levels of gibberellins were found in shoots of 11-day-old RL-grown plants, and the difference between RL and BL-grown plants increased with age. The 2.5-times higher level of IAA was found in shoots of 11-day-old BL-grown plants compared with RL-grown ones. IAA levels in shoot abruptly decreased with age regardless of light quality. Compared with RL, BL increased the contents of IAA and cytokinins (zeatin plus zeatin riboside and isopentenyladenine plus isopentenyladenosine) severalfold in hypocotyls of 11- and 14-day-old plants. By day 21, IAA content in hypocotyls decreased in BL, while it increased under RL. Unlike IAA, an increase in cytokinins of hypocotyls continued by day 21, which was much more pronounced in RL-grown plants. These findings indicate that both IAA and cytokinins are involved in tuber initiation regardless of light quality, while cytokinins appear to stimulate the assimilate flow to developing storage tissue. Specific morphogenetic responses of radish plants to BL or RL seem therefore to be closely associated with the specific action of light quality on phytohormones in shoot and hypocotyl: RL enhances sink strength of aboveground organs (petioles and stem) by stimulating gibberellins, whereas BL stimulates assimilate flow to hypocotyls by an increase in IAA, cytokinins, and, probably, ABA. Mechanisms by which BL- or RL-grown plants maintain contrasting levels of different hormones in shoots and hypocotyls are discussed.

Effects of Growing Season and Fungicide Type on the Development ofAlternaria solaniand on Potato Yield

The intensity of early blight disease caused by Alternaria solani and its effects on yield were evaluated in potato crops in the autumn (four experiments), winter (one experiment), and spring (five experiments) growing seasons in Israel. Analysis of disease progress curves revealed that early blight is more important in the autumn and winter than in the spring in the northern Negev region of Israel. Similarly, differences in yield between fungicide-treated and nontreated plots were significant (P < 0.05) in four of the five autumn and winter experiments (20.6 to 24.0% increase) but in none of the spring experiments. In the autumn and winter seasons, early blight did not affect numbers of tubers produced per unit area but reduced tuber weight. The efficacy of the systemic fungicides tebuconazole and difenoconazole against A. solani was compared with that of the common protectant fungicides chlorothalonil and mancozeb. Tebuconazole significantly decreased lesion expansion rate and chlorothalonil did not. In some of the autumn and winter experiments, but in none of the spring experiments, the systemic fungicides were significantly more effective than the protectants in suppression of A. solani.

CHIPPING QUALITY AND YIELD OF 'NORCHIP' POTATOES DAMAGED BY SIMULATED HAIL

ABSTRACT *Norchip' potato plants were subjected to simulated hail damage in a two-factor experimental design. The factors were degree of damage and time of damage in weeks post emergence. Hail was simulated by striking plants with lead spheres tethered to a hand-held rotating shaft. Losses due to simulated hail damage were assessed as quality loss, as measured by pre-harvest sugar concentration and post-harvest chip color, as yield loss, and as specific gravity loss. The experiment was replicated for four years. The results suggest that, in general, hail damage had little influence on chip color but could reduce yield to 64% of control by causing both reduced tuber weight and lower tuber number. Average specific gravity (an important quality attribute of chip potatoes) also fell from 1.096 to 1.085.

Seismic Stress Effects on Reproductive Structures of Tomato, Potato, and Marigold

Periodic seismic (shaking) stress influenced the growth of sexual and asexual reproductive structures of three cultivated species. It delayed anthesis of Lycopersicon esculentum Mill. 'Patio' but not of Tagetes erecta L. 'Jubilee' or Solanum tuberosum L. 'Kennebec'. Shaken 'Jubilee' marigold plants produced the same number of flowers as undisturbed plants, but flowers of shaken plants were smaller. In contrast, seismic-stressed 'Patio' tomato produced fewer buds and flowers, but fruit set was enhanced relative to that of controls. Seismic stress also reduced tuber weight of 'Kennebec' potato, whereas tuber number was unaffected. The overall effect of seismic stress was to reduce the growth of reproductive structures and, in some cases, the number of reproductive structures that developed.