Opaque globules formed on bean callus induced on primary leaf explants cultured on induction media (IM) containing 10 to 30 mg/l 2,4-D. Calli with globules produce structures reminiscent of somatic embryos (embryoids) after subculture in a liquid challenge medium (LCM). Calli maintained on IM for 2, 3, 4, and 5 weeks produced significantly more (26 to 34/callus) embryoids in LCM than calli maintained on IM for one week (12/callus). Well developed embryoids only occurred after calli were subculture in liquid B5 with 0.1 to 1.0 mg/l IBA. Calli subculture in LCM with > 10 mg/l IBA turned necrotic and died. Embryoids produced in B5 with 2,4-D and NAA (0.1 to 1.0 mg/l) proliferated roots and formed “frosty” appearing structures, respectively. No differences were detected in number or quality of embryoids produced in LCM from callus maintained on IM in continuous light or darkness regardless of the induction time. Ethylene accumulation in IM cultures inhibited globule formation.
R. A. Hoyos and G. L. Hosfield
N.N. Wassimi, G.L. Hosfield, and M.A. Uebersax
Culinary quality in dry bean (Phaseolus vulgaris L.) depends on attributes of seeds prevailing at harvest and is determined by the genetic architecture of cultivars and by unpredictable environmental factors. Variation among genotypes for culinary quality has been shown to be heritable; however, the efficacy of selection depends on a knowledge of the genetic control of the measured traits. A diallel mating design was used to estimate the combining ability of parents and determine the inheritance of nine culinary quality traits important to processors and consumers. Genetic variability among eight parents, 56 F2, and 56 F3 progenies was confirmed by significant mean squares from analyses of variance. Significant variability detected between F2 and F3 progenies for soaked bean weight (SBWT), soaked bean water content (SBWC), and clumps (CLMP) was due to inbreeding effects. General combining ability (GCA) components were highly significant and overshadowed specific combining ability (SCA) components in the F2 and F3 for SBWT, SBWC, split beans (SPLT), and the washed-drained weight coefficient (WDWTR), indicating that additive variance predominated. Ratios of GCA: SCA components were equal to or less than unity for CLMP, washed-drained weight (WDWT), and texture (TEXT), indicating that both additive and nonadditive effects contributed to trait expression. Significant SCA effect variances were noted for `Sanilac', `San Fernando', `Nep-2', and `A-30' for WDWT and TEXT, implying that progeny from crosses of these parents had higher or lower mean values for the traits titan the average expected on the basis of GCA. Graphs of the regression of Vr on Wr showed that genes controlling WDWT and TEXT were completely dominant in most cases. Recurrent selection, which seeks to concentrate favorable alleles with additive effects in populations, may he an effective breeding procedure to improve the culinary quality of dry beans. It is not feasible to breed for TEXT and WDWT simultaneously because of a negative correlation between the traits.
J.D. Kelly, G.L. Hosfield, E.G. Ernest, J. Taylor, M. Uebersax, and G.V. Varner
M.C. Posa, J.D. Kelly, G.L. Hosfield, and K.C. Grafton
Two recombinant inbred populations of kidney beans were developed and evaluated for canning quality. One population, composed of 75 recombinant inbred lines (RILs), was from a Montcalm/California Dark Red Kidney 82 cross. The second population, with 73 RILs, was from a Montcalm/California Early Light Red Kidney cross. RILs from both populations were planted in North Dakota in 1996 and Michigan in 1996 and 1997. Beans of each RIL were thermally processed using established procedures. Appearance and degree of splitting of each sample and the check varieties were scored subjectively on a 1-7 scale to represent the minimum and maximum acceptability levels of the traits, respectively. Genotypes and genotype × environment interactions were highly significant based on analyses of variance. In the 75 RIL population, seven lines, based on appearance, consistently appeared in the top 25% in all environments (mean = 4.5; range = 4.0-6.1), and four had consistently high acceptability scores (mean = 4.6; range = 4.0-6.3) for the degree of splitting trait. In the population with 73 RILs, nine lines consistently appeared in the top 25% in all environments based on appearance (mean = 4.6; range = 4.1-5.3). For degree of splitting, nine lines had consistently high acceptability scores (mean = 4.2; range = 3.7-5.1). Appearance and splitting of cooked dry bean are quantitatively inherited traits. The field experiments were useful to obtain RILs for screening to identify molecular markers associated with QTLs. Three primers—OQ11, ON186, and OF5—reported to be useful RAPD markers for processing quality in navy beans are of special interest in the current study.