Sess07 3 khamassy n., ilahy r. & boukhris bouhachem s. - potato yield variation as affected by virus seed degeneration and growth conditions in tunisia
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Sess07 3 khamassy n., ilahy r. & boukhris bouhachem s. - potato yield variation as affected by virus seed degeneration and growth conditions in tunisia

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    Sess07 3 khamassy n., ilahy r. & boukhris bouhachem s. - potato yield variation as affected by virus seed degeneration and growth conditions in tunisia Sess07 3 khamassy n., ilahy r. & boukhris bouhachem s. - potato yield variation as affected by virus seed degeneration and growth conditions in tunisia Presentation Transcript

    • Potato yield variation as affected by virus seed degeneration and growth conditions in Tunisia Khamassy N., Ilahy R. and Boukhris-Bouhachem S. June 2013
    • Strategic Crop since 1984 16% of vegetable areas 3 main seasons Crop Seed tubers Value = 40% of Crop Costs Seed Importation Value = 23 M. US$/ year Problems regarding Local Certified Seed Production Potato Crop in Tunisia 32 Kg / Capita / Year
    • WC AC SuC SpC PL HAR Potato Crop in Tunisia: Growing seasons Imported seed
    • SEEDS 1. Sources : - Imported Seeds : From E.U ( France, Netherlands) - Local Seeds • Certified seeds (20%) • Non-certified Seeds (80%) 2. Cultivars : • Spunta (mid early 80% of planted area) • Nicola, Obelix, Atlas, Mondial, Liseta…
    • Summer C. Autumn C. Winter and Spring C. Summer C. I.S L.S I.S : Imported Seed L.S: Local Seed Seed Sources per Season Crop
    • Cultivar : Spunta Maturity : Mid early Tuber Shape : Long Tuber size : Medium Eyes Depth : Shallow Skin Colour : Yellow Flesh Colour : Light yellow Average Yield : 30 tons/ha Tolerance : PVY n
    • Potato Virus Y, PVY ( Spring crop and Autumn crop) MAIN PESTS AND DISEASES
    • MAIN SEED PRODUCTION PROBLEMS Cold storage costs (expensive) Diseases (viruses, fungus, bacteria)
    • Seed classes SE E A B Viral diseases tolerance (%) (PVY, PLRV, PVA, PVX, PVS) 0.5 2 10 - Viruses diseases rates too low to allow a successful local seed program However: Epidemiological aphids patterns High yields were recorded from highly virus infested seeds (non certified farmer seeds with more than 30% infestation) in the autumnal crop Legislation…
    • Yield reduction caused by virus diseases Yield (MT/HA) and Yield reduction (%) H.P Beukema et al, 2000 PLRV/PVYo PVYn PVX/PVSVirus infestation (%) Yield (MT/HA) Yield decrease Yield (MT/HA) Yield decrease Yield (MT/HA) Yield decrease 00% 25 MT (0.0%) 25 MT (0.0%) 25 MT (0.0%) 02% 24.88 (0.5%) 24.93 (0.3%) 24.98 (0.1%) 05% 24.68 (1.3%) 24.81 (0.8%) 24.94 (0.2%) 10% 24.34 (2.7%) 24.60 (1.6%) 24.86 (0.6%) 15% 23.98 (4.1%) 24.39 (2.4%) 24.79 (0.8%) 20% 23.61 (5.6%) 24.16 (3.4%) 24.72 (1.1%) 25% 23.22 (7.1%) 23.93 (4.3%) 24.64 (1.4%) 50% 20.84 (16.7%) 22.50 (10%) 24.17 (3.3%) Some authors reported slight effect of viral diseases on potato yields (Van der Zaag, 1987; Beukema, 2000)
    • Objectives Obtaining accurate data regarding the incidence of specific viral diseases on potato yielding Methodology: Evaluating the potato performances of SE, E, iA, lcA, and nc Consumption class seeds as affected by various PVY infestation levels.
