PHYSIOLOGICAL CHARACTERISTICS LEADING TO DIFFERENCES IN DROUGHT TOLERANCE IN PHASEOLUS VULGARIS AND P.

ACUTIFOLIUS

Jesse Riaz Traub James Kelly Wayne Loescher Plant Breeding, Genetics, and Biotechnology Michigan State University East Lansing, Michigan USA

We have assessed numerous common bean genotypes with varying degrees of stress tolerance, including tepary (P. acutifolius), to identify traits correlated with drought tolerance. Techniques included: Metabolomics – untargeted and targeted LC/MS Biochemical assays – conventional methodologies Gas exchange – Li-Cor 6400XT equipment Fluorescence parameters – with new, inexpensive, and field appropriate equipment

Metabolomic studies showed most components little changed with drought stress, but leaf concentrations of certain soluble carbohydrates increased with drought, sometimes dramatically, especially in more tolerant genotypes, suggesting correlations with tolerance and observed leaf water potentials.

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100

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Jaguar SER Tepary Zorro

umol

all

suga

r / g

dry

leaf

tiss

ue

Total micromoles of osmotica in leaf tissue

d

Note: targeted LC/MS showed no significant differences in ABA levels

Drought affected numerous photosynthetic traits. Assimilation versus CO2 concentration analyses (A/Ci curves) did not indicate parameters related to drought tolerance, but rubisco carboxylation and electron transport rates were clearly related to general productivity

Lower stomatal conductances were invariably associated with drought tolerance regardless of water treatment.

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Stom

atal

Con

duct

ance

(mol

H2O

m-2

s-1)

Day

Conductance JaguarSER16TeparyZorroJaguarSER 16TeparyZorro

71% 28% 21% 13% Pot capacity:

Grafting showed that stomatal conductance and tolerance were primarily controlled by shoot factors, not roots.

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Stom

atal

Con

duct

ance

(mol

H2O

m-2

s-1)

Days after watering

Conductance

jag/jag

jag/tep

tep/jag

tep/tep

Increasing temperatures showed no effects until 45°C when gas exchange, fluorescence, oxidative stress, and visual assessments indicated distinct genotypic differences. Fluorescence methods were useful for heat tolerance screening, and were correlated with field observations of drought tolerance.

CO2 assimilation measured with Li-Cor 6400

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tep fuj 544 zor 549 553 538 539 548 546 545 jag ser 550 541

Stom

atal

Con

duct

ance

(mol

H2O

m-2

s-1)

Genotype

Stomatal Conductance via Li-Cor 6400

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45 C

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0.55

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0.65

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tep ser 549 zor 538 539 jag fuj 550 544 541 548 546 545 553

Phot

osys

tem

II e

ffic

ency

Genotype

Photosystem II efficiency via PhotosynQ 35 C40 C45 C

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tep 544 jag zor ser 538 545 553 fuj 539 549 546 550 548 541

Non

-pho

toch

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al q

uenc

hing

Genotype

Non-photochemical quenching via PhotosynQ

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Tem

pera

ture

(°C)

Phot

osyn

thes

is (u

mol

CO

2 m

-2 s-

1)

Day

Photosynthesis via Li-Cor 6400

538 541 553

jag tep temp

Conclusions: 1. Plant breeders can easily use new, inexpensive and convenient methods* to supplement or bolster field data and characterize stress tolerance of bean lines. 2. Most importantly, to improve drought tolerance in bean germplasm, our data emphasize the need to select for: a. lower stomatal conductance b. and higher heat tolerance

* ‘PhotosynQ’ <- New Old - >