J Hered (1959) 50 (5): 233-237.
Shigemi Honma and Otto Keeckt*
* Michigan Agricultural Experiment Station. Journal Article Number 2371.

Figure 13
A—Shows mature leaves of Phaseolus lunatus; B— those of P. vulgaris.

WITHIN Phaseolus vulgaris there is need for a snap bean combining green cotyledons with a green seed coat color. Various intravarietal crosses have yielded light green seed coat progenies, but none with green cotyledons. The cross between P. vulgaris and P. lunatus, a lima bean, was attempted to combine a darker green seed color with green cotyledon in the snap bean.

Interspecific crosses in the genus Phaseolus have been reviewed elsewhere3. Since then, however, Rudorf6 reported a successful cross using P. coccineus as maternal parent with P. vulgaris. Numerous investigators have previously reported the reciprocal cross. Wall7 reported the use of intervarietal F1 hybrids of one species crossed with a "pure" variety of another was slightly superior to the best variety X variety in obtaining interspecific crosses of P. vulgaris X P. coccineus. Successful interspecific crosses involving the species P. vulgaris X P. lunatus to the writer's knowledge have not been reported, although Kooiman4 reported attempts of crosses were made without success.

The findings reported here are, of necessity, limited since large populations are difficult to obtain from a small number of interspecific hybrids.

Parental Description

Numerous varieties of P. vulgaris and P. lunatus were used in the investigation without success. Since no crosses resulted from using pure strains, intraspecific F1 plants of P. vulgaris, (Contender X Blue Lake) F2 X (Kentucky Wonder Contender) F2 and the intraspecific F2 plants of P. lunatus Fordhook X Clark's Bush selection were used.

Morphological differences in characters of these two species are illustrated in Figures 13-15 and Table I. The measurements of leaf shapes were taken from field-grown plants. The primary leaves of the lima are darker green in color with distinct veining as compared to indistinct veining and lighter green color of the snap bean. The length of the petioles of the primary leaves are longer in the lima bean than in the snap bean.

Figure 14
A—Phaseolus vulgaris with round to oval and slender pods with long spurs; B—P. lunatus with short flat pods and short spurs.

The flowers of P. lunatus differ from the snap bean in shape as well as color of the floral part. In the snap bean the banner is either white or colored as the rest of the floral parts while in the lima the banner is of a different color from the wings, usually greenish-yellow with a purple tinge. Flowers in the common bean are borne on ends of short peduncles in a close aggregate of clusters, while flowers in the lima bean are borne in racemes at the ends of long peduncles.

The pod of the lima bean is large, thick, broad, and heavy about three to five inches long. Pod margins are thick and have a short, stout, blunt beak, and a spur located to the side of the apex. (Figure 14). Pods of the common bean are slender, straight, or curved, flat or oval in cross section. The pod length ranges from four to eight inches with a prominent beak.

The seeds of P. lunatus are flat or thick, and oval with a more or less conspicuous line radiating from the hilum. Seeds of P. vulgaris are elliptical in cross section and kidney shaped. (Figure 15).

Parental differences noted are similar to that described by Freeman1 and Hedrick2 for these two species.


Methods used in pollination were similar to those described by the authors in a previous paper3. An unrecorded number of pollinations using several varieties of the two species set pods but generally aborted within seven days. A few remained longer, but no seed developed in the pods. Species hybridization was attempted using heterozygous parental plants. Numerous pollinations using P. vulgaris as the female parent yielded two pods with mature seeds. Ten seeds resulting from the cross were grown in the greenhouse. Numerous reciprocal crosses were attempted using pure and heterozygous plants but no pod development occurred.

TABLE 1. Comparison of true differences between segregates end parents for mature terminal end lateral leaves

Leaflet Phaseolus vulgaris Phaseoluslunatus Segregate Range P*
  Average Average Average    
Terminal: length 8.26 ± 1.22 mm 12.86 ± 1.73 min 12.87 ± 2.29 mm 6.25 - 19.00 mm .01
  width 6.42 ± 1.38 mm 7.28 ± 1.02 mm 8.20 ± 2.11 mm 2.45 - 12.57 mm .34
Ratio: length/width 1.31 ± .17 1.77 ± .12 1.66 ± .52 1.30 - 4.53 .68
Lateral: length 7.60 ± 1.57 mm 11.54 ± 1.88 mm 10.73 ± 1.94 mm 4.55 - 15.60 mm .09
  width 5.75 ± 1.72 mm 6.63 ± 0.96 mm 7.20 ± 1.97 mm 1.90 - 10.77 mm .45
Ratio: length/width 1.33 ± .09 1.74 ± .14 1.59 ± .56 1.80 - 4.87 .75
*Possibility of true difference between segregate and P. vulgaris.


Figure 15
Figure 16
Seeds of Phaseolus lunatus (A) and P. vulgaris (B) are shown above. Seed shape of the F1 (C) are intermediate between the two parents.   Seed shapes and sizes in the segregating generation are shown above.

F1 Hybrid Characteristics

The F1 seedlings together with the parental plants were grown in pots in the greenhouse. The seeds were germinated in a quartz sand medium. As soon as the radicle was approximately one inch in length the seedlings were transplanted to pots of soil. All seedlings reached maturity. Eight of the 10 F1 hybrids were morphologically similar to the P. vulgaris parent with varying degrees of self-fertility. Pod and seed shape of the F1 plants were intermediate between the two parents. (Figure 15). Two of the progenies were of willow leaf types and were sterile.

