HOW LONG DO HONEY- BE ES^^^;^;

1 t %

HOW LONG DO HONEY-

BE ES^^^;^;

_,,

CARRY

GERMINABLE

POLLEN

' t T n

-.

~ , ' f " ,

3 /

. -L

-

'

O N

THEM?

I N S T I T U U T V O O R DE V E R E D E L I N G V A N T U I N B O U W G E W A S S E N W A G E N I N G E N ( N E D E R L A N D )

Euphytim 11 (1962): 53-56

HOW

LONG

DO HONEY-BEES CARRY

GERMINABLE

POLLEN

ON T H E M ?

A. KRAAI

Xnstitute of Horticultural Plant B d i n g -Wageningen With 2 figures

Received 1 J Nov. 1961

Bees are used to pollinate plants in isolation cages. Usually the bees have previously flown about freely in the open air and may have gathered pollen from the same plant species.

Now the question arises whether the bees can contaminate with this pollen plants with whick they are enclosed in an isolation cage. In this connection a number of experirnents were undertaken to find out how Iong becs are loaded with germinable pollen. Tt appeared that the risk of contamination was practicalIy elirninated by keeping the bees in a house or empty isolation cage for 12 hours.

In the breeding of various crops bees can be used to advantage to do the pollination work in isolation cages (KRAAI, 1954). The bees may previously have flown about freely in nature, visiting flowering plants that are closely related to the isoIated speci-

mens, and consequently they rnay carry pollen that wilt cause undesired cross-fertili- zation. To determine the extent of this danger a number of experiments were carried out during the years 1953 to 1959.

MATERIALS AND METHODS

First the bees were enclosed for 18 to 72 hours in an isolation cage containing flowering plants with easiiy rrecognjzable dominant characters. Then they were re- turned for one night to 8 days to a very smalI bee-hive specially designed for these experiments, or they were put in a polIination cage without flowers, where they were fed sugar water. Next they were placed for one day in another isolation cage housing 1 or 2 fiowering plants of the same species, but now with readily recognizable recessive characters. The seed of the latter plants was aftemards harvested, sown out and inspected for contamination. The number of seeds per combination annuaIly sown for this purpose was usudly over 100. The following plants were used for these experi- ments :

W i t h d o m i n a n t c h a r a c t e r s :

Red cabbage

-

Langedijker Rode bewaar

Borecale

-

Westlandse hatf hoge

Brussels sprouts - Roodnerf

TAE3.E 1. PLANTS USED FûR THE CONTAMTNATION EWERlMENTS

2

1 I

Number of years tated

Blue comiiower

Reddish brown wallflower

1

1

Borecale

1 Begonia semperfloreni, rid

1 1

1 1

Plants with dominant characters which were

visited fint 1 1 1 1 12 hours 12 h o m 20 hours 36 houn 36 hours 44 hours 44 hours 84 hours 90 hours UW) hours 12 hours 12 hours 12 hours 20 h o m 36 hourî 44 hours 12 hours 20 hours

i

36 hours 4 4 hours 12 hours

!

20 hours 36 hours 44 hours M) hours 12 houm 20 hours 36 hours 44 hours Duration of sub- sequent enclosure without flowers Brussels sprouts

Round red radish

1

(1) one of the plants gave 10 % wntamination in the off-spring (see text)

Plants with recessive characters which were visited afterwards Species

1

Number Savoy cabbage White cabhage White cahbage Savoy cahbage White cabbage Savoy cabbage White cabbage White cabbage Savoy cabbage Savoy cabbage White cabbage White cabbage Lone white radish

~ o n g white radish

Long white radish

1 1 1 1 Totalnumber Of planrs inspected ~ o n g white radish White wmflower White wmflower White wmiiower White wmflower

Yellowish white walüiower Yellowish white walüiower Yellowish white wallflower Yellowish white walMower Yellowish white walüiower Begonia semperflorens, white Begonia semmrflorens, white

% contaminated

.

Begonia semperflorens, white Begonia semperfloreus, white

O and 10 (1)

A. K R A A I

Blue cordower

-

Centaures c,vanus

Reddish brown wdlflower

-

Cheii-anihu,~ cheiri

Begonia sewperfiorens, diploid red - Ball's Rode

W i t h recessive c h a r a c t e r s :

White cabbage - Langedijker Witte Bewaar

Savay cabbage

-

Langedijker Gele Bewaar

Long white radish

-

IJskegel (Icicle) White cornfiawer

-

Centaures cyanus

Yellowish white wallflower

-

C h e i r a n t h ~ ~ ~ cheiri (White Gem)

Regonia ~emperjîorens, dipl oid white - Snowbank

The results are shown in table 1. Only in one case, in the progeny of one of the three savoy plants, did 10

%

contamination occur (4 of the 40 plants). Presumably the pIant in question partly already flowered and had been pollinated with pollen of red cabbage before being placed in the isolation cage. I n later experinents special care

was taken to remove such Rowers as were aIready open before the plants were isolated. Further contamination did not occur. From this it may be concluded that there is generally no risk in allowing bees that have visited plants of a certain crop to visit other plants of the same crop after one night's enclosure in a bee-house. Apparently,

after being enclosed for 12 liours, they no longer carry germinable pollen on them.

Hos Iang dragen byen kiemkrachrig stuifvzeel hg zich ?

Voor het bestuiven van planten in geïsoleerde ruimten worden bijen gebruikt. Meestal hebben deze voordien in het vrije veld gevlovgen en daar wellicht op dezelfde plantensoort stuifmeel verzaineld. De vraag was of zij daarmee op de planten in de isoIatieruirnte waaraan zij worden toegevoegd verbastering kunncn veroorzaken. In verband hiermee zijn enige proeven genomen om na te gaan hoe lang bijen kiemkrach-

tig stuifineel bij zich dragen. Hierbg bIeek dat dit al niet meer het p a l was, wanneer de bijen gedurende een periode van 12 uur opgesloten werden in hun kast of in een isolatiekamer zonder bloemen. Het Iijkt dus wel verantwoord voor bestuivingsdoelein- den bijen te gebruiken die een nacht opgesloten zijn geweest.