A Hunter Color Difference meter and a white-paint color chart were used to determine the degree of whiteness among 8 white-seeded Great Northern (GN) cultivars of Phaseolus vulgaris. A correlation coefficient of +0.84 was found between the 2 methods. The former method provided better separation of cultivars for degrees of whiteness than the latter method. Two genetic studies were conducted, with seed-coat whiteness determined by use of the white-paint color strip. ‘GN Emerson’ had the whitest seed-coat. The inheritance of seed-coat whiteness was investigated in 1978 using parents, F2s of the crosses Plant Introduction (PI) 165078 (bright white) with ‘GN Emerson’ (moderately bright white), ‘GN Valley’ (dull white) and ‘GN UI 59’ (dull white) and in the reciprocal cross ‘Bulgarian White’ (brightest white) × ‘GN UI 59’ (dull white). A quantitative pattern of inheritance was observed. Broad sense heritability estimates for this trait ranged from 46 to 57%. The Gardner and Eberhart model, Analysis II, was used in 1979 to estimate genetic effects for the trait in a 6 parent diallel cross involving ‘GN Emerson’, ‘GN UI 59’, ‘Bulgarian White’, ‘GN Star’ (dull white), ‘GN 1140’ (dull white) and ‘GN D-88’ (dull white). Additive genetic effects were predominant; but heterosis effects were also important, including significant effects for specific combining ability, and reciprocal crosses. ‘Bulgarian White’ showed high combining ability for brighter whiteness. The genetic data indicate that improvement of seed-coat whiteness in dry beans should be relatively easy to accomplish.

Variations occurred in the rate of water uptake of seeds of different dry bean cultivars (Phaseolus vulgaris L). ‘Pinto UI11’ had a higher water uptake by 24 hours than the other 6 cultivars. The micropyle was the main site for water entry in white-seeded ‘Great Northern’ and it is inferred that the raphe and or hilum areas were mainly involved in water uptake in ‘Pinto UI11’. No water uptake through the seed coat of seeds of 7 cultivars occurred by 2, 4, or 8 hours and only a small amount by 24 hours, except ‘GN Star’ where no water uptake was noted indicating that it had an impermeable seed coat during that period.

Seed-coat cracking injury was determined in Great Northern (GN) dry bean lines in 1977, 1978 (also Pintos in 1978) using 3 methods as follows: Vogel small plot thresher (field), seed dropping, and a controlled rotating impact disk machine. Differences in susceptibility for seed-coat cracking were observed within each testing method. Overall, ‘GN Emerson’, near-isogenic determinate ‘GN Nebraska #1’ and ‘Pinto UI 111’ had the best resistance to seed-coat cracking. A genotype × year interaction for seed injury occurred with the Vogel thresher but not with the other 2 methods. The other 2 methods gave consistent results but the rotating disk machine method was preferred because of ease, rapidity of operation and standardization of the rotation speed. The early and late maturing determinate near-isogenic lines of ‘GN Nebraska #1’ had less seed-coat injury than the early and late indeterminate lines using the Vogel and rotating impact disk method. The early determinate line had the least amount of seed-coat injury for all three methods. ‘Pinto UI 111’, ‘Bulgarian White’, and ‘GN D-88’, which exhibited the best resistance to seed-coat cracking in the 7 parent diallel crossing study, had the most uniform seed-coat thickness as well as having thick seed coats. The cultivars which had thin or thick but non-uniformly thick seed coats were susceptible to seed-coat cracking. Differences in thickness in macrosclerid, os-teosclerid and parenchyma cell layers of the seed coat were observed between cultivars, but no relationship between these cell layers and the seed-coat cracking response was established. Seed-coat cracking was quantitatively inherited. ‘Bulgarian White’, ‘Pinto UI 111’ and ‘GN D-88’ showed high combining ability for resistance to seed-coat cracking. The estimates of the genetic effects indicated that additive effects were mainly involved.