Agriculture Reference
In-Depth Information
consequently possess highly defined characteristics. Rootstocks mainly result from
even more lengthy selection programmes and are retained in commercial use for
decades. Many of their characteristics began being identified in the late nineteenth
century and variation within rootstocks is noted in Bedford and Pickering (
1919
)
and amplified by Bunyard (
1920
) and Hatton (
1920
). Scion growth control via the
manipulation of pip and stone rootstock vigour played and still plays a major role in
increasing fruit quality and quantity. Bunyard (
1920
) noted the history of Paradise
rootstocks and their origins. This was followed by several years of careful analysis
of selections of these stocks demonstrating how the yield of the scion varied with
different stocks. 'Lane's Prince Albert' when grafted and budded on stock number
IX was the highest yielding (Hatton
1927
). This work led on to the subsequent de-
velopment of the 'Malling (M)', 'Malling-Merton (MM)' and 'East Malling-Long
Ashton (EMLA)' clones as described, for example, by Preston (
1955
). Apple root-
stocks selected by British research stations (East Malling, John Innes and Long
Ashton) in the early part of the twentieth century currently still dominate commer-
cial practice internationally. The rootstock known as Malling no. 9 (M9) is still to
be found in almost every apple orchard worldwide. The studies of rootstock vigour
and stabilisation of original selections taken from commercial material resulted
in rootstocks with predictable and reliable properties. Recently, further sources of
rootstocks have appeared from Eastern Europe and North America resulting from
continuing studies aimed at engendering improved performance of the scion culti-
vars. None of these, however, have achieved the market dominance of the original
British material, especially M9, to date. These rootstocks quite literally support a
worldwide market in the single largest internationally-traded fruit commodity, the
apple, and have done so for nearly a century.
Scion Sterility and Fertility Barriers
Explanations of the biological processes of scion pollination across barriers of self-
sterility and incompatibility were elucidated by Hatton, Amos, Hoblyn, Crane and
Lawrence (Dixon
2006
). These workers founded the science of cytogenetics re-
sulting in an understanding of underlying incompatibility of fertilisation between
cultivars of apple, pear and, in particular, cherries and plums. They recognised
groups of cultivars which could be planted successfully so that pollination would
be successful and those where it would fail. The result of this work has provided
generations of fruitgrowers worldwide with the ability for designing orchard lay-
outs which would ensure cross-pollination and successful high yielding and high
quality cropping. Consequently, cultivars are now specified into their compatibility
groups even where they are destined for hobby gardeners. Working out these groups
required dedicated laboratory studies of the growth or failure of the pollen tube
into the ovary and transmission of male gametes for successful pollination. This
work extended into field vegetables in the 1950s showing that in
Brassica
spp. in
particular the presence of specific sterility (S) alleles in the genotype regulated the
success or failure of fertilisation and resultant development of seed crops. Prior to