    • RESULTS AND DISCUSSION Origin Virus infect ion rates (%) Cover crop (%) Stem number (m²) Total yield Kg/m² Commerc. yield (Kg/m²) Tuber weight (g/tuber) Commerc. tuber nb/m² Non commerc. tuber nb/m² 2007 trials Yield (kg/m²) 01 (SE) 0 50 a 10.00 a 2.46 a 2.34 a 103 abc 21.20 a 4.04 b 4.24 (6%) 02 (E) 2 52 a 8.04 b 2.65 a 2.47 a 141 a 18.20 ab 4.08 b 4.44 (15%) 03 (iA) 4 48 a 8.20 b 2.42 a 2.33 a 130 ab 16.00 bc 4.00 b 4.00 (25%) 04 (lA) 8 49 a 10.08 a 1.82 b 1.71 b 85 bc 16.20 bc 5.40 b 4.24 (38%) 05 (Cons) 50 34 a 8.04 a 1.63 b 1.33 b 74 c 12.08 c 10.00 a 4.05 (90%) Mean trial 12.80 46.60 8.87 2.20 2.03 106 16.73 5.50 4.19
    • RESULTS AND DISCUSSION Deficient field management negatively affected crop growth: Ground cover and stem numbers were 50% of a normal crop growth yield decrease was qualitatively 50% of the potential yield and qualitatively 50% of the potential tuber weight irrespective of virus infection rate No significant yield decrease was observed between 0% and 4% PVY infection level. At higher infection levels (8% and 50%), yield decreased significantly compared to the previous infection levels.
    • y = -0,0037x + 4,7307 R 2 = 0,5051 4,3 4,4 4,5 4,6 4,7 4,8 4,9 5 0 20 40 60 80 100 Totalyield(kg/m²) y = -0,0175x + 2,6199 R 2 = 0,6354 0 0,5 1 1,5 2 2,5 3 0 10 20 30 40 50 60 Totalyield(kg/m²) y = -0,0103x + 3,2491 R 2 = 0,1125 0 0,5 1 1,5 2 2,5 3 3,5 4 4,5 5 0 20 40 60 80 100 Viral infection (%) Totalyield(kg/m²) Suitable agricultural management Deficient agricultural management Suitable agricultural management Physiologically aged seeds (non published data) Effect of virus infection level on potato yield under different growing conditions
    • CONCLUSION Based on these actual results: PVY incidence on potato yield loss seems to be not relevant, at least if crop management and seed ageing factors are respected. The viral disease tolerance standards must be reviewed when at least it deals with PVY and Spunta cultivar. In Tunisia, already the standards of viruses tolerance are as following (BS 0%; SE 2%; E 5%, A 10% and B 15%) Crop management is more determinant than PVY infection rates on yield (Q&Q). When crop management is deficient, the effect of viruses on yield reduction is economically significant.
    • MNT (0%) SE (2%) E (5%) A (10%) B/C (15%) (CAS) Seed Class Yield Reduction (%) Yield/20T (0%viruses) E (10%v.) -1.26% (A) 19.7 T/ha A (20%v.) -3.4% (B/C) 19.3 T/ha B/C (50%v.) -10% 18 T G1 G2 G4 G3 Applied schema for Local Seed production program since 2009 Certified seed
    • Further studies have to be made before generalising such assumption. (defining virus resistance levels of all the cultivars registered in the National Official Catalogue). PERSPECTIVES Accurate data regarding the number of multiplication cycles to adopt in a local seed program.
    • Yield reduction caused by virus diseases Yield (MT/HA) and Yield reduction (%) H.P Beukema et al, 2000 PLRV/PVYo PVYn PVX/PVSVirus infestation (%) Yield (MT/HA) Yield decrease Yield (MT/HA) Yield decrease Yield (MT/HA) Yield decrease 00% 25 MT (0.0%) 25 MT (0.0%) 25 MT (0.0%) 02% 24.88 (0.5%) 24.93 (0.3%) 24.98 (0.1%) 05% 24.68 (1.3%) 24.81 (0.8%) 24.94 (0.2%) 10% 24.34 (2.7%) 24.60 (1.6%) 24.86 (0.6%) 15% 23.98 (4.1%) 24.39 (2.4%) 24.79 (0.8%) 20% 23.61 (5.6%) 24.16 (3.4%) 24.72 (1.1%) 25% 23.22 (7.1%) 23.93 (4.3%) 24.64 (1.4%) 50% 20.84 (16.7%) 22.50 (10%) 24.17 (3.3%)
    • (1): E importée (2): E locale (3): A importée (4): A locale (1) (2) (3)(4) Récolte 25-06-05 CS 2005: Etat de la culture au 30 JAP
    • Récolte 26-01-05
    • mars avril mai 0 5 10 15 20 25 30 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Batan Bousalem Sidi M Douala Population dynamic of aphid vectors related to potato development in Tunisia Period of susceptibility Boukhris-Bouhachem S (2007)