Some dry bean lines (L) Phaseolusvulgaris resistant (R) (compatible reaction) to Xanthomonascampestris var. phaseoli (Xpc) developed in the temperate zone express susceptibility (S) in the field in the tropics and tropical lines (S) express moderate R in the temperate zone. There is only limited information on the influence of P on Xpc reaction in dry beans. Experiments were conducted in growth chambers (GC) and in the field (NE, Dominican Republic, Puerto Rico) to investigate the influence of P and P × temperature (T) on the reaction of L to Xpc. A split-plot design was used with T as the main-plots and P and L as sub-plots in the GC experiment and with P as main-plots and L as sub-plots in the field experiments. The disease reactions were more severe on L under short P and under higher T than under shorter P and lower T. No interactions were detected among these treatments. PC-50 showed moderate R, delayed flowering, flower bud abortion, and increased branching under long P (field, NE). These results have implications for breeders in the evaluation of field R of L from different latitudes and for their value in breeding.
We studied leaf and pod reactions of 18 Phaseolus vulgaris germplasm lines (three temperate and 15 tropical) to four Xanthomonas campestris pv. phaseoli (XCP) (Smith) Dye strains and seven Uromyces appendiculatus (UA) (Pers.) Unger races. Line × XCP interaction was significant for leaf and pod reactions. The common bean lines XAN-159, BAC-6, and XAN-112 had the best combined leaf and pod resistance to XCP. Line × UA race interactions were significant (P = 0.05). Lines IAPAR-14 and BAC-6 had the best combined resistance to XCP and UA.
An association between abaxial leaf pubescence (ALP) and adult plant resistance (APR) on trifoliolate leaves was reported previously. Recombinant inbred (RI) lines from crosses PC-50 (P1) with XAN-159 (P2) and BAC-6 (P3), and P3 with HT7719 (P4) were used to study the inheritance of specific resistance (SR), APR and ALP. P1 is resistant to A88TI-4b and has abaxial hairs on the trifoliolate leaves while P2, P3, and P4 are all susceptible (S) and have glabrous (G) leaves. P3 is resistant to D85C1-1. SR to A88TI-4b on primary leaves (PL) was determined by a single dominant gene with an additional dominant gene for APR on the 4th trifoliolate leaves in P1 × P2. ALP was governed by a single dominant gene with no association with APR. SR to A88TI-4b on PL in P1 × P3 was controlled by a single dominant gene. SR to DC85C1-1 on the PL was determined by a single dominant gene in P3 × P4.
Common bacterial blight (CBB) incited by the bacterial pathogen Xanthomonas campestris pv. phaseoli (Smith) Dye is an important disease of common bean. In a previous study, QTL associated with CBB resistance were described based on RAPD marker analysis of a recombinant inbred population derived from the common bean cross BAC-6 (R) × HT-7719 (S) (resistant × susceptible). The objective of this research is to confirm these previously described candidate marker locus-QTL associations using an inbred backcross PC-50 (S) × BAC-6 (R) and a recombinant inbred Venezuela 44 (S) × BAC-6 (R) population. Two markers previously found to be associated with QTL for CBB resistance in the BAC-6 × HT-7719 population were found to account for 30% of the phenotypic variation for CBB resistance in the PC-50 × BAC-6 inbred backcross population. The three most resistant BC2F3 lines based on marker locus genotypes were ranked 1, 3, and 7 (out of 64) based on phenotypic evaluation. These results provide important confirmation of marker locus-QTL associations and indicate that RAPD markers linked to loci controlling the expression of CBB resistance in common bean may be used to transfer resistance genes into susceptible breeding material.
Disease of beans, particularly common bacterial blight (CBB) (DR, NE), rust (DR, NE), web blight (WB) (DR) and bean golden mosaic virus (BGMV) (DR) are major constraints to bean yields and seed quality. The objectives were to identify resistant (R) germplasm, to conduct genetic studies, to develop R cultivars (DR, NE), to improve research facilities and capabilities (DR), to train personnel and educate graduate students (DR, NE). The expected impact is (1) the improvement of breeding programs, yields and income to farmers and (2) returning specialists will permit improved research in the DR. The most significant advances in research were as follows: (i) BAC-6 dry bean breeding line was found to be R to CBB seed infection, (ii) The reaction to CBB was inherited quantitatively with low NSH estimates, (iii) Rust race nonspecific R was correlated with abaxial leaf pubescence; the latter trait was inherited qualitatively, (iv) R to BGMV and WB were identified and (v) Improved cultivars and breeding lines were developed (DR, NE).
Our objective was to identify QTL for seed weight (SW), length, and height segregating in a recombinant inbred line (RIL) population from the cross `PC-50' (Larger SW) × XAN-159 (Smaller SW). The parents and RILs were grown in two separate greenhouse experiments in Nebraska, and in field plots in the Dominican Republic and Wisconsin. Data analysis was done for individual environments separately and on the mean over all environments. A simple linear regression analysis of all data indicated that most QTL appeared to be detected in the mean environment. Composite interval mapping (CIM) analysis was then applied to the means over environments. Eight QTL for SW were detected on common bean linkage groups (LGs) 3, 4, 5, 6, 7, and 8. All eight markers associated with these QTL were significant in a multiple regression analysis (MRA), where the full model explained 63% of the variation among SW means. Six QTL for seed length were detected on LGs 2, 3, 4, 8, and 11 using CIM. The markers associated with the three seed length QTL on LGs 2, 8, and 11 were significant in a MRA with the full model explaining 48% of the variation among seed length means. Three QTL for seed height on LGs 4, 6, and 11 explained 36% of the phenotypic variation for trait means. Four of the six QTL for seed length and two of three QTL for seed height also appeared to correspond to QTL for SW.
