The Road to Productivity

Mary Lu ArpaiaUniversity of California,

Riverside

The ultimate crop that one harvests is dependent upon many factors:

• On/Off status• Overall tree health• Conditions during

flowering and fruit set • Conditions during

subsequent fruit development

This presentation will focus on one small

aspect of productivity -Pollination

Terminology

The avocado flower

Stigma

Ovule - Seed Ovary – Fruit Flesh and Peel

StyleAnther/Filament –Source of Pollen

Pollination Terms:

Pollination – the transfer of pollen from the anther to the stigma.– Cross pollination – the pollen deposited on

the stigma is from another cultivar.– Close pollination – the pollen deposited on

the stigma is from another flower of the same tree or cultivar.

– Self pollination – the pollen deposited on the stigma is from the same flower.

Pollination Terms:

Pollinator: The agent which transfers pollen from the male to the female floral organ.

Pollinated Tree: A cultivar that receives the pollen (i.e. Hass).

Pollinizer: A cultivar that donates pollen to another cultivar.Common Hass pollinizers: Bacon, Zutano, Ettinger, Edranol, Walter Hole.

Pollination Terms:Fertilization – the fusion of the male

gamete with the female gamete forming the zygote.

Effective Pollination – pollination which leads to fertilization.

Non effective pollination – pollination which does NOT lead to fertilization.

Avocado Flower

Behavior

Avocado flowering characteristics

• Attraction: the whole tree acts like a giant inflorescence with many small flowers.

• Small fertilization percent: thus most flowers do not set fruit.

• Competition: between fruits and growth, as well as among the fruits, which leads to high rate of primary-fruit abscission.

♀ ♂There are 2 phases to avocado flowering

This is called Synchronous Dichogamy

Source: I. Hormaza

FEMALE PHASE MALE PHASE

The avocado flower

Female Phase

Male Phase

Ish Am, PhD. Thesis

FEMALE PHASE

MALE PHASE

Timing of flowering for “A” and “B” flower types.

DAY 1 DAY 2MORNING AFTERNOON MORNING AFTERNOON

Flow

er-ty

pe c

ultiv

ar

“A”

“B”

DAY 1

DAY 2

MORNING

AFTERNOON

MORNING

AFTERNOON

The sequence of timing for “A” and “B” flower types under field conditions.

Morning AfternoonFl

ower

-type

cul

tivar “A”

“B”

Morning

Afternoon

Avocado Flowering Sequence

Type A

Type B

Female flowersMale flowers before dehiscenceMale dehiscing flowers

Overlap within the tree occurs

Source: I. Hormaza

Fruit Set

• Millions of flowers during bloom• Long flower duration

Are all flowers created equal?

05

1015202530354045

20 40 60 80 100 120 140 160 180 200 220

Nº F

lore

s

Σ Densidad óptica ( x104)

I2KIN

o. o

f flo

wer

s

Optical density x104

- NO EXTERNAL DIFFERENCES AMONG FLOWERS- GREAT DIFFERENCES IN STARCH CONTENT

Source: I. Hormaza

02468

1012141618

Caídas Cuajadas

ΣD

ensi

dad

óptic

a (x

104 )

Opt

ical

den

sity

x10

4

Dropped Retained Source: I. Hormaza

‘Fuerte’ pollen on anther flap ‘Hass’ pollen grain(SEM x2000)

From: G. Ish Am

The avocado pollen grain

Hand pollinated ‘Hass’ stigmas by ‘Ettinger’ pollen. Four hrs of germination.

