Simple sequence repeat (ssr) genetic analysis of cassava mosaic disease resistance in selected f1 populations of cassava

Thesis Abstract

Cassava mosaic disease caused by begomoviruses is the most widespread disease of cassava
in Africa. Simple sequence repeat (SSR) genetic analysis of an F1 population of cassava was
carried out to identify new sources of CMD resistance. Genomic DNA extracted from parents
and progeny was amplified using polymerase chain reaction (PCR).The broad objective of the study was to investigate the socio-economic and
cultural dimensions of food security among selected ethnic groups in North Central
Nigeria. Specifically, the study was designed to determine food culture and practices of
the respondents; determine the household food security status (energy availability) across
ethnic groups; determine dietary diversity of the households across cultures; identify
perceived constraints militating against household food security; and describe the coping
strategies utilized by the households during food shortages. Seven hypotheses and a
conceptual framework were developed for the study. The population of the study consists
of all ethnic groups in North Central Nigeria. The zone comprises about 60 ethnic groups.
Specifically, the study was carried out among Tiv, Igala and Eggon ethnic groups of
Benue, Kogi and Nasarawa States. A multi-stage sampling technique was adopted for the
study. Three ethnic groups (Tiv, Igala and Eggon) and one village per ethnic group PCR amplifications were
run on polyacrylamide and agarose gels. SSR marker technology was used to identify markers
linked to CMD resistance via bulk segregant analysis (BSA).
One hundred and forty
molecular markers from the International Center for Tropical Agriculture (CIAT) were used
to screen the parents, contrasting bulks and the individuals that make up the contrasting bulks.
The bulk segregant analysis produced forty polymorphic markers. Screening of the
contrasting individuals with the polymorphic markers revealed four candidate markers (SSRY
238, SSRY 51, SSRY 76 and SSRY 20) linked to CMD resistance. The correlation coefficient
values between genotypic and phenotypic data classes for candidate markers were generally
low. The t-test value between both genotypic classes (absence of band versus presence of
band) were not significant (P>0.05) in each of the four markers. The results from this study
suggest that there are at least two new CMD resistance genes in the mapping population.