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the latter frequently had 70 to 90 percent of
leaf rust. Apparently the only fields sown to
Inia that were significantly affected yieldwise
by leaf rust were those sown in January. Under
these conditions Tobari 66 and Noroeste 66
sometimes outyielded Inia and Siete Cerras.
The second group of most extensively
grown varieties were the white grain variety
Siete Cerras (equivalent to Mexipak 65 and
Kalyansona in Pakistan and India respectively)
and its red grain sister Super X (equivalent to
Indus and PV 18). This year both of these
varieties performed superbly as far as grain
yield was concerned. In general, both were
favored by absence of rust and by the longer
than normal low temperatures at time of grain
filling. When heavily fertilized (120-40-0 or
140-40-0) and given five irrigations most commercial
fields of these varieties generally outyielded
Inia 66 by 500 to 700 kilos per hectare,
Le., 4500 kilos versus 5000 kilos per hectare.
Wherever only four irrigations were given, Inia
66 because of its earliness generally outyielded
Siete Cerras by 300 to 500 kilos per hectare.
The commercial variety situation in Mexico
now calls for the rapid multiplication and distribution
of several new varieties. The varieties
Ciano 66, Azteca 66, Noroeste 66, Nortefio
67 and Tobari 66, all possess excellent milling
and baking quality and remain highly resistant
to the prevalent races of the rust. All, however,
are being rapidly driven out of production by
the higher yielding varieties Inia 66, Siete Cerros
and Super X. For this reason, the National
Institute of Agricultural Research has now
named four new varieties, as indicated in the
following section, to replace the aforementioned
varieties and diversify the varieties sown and
thereby provide better protection against diseases.
.
Losses from insects were minimal during
the past season. There were local infestations
of both army worm and greenbug in Sonora
during early January, but both were successfully
controlled by timely application of insecticides.
Weeds contributed more to yield reductions
than all of the combined reductions from diseases
and insects. There are many farms in
Sonora and Sinaloa where near perfect weed
control is obtained through the proper rotations
employing winter and summer row crops combined
with winter cereals. Most of the farmers
who employ proper crop rotation practices to
obtain good weed control also employ supplementing
chemical weed control when necessary.
Frequently one can observe poorly man-
aged farms, adjacent to ones on which near
perfect weed control is obtained, where 30 to
50 percent reductions in wheat yields are resulting
from weeds.
The two most serious weeds limiting wheat
yields in Mexico are wild oats (Avena fafua)
and the so-called "Alpiste" or giant fox tait
(Phi/aris sp.). A very large research effort designed
to reduce losses from weeds employing
both cultural practices and chemicals is
being conducted by Ing. Isidra Martinez of the
CIANO staff.
Varietal Development of Bread Wheats
The task of varietal improvement is a never
ending job. It must strive to develop new varieties
that increase the genetic potential for
grain yield, improve the agronomic type so
that it will be better suited to more intensive
agriculture, improve both the spectrum and
depth of disease and insect resistance and
improve both the industrial and nutritional
quality of the grain.
The breadth of adaptation of the so-called
"Mexican-dwarf wheat varieties" and their high
yield over a wide range of conditions has provoked
new thinking concerning the validity of
the old concepts of the superiority of narrowly
adapted varieties, based on the idea of the
strict relationship of variety-environment interaction.
CIMMYT being an international research
institute that is both directly and indirectly
collaborating with many national wheat breeding
programs operating under widely different
climatic conditions in different parts of the
world has a unique challenge. It should be
possible through the international cooperative
network of research organizations to further
greatly improve on the varieties now available.
Best overall progress will be made by close
cooperation between the CIMMYT Mexican
program and "national programs in different
parts of the world.
New Mexican Commercial Bread
Wheat Varieties
Last month four new varieties were named
by C.I.A.N.O. and I.N.I.A. for commercial release
in Mexico. Three of these varieties, Nuri 70,
Yecora 70 and Saric 70, are derivatives of the
promising cross 11-23584 whose parents are
(Ciano "s" x Sonora 64-Klein Rendidor) x Siete
Cerras. Last year a number of these lines were
found to be unusually high yielding in prelim-
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