Volume 49 Number 4 Article 43
Year 1995 Month 10
Title: Determination of Cold Hardiness and Estimation of Potential Breeding Value of Apricot Germplasm
Authors: R.E.C. Layne and M.F. Gadsby
Abstract:
Controlled laboratory freezing tests were carried out on dormant apricot (Prunus armeniaca
L.) shoots preconditioned to attain maximum
cold hardiness.
Determinations were made of
the temperatures required to kill 50% of the flower
buds [T50 (FB)] and 50% of the shoot xylem [T50
(SX)]. The 27 genotypes in this study differed
significantly from each other in T50 (FB) and T50
(SX). Using 'Goldcot' as the climatically adapted
hardy standard, 27 genotypes were placed in
three hardiness classes; those more hardy than
'Goldcot,' those equally hardy as 'Goldcot' and
those less hardy than 'Goldcot.' The mean T50
(FB) was -28.7C and the mean T50 (SX) was
-35.3C, indicating that shoot xylem hardiness of
apricots was at least several degrees greater than
flower bud hardiness.
The range in flower bud
hardiness among the 27 genotypes was 2.8C while
that for shoot xylem hardiness was 6.7C. Seven
genotypes had hardier flower buds than 'Goldcot'
including two named Harrow cultivars ('Harlayne'
and 'Haggith'), four numbered Harrow
selections (H7814180, HW-446, H8205044 and
HW460) and one other cultivar ('Manchu').
Among 16 genotypes equally bud hardy as 'Goldcot,'
four were named Harrow cultivars ('Harcot,'
'Harglow,' 'Hargrand' and 'HarogenO and eignt
were numbered Harrow selections.
One named
Harrow cultivar ('Hag-gith') was more wood
hardy than 'Goldcot'; while three Harrow cultivars ('Harlayne' 'Harcot' and 'Hargrand') and
seven numbered Harrow selections were equally
wood hardy.
The goal of breeding apricot cultivars equal to or more cold hardy than 'Goldcot'
was achieved because bud hardiness of six of the
seven Harrow introductions was equal to or
greater than 'Goldcot.' The potential breeding
value of the 14 named cultivars was estimated by
using their total long term performance ratings
for 14 attributes, then applying the bud and wood
hardiness classifications made here as additional
factors.
The ranking of breeding value for the 14
named cultivars from highest to lowest was as
follows: 'Harlayne' > 'Harcot' = 'Hargrand' =
'Harval' > 'Harglow' = 'Harogem' > 'J.L. Budd' >
'Manchu' > 'Gibbs' = 'Sunglo > 'Haggith' ='Veecot'
> 'Stella' > 'Goldcot.' The potential breeding
value of the six named Harrow introductions for
the fresh market exceeded that of the eight other
cultivars, including 'Veecot' and 'Goldcot,' the
two commercial standards.
Consequently, they
warrant greater use as parents and wider testing
as cultivars.
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