Common blight, web blight, and rust, incited by the bacterial pathogen Xanthomonas campestris pv. phaseoli (Smith) Dye (Xcp) and the fungal pathogens Thanatephorus cucumeris (Frank) Donk (Tc) and Uromyces appendiculatus (Pers.:Pers) Unger, respectively, are important diseases of common beans (Phaseolus vulgaris L.). The objectives of were to construct a linkage map, and to locate CBB, rust, and WB resistances and plant architecture traits using RAPDs. Ten linkage groups were identified. Eighty-nine RAPD markers and rust resistance were mapped in 128 RI lines of the cross BAC-6 and HT-7719. Regression analysis and interval mapping using MAPMAKER/QTL were used to identify genomic regions involved in the genetic control of the traits. One, two, two, and three putative QTLs were identified for leaf, seed, and pod reactions to Xcp, and foliar reaction to Tc. These regions accounted for 11%, 9%, 32%, and 30% of the phenotypic variation in the resistances. Two, two, and three regions were identified for plant uprightness, branch density, and pod distribution. These regions accounted for 27%, 13%, and 16% of the phenotypic variation. Unassigned marker G17d influenced some of the phenotypic variation in all three traits. A rust resistance gene controlling pustule size on primary leaves was located in linkage group 1.
Common bacterial blight(CBB) and rust diseases, incited by the bacterial pathogen Xanthomonas campestris pv. phaseoli (Smith) Dye (Xcp) and Uromyces appendiculatus, respectively, are important diseases of common beans (Phaseolus vulgaris L.). The objectives were to construct a molecular linkage map, to locate CBB resistances, rust resistances and leaf pubescence using RAPDs. Sixteen linkage groups with 22 unassigned markers were identified. 178 RAPD markers and 8 morphological markers were mapped in a Population of 70 RI lines. Regression analysis and interval mapping using MAPMAKER/QTL were used to identify genomic regions involved in the genetic control of the traits. One, two, and three putative QTLs were identified for seed, pod and leaf reactions. These regions accounted for 18%, 25%, and 35% of the phenotypic variation in CBB resistance. A chromosome region on linkage group 1 carried factors influencing all three traits. Rust resistance genes controlling the reactions on the primary and on the 4th trifoliolate leaves (adult plant resistance) were located in linkage group 16. The genes for abaxial leaf pubescence was located on linkage group 9.
Heritabilities (H) of seed transmission and leaf and pod reactions to common bacterial blight (CBB) Xanthomonas campestris pv. phaseoli (Xcp) and to web blight (WB) Thanatephorus cucumeris (Tc) were studied. The reaction to CBB was quantitatively inherited. H values of .36, .46, and .34 for leaf reaction, .14, .12, and .27 for pod reaction, .53, .26, and .36 for seed transmission were estimated based on variation of F6 lines derived from bean crosses 'PC-50' × XAN-159, 'PC-50'× BAC-6, and 'Venezuela 44' × BAC-6 (greenhouse, NE). No significant correlations were detected between leaf and pod reactions or between pod reaction and seed transmission. Quantitative inheritance patterns were observed for leaf reactions to Xcp, Tc, and architecture (AR) in F6lines from the cross BAC-6 × HT 7719 (field, Dominican Republic). H values of .23 (CBB), .14 (WB), and .30 (AR) were obtained. No significant correlations were detected between CBB with WB or AR. A low correlation (+.22) was found between WB and AR.
Randomly amplified polymorphic DNA (RAPD) molecular markers were used to construct a partial genetic linkage map in a recombinant inbred population derived from the common bean (Phaseolus vulgaris L.) cross PC-50 × XAN-159 for studying the genetics of bacterial disease resistance in common bean. The linkage map spanned 426 cM and included 168 RAPD markers and 2 classical markers with 11 unassigned markers. The seventy recombinant inbred lines were evaluated for resistance to two strains of common bacterial blight [Xanthomonas campestris pv. phaseoli (Smith) Dye] (Xcp). Common bacterial blight (CBB) resistance was evaluated for Xcp strain EK-11 in later-developed trifoliolate leaves and for Xcp strains, DR-7 and EK-11, in first trifoliolate leaves, seeds, and pods. One to four quantitative trait loci (QTLs) accounted for 18% to 53% of the phenotypic variation for traits. Most significant effects for CBB resistance were associated with one chromosomal region on linkage group 5 and with two regions on linkage group 1, of the partial linkage map. The chromosomal region (a 13-cM interval) in linkage group 5 was significantly associated with resistance to Xcp strains DR-7 and EK-11 in leaves, pods, and seeds. The regions in linkage group 1 were also significantly associated with resistance to both Xcp strains in more than one plant organ. In addition, a seedcoat pattern gene (C) and a flower color gene (vlae) were mapped in linkage groups 1 and 5, respectively, of the partial linkage map. The V locus was found to be linked to a QTL with a major effect on CBB resistance.