Characteristic, of the F1 Generation

Since only a limited number of seeds were obtained from the hybrid plants, notes and illustrations were made from F2 and F3 plants. The 112 progenies from the hybrids with the parents were grown in pots in the greenhouse.

Measurements of mature leaf parts were made from 200 F2 hybrids and the probability of true difference between the hybrid and P. vulgaris are shown in Table I. A difference in length of terminal leaves between hybrids and P. vulgaris parent is suggested. The P value of .09 for the lateral leaves is suggestive of a difference between the P. vulgaris parent and the segregated material. It is of interest to note from the table, the range in leaf sizes obtained from the segregating population. Observations on leaf shape of the F2 population were similar to that noted in the F3 population and a representative sample is illustrated in Figure 17.

Variations in mature pod shapes are obvious in Figure 18. Recombination of spur types and pod shapes can be noted. Variations in spur lengths and pod shapes suggest polygenic inheritance for these characters. Seed shapes and sizes are shown in Figure 4. A recombination of colors was noted in the population. The appearance of these colors was expected since heterozygous plants were used to obtain the cross. No attempt was made to factorily analyze the color, shape, or size inheritance. Only one plant yielded a light green seed coat color.

Fertility of the progenies varied as indicated from normal set to no set. Sterile types were generally associated with the crinkle, narrow or willow leaf, virescent plants. Plants with lanceolate leaves, in most cases, failed to survive. These plants died at various stages up to the time of flowering. Few obvate-lanceolate leaf plants dropped their leaves after pod set and failed to produce viable seeds. The amount and degree of floral development of the progenies appeared to be associated with leaf type, i.e., a larger number of normal flowers were produced as the leaf shape approached ovate or normal types. Similar observations were made by Lamprecht5. No cytological studies were made to relate the anomalies observed to chromosome deletions as suggested by Lamprecht5.

Plant types observed ranged from the lima bean type to common bean types. No parental types were recovered from the F2 or F3 populations.


Success in crossing the parents to the interspecific hybrids varied. Some of the hybrid plants crossed readily to both parents while others failed to set pods. Backcrosses to P. lunatus resulted in viable seeds, however, and both normal and abnormal plants also resulted. Crosses with P. vulgaris parents resulted in viable seed with fewer abnormal plants than backcrosses with P. lunatus. Anomalies observed were similar to those found in F2 and F3 populations.

Backcrosses of the F1 plants, to the P. lunatus parents were not as successful as when P. vulgaris plants were used. Only a small number of backcrosses were obtained with P. lunatus.

Figure 17
The various leaf types in the segregating generation are shown above.


Figure 18
Hybrid pod shapes are shown above. Note recombination of size and shape of both parents in the segregating generation.



The data and figures demonstrate that a hybrid was secured between P. vulgaris and P. lunatus. It is apparent that the use of gametic diversity aided in making the interspecific cross. Although the lima bean parent failed to carry the desired characteristic green seed coat and green cotyledon in the initial cross, a segregate was found with light green seed coat color. The desired characteristics can be transferred readily by crossing the segregant with a lima bean possessing green seed coat and cotyledons as demonstrated by the backcross to the hybrid.

In the F2. as well as in the F3 no parental types were recovered although a few approached the P. vulgaris type. It is of interest to note the association of the lethal character with willow leaf type plants and the age of the plant. This observation was also noted in the backcross F2 and F3 populations.


Numerous crosses using heterozygous parents of P. vulgaris and P. lunatus made it possible to obtain 10 hybrid plants. Eight hybrid plants were similar to the P. vulgaris plants while two others failed to resemble any of the parents and appeared as willow-leaf sterile plants. The fertility of the eight plants ranged from low to normal. Backcrosses of both parents to the hybrid were made with little difficulty. Segregation for leaf type, seed and pod shape were noted in the F2 and F3 populations. Variations in the characters suggest a quantitative type of inheritance.

Literature Cited

  1. FREEMAN, G. F. Southwestern beans and teparies. Arizona Agr. Expt. Sta. Bul. 68. 1912.
  2. HEDRICK, U. P. The Beans of New York. J. R. Lyon Co. Albany. 1931.
  3. HONMA, S. and OTTO HEECKT. Bean interspecific hybrid involving Phaseolus coccineus and P. lunatus. Proc. Amer. Soc. Hort. Sci. 72:360-364. 1958.
  4. KOOIMAN, H. N. Monograph on the genetics of Phaseolus. Biblio. Genetica 8:296-409. 1931.
  5. LAMPRECHT, H. Die artgrenze zwischen Phaseolus vulgaris and Phaseolus multiflorus. Lam. Hereditas 27:51-175. 1941.
  6. RUDORF, WILHELM. New beobachtungen an bastarden von Phaseolus vulgaris x Phaseolus multiflorus and P. multiflorus x P. vulgaris. Proc. 9th Internat. Cong. Genetics. 844-845. 1953.
  7. WALL, J. R. Interspecific hybridization on Phaseolus and in Cucurbita. I. Gametic diversity as an aid to interspecific hybridization in Phaseolus  and Cucurbita. II. Recombination in species crosses in Phaseolus and Cucurbita. Diss. Abstr. 16:436. PubI. No. 15609. 1956.

Beans Biblio