Mark J. Bassett

Efficient detection of asparagus monoploids for the production of colchiploid inbreds

SummaryAn experiment was conducted to develop a method for monoploid seedling detection which is more efficient than making cytological examinations of twin seedlings. A recessive seedling marker gene (basal stem color) was used to detect parthenogenesis in female plants. Out of 10 seedlings showing the marker character, 9 were monoploid as expected. The frequency of parthenogenesis among single seedlings was approximately 1 seedling in 2,400. The marker gene technique increases the efficiency of cytological examination from approximately 1 or 2% to 90%.

A procedure for combining a quantitative inheritance study with the first cycle of a breeding program

SummaryThe number of effective factors controlling the inheritance of a quantitative character can be estimated by analysis of F3 lines where the parental lines are homozygous. The procedure is illustrated with data from a study of pod length inheritance in common bean (Phaseolus vulgaris L.). The mean pod length of ‘Sprite’, the parent with longer pods, was compared statistically with the means of F3 progenies derived from F2 plants obtained from the appropriate tail of the F2 frequency distribution for pod length. The data indicate that analysis of F3 progenies avoids much of the underestimation of the effective factor number which is characteristic of other procedures. The number of effective factors was estimated to be a minimum of 4 and the correlation between random F2 parents and F3 progeny means was r=0.82.

Inheritance of the virgata pattern of partly colored seed coats in 'Early Giant' common bean

The inheritance of the virgata pattern of partly colored seed coats found in common bean (Phaseolus vulgaris L.) ‘Early Giant’ (EG) was studied by a series of test crosses with line 5-593 and genetic stocks developed by backcrossing selected genes into the recurrent parent 5-593, a Florida dry bean breeding line with a self-colored, black seed coat with genotype T Z Bip P [C r] J G B V Rk. Analysis of the F2 from the cross EG × 5-593 led to the hypothesis that the virgata pattern of EG has genotype t z bipvgt, where vgt stands for virgata. The test cross EG × t z virgarcus BC3 5-593 confirmed the hypothesis that EG carries t z from data recorded in F1, F2, and 27 F3 progenies from randomly selected F2 plants. The F3 segregation was also consistent with the hypothesis that a single recessive gene converts virgarcus into virgata. The test cross EG × t z bip bipunctata BC3 5-593 failed to show genetic complementation in F1 progeny, and the F2 segregated 3:1 for the parental phenotypes virgata and bipunctata, respectively. Including previously published data, all possible crosses were made among bipunctata, virgata, and virgarcus parents, supporting a multiple allelic series at Bip. We propose the gene symbol bipvgt for the new allele at Bip, where the allelic series has the order of gene dominance Bip > bipvgt > bip. Based on test crosses, the complete seed-coat color and pattern genotype of EG is tz bipvgtP [C r] J G B vlaerkd.