RA 00048.pdf - OAR@ICRISAT

Population Improvement in Sorghum in Nigeria
A. Tunde Obilana
Abstract
The population improvement program in Nigeria utilizes four genetically broad-based random-mating populations as
base materials, and two main recurrent selection methods: S1 progeny testing and stratified mass selection.
Progress made so far is indicated and discussed comparatively in terms of increased grain yield and Striga
resistance, for and among the four populations: B composite, Y composite, YZ composite and MSAR composite,
using the two recurrent selection procedures. The implication of using the ms7 type of sterility system and its
proportion in the original and advanced generation cycles is indicated.
A proposal for the possible use of a combined recurrent selection method: S1 testing plus mass selection (female
choice); for an environment with single growing season and additional irrigation, is discussed towards maximizing the
genetic gain from selection for yield and multiple disease resistance.
Breeding for Multiple Insect and Disease Resistance in Sorghum
B. S. Rana, V. Java Mohan Rao, V. U. Singh, S. Indira, and N. G. P. Rao
Abstract
Sorghum being predominantly a low input crop of the semi-arid tropics, the simultaneous incorporation of resistance
to major pests and diseases in improved cultivars is essential to confer greater levels of stability to production. While
individual sources of resistance have no doubt been documented, efforts have also been made recently to identify and
develop sources exhibiting resistance to groups of pests and diseases. These will be documented. The mechanism
governing resistance to most sorghum pests is nonpreference. Disease resistance as in downy mildew and charcoal
rot is a quantitative threshold character. The nature of inheritance is generally additive for threshold characters and for
insect resistance. Stability of resistance is also under genetic control. It is possible to develop a genetic basis for
multiple resistance and pyramid genes for resistance. The plant breeding implications of breeding for multiple
resistance to sorghum pests and diseases will be discussed.
Pleiotropic Effects of g1 Glossy Gene in Sorghum on Leaf Structure,
Leaf Digestion, and Disease Resistance
lsao Tarumoto
Abstract
Some of the pleiotropic effects of the g1 glossy gene in sorghum were examined. The outer-side cell walls of cuticles
of glossy leaves in SC-112 and Rancher were observed to be thicker and harder than those of nonglossy leaves in
Zairai-Token. The nonglossy isogenic plants were always somewhat higher in leaf digestibility than the glossy isogenic
plants. This suggests that the thicker and harder cell walls of cuticles in the glossy leaves would be more resistant to
the attack of cellulose enzymes than the highly dense epicuticular waxes on the nonglossy leaf surfaces. The
relationship between glossiness and resistance to sorghum leaf blight suggests that the resistant gene to leaf blight
would be independently inherited of the g1 glossy gene.
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