Abstract:

Various activities were carried out during this reporting period and these included:
evaluation in 5 locations of the 62 three way cross and 84 single cross hybrids locally
developed, however their yield data is not presented because the crop is not ready yet for
harvesting. Private seed companies which will market some of these hybrids once
released, were involved in selection of both the three way cross and single cross hybrids
in two locations, Namulonge in Central and Bulindi in Western Uganda. From 62 three
way cross hybrids, 10 are standing out well in terms of disease resistance, plant aspect,
husk cover, big ears, medium height and ear placement. These 10 hybrids will further be
tested in the March planting in at least 3 more locations and possibly on-farmers' field.
Also to be carried out during the March planting is the multiplication of the parental lines
and constituting the hybrids themselves. The same will be done for the single crosses.
The seventy three inbred lines used to create three-way crosses were grouped into
potential heterotic groups based on grain yield. The inbred lines were crossed to two
single cross testers (A and B). Line x tester analysis was carried out and general (GCA)
and specific (SCA) combining ability effects for grain yield were estimated and the
significance of the GCA and SCA effects was determined. Ten inbred lines showed
significant GCA effects for grain yield. Thirty one inbred lines were classified into
heterotic group A, twenty five into heterotic B and seventeen could not be clearly
classified into either heterotic group. This knowledge of heterotic grouping will allow
the program to design appropriate breeding strategies using these inbred lines.
In pursuance of the short term strategy, hybrids from CIMMYT-Kenya to cater for the
mid-altitude ecologies and CIMMYT-Ethiopia for the highland ecologies were evaluated
for their performance and adaptability in Uganda with the objective of directly releasing
those found doing well. For the mid-altitude ecologies, at least 2 double cross hybrids as
selections from previous evaluations were further tested in two locations and three have
shown a lot of potential giving a yield of 8 tons in some locations and had good levels of foliar diseases particularly turcicum leaf blight and maize streak virus. Among the
highland hybrids evaluated, 6 gave yields of over 10 t/ha.
In some areas of the country, Striga still posses a big threat to maize production. One
management strategy reported to be doing well in Kenya is through use of Imazapyr
resistant maize which kills striga when attempting to attach itself on maize. This
technology was tried in Eastern Uganda in two districts, Bugiri and Busia by testing open
pollinated varieties and hybrids which are resistant to the herbicide. 6 sets of trials were
obtained from CIMMYT-Kenya and their performance was not as good as expected
because of, (i) A lot of striga plants were found attached on the maize and the counts
could go as high as 50 plants per square meter (ii) Almost all materials tested succumbed
to turcicum leaf blight. The disease levels were quite high as reflected by mean scores of
4 and above, clearly showing that the materials are very susceptible (the yields were also
low for certain materials. The dream of utilizing these materials is still far from reality
given these drawbacks.
The maize weevil is still posing a lot of damage to maize particularly in storage,
especially where protective insecticides are not used. In an effort to search for materials
tolerant to weevils, screening of elite germplasm was carried out in the laboratory at
Namulonge. This study is part of a continuous study aimed at selecting materials that can
be used for developing weevil-resistant maize varieties. The materials used comprised of
advanced maize lines, single and double cross hybrids. The results revealed variation in
progeny numbers, weights of dust and percent weight loss. This is indicative of the
differential susceptibility of different lines.