INVESTIGATING HEAT TOLERANT TRAITS IN PEA CULTIVARS
Rosalind A. Bueckert, Tom Warkentin, Dept. of Plant Sciences & CDC, Univ. Saskatchewan [email protected] (306)-966-8826
HEAT REDUCES TIME SPENT IN REPRODUCTION
DURATION OF HEAT REDUCES YIELD
2000
2003
2005
2006
2007
2008
2009
6000
5000
4000
Saskatoon
Outlook
60
12
14
16
18
20
22
24
26
28
30
o
Number of days above 28 C
Heat tolerant cultivars achieved greater pod retention
through early flowering, and a longer flowering duration.
An overview of our findings and future strategies to screen
genotypes for other heat tolerant traits is below.
55
50
45
40
35
30
25
20
20
21
22
23
24
25
26
27
28
29
55
50
40
30
25
21
22
23
24
25
26
27
28
29
30
o
Pea under irrigation in Arizona (30 to 40°C) can still set
pods and fill seed when irrigated. Out of 94 cultivars,
24 were able to set 6 orCultivar
more pods from normal (grey
bars) and late (cyan - hot) seeding-date trials.
Mean daily maximum temperature in reproduction ( C)
Naparnyk was able to produce most pods in this hot
environment, and this cultivar was indeterminate, with
normal leaves. In addition to timing of flowering date and
duration of flowering (phenology), various canopy traits
likely reduce heat stress by maintaining cool leaves.
HEAT MAKES FLOWERS AND PODS FALL OFF
5000
Aborted fraction of all potential pods in 2011, two seeding dates
Early
Late
4000
Early
Late
Aborted fraction (%)
90
Node with
set baby pods
Yield kg ha
-1
100
4
35
Pea yield in 2011, Early and Late seeding
Flowering node
6
0
HEAT REDUCES YIELD IN LATE SEEDED PEA
Developing node
flower buds
8
45
20
Mean daily maximum temperature in reproduction (oC )
10
2
20
30
12
11
10
Reproductive phase (days)
1000
2000
2003
2005
2006
2007
2008
2009
60
14
10
3000
2000
In 2013 we mapped pod yield at specific nodes in controlled
heat in the growth chamber. We also measured pollen
viability on a subset of five cultivars from one field site
(2012), noting abnormal pollen tube germination in vitro at
temperatures > 30 °C.
16
Irrigation (Outlook) ameliorates heat stress and more days
are spent in reproductive growth.
Reproductive phase (days)
-1
Yield (kg ha )
In 2010 to 2012, 12 cultivars were grown in the field in two
soil zones at a normal and late seeding date to investigate
yield formation. Daily maximum temperatures >29 °C
caused abortion of flowers and young pods. Yield losses
were greater in the later seeded plots where flowering was
displaced into warmer temperatures.
At Saskatoon, the dryland site, 25.5°C or higher reduced
reproduction to 35 days or less.
et
Su
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rs
CD
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CD
yk
C_
Go
ld
SW
en
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Ra
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n
7000
FUTURE RESEARCH – COOLING THE CANOPY
Ro
ck
The more days , say 20 + in a season with maximum
temperatures above 28°C, the less yield for dryland pea.
Time spent in reproductive growth is reduced by warm
temperature. The higher the mean maximum temperature,
the less days spent in reproductive growth, and yield is
reduced.
PS
05
Field pea is a major grain legume crop in western Canada.
However, pea cultivars are heat sensitive and readily abort
flowers and young pods in air temperatures above 30 °C,
resulting in reduced and unstable yield from year to year.
Our goal is to improve pea heat tolerance through a
combination of phenology, pollen viability and canopy
traits.
