Thomas E Michaels

OAC Rex common bean

OAC Rex is an upright indeterminate bush white bean (Phaseolus vulgaris L.) cultivar intended for use in areas with greater than 2800 crop heat units. It has good yield potential in either wide or narrow row production. It is resistant to races 1 and 15 of bean common mosaic virus and is the first common bean cultivar resistant to common bacterial blight (Xanthomonas axonopodis pv. phaseoli) in Ontario. Seed has acceptable cooking and canning quality. Key words: Phaseolus vulgaris L., white bean, common bean, common bacterial blight, cultivar description

An improved breeding strategy for autotetraploid alfalfa (Medicago sativa L.)

Alfalfa cultivar development will be enhanced by breeding strategies whichutilize the full potential of autotetraploid population genetic structures. Thisstudy evaluates the effectiveness of an allelic selection scheme, which wasdeveloped to overcome limitations of inbreeding depression and to exploitgeneral and specific combining ability effects in autotetraploid populations.Allelic selection entails the minimization of non-additive genetic effects byselecting among full-sib families (F1) which are at uniform levels ofheterozygosity. Such F1 lines are developed by crossing individuals fromtwo unrelated random mating populations. Selected F1 lines wereintercrossed to form an improved population. Eight random matingpopulations of alfalfa were developed to study the effectiveness of allelicselection. Selection for increased dry matter yield resulted in alfalfapopulations with 38 percent greater yield than the parent populations. Twocycles of intercrossing, among selected F1 lines, did not dissipate the gainfrom selection. This result has important implications for synthetic cultivardevelopment in which a major limitation is the decline in productivity withadvancing generations of seed increase. A positively correlated response toselection for dry matter yield was observed for plant height and stemdiameter. The results of this research indicate that continued testing of theallelic selection scheme is warranted and could have a significant impact onthe breeding of autotetraploid alfalfa, particularly for synthetic cultivardevelopment.

Marker-assisted selection for complex trait in common bean (Phaseolus vulgaris L.) using QTL-based index

A procedure was developed for marker-assisted selection of complex traits for common bean (Phaseolus vulgarisL.) using an index based on QTL-linked markers and ultrametric genetic distances between lines and a target parent. A comparison of the mean seed yields of the top five lines selected by different schemes demonstrated that the highest yielding group was selected on the basis of a combination of phenotypic performance and a high QTL-based index,followed by groups identified by a high QTL-based-index, conventional selection,and a low QTL-based-index. This study demonstrated a simple way to use information obtained from QTL studies to make selection decisions. The study also showed that the use of the QTL-based-index in conjunction with the ultrametric genetic distance to the target parent would enablea plant breeder to select lines that retain important QTL in a desirable genetic background. Therefore, this type of MAS would be expected to be superior to the phenotypic selection.

Genetic variances, heritabilities and genetic correlations of grain yield, harvest index and yield components for common bean (Phaseolus vulgaris L.) in sole crop and in maize/bean intercrop

Breeding of common bean (Phaseolus vulgaris L.) for intercropping with maize (Zea mays L.) is usually done in bean sole crop nurseries. However, bean cultivar evaluations have identified significant cultivar × cropping system interactions. The objective of this study was to determine whether intercrop and sole cropping systems have different effects on phenotypic and genetic variance components of bean populations. Unselected F2 and F3 populations of 16 crosses of common bean were evaluated in the two cropping systems at Elora and Woodstock, Ontario, Canada, in 1993 and 1994. Significant population × cropping system interaction was found for grain yield and pods per plant. Genetic correlations between cropping systems were lowest for grain yield and pods per plant and highest for seed weight and seeds per pod. There were few differences between cropping systems for genetic variances. Genotype × location variance was higher in intercrop than in sole crop. Broad-sense heritabilities and narrow-sense heritab...