Shoval, 1987

1-4 pollen grains

>20 pollen grains

5-19 pollen grains

Percent of pistil length

Perc

ent

of f

lowe

rsPollen tubes

Reach:

Avocado Pollen Germination Rate

Effect of competitionbetween and cooperationamong the pollen grains

Early dropped Initially retained Fruit set

01020304050607080

Early dropped Initially retained Fruit set

Ger

min

atio

n (%

) ab

b

Hass Flowers/Fuerte Pollen

Pollen germination does not appear to be limiting

NUMBER OF POLLEN GRAINS ON STIGMA AND FLOWER FATE

05

101520253035

� 0 �1-5 �6-10 �11-15 �16-20 �21-25 �26-30 �31-35 �36-40 �>41

Flow

ers (

%)

Early drop

05

101520253035

� 0 �1-5 �6-10 �11-15 �16-20 �21-25 �26-30 �31-35 �36-40 �>41

Flow

ers (

%)

Initial retention

05

101520253035

� 0 �1-5 �6-10 �11-15 �16-20 �21-25 �26-30 �31-35 �36-40 �>41

Flow

ers (

%)

Final fruit set

1-5

1-5

1-5

1-5

>40

>40

>40

Temperature and Humidity

0

20

40

60

15ºC 20ºC 25ºC 30ºC Campo

% G

erm

inac

ión

Temperatura

Femenino Masculino

0

20

40

60

50% 75% 95%

% G

erm

inac

ión

Humedad relativa

Femenino MasculinoSource: I. Hormaza

Temperature and Relative Humidity Impacts Pollen Germination

Sedgley and Annells, 1981• Kept trees at 3 temperature regimes

(Day/Night): 91/82; 77/68; 63/54• Flowering cycle: At 63/54 prolonged from 36

hr to 72 hr• Overlap: most overlap occurred at 77/68• Fertilization: occurred at all temps but lowest

at 63/54• Embryo development: occurred at all

temperatures but fruitlets abscised at high temps and growth very slow at low temp

Temperature fluctuations during floweringIrvine, CA

TEMP

RH

0 2 4 6 8 10 12 14 16 18 20 22 24

Time of Day (hr), PST

Male Stages

New Male Stages

Female Stages

Female Stages

Hot Day/ Moderately Cool NightTemp. Max. 31.9°CTemp. Min. 8.2°C

Cool Day/Cool NightTemp. Max. 20.9°CTemp. Min. 6.2°C

23 April 2004

14 April 2004

Stages from previous day

87F Day/47F Night

68F Day/43F Night

Temperature influences the timing of the female and male stages

Do You Need Pollinizers?

Survival of cross vs. self progenies

Source: Degani, Goldring and Gazit. 1989. J. Amer. Soc. Hort. Sci. 114:106-111 Via www.avocadosource.com

Percent of crossed ‘Hass’ fruits by both ‘Ettinger’ or ‘Fuerte’ according to time after fruit set.

0102030405060708090

May 5 Sept 10 Oct 22

Sampling Date

% o

ut-c

ross

ing

Chart3

May 5

Sept 10

Oct 22

Sampling Date

% out-crossing

22.8

72.4

83.6

Sheet1

May 522.8

Sept 1072.4

Oct 2283.6

Sheet1

Sampling Date

% out-crossing

Sheet2

Sheet3

MATERIALES Y MÉTODOS

5 Replicated BlocksEach Net House had Honey Bees

TMTO Descripción0 Control, No Net House, 5,5% Edranol

1 Net House, 12 Hass + 0 Edranol

2 Net House, 11 Hass + 1 Edranol

3 Net House, 10 Hass + 2 Edranol

Resultados

TMTO Frutos 2012 Frutos 2013 Frutos 2014 ∑ 2012-2014

0 50,51 ± 57,88 a -- -- --

1 19,30 ± 43,97 c 138,90 ± 67,62 ab 49,25 ± 59,70 b 207,45 ± 85,58 b

2 22,89 ± 42,21 bc 151,98 ± 70,06 a 79,25 ± 62,82 a 254,13 ± 89,35 a

3 41,48 ± 50,30 ab 121,52 ± 67,28 b 74,70 ± 77,96 ab 237,70 ± 106,05 ab

Cuadro 1. Efecto de los distintos tratamientos en el promedio de número de frutos obtenidosen paltos var. Hass. Encón, Panquehue.

