M. W. Adams

Evaluation of common bean cultivar relationships by means of isozyme electrophoretic patterns

SummaryElectrophoretic isozyme technique was applied on primary leaf, stem, and root tissues from seedlings of 34 U.S. major common bean (Phaseolus vulgaris L.) cultivars belonging to 19 commercial classes (Great Northern, Kidney, Navy, Pinto, Red Mexican, Tropical Black, California Small White, Idaho Flat Small White, Pink, and Cranberry). Among the isozyme systems studied, peroxidase (PER) and esterase (EST) were found to be suitable for cultivar identification within most commercial classes and for estimating the genetic relationships among the cultivars of the same class or among the classes. Acid phosphatase (PHOS), due to high proportions of monomorphic bands, could not be considered a good system for such purposes. Within each isozyme system, no pattern was found to be exclusive to any particular commercial class.Based on the number of polymorphic bands in common between each cultivar pair, a banding-similarity index was calculated. The indices were found to be highly significantly correlated with genetic distances obtained by Principal Component Analysis (PCA). In those comparisons where a pedigree relationship could be calculated, a non-significant correlation with similarity indices was obtained. Certain cultivar pair relationships, a minority of the whole, were incorrectly predicted by the isozyme technique. Caution is indicated when this technique is the only basis of assigning relationship. In a few cases, the similarity indices pointed either to close genetic relationships or the lack of such relationships, whereas the reverse is known from pedigree or PCA distance estimates. The reason for such discrepancies is discussed.Some isozymes were unique to a certain tissue, while others were present in more than one. Upon the compilation of bands from all the cultivars, for the leaf, stem, and root tissues respectively. 6, 4, and 0 EST, 9, 10, and 8 PHOS, and 7, 6, and 7 PER bands were obtained.

An electrophoretic survey of seedling isozymes in several Phaseolus species

SummaryStarch-gel electrophoresis was used to study esterase, acid phosphatase, and peroxidase isozyme patterns in the primary leaves, stems, and roots of 13 species within the genus Phaseolus (P. acutifolius, P. adenanthus, P. angularis, P. atropurpureus, P. aureus, P. bracteatus, P. calcaratus, P. lathyroides, P. mungo, P. ricciardianus, domestic P. vulgaris, and wild P. coccineus and P. vulgaris). Most species showed unique banding patterns in each isozyme system. However, a close similarity in banding patterns was observed for the domestic P. vulgaris, wild P. vulgaris, and wild P. coccineus indicating close genetic relationships, possibly through species introgression or common descent.Great differences in isozyme patterns were found for different tissues from the same species in all systems indicating the high tissue specificity of isozymes. Upon compilation of bands from all the species, a very large number of isozymes were obtained in each system or tissue, making the electrophoretic isozyme technique of high potential in studies of isozyme variants in this genus.

An estimation of homogeneity in crop plants, with special reference to genetic vulnerability in the dry bean, Phaseolus vulgaris L.

SummaryA general method of quantitatively assessing genetic similarity among a set of cultivars of a given crop is proposed, and its application to dry beans in the United States is demonstrated. The method is based upon the multi-variate technique of Principal Components Analysis. Using this method it was possible to calculate a ‘distance’ metric between any two cultivars in the set and to show that such distances were highly inversely correlated with genetic relationship estimated from a knowledge of breeding ancestry.On the basis of distances among cultivars within given production regions (states in the US in this case) and knowledge of the acres of each cultivar grown in the region, an average weighted distance metric appropriate to each was calculated. Each derived distance metric serves as an index of ‘genetic homogeneity’ for the crop in that region. Arguments are presented for relating the degree of vulnerability to a disease epidemic to the distance index. Indexes are calculated for nine of the major bean producing states in the US from which it is concluded that, from the standpoint of genetic vulnerability, Colorado is most vulnerable and California least vulnerable to a region-wide epidemic affecting the bean crop. It is suggested that the method demonstrated here is of nearly universal applicability, and particularly meaningful with respect to self-fertilizing crops.

A factor analysis of plant variables associated with architecture and seed size in dry bean

SummaryA knowledge of the biological and functional relationships among traits would be of benefit to plant breeders in the choice of traits to use for increasing efficiency of selection in a breeding program. Principal factor analysis was used to identify biological and functional relationships among dry bean (Phaseolus vulgaris L.) traits in segregating populations of a phenotypic recurrent selection program designed to introduce upright architecture into medium-sized dry bean.Two biological interpretations were assigned to factors extracted in the analysis of four seed/pod traits. The first was a size factor, loaded with seed weight and pod width, and the second a number factor, which was loaded with number of seeds per pod and pod length. Similarly, three factors were extracted from the analysis of fifteen architectural traits. The first factor was interpreted as an elongation factor, and was loaded with internode length measurements, while the second factor was interpreted as a structural factor, and was further divided into two subclasses namely, sturdiness factor and profile factor. The sturdiness factor comprised hypocotyl diameter and hypocotyl length, while the profile factor comprised branch angle and number of basal branches. The third factor which was called a reproductive factor was loaded with pod distribution traits and the number and location of nodes on which pods were borne.

Secondary tillage and traffic compaction modifications of the growth and production of dry edible beans and soybeans

Tillage related soil compaction can reduce crop growth and productivity. Although secondary tillage is applied to soils to improve the contact between seeds and soil, little is known regarding the adverse effects of excessive secondary tillage and wheel traffic on plant growth and productivity. This study addressed the influences of three levels of secondary tillage on soil porosity and the establishment, growth, and yield of dry edible beans (Phaseolus vulgaris L.) and soybeans (Glycine max L.) on clay (fine, illitic, calcareous, mesic, Aeric Haplaquept) and loam (fine-loamy, mixed, nonacid, mesic, Mollic Haplaquept) soils. Soil porosities were significantly affected by the secondary tillage and traffic treatments to a depth of 15 cm (6 in.) for both soil types. Dry edible bean plants were more susceptible to the tillage and traffic compaction than soybeans. Emergence, plant dry weight, final plant population, and yield of dry beans were reduced by the excessive secondary tillage treatments.

Expected correlated responses in selecting dry beans for tolerance to soil compaction

SummaryParents and F2 progenies of an 8×8 diallel cross were grown under non-compacted and compacted soil conditions. Soil compaction reduced yield, pods per plant, and seeds per pod; however, an increase in seed wieght and no effect for pod length were observed. With the exception of pods per plant, the remaining traits had larger genetic variances under non-compacted soil conditions. Phenotypic correlations involving yield and related traits were similar under the two conditions. Tolerance to soil compaction and mean performance over the two soil conditions were defined. Genetic correlations in terms of: (1) the ratio of genetic variances under the stress and non-stress conditions, and (2) the correlation between performance under the two conditions, were calculated and discussed.