Yield and insect injury in leafhopper (Empoasca fabae Harris and Empoasca kraemeri Ross & Moore) infested dry beans in Ontario and Colombia

Recombinant inbred lines derived from a cross between a leafhopper-susceptible bean (Phaseolus vulgaris L.), Berna Dutch brown and leafhopper-resistant selection EMP 419 were examined for resistance to the leafhopper species Empoasca abae (Harris) and Empoasca kraemeri Ross and Moore in Ontario, Canada and Colombia, South America, respectively. In both Ontario and Colombia there were significant positive correlations of visual injury scores with percent reductions in seed count, seed yield and seed weights. Leafhopper injury symptoms were significantly correlated with degree of stunting in Ontario, while only leaf burn scores were correlated with stunting in Colombia. Nymph counts were significantly and positively correlated with leaf curl scores in Ontario but not in Colombia, despite significant rank correlations of leaf burn scores and leaf curl scores between these locations. In a second experiment comparing the effects of E. fabae nymph infestations on set of 23 resistant and 5 susceptible recombinan...

Evaluation of a DNA probe for the quantitative detection of common bacterial blight in common bean and its application in a breeding program

SummaryBreeding of Phaseolus vulgaris L. for resistance to common bacterial blight (CBB) can be done with visual evaluations of symptoms to distinguish broad resistance classes, but a more quantitative measure was needed for genetic studies of resistance. A novel method of evaluation was developed by quantifying Xanthomonas campestris pv. phaseoli (XCP) in bean leaf tissue infected with CBB using a 32P-labeled probe and densitometric analysis of hybridization signals. Quantification of bacterial populations using the probe was highly correlated (r=0.98) with the number of colony forming units (CFU) from plate counts of the same leaf samples. The probe was used to follow XCP population dynamics on susceptible (BAT 41) and resistant (OAC 88-1) bean genotypes. OAC 88-1 supported a maximum XCP population which was approximately tenfold less than BAT 41. The probe was also used to study an F2/F3 population segregating for resistance. Narrow sense heritability estimates were less for resistance measured on the basis of bacterial populations (0.18–0.26) than on visual scores of symptoms (0.29–0.38). The anticipated response to selection for CBB resistance would be less based on bacterial numbers than based on symptom expression in this population. In breeding for resistance to CBB, selection based on visual symptoms combined with measurements of XCP populations using a DNA probe can be used to develop bean genotypes that are both resistant to symptom development and bacterial multiplication.

Lightning common bean

Lightning is an upright short vine (type IIa) white bean (Phaseolus vulgaris L.) cultivar intended for use in areas with greater than 2600 crop heat units. It has excellent yield potential in either wide or narrow row production and is resistant to races 1 and 15 of bean common mosaic virus. Seed has high cooking and canning quality. Key words: Phaseolus vulgaris L., white bean, common bean, cultivar description

OAC THUNDER COMMON BEAN

OAC Thunder is an indeterminate bush white bean (Phaseolus vulgaris L.) cultivar intended for use in areas with greater than 2600 crop heat units. It has excellent yield potential in either wide or narrow row production and is resistant to races 1 and 15 of bean common mosaic virus. Seed has acceptable cooking and canning quality. Key words: Phaseolus vulgaris L., white bean, common bean, cultivar description

OAC Derkeller common bean

OAC Derkeller (CFIA registration no. 6594) is a determinate bush dark red kidney bean (Phaseolus vulgaris L.) cultivar with early maturity and good yield potential. Seed has good cooking and canning quality.Key words: Phaseolus vulgaris L., kidney bean, common bean, cultivar description

Early generation testing of common bean (Phaseolus vulgaris L.) populations in sole crop and in maize/bean intercrop

Few plant-breeding studies have examined methodology for improving common bean (Phaseolus vulgaris L.) yields by selecting in an intercrop situation. We hypothesized that early-generation testing would be as useful in a maize (Zea mays L.)/bean intercrop as in sole crop for identifying superior bean populations for yield. F2 to F5 bulks of six selected crosses and their F5-derived advanced lines were evaluated in sole crop or intercrop. The F2 and F5 bulks were evaluated together in a preliminary trial in one location, while the advanced lines were evaluated with the F3s in one location, and with the F4s in two locations. Within sole crop, selection of the best three populations, based on F2 performance, provided 67% of the top advanced lines. The rank correlation between average bulk yield across generations and the average line yield was positive and significant. Within intercrop, selection of the best three populations provided 56% of the top advanced lines. The rank correlation between advanced line y...