Pod number per plant
RATIONALE
80
70
60
50
3000
2000
1000
40
30
0
20
10
0
Oldest node with
two pea pods
r
al ial er ss a
e en a
a
w
e
v
s
k
t
e
k
o
l
e
p
a
p
i
g tr
d
li
ld s
e
as rn nn op tl
Al Ca nte Co Cu D Ec Go Ka Mea Sa S
Ce
Cultivar
l
a eva ial
er
er lass lta ipse den pa ow ge
k
k
i
p
s
n
r
n
t De cl
s ad
l
o
a
Sa St
Al Car nten Co Cu
E
Go Ka Me
Ce
Cultivar
Distal and proximal (basal) positions
Proximal dominant, distal likely to abort
CONCLUSIONS
Heat stress in pea reduces time spent in reproduction. Heat causes abortion of flowers, pods
and seed. Seed size is also reduced. Pollen viability in vitro is reduced by heat. Genotypic
variation is apparent in heat sensitivity and tolerance.
distal
FUTURE RESEARCH
We are in the process of characterizing heat tolerance through early flowering and flower
duration via Recombinant Inbred Lines. We are also looking at pollen biology to find pea
genotypes that can pollinate better under high temperature. We also plan to look at
vegetative traits such as leaf type, leaf size, tendril and petiole thickness, leaf color, pigment
and wax (cuticle) to help in transpirational responses and canopy cooling.
proximal
POLLEN GRAINS ARE SMALLER WITH LESS VIGOR
POLLEN TUBES BECOME LONGER AND THINNER
35oC
25oC
25oC
Vn- Vegetative
nucleus
Gn- Generative
nucleus
(gives rise to 2
sperm nuclei)
Pt- Pollen tube
Cp- Callose plug
Germinating pollen
Pt
Vn
Treatment
Pod weight
(g)
Pea
weight
(g)
Pea
number
Failed
Aborted sites
pollination % of funiculi
Failed peas
% of set peas
Temp 25 C
34 C
0.79 a
0.69 b
0.67 a
0.60 b
3.16 a
3.10 a
2.95 a
2.90 a
52.2 a
51.9 a
9.1 a
10.8 a
Node 1
2
3
4
1.14 a
0.88 b
0.65 c
0.29 d
0.99 a
0.76 b
0.55 c
0.23 d
4.55 a
3.77 b
2.83 c
1.36 d
1.80 d
2.35 c
3.00 b
4.55 a
34.4 d
42.7 c
54.8 b
76.4 a
9.6 a
11.3 a
12.2 a
6.8 a
Pod position
proximal
distal
0.98 a
0.50 b
0.84 a
0.44 b
4.05 a
2.20 b
1.98 b
3.87 a
38.4 b
65.8 a
13.8 a
6.1 b
Node 1 25 C
34 C
1.07 a
0.90 b
0.88 a
0.10 b
4.77 a
4.33 a
1.71 a
1.88 a
32.4 a
36.4 a
6.9 a
10.4 a
25oC
*
*
Width
Area
*
25oC 35oC
Four hours incubation of pollen in vitro from cv. Alaska at 25oC
and 35oC. Non viable and heat treated pollen is smaller than
normal viable pollen. Pollen germination is reduced by heat,
and pollen tube germination in 35oC results in longer, thinner
abnormal tubes.
Dimension of pollen tube (µm)
35oC
Percentage germination (%)
Dimension of pollen grain (µm)
Pea in three days of controlled heat (ramped from 18 to 34°C for 6 hours) reduces pod
weight and pea weight. Nodes were treated with heat just as the flowers of node 1
opened. Heat also reduced the distal pod weight. Measurements were made 20 days
after heat treatment started. Mean of 3 reps and 10 cultivars. Note that node position
and pod position within a node also have developmental responses.
Pt
Gn
25oC
Length
35oC
Cp
25 µm
***
HEAT REDUCES POD WEIGHT AND SEED WEIGHT PER POD
35oC
***
***
Length
Width
Area
Funding from Agriculture Development Fund of Saskatchewan, Western Grains Research
Foundation, Saskatchewan Pulse Growers Association and the NSERC-CRD program.
We thank Jannatul Ferdose for pollen measurements and Donna Lindsay for measurements
from the growth chamber study.