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IV. Impact on Seed Industry

IV. Impact on Seed Industry

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3 46



W. W. HANNA



Will farmers save their own seed instead of purchasing new seed each year?

Some will probably save their own seed since obligate apomictic hybrids will

breed true. In the author’s opinion, most farmers will continue to purchase seed

because they recognize the advantages of planting high quality, treated and sized

seeds. Apomixis would lower seed production costs for industry. It will probably

be more economical for farmers to purchase seed each year than to purchase and

operate the equipment needed to process their own seed.

Another concern is control of rights to germ plasm. Rights to specific apomictic

cultivars can be controlled through patents since apomictic cultivars are vegetatively propagated through seed. Cultivars would need to be documented by morphological, biochemical, and molecular methods and descriptors. Documentation

methods would need to be refined and precise because of a proliferation of cultivars in the market, some with only small genetic differences.



V. INTERNATIONALIMPACT

All farmers can benefit from apomictic hybrids because apomixis maximizes

the opportunity to develop and make available superior genotypes to be grown on

the farm. However, the greatest impact of apomictic hybrids would be in lesser

developed countries where the largest portion of the world’s population is located,

hybrids may not be widely grown, and farmers are accustomed to saving their

seeds from year to year.

Hybrids usually result in an increase in production, with the amount depending

on genotypes and crop. In countries where yields are low and food supplies are

limited, any increase in production due to hybrid vigor is welcomed. Ouendeba

et al. (1992) obtained an 81% increase in grain yield for pearl millet in a population cross between landraces from Sudan and Nigeria. If the vigor of that landrace

hybrid could be fixed, it would revolutionize pearl millet grain production in West

Africa and at the same time maintain the adaptability and diversity of local germ

plasm. Up to 73% heterosis has been reported for rice hybrids (Virmini et al.,

1982). Using apomixis to fix hybrid vigor in rice would have a major impact on

food production around the world.

The widespread use of a few apomictic cultivars should be a concern but probably not a reality. The ability to rapidly create new stable cultivars using apomixis

would greatly reduce problems due to pest epidemics. If an apomixis gene(s) was

readily available to be used in cultivar development, there would be a proliferation

of new cultivars with different heights, maturities, qualities, adaptations, etc. Various combinations of these apomictic cultivars could be mixed in numerous combinations to provide reliable production in diverse environments to meet the needs

of the farmer.



USE OF APOMLXIS



347



VI. EVALUATION

There is no genetically controlled character that could have a greater impact on

food, forage, and fiber production around the world than apomixis. Apomixis is

being used to develop cultivars in forage and turf grasses and in Citrus rootstock.

We have made significant progress in transferring a gene(s) controlling obligate

apomixis from a wild species to cultivated pearl millet. Apomictic cultivars in

pearl millet should be possible when the problem related to retaining seed set on

apomictic backcross-derived plants is solved (Dujardin and Hanna, 1989a). Wild

apomictic species have been crossed with maize and wheat, but high sterility and

facultative apomictic behavior have been encountered. Male fertility is needed in

these species crosses to transfer apomixis to the cultivated species and to use it in

cultivar development.Facultative apomixis has been reported in sorghum and rice

but no obligate apomixis has been reported in the cultivated or wild species.

It appears that molecular methods may be needed to transfer genes controlling

apomixis to our major grain crops such as maize, wheat, rice, sorghum, and soybean and many other important food, forage, and fiber crops if apomictic cultivars

are to be developed in these species. This will require isolation of a stable gene(s)

(preferably dominant) controlling obligate apomixis, insertion of the gene(s) into

the genome of a target species, expression of obligate apomixis in the target species, and replication of the gene(s) controlling apomixis in the genome of the

target species. One can readily see that many questions need to be answered and

many obstacles overcome regarding the wide use of apomixis in cultivar development. It will not be easy to isolate and transfer the gene controlling obligate

apomixis and use it to produce apomictic cultivars in our major world crops, but

it should be possible, especially with the major advances being made in molecular

biology. It is worth the effort because of its potential impact around the world.



