cotton - Greenmount Press

confidence in the ranking of new breeding lines compared with
control varieties.
The analyses show that some sites have been more reliable in
providing accurate data than other sites. With this information
we believe that six reliable sites, repeated over three seasons
using three to four field replications can provide equal or better
data than what was previously obtained with up to 12 sites with
four replications over a similar period. Economy and efficiency
gains with such a change are obvious. It is challenging to get six
conventional trial sites in this transgenic era. If sites are found,
there are difficulties with pest control and avoiding glyphosate
drift.
Yield progress
In the period from 1980 to 1994, yield improvement due to
new varieties was modest, averaging about 9 kg lint per hectare
per year. The highest yielding varieties were Sicala V-2 and Sicot
189. The greatest improvements due to breeding were in the
cooler short season locations, although from a lower yield base.
Regional adaptation of varieties was strong, with Siokra 1-4 and
Sicot 189 having relatively better yield in warmer full season
locations, while Siokra V-15 and Sicala V-2 were relatively better
in cooler short season locations.
In the period from 1995 to 2009, yield improvements due
to new varieties doubled to about 18 kg lint per hectare/year
with Sicot 71 being the highest yielder. Regional adaptation of
varieties was reduced compared with the 1980 to 1995 period,
but Sicot 80 and Sicot 71 had relatively better yield in warmer full
season locations, while Sicala 40 was relatively better in cooler
short season locations.
Varieties can also be ranked for their stability in yield across
Measuring
Module Moisture
years and environments. Sicot 71, Sicot 189 and Siokra V-16
were average in stability. One group of varieties which tended to
yield relatively more at high yielding sites, but relatively less at low
yielding sites, were CS 50, Sicot 53, Sicot 80 and Siokra L23. At
the other end of the spectrum were varieties such as Sicala V-2,
Sicala 40 and Sicot 75 with relatively lower yield at high yielding
sites, but relatively better at low yielding sites.
Over the period 1980–1994 to 1995–2009, there was a 95
kg per hectare increase in lint yield due to management alone.
Components of that increase were likely to have been better
management of soil, water, nutrition and pests – these aspects
have not been measured or classified to allow a thorough
interpretation of what specific management contributed to this
yield increase.
One remarkable aspect of the pooled analysis was the
existence of a strong variety by management interaction for
yield – modern varieties responded better to modern agronomy
than older varieties. The data shows that variety contributed 48
per cent of the yield gain (160 kg per hectare); management
contributed 28 per cent (95 kg per hectare); and the interaction
between variety and management contributed 24 per cent (80 kg
per hectare for the best varieties) (Figure 2).
On examination of variety disease rankings, it is evident
that Verticillium wilt resistance was a strong component of the
variety by management interaction because older Verticillium
wilt susceptible varieties such as Siokra 1-4, Siokra L22, Siokra
L23 and CS50 were unable to respond to modern management.
A variety such as Sicot 71 with high yield potential and good
disease resistance can respond to best agronomy.
Even up to 2002, an economic assessment of the cotton
FIGuRE 2: The components of cotton yield
increase from 1985–1995 to 1995–2009.
Improved varieties contributed nearly half
of the yield increase, increased management
another 28 per cent, and better response to
modern management by modern varieties
contributed 24 per cent
Please contact us to find out more
www.vomax.com.au
Richard Millyard:
0428 573 511
richardm@vomax.com.au
Data from 1985 to 2009 with 325 experiments comparing the same conventional varieties.
22 — The Australian Cottongrower December 2012–January 2013