Abstract
Achieving an optimal crop stand, especially in mineral soils, has been a great challenge in carrot production. Cool soil temperatures, crusting and low moisture availability are some of the factors that contribute to poor germination, slow seedling emergence and reduced vigor. Several anticrustants such as humic acid, orthophosphoric acid and F-68 were applied to soil immediately after sowing. Although soil application of humic acid promoted early seedling emergence there was no significant difference in crop stand among any of the treatments after 41d after sowing. There was no significant yield difference among any of the anticrustant treatments. Primed seeds promoted early emergence with the cv. Indiana but not with cv. Newport. Priming did not alter root length, yield or grades. GA3 promoted germination at 5°C but there was no synergistic effect with any of the salicylates. Optimal soil moisture for early and uniform seedling emergence was 35-40% Field Capacity (FC). Soil moisture above 40% and below 35% FC reduced seedling emergence significantly. Seed preconditioning using natural and synthetic antistress and antioxidant compounds, glycinebetaine (100 mg L) and AMBIOL, a derivative of 5-hydroxybenzimidazole (0.1 mg L) both promoted emergence at 40% FC but at a limiting low moisture content of 25% FC, Ambiol was the most effective. Seed bioconditioning using endophytic beneficial bacteria (EPBBs) obtained from carrot crowns, Pseudomonas fluorescens #37 and P. putida #144 both enhanced seedling growth in vivo. Bacillus magnetarium promoted root length but did not increase biomass of the seedlings. Optimal carrot emergence under low soil temperature and moisture conditions can be achieved through seed preconditioning using GA3 and Ambiol and through bioconditioning using selective EPBBs. INTRODUCTION Sporadic and delayed seedling emergence is a major problem in processing carrot production in cool, dry mineral soils that results in a reduced crop stand, directly lowering root yield and grades. Although germination and vigor are gene controlled, seed size, viability, sowing depth, soil moisture, oxygen concentration and temperature all can influence germination, emergence and vigor (Bewley and Black, 1982; Rajasekaran et al., 1992; Hartman et al., 1997; Rajasekaran et al., 2002). Soil crusts can act as physical barriers limiting emergence, resulting in poor stands (Bewley and Black, 1982). Low soil temperature and moisture affect both germination percentage and vigor value (Kotowski, 1926; Bewley and Black, 1982; Rajasekaran et al., 1992; Rajasekaran et al., 2002). Proc. XXVI IHC – Transplant Production and Stand Establishment Eds. S. Nicola, J. Nowak and C.S. Vavrina Acta Hort. 631, ISHS 2004 Publication supported by Can. Int. Dev. Agency (CIDA) 106 Temperatures below 20°C limit carrot seed germination (Rajasekaran et al., 2002). Soil moisture deficit can also reduce seed germination through osmotic effects delaying imbibition and/or inhibiting radicle and plumule elongation thereby limiting emergence (Bewley and Black, 1982). Soil drying can eventually lead to soil crusting, especially in mineral soils with low organic matter, obstructing and/or preventing seedling emergence partially or completely (Robbins et al., 1972). Preventing soil crust formation may facilitate seedling emergence. Anticrustants such as phosphoric acid and humic acid have been used to prevent crusting with different degrees of success (Robbins et al., 1972; Hemphill, 1982; Orzolek, 1987). Pregerminated seeds are also used with different degrees of success (M. Upton, Bejo Seeds, New York, personal communication). Pretreating seeds with salicylates such as acetylsalicylic acid, 2,6-dihydroxybenzoic acid and salicylic acid all promote germination at a limiting temperature of 5°C (Rajasekaran et al., 2002). Since salicylates promote seed germination at low temperatures and GA is critical for seed germination and elongation, it is possible that GA could be limiting under low temperature and germination under low temperature can be promoted by seed preconditioning using GA. It is also possible that GA may have synergistic effects in promoting germination when treated with salicylates. Seed treatments using GA3, benzyl adenine (BA), potassium nitrate, phosphate and chloride (Cantliffe et al., 1987), polyethylene glycol (Dearman et al., 1987), ABA (Finch et al., 1989) are all known to promote germination of carrot seeds to different degrees. However, the possibility of using antistress compounds and antioxidants to promote emergence, under limiting moisture conditions, has received relatively little study. Water stressed carrots synthesize a quaternary ammonium compound, glycinebetaine (Caldwell, 2001; Caldwell et al., 2001; Caldwell and Rajasekaran, 2002) which protect carrot plants (Caldwell, 2001). This suggests that that glycinebetaine may be used to enhance emergence, confer osmoprotection and invigorate seedlings under moisture deficit. Ambiol, a derivative of 5-hydroxybenzimidazole enhances drought tolerance of carrot seedlings and confer membrane protection (Rajasekaran and Blake, 2002; Borsos-Matovina and Blake, 2000; Vishnevetskaia and Roy, 1999); however, it is not known whether Ambiol promotes seedling emergence under limiting moisture conditions. Endophytes are known to colonize plant parts including roots and promote plant growth, increase pest and disease resistance and confer protection against various abiotic stresses (Nowak, 1998; Nowak et al., 1995; Conn et al., 1997, Sturz et al., 1998). Although seed bioconditioning with beneficial microorganisms has been known for some time (reviewed in McQuilken et al., 1998), there is no information on utilization of carrot specific endophytes and their roles in invigorating carrot seedlings. Experiments were conducted to determine whether 1) anticrustants promote seedling emergence; 2) seed priming increases emergence in crusty soils; 3) thermogenic compounds and/or GA3 promote germination under limiting low temperature; 4) glycinebetaine and Ambiol promote emergence under low moisture conditions; 5) bioconditioning using carrot endophytes invigorates seedlings. MATERIALS AND METHODS Daucus carota var. Sativus L. cultivar Oranza (Bejo Seed Company, New York, USA) was used in all our studies or as specified in each of the experiments. Field experiments were conducted in Kings County, Nova Scotia, Canada. The soil in the field location was classified as Queens series, a sandy loam texture of moderate to high fertility, with pH of 5.5-6.5 and 1.5-3% organic matter. The fields were generally under a carrot-grain-forage rotation. Seeding was done at a rate of 33 seeds per 30 cm on raised hills spaced at 60 cm using a Stanhay pneumatic seeder. Standard crop production practices were followed.
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Claims 20
Claim · model-written summary
Humic acid promoted early carrot seedling emergence.
- Taxon
- CARROTS
Daucus carotat0 - Treatment
- soil application of humic acide0
- Outcome
- early seedling emergencee0
- Direction
- promotede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“soil application of humic acid promoted early seedling emergence”
t0“CARROTS”
Claim · model-written summary
Crop stand did not differ significantly among anticrustant treatments after 41 days.
- Taxon
- CARROTSDaucus carotat0
- Treatment
- treatmentse0
- Outcome
- crop stande0
- Direction
- no significant differencee0
- Qualifier
- after 41d after sowinge0
- Comparator
- any of the treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was no significant difference in crop stand among any of the treatments after 41d after sowing”
t0“CARROTS”
Claim · model-written summary
Yield did not differ significantly among anticrustant treatments.
- Taxon
- CARROTSDaucus carotat0
- Treatment
- anticrustant treatmentse0
- Outcome
- yielde0
- Direction
- no significante0
- Comparator
- any of the anticrustant treatmentse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“There was no significant yield difference among any of the anticrustant treatments.”
t0“CARROTS”
Claim · model-written summary
Seed priming promoted early emergence in Indiana.
- Taxon
- CARROTSDaucus carotat0
- Material
- cv. Indianae0
- Treatment
- Primed seedse0
- Outcome
- early emergencee0
- Direction
- promotede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Primed seeds promoted early emergence with the cv. Indiana but not with cv. Newport.”
t0“CARROTS”
Claim · model-written summary
Seed priming did not promote early emergence in Newport.
- Taxon
- CARROTSDaucus carotat0
- Material
- cv. Newporte0
- Treatment
- Primed seedse0
- Outcome
- early emergencee0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Primed seeds promoted early emergence with the cv. Indiana but not with cv. Newport.”
t0“CARROTS”
Claim · model-written summary
Priming did not alter carrot root length, yield or grades.
- Taxon
- CARROTSDaucus carotat0
- Treatment
- Priminge0
- Outcome
- root length, yield or gradese0
- Direction
- did not altere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Priming did not alter root length, yield or grades.”
t0“CARROTS”
Claim · model-written summary
GA3 promoted germination at 5°C.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“GA3 promoted germination at 5°C”
t0“CARROTS”
Claim · model-written summary
GA3 had no synergistic effect with salicylates.
- Taxon
- CARROTSDaucus carotat0
- Treatment
- GA3e1
- Outcome
- synergistic effecte0
- Direction
- no synergistic effecte0
- Comparator
- salicylatese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“there was no synergistic effect with any of the salicylates”
t0“CARROTS”
e1“GA3 promoted germination at 5°C”
Claim · model-written summary
Early uniform seedling emergence was optimal at 35-40% field capacity.
- Taxon
- CARROTSDaucus carotat0
- Outcome
- early and uniform seedling emergencee0
- Direction
- Optimale0
- Value
- 35-40% Field Capacitye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Optimal soil moisture for early and uniform seedling emergence was 35-40% Field Capacity (FC).”
t0“CARROTS”
Claim · model-written summary
Moisture above 40% field capacity significantly reduced seedling emergence.