Letras distintas indican que existen diferencias significativas. (Test de Tukey, P ≤ 0,10).

Hass yields decrease significantlywith increasing distance from ‘Ettinger’

Source: Guil et al. 1986. Alon Hanotea 40:443-455

Pollinizer Varieties: 8Field trial replicates: 6Pollinizers interset with Hass

DeBusschere Pollinizer Trial – Coastal Ventura County

Does distance play a role?

Debusschere Pollination Project – 2001 – 2008Cumulative fruit count as a function of distance from pollinizer

0

200

400

600

800

1000

1200

Within Row 27 ft 54 ftDistance from Pollinizer

Cumulative count

Debusschere Pollination Project – 2001 – 2008Cumulative fruit count as a function of Pollinizer variety and distance from pollinizer

0

200

400

600

800

1000

1200

1400

Fuerte Zutano Ettinger Bacon Sirprize BL667 BL516 HarvestNearest Pollinizer Variety

With-in Row 27 feet 54 feet “A” flower type

Multiple pollinizers

Bacon + Ettinger + Zutano

Flowering periods – Oxnard, 2002

BL516

BL667

Sir Prize

Harvest

GEM

Lamb Hass

Hass

0 20 40 60 80 100 120 140 160 180Julian Date

2005200420032002

Duration of bloom over 4 years

Irvine, CA

How do you get the pollen to the flower?

ACW Trial – 2010M. Hoddle, M.L. Arpaia, R. Hofshi

4 Treatments:1) Outside control2) Net House with Bees3) Net House Small insects4) Net House where all trees sprayed to eliminate insects

ACW Trial – 2010M. Hoddle, M.L. Arpaia, R. Hofshi

0

10

20

30

40

50

60

70

Small Insects Insecticide Bees Control Water control

Avg

. Fr

uit

Num

ber

0

50

100

150

b b a a

SmallInsects

Insecticide Honeybees ControlAve

rage

Fru

it N

umbe

r

Encon Trial – 2011R. Hofshi, J. Schmidt, F. Mena, F. Gardiazabal, M. L. Arpaia

4 Treatments:1) Outside control2) Net House with Bees3) Net House Small insects4) Net House where all trees

sprayed to eliminate insects

5 Field Replications14 trees per net house

To maximize yield one needs:

Sufficient cross pollination

Effective pollination

Efficient pollinator(many honey bees)

Pollinizers in close proximity

The Road to ProductivityThe ultimate crop that one harvests is dependent upon many factors:Slide Number 4TerminologySlide Number 7Slide Number 8Pollination Terms:Pollination Terms:Pollination Terms:Avocado Flower BehaviorAvocado flowering characteristicsSlide Number 14Slide Number 15Slide Number 16Timing of flowering for “A” and “B” flower types. The sequence of timing for “A” and “B” flower types under field conditions.Avocado Flowering SequenceSlide Number 20Fruit Set�Slide Number 24Slide Number 25Slide Number 27Slide Number 28Slide Number 29Avocado Pollen Germination RateSlide Number 31Slide Number 32Temperature and HumiditySlide Number 34Sedgley and Annells, 1981Temperature fluctuations during flowering�Irvine, CASlide Number 39 Do You Need Pollinizers?Survival of cross vs. self progeniesSlide Number 42Materiales y MétodosResultadosHass yields decrease significantly with increasing distance from ‘Ettinger’Slide Number 46Debusschere Pollination Project – 2001 – 2008�Cumulative fruit count as a function of distance from pollinizerDebusschere Pollination Project – 2001 – 2008�Cumulative fruit count as a function of Pollinizer variety and distance from pollinizerMultiple pollinizersFlowering periods – Oxnard, 2002Slide Number 51Slide Number 52Slide Number 53Slide Number 54Slide Number 55Slide Number 56Slide Number 57To maximize yield one needs: