| dc.description.abstract | Five popular bean cultivars susceptible to bean common mosaic virus, halo blight
Pseudomonas phaseolicola and anthracnose Colletotrichum lindemuthianum were
crossed in a dial lei with two other cultivars resistant to these pathogens. Progenies were
evaluated at the National Horticultural Research Centre - Thika and the University of
Nairobi - Kabete. Lines combining resistance to two or more of the diseases were
selected. Mode of inheritance of resistance to BCMV in cultivar L226-10 (52) and that
of resistance to Pseudomonas phaseolicola and Col/etotrichum lindemunthianum in
NB-123 were studied.
Out of 1800 pollinations of the diallel crossing to seven bean cultivars, 1400 were
successful, giving an overall 78.3% of successful crosses with each pod containing 3-7
seeds. L226-10 (52) was rated resistant to BCMV isolate 510 both in the green house
and in the field. The F1' F2 and F3 progenies of the crosses GLP-2 x GLP-24, GLP-2 x
M535, GLP-288 x GLP-24, GLP-24 x GLP-2, GLP-24 x M535, GLP-x.92 x M535, M535
x GLP-2, M535 x GLP-2, M535 x GLP-288, M535 x GLP-24 and M535 x GLP-x.92 were
highly tolerant to the virus isolate both in the green house and in the field. NB-123 was
rated resistant to Pseudomonas phaseolicola both in the green house and in the field.
The F1' F2 and F3progenies with NB-123 and M535 as one of the parents were resistant
to the pathogen both in the green house and in the field. NB-123 was rated resistant to
Coletotrichum lindemuthianum both in the green house
and in the field. The Fl' F2 and F3 progenies with M535 and NB-123 as one of the
parents had a high degree of resistance to the pathogen both in the green house and
in the field.
Segregation of the F2 progenies for resistance to BCMV of the crosses GLP-2 x
L226-10 (52), GLP-x.92 x L226-10 (52) and their reciprocals did not differ from the
expected ratio 3:1 (resistantsusceptible). Segregation of the F3 progenies for resistance
to BCMV of the same crosses and their reciprocals also did not differ from the expected
ratio 2:1 (segregating:non-segregating). It was therefore concluded that resistance to
BCMV in L226-10 (52) is governed by a single dominant gene.
TAe segregation of the F2 progenies for resistance to Pseudomonas phaseolicoJa
of the crosses GLP-2 x NB-123, GLP- x.92 x NB-123 and their reciprocals differed from
the expected ratio 3:1 (resistantsusceptible). Segregation of the F3 progenies for
resistant to Pseudomonas phaseoJicoJa of the same crosses and their reciprocals differed
from the expected ratio 2:1 (segregating:non-segregating).lt was therefore concluded
that resistance to Pseudomonas phaseolicoJa in NB-123 is not governed by a single
dominant gene.
The segregation of the F2 proqenies for resistance to CoJ/etotrichum
Jindemuthianum of the crosses GLP-2 x NB-123, GLP-x.92 x NB-123 and their reciprocals
did not differ from the expected ratio 3:1 (resistant:susceptible). Segregation of the F3
progenies for resistance to CoJ/etotrichum Jindemuthianum for the
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