- Taxon
- CARROTSDaucus carotat0
- Treatment
- Soil moisture above 40%e0
- Outcome
- seedling emergencee0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Soil moisture above 40% and below 35% FC reduced seedling emergence significantly.”
t0“CARROTS”
Claim · model-written summary
Moisture below 35% field capacity significantly reduced seedling emergence.
- Taxon
- CARROTSDaucus carotat0
- Treatment
- below 35% FCe0
- Outcome
- seedling emergencee0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Soil moisture above 40% and below 35% FC reduced seedling emergence significantly.”
t0“CARROTS”
Claim · model-written summary
Glycinebetaine promoted emergence at 40% field capacity.
- Taxon
- CARROTSDaucus carotat0
- Treatment
- glycinebetaine (100 mg L)e0
- Outcome
- emergencee0
- Direction
- promotede0
- Qualifier
- 40% FCe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“glycinebetaine (100 mg L) and AMBIOL, a derivative of 5-hydroxybenzimidazole (0.1 mg L) both promoted emergence at 40% FC”
t0“CARROTS”
Claim · model-written summary
AMBIOL promoted emergence at 40% field capacity.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“glycinebetaine (100 mg L) and AMBIOL, a derivative of 5-hydroxybenzimidazole (0.1 mg L) both promoted emergence at 40% FC”
t0“CARROTS”
Claim · model-written summary
Ambiol was the most effective emergence treatment at 25% field capacity.
- Taxon
- CARROTSDaucus carotat0
- Treatment
- Ambiole0
- Outcome
- emergencee1
- Direction
- most effectivee0
- Qualifier
- 25% FCe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“at a limiting low moisture content of 25% FC, Ambiol was the most effective”
e1“both promoted emergence at 40% FC”
t0“CARROTS”
Claim · model-written summary
Pseudomonas fluorescens #37 seed bioconditioning enhanced seedling growth.
- Taxon
- carrotDaucus carotae0
- Treatment
- Seed bioconditioninge0
- Interactor
- Pseudomonas fluorescens #37
.JPG?width=60)
Pseudomonas fluorescense0symbiont - Outcome
- seedling growthe0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.JPG?width=500)
Verbatim
e0“Seed bioconditioning using endophytic beneficial bacteria (EPBBs) obtained from carrot crowns, Pseudomonas fluorescens #37 and P. putida #144 both enhanced seedling growth in vivo.”
Claim · model-written summary
P. putida #144 seed bioconditioning enhanced seedling growth.
- Taxon
- carrotDaucus carotae0
- Treatment
- Seed bioconditioninge0
- Interactor
- P. putida #144
Pseudomonas putidae0symbiont - Outcome
- seedling growthe0
- Direction
- enhancede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Seed bioconditioning using endophytic beneficial bacteria (EPBBs) obtained from carrot crowns, Pseudomonas fluorescens #37 and P. putida #144 both enhanced seedling growth in vivo.”
Claim · model-written summary
Bacillus magnetarium promoted carrot root length.
- Taxon
- CARROTSDaucus carotat0
- Treatment
- Bacillus magnetariume0
- Interactor
- Bacillus magnetariume0symbiont
- Outcome
- root lengthe0
- Direction
- promotede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Bacillus magnetarium promoted root length but did not increase biomass of the seedlings.”
t0“CARROTS”
Claim · model-written summary
Bacillus magnetarium did not increase carrot seedling biomass.
- Taxon
- CARROTSDaucus carotat0
- Treatment
- Bacillus magnetariume0
- Interactor
- Bacillus magnetariume0symbiont
- Outcome
- biomass of the seedlingse0
- Direction
- did not increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Bacillus magnetarium promoted root length but did not increase biomass of the seedlings.”
t0“CARROTS”
Claim · model-written summary
The authors recommend GA3 and Ambiol seed preconditioning for emergence under low soil temperature and moisture.
- Taxon
- carrotDaucus carotae0
- Outcome
- seed preconditioning using GA3 and Ambiole0
- Qualifier
- low soil temperature and moisture conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Optimal carrot emergence under low soil temperature and moisture conditions can be achieved through seed preconditioning using GA3 and Ambiol”
Claim · model-written summary
The authors recommend selective EPBB bioconditioning for emergence under low soil temperature and moisture.
- Taxon
- carrotDaucus carotae0
- Outcome
- bioconditioning using selective EPBBse0
- Qualifier
- low soil temperature and moisture conditionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Optimal carrot emergence under low soil temperature and moisture conditions can be achieved through seed preconditioning using GA3 and Ambiol and through bioconditioning using selective EPBBs.”
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Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.