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3 48



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A



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Index

A

Acetolactate synthatase inhibitors, crop resistance, 84-87

Acetyl-CoA carboxylase inhibitors, crop resistance, 87-89

Agriculture

definition, 4

impact on subsurface microbial ecology,

1-57

background definitions, 3-4

dynamic bounding sphere metaphor, 2

function, 22-35

metabolic status, 30-32

nutrient cycling, 32-35

responsiveness to change, 22-30

habitat structure, 5-22

geology, 5-8

hydrology, 5-8

organisms, 8-22

actinomycetes, 19-20

fungi, 19-20

protozoa, 21 -22

management practices, 36-46

crop, 39-43

livestock, 45-46

pest, 43-45

soil, 39

water, 37-38

measurement, 47-56

geochemical changes, 52-54

integrated effects testing, 54-56

physical changes, 49-52

subsurface versus surface habitats, 46-47

Aluminum

phytotoxicity, 120- 122

wheat tolerance

binding in cell wall, 129- 130

exclusion at the plasmalemma, 131- 132

genetic basis, 137- 143

manganese tolerance relationship, 145- 146

organic acid accumulation, 127- 129

root mucilage production, 130- 131

tolerant protein synthesis, 132- 134



351



Ametryne, crop resistance, 80-84

Ammonia

nitrate ratio effect on plant growth, 243-246

volatilization, nitrification inhibitor induced,

240- 24 I

Apomixis, 333-347

breeding, 337-345

advantages, 338-339

genetic vulnerability, 345

methods, 340-345

chemical control, 344-345

dominant gene, 341

facultative apomixis, 344

interspecific hybrids, 344

recessive gene, 341 -344

plant identification, 339-340

controlling genes, 334-337

expression, 336-337

genetics, 337

sources, 335-336

impact on seed industry, 345-346

international impact, 346

Arylox yphenoxypropionates, crop resistance,

87-89

Ascochyta blight, in lentil, 300

Asulam, crop resistance, 99

Atrazine, crop resistance, 80-84



B

Bacteria, see Microbes

Bipyridiliums, crop resistance, 98-99

Blight, ascochyta, in lentil, 300

Breeding, see Plant breeding

Bromoxynil, crop resistance, 92-93



C

Chromate, microbial reduction, 210-215

bioremediation of contaminated soils, 214-215

mechanisms, 212-214

microorganisms, 210-2 12

Contamination, see Environmental contamination



352



INDEX



Corn, nitrification inhibitors effect on yield,



248-249



Fungi

seedborne disease, in lentil, 300

subsurface habitat structure, 19-20



Cotton, nitrification inhibitors effect on yield, 252

Crops, see speciJiccrop

Cyanamide, crop resistance, 96

G

Cyanazine, crop resistance, 80-84

Cyclohexanediones, crop resistance, 87-89

Genetics, see Plant breeding

Geology, subsurface microbial habitat structure,



D



Dalapon, crop resistance, 96-97

Denitritication, rate reduction by nitrification inhibition, 241

2,4-Dichlorophenoxyaceticacid, crop resistance,



93-94

Dicyandiamide

nitrification inhibition, 234-243

nitrogen loss and immobilization, 240-243

relative effectiveness, 236-238

soil factors affecting effectiveness, 239-



240

phytotoxicity, 252-254

Dihydropteroate synthase inhibitors, crop resistance, 99

Diquat, crop resistance, 98-99

Dynamic bounding sphere metaphor, impact of

agricultural practices on subsurface microbial ecology, 2



E

Ecology, see Microbes, subsurface ecology

Environmental contamination

bioremediation by microbial reduction

chromate, 214-215

organic compounds, 195- 197

selenium, 208-2 10

uranium, 204-205

nitrates, 256-264

ozone layer depletion, 264-269



F

Fertilizers

impact on subsurface microbial habitats,



39-43,52-54

lentil requirements, 296

nitrogen immobilization by microorganisms,



242-243

nitrogen use, 234-235



5-8

Global warming, 268-269

Glufosinate, crop resistance, 94-96

Glyphosate, crop resistance, 89-91

Greenhouse gases, 268-269

Groundwater, see also Water management

definition, 3-4

nitrate contamination, 256-264

nutrient cycling, 32-35

subsurface microbial habitat structure, 5-8



H

Herbicides, crop resistance, 69- 101

chemical families, 80- 100

acetolactate synthatase inhibitors, 84-87

acetyl-CoA carboxylase inhibitors, 87-89

bipyridiliums, 98-99

bromoxynil, 92-93

cyanamide, 96

dalapon, 96-97

dihydropteroate synthase inhibitors, 99

glufosinate, 94-96

glyphosate, 89-91

mitotic inhibitors, 99- 100

phenoxycarboxylic acids, 93-94

phosphinothricin, 94-96

phytoene desaturase inhibitors, 97-98

protoporphyrinogen-oxidaseinhibitors, 98

triazines, 80-84

mechanisms, 71 -77

exclusion, 72-76

site of action alteration, 76-77

site of action overproduction, 77

variant selection, 77-80

biotechnological techniques, 78-80

genetic sources, 78

traditional plant-breeding techniques, 78

Human health, nitrate effects, 254-256

Hydrogen, oxidation by iron and manganesereducing microorganisms, 176- 181

Hydrology, see Groundwater: Water management



INDEX

I

Imidazolinones, crop resistance, 84-87

Iron, microbial reduction, 176-201

activity monitoring, 186- 187

effects on plant growth, 201

effects on soil properties, 199-200

electron flow in anoxic soils, 192-195

electron transport, 183- 184

interaction with other microbially catalyzed

redox processes, 190- 192

isolation, 184- 186

mechanisms, 187- 190

microorganisms, 176- 183

hydrogen oxidation, 176- 181

magnetotactic bacteria, 182- 183

organic matter oxidation, 176- 18 I

sulfur-oxidizing reducers, 181- 182

organic contaminant degradation, 195- 197

oxide formation, 197- 199

Irrigation, impact on subsurface microbial habitats, 37-38.49-52



L

Lentil, 283-327

background, 284-291

Cytology, 288-289

origin, 286-287

plant description, 289-291

taxonomy, 287-288

breeding methods, 3 18-32 I

backcross, 320-321

bulk populations, 319

pedigree selection, 3 19-320

pure line selection, 3 18

single seed descent, 320

breeding objectives, 32 1 -326

cultivar quality, 324

diseases, 322-323

insects, 324

mechanical harvesting adaptation, 325-326

orobanche, 323-324

root rot/wilt complex, 323

seed yields, 32 1-322

straw yields, 321-322

fertilization. 296

genetics, 307-3 17

germ plasm collection, 307-308

inherited traits, 308-3 17



353



association among traits, 317

cotyledon color, 3 10

epicotyl color, 3 12

flower color, 3 10-3 1 1

flower number, 312

genetic variance, 314-315

growth habit, 312

heritability estimates, 3 15-3 I6

isozymes, 313-314

pod indehiscence, 3 13

seed coat color, 3 11-3 12

virus resistance, 3 13

interspecific hybridization, 3 17

wild species, 308

hybridization methods, 303-307

environmental conditions, 303-304

equipment, 304

female flower emasculation, 304-305

pollination, 305-306

production, 291 -295

cultivars, 294-295

land requirements, 291 -292

seedbed preparation, 293

seeding, 293-294

seed quality, 292

seed treatment, 292

production constraints, 298-303

diseases, 299-302

environmental stress, 302-303

insects, 298-299

uses, 297-298

weed control, 297

Livestock management, impact on subsurface

microbial habitats, 45-46



M

Magnetotactic bacteria, iron reduction,

182-183

Malate, aluminum chelation in tolerant wheat,

128-129

Manganese

microbial reduction, 176-201

activity monitoring, 186- 187

effects on plant growth, 201

effects on soil properties, 199-200

electron flow in anoxic soils, 192-195

electron transport, 183- 184

environmental reduction mechanisms,

187- I90



3 54



INDEX



Manganese, (continued)

interaction with other microbially catalyzed

redox processes, 190- 192

isolation, 184- 186

microorganisms, 176- 183

hydrogen oxidation, 176- 181

organic matter oxidation, 176- 181

sulfur-oxidizing reducers, 181- 182

organic contaminant degradation, 195- 197

oxide formation, 197- 199

phytotoxicity, 120- 122, 134-135

wheat tolerance

aluminum tolerance relationship, 145- 146

distribution, 134- 135

genetic basis, 143- 145

mechanisms, 135-136

uptake in roots, 134- 135

Methane, production inhibition by iron oxides,

191

Microbes

chemical reduction, 175-217

chromate, 2 10-2 15

bioremediation of contaminated soils,

214-215

mechanisms, 2 12-214

microorganisms, 210-212

iron, 176-201

activity monitoring, 186-187

effect on plant growth, 201

effect on soil properties, 199-200

electron flow in anoxic soils, 192-195

electron transport, 183- 184

environmental reduction mechanisms,

187- 190

interaction with other microbially catalyzed redox processes, 190- 192

isolation, 184- 186

microorganisms, 176- I83

hydrogen oxidation, 176- I8 1

organic matter oxidation, 176- 181

reduction by magnetotactic bacteria,

182- 183

sulfur-oxidizing reducers, 181- 182

organic contaminant degradation, 195197

oxide formation, 197- 199

manganese, 176-201

activity monitoring, 186- 187

effect on plant growth, 201

effect on soil properties, 199-200



electron flow in anoxic soils, 192-195

electron transport, 183-184

environmental reduction mechanisms,

187-190

interaction with other microbially catalyzed redox processes, 190- 192

isolation, 184- 186

microorganisms, 176- 183

hydrogen oxidation, 176- 181

organic matter oxidation, 176- 181

sulfur-oxidizing reducers, 18 1 - 182

organic contaminant degradation, 195197

oxide formation, 197- 199

selenium, 205-2 10

bioremediation of contaminated soils,

208- 2 10

enzymatic mechanisms, 207-208

microorganisms, 205-207

uranium, 202-205

bioremediation of contaminated soils

and water, 204-205

enzymatic mechanisms, 203

enzymatic versus nonenzymatic reduction, 203-204

microorganisms, 202-203

immobilization of nitrogen fertilizer, 242243

metabolic status in subsurface habitats, 3032

responsiveness to environmental change,

22-30

subsurface ecology, 1-57

agricultural impact, 35-57

management practices, 36-46

crop, 39-43

livestock, 45-46

pest, 43-45

soil, 39

water, 37-38

measurement, 47-56

geochemical changes, 52-54

integrated effects testing, 54-56

physical changes, 49-52

subsurface versus surface habitats,

46-47

background definitions, 3-4

dynamic bounding sphere metaphor, 2

function, 22-35

metabolic status, 30-32



INDEX

nutrient cycling, 32-35

responsiveness to change, 22-30

habitat structure, 5-22

geology, 5-8

hydrology, 5-8

organisms, 8-22

actinomycetes, 19- 20

fungi, 19-20

protozoa, 21 -22

Mitotic inhibitors, crop resistance, 99- 100



N

Nitrapyrin

nitrification inhibition, 234-243

nitrogen loss and immobilization, 240-243

relative effectiveness, 236-238

soil factors affecting effectiveness, 239240

phytotoxicity, 252-254

Nitrates

ammonium ratio, effect on plant growth,

243 - 246

environmental effects, 262-269

global warming, 268-269

groundwater content, 262-264

ozone depletion, 264-268

health effects

animal, 256

in drinking water, 256-261

human, 254-256

in vegetables, 261 -262

iron reduction inhibition, 190

Nitrification inhibitors, 233-269

ammoniumhitrate ratios, 243 -246

effect on crop yields, 246-252

corn, 248-249

cotton, 252

potato, 251 -252

rice, 247-248

sorghum, 249-250

sugarcane, 25 1

wheat, 249-250

environmental effects, 262-269

global warming, 268-269

groundwater content, 262-264

ozone depletion, 264-268

and nitrates

animal health, 256

in drinking water, 256-261



355



human health, 254-256

in vegetables, 261 -262

nitrogen loss, 240-242

ammonia volatilization, 240-241

denitrification, 241

immobilization by microorganisms, 242243

from plants, 241 -242

urea hydrolysis, 240

phytotoxicity, 252-254

relative effectiveness, 236-238

soil factors affecting effectiveness, 239-240

organic matter, 238-239

pH, 240

soil water, 240

temperature, 239-240

Nitrogen

annual fertilizer use, 234-235

immobilization by microorganisms, 242-243

IOSS, 240-242

Nitrous oxide, ozone depletion, 264-269

Nutrient cycling, in subsurface microbial habitats, 32-35



0

Organic matter

effect on nitrification inhibitor effectiveness,

238 - 239

oxidation by iron and manganese-reducing

microorganisms, 176- I8 1

Orobanche, in lentil, 323-324

Ozone, depletion, 264-269



P

Paraquat, crop resistance, 98-99

Pesticides, see also speciJic chemical compound

impact on subsurface microbial habitats,

54-56

Pest management

impact on subsurface microbial habitats,

43-45

in lentil, 298-299,324

pH, effect on nitrification inhibitor effectiveness,

240

Phenoxycarboxylic acids, crop resistance, 93 -94

Phosphinothricin, crop resistance, 94-96

Phytoene desaturase inhibitors, crop resistance,

97-98



3 56

Phytotoxicity

acid soils, 120-122, 134-135

nitrification inhibitors, 252-254

Plant breeding

acid tolerance in wheat, 146- 161

approaches, 159- 161

cultivar development, 161

genetic pool variation, 149- 151

justification, 147- 149

screening strategies, 151- 159

apomixis, 333-347

advantages, 338-339

controlling genes, 334-337

expression, 336-337

genetics, 337

sources, 335-336

genetic vulnerability, 345

impact on seed industry, 345-346

international impact, 346

methods, 340-345

chemical control, 344-345

dominant gene, 341

facultative apomixis, 344

interspecific hybrids, 344

recessive gene, 341 -344

plant identification, 339-340

for herbicide resistance, 78

lentils

genetics, 307-3 17

germ plasm collection, 307-308

inherited traits, 308-317

association among traits, 3 17

cotyledon color, 3 10

epicotyl color, 3 I2

flower color, 3 10-3 I 1

flower number, 3 12

genetic variance, 314-315

growth habit, 3 12

heritability estimates, 315-3 16

isozymes, 313-314

pod indehiscence, 313

seed coat color, 3 I 1-3 12

virus resistance, 3 13

wild species, 308

hybridization, 303-307

environmental conditions, 303-304

equipment, 304

female flower emasculation, 304-305

pollination, 305-306

methods, 3 18-32 1



INDEX

backcross, 320-321

bulk population, 319

pedigree selection, 3 19-320

pure line selection, 3 18

single seed descent, 320

objectives, 32 1-326

cultivar quality, 324

diseases, 322-323

insects, 324

mechanical harvesting adaptation, 325326

orobanche. 323-324

root rot/wilt complex, 323

seed yields, 321 -322

straw yields, 32 1-322

screening strategies

field evaluation, 157- 159

nutrient solution culture, 152- 156

soil bioassays, 156- 157

tissueculture, 151-152

Plant growth

annual nitrogen fertilizer use, 234-235

effects of microbial reduction, 201

Plasmalemma, aluminum exclusion in tolerant

wheat, 131-132

Pollution, see Environmental contamination

Potato, nitrification inhibitors effect on yield,

25 1-252

Prometryn, crop resistance, 80-84

Protoporphyrinogen-oxidase inhibitors, crop resistance, 98

Protozoa, subsurface habitat structure, 8-22



R

Reduction, see Microbes, chemical reduction

Reproduction, see Plant breeding

Rice, nitrification inhibitors effect on yield,

247-248

Root mucilage, production in aluminum tolerant

plants, 130- 131

Root rot/wilt complex, in lentil, 299-302, 323

Rust, in lentil, 300



S

Seed industry, see Plant breeding

Selenium, microbial reduction, 205-2 10

bioremediation of contaminated soils, 208210



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IV. Impact on Seed Industry

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