Germplasm Characterization and Evaluation and the Importance (and Challenges) of Field Genebanks

Transcription

1 Germplasm Characterization and Evaluation and the Importance (and Challenges) of Field Genebanks A background on CIAT s cassava collection Field genebanks as a component of a comprehensive conservation system A knowledge system that begins with farmers Characterization Evaluation

2 The original collection: Foresight in the 1960s

3 CIAT s first annual report (1969): to explore and collect cultivars and related wild species of Manihot in the countries where variability is present, with emphasis in the primary centers of origin (Northern South America and Middle America), in order to establish a germplasm bank representative of the world s variability

4 May of 1969, began collection in Colombia, by Victor Manuel Patiño, director of the Cauca Valley Botanical Garden assisted by Pablo Daza, cassava expert at CIAT. By end of 1970: Colombia 1884 Ecuador 123 Puerto Rico 60 Panama 118 Peru 8 Venezuela 330 Mexico 70 Total: 2593

5 Cassava in vitro techniques developed in the late 1970s, and the genebank passed to in vitro culture by mid-1980s.

6 Table 7. Comparison of key costs (US$ per accession, 2000 basis) for conserving and distributing a cassava accession for one year in CIAT s genebank. In vitro Cryoconservation Existing New Without With Field Cost category accessions accessions regeneration regeneration genebank Conservation Storage a Subculturing b Viability testing 7.96 Regeneration (cryo.) Disease indexation Conservation total cost Distribution Storage Subculturing Dissemination Distribution total cost Source: Koo et al., a Storage costs for the field genebank are the same as the cost of field maintenance. b Storage and subculturing costs for in vitro are allocated equally between conservation and distribution.

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8 Estimated unique landrace varieties In CG In situ Ex situ centers Americas 15,925 5,131 4,851 Africa 7,480 3,743 2,112 Asia/Oc. 2,965 1, World 26,370 10,006 7,220 Source: Hershey, 2010

9 The decision process to eliminate the field genebank at CIAT 1969: At establishment CBB became epidemic, and a pathologist hired to solve the problem 1980s: Occasional frogskin incidence; outbreak of superelongation disease. 1990s: Explosion of whiteflies and frogskin disease at the CIAT station; resulted in a plan for cassava-free periods to manage whiteflies

10 Field genebanks of cassava The positives Access for characterization and evaluation Low tech anyone can do it In some situations can provide a secure system of conservation at reasonable cost Can be a backup to a more secure in vitro system

11 Field genebanks of cassava The negatives In high pest/disease pressure situations, some accessions may not survive May be a constant source of susceptible material to promote pest and disease pressure, e.g. whiteflies, CBB, CMD in an experiment station Cannot be used as a source of material for international germplasm transfer.

12 The new strategy: a bonsai genebank

13 A knowledge system that begins with farmers

14 MANIHOT COLLECTION FORM (part 1 of 2) From Gulick et al (IPGRI) GENUS: SPECIES: SUBSPECIES: COLLECTORS' INITIALS: COLLECTION NUMBER: INSTITUTION RESPONSIBLE: DATE OF COLLECTION (Day/Month/Year): / / COUNTRY OF COLLECTION: PROVINCE/STATE: LOCALITY: Nearest town/village: Distance (km): Direction from town: LATITUDE: Degrees: Minutes: N S LONGITUDE: Degrees: Minutes: E W ALTITUDE: (m) COLLECTION SOURCE (circled): Wild 1 Village market 5 Farmer's field 2 Commercial market 6 Store 3 Institution 7 Backyard 4 Other: 8 SAMPLE STATUS (circled): Wild 1 Primitive variety/landrace 4 Weedy 2 Improved variety (breed) 5 Breeder's line 3 Other: 6 LOCAL NAME: NUMBER OF PLANTS SAMPLED: PHOTOGRAPH (circled): Yes No TYPE OF SAMPLE: (circled): Vegetative 1 Seed 2 Both 3 HERBARIUM SPECIMEN (circled): Yes No QUANTITY OF MATERIAL (number of seeds, stem pieces, tubes in vitro): PRIMARY MORPHOLOGICAL DESCRIPTORS (cultivated cassava only) (circle number): Colour of apical leaves: 3=light green; 5=dark green; 7=purplish green; 9=purple Leaf lobe form: 1=linear; 2=elliptic; 3=lanceolate Petiole colour: 1=yellowish green; 2=green; 3=green with slight red; 5=green with red; 7=red; 9=purple Apical pubescence: 0=absent; 3=little; 5=moderate; 7=high Stem epidermis colour (internal surface): 1=silver green; 2=light brown/orange; 3=dark brown Stem periderm colour: 1=light green; 2=dark green; 3=yellow Root surface colour: 1=white or cream; 2=yellow; 3=light brown; 4=dark brown Root flesh colour: 1=white; 2=cream; 3=yellow; 4=pink Flowering: 0=absent; 1=present Storage root peduncle: 1=sessile (absent); 2=short (<5cm); 3=intermediate/long (>5cm) Root cortex colour: 1=white or cream; 2=yellow; 3=pink; 4=purplish MANIHOT COLLECTION FORM (part 2 of 2) GROWTH HABIT (circled): Tree 1 Bush 2 Vine 3 Other PART OF PLANT UTILIZED (circled): Roots 1 Foliage 2 PRINCIPAL USE (circled): Human consumption - fresh 1 Animal consumption - dry or processed 4 Human consumption - dry or processed 2 Starch extraction 5 Animal consumption - fresh 3 Other 6 SPECIAL QUALITIES (according to farmer) (circled): Yield 1 Disease resistance 5 Starch content 2 Pest resistance 6 Eating quality 3 Edaphic adaptation 7 Root storability 4 Other 8 NOTABLE DEFECTS (according to farmer): DISEASES AND PESTS PRESENT AND SEVERITY: (Severity: 1=little damage; 2=moderate damage; 3=severe damage) Diseases/Pests Severity Diseases/Pests Severity WILD SPECIES AND ASSOCIATED CROPS: TOPOGRAPHY (circled): Marshy 1 Rolling hills 5 Flood plain 2 Steep hills 6 Riparian 3 Mountainous 7 Flat not flood-prone 4 Other 8 VEGETATION (circled): Rainforest 1 Thorn woodland 6 Humid forest 2 Scrub desert 7 Semi-humid forest 3 Desert 8 Dry forest 4 Other 9 Very dry forest 5 SOIL TEXTURE (circled): Sandy 1 Clayey 5 Sandy loam 2 Silt 6 Loam 3 Organic origin 7 Clay loam 4 Other 9 DRAINAGE (circled): Poor 1 Moderate 2 Good 3 Excessive 4 SLOPE (circled): Flat or almost flat ( < 4 o ) 1 Moderate slope (4-14 o ) 2 Steep slope ( >14 o ) 3 Source: Adapted from Gulick et al. (1983); CIAT (1994); IPGRI (1995)

15 Characterization at collection site )(collector information) (p. 1) PRIMARY MORPHOLOGICAL DESCRIPTORS (cultivated cassava only) (circle number): Colour of apical leaves: 3=light green; 5=dark green; 7=purplish green; 9=purple Leaf lobe form: 1=linear; 2=elliptic; 3=lanceolate Petiole colour: 1=yellowish green; 2=green; 3=green with slight red; 5=green with red; 7=red; 9=purple Apical pubescence: 0=absent; 3=little; 5=moderate; 7=high Stem epidermis colour (internal surface): 1=silver green; 2=light brown/orange; 3=dark brown Stem periderm colour: 1=light green; 2=dark green; 3=yellow Root surface colour: 1=white or cream; 2=yellow; 3=light brown; 4=dark brown Root flesh colour: 1=white; 2=cream; 3=yellow; 4=pink Flowering: 0=absent; 1=present Storage root peduncle: 1=sessile (absent); 2=short (<5cm); 3=intermediate/long (>5cm) Root cortex colour: 1=white or cream; 2=yellow; 3=pink; 4=purplish

16 Farmer use and preference traits (p. 2) PART OF PLANT UTILIZED (circled): Roots 1 Foliage 2 PRINCIPAL USE (circled): Human consumption - fresh 1 Animal consumption - dry or processed 4 Human consumption - dry or processed 2 Starch extraction 5 Animal consumption - fresh 3 Other 6 SPECIAL QUALITIES (according to farmer) (circled): Yield 1 Disease resistance 5 Starch content 2 Pest resistance 6 Eating quality 3 Edaphic adaptation 7 Root storability 4 Other 8 NOTABLE DEFECTS (according to farmer): DISEASES AND PESTS PRESENT AND SEVERITY: (Severity: 1=little damage; 2=moderate damage; 3=severe damage) Diseases/Pests Severity Diseases/Pests Severity ASSOCIATED CROPS:

17 % with passport data Origin No. of Accessions Basic Complete Argentina Bolivia Brazil China Colombia Costa Rica Cuba Dominican Rep Ecuador Fiji Guatemala Indonesia Malaysia Mexico Panama Paraguay Peru Philippines Puerto Rico Thailand United States Venezuela

18 Based originally on CIAT/Embrapa. Descriptors for Cassava

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20 Descriptors to be scored at three months after planting (2) Apical leaf traits Descriptors to be scored at six months after planting (14) Leaf and petiole traits Flowering/pollen production traits Descriptors to be scored at nine months after planting (9) Stem traits Descriptors to be scored at harvest (25) Fruit/seed traits Plant shape Root traits

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33 45. Cortex thickness Measure from three roots, at the proximal (closest to stem), mid- and distal (furthest from stem) ends. Use calipers if available; otherwise try to estimate. 1 Thin 2 Intermediate 3 Thick 46. Dry matter content (%) See Annex II for details. Measure on three plants. 48. Harvest index See Annex III for details. Measure on 4 6 plants/clone. 49. Cyanogenic potential (CNP) See Annex IV for details. Score 1 9 for four plants/clone and three roots/ plant. 50. Postharvest deterioration Optional descriptor. See Annex V for details. 47. Starch content (%) See Annex II for details. Measure on three plants

34 Additional descriptors and tools Photos Herbarium samples Molecular descriptors the toward low-cost sequencing Cytological characterization (might be targeted to sub-samples such as the core collection)

35 Figure 8.3d. Fieldbook - evaluations at harvest. PROJECT: PLOT PLANTS HARVESTD HARV EASE ROOT LNGTH PED LNGTH ROOT CLR FLSH ROOT FORM CONSTRIC FOL. EVAL ROOT EVAL NO. COMMER. ROOTS ROTTED ROOTS (%) SHOOT WEIGHT (KG) ROOT WEIGHT (KG) HCN SELECT DRY MATTER (%) SEL ZONE 1 SEL ZONE 2 SEL ZONE

36 Ease of harvest 1. Easy 2. Intermediate 3. Difficult Root length 1. Short 2. Medium 3. Long Peduncle (neck) length 1. Short 2. Intermediate 3. Long Root form 1. Conical 2. Conicalcylindrical 3. Cylindrical 4. Irregular Root constrictions 1. None or few General root or shoot (foliage) evaluation 1. Excellent 2. Good 3. Fair 4. Poor 5. Very poor Cortex pigmentation 1. None 2. Slight 3. Intermediate 4. Intense Root surface color 1. Light 2. Light brown 3. Dark brown Flesh color 1. White 2. Cream or light yellow 3. Yellow 4. Deep yellow to orange 2. Intermediate 3. Many Formula for determining percent root dry matter content: x [weight in air /(weight in air weight in water)] 142

37 The bottom line... Cassava genetic resources management can be made more effective and efficient by: centralized highly secure conservation decentralized working collections high level of coordination and collaboration centralized virus-indexing and international distribution a common cassava registry --(accession matching) continued research into conservation techniques

38 A Global Network for Cassava Genetic Resources IPGRI 1993 Excellent overview of status quo Thoughtful plans for future needs Proposed strengthening national program ability for secure conservation in vitro Coincided with era of declining funding and policy uncertainty

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40 Cassava Bioversity s Crop Genebank Knowledge Base Conservation Characterization Regeneration Safety duplication ent&view=article&id=132&itemid=232&lang=english