Je. Barron et al., Response to selection for seed yield and nitrogen (N-2) fixation in commonbean (Phaseolus vulgaris L.), FIELD CR RE, 62(2-3), 1999, pp. 119-128
This study examined the feasibility of recurrent selection for enhanced N-2
fixation in common bean (Phaseolus vulgaris), and sought to generate breed
ing lines with the high N-2-fixing ability. Following their selection as su
perior in N-2 fixing ability, the landrace Puebla 152, and the CIAT breedin
g lines BAT 271 and RIZ were intercrossed, and 17 F-2.3 lines derived from
the progeny used to initiate two cycles of recurrent selection. Each cycle
included crossing, selfing, multiplication and field testing phases, and oc
cupied one year. Field testing was undertaken on an irrigated, leached, loa
my sand with 9 to 14 mg total N kg(-1). Plants were inoculated with Rhizobi
um etli UMR 1632, with 17 of 490 F-2.3 derived lines per cycle selected for
seed yield and shoot dry weight under conditions of N limitation. Selectio
n progress was evaluated by comparing the C-0, C-1, and C-2 parents, and se
lections from the C-2 population, for biological and seed yield, and N accu
mulation under the same N-limited field conditions. The C-2 parents yielded
an average of 11% more than the C-0 parents, and were 15% and 13% better i
n shoot dry weight and shoot N per plant, respectively. Several lines perfo
rmed significantly better than any parent or check cultivar under the low N
field conditions. Among cross-differences for seed yield and shoot dry wei
ght occurred in both the C-1 and C-2 populations, with GCA accounting for m
ore of the variation than SCA in both populations. Not all the parents were
well adapted to Minnesota, and several Cycle 1 F-2.3 lines were late to fl
ower and mature, resulting in a negative correlation between these traits a
nd seed yield and seed N. Selection emphasis on lines maturing in 98 days o
r less reversed this relationship in the C-2 parental group. We conclude th
at selection based on both plant and seed parameters is essential. (C) 1999
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