Inheritance of Bush Habit in Cucurbita pepo L.

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Cucurbit Genetics Cooperative Report 11:70-71 (article 30) 1988

Y.H. Om, D.G. Oh, and K.H. Hong
Vegetable Division I, Horticultural Experiment Station, Suweon 170, Korea

Bush growth habit in squash isAvery important character for dense planting, especially under the plastic house cultivation. Toi breed bush-type pepo cultivars for the cultivation, it is an essential step to investigate the inheritance of the bush habit.

Several researchers reported the inheritance of bush-type in C. pepo (1, 3, 4) and C. maxima (1, 2), which include some controversial results., It was generally recognized that the bush character is almost completely dominant during the early growth stage, and recessive or incompletely dominant during the late growth stage.

In Cucurbita pepo L., the bush-type variety ‘Zucchini’ was crossed with the vine-type ‘PI 285611’. The inheritance of bush habit was studied in F2 and BC1F1 populations. The length of main stem was measured in the three different growth stages; early, middle, and late stages.

The frequency of distribution of vine length in each stage is presented in Fig. 1. The mean of the F1 hybrid population leaned slightly toward the vine, but it was always below the mid-parent value. The segregation ratios of the F2 and BC1F1 populations were 3:1 and 1:1, respectively, with the bush partially dominant to the vine regardless of the growth stages. The segregation ratios were accepted at the 10 to 50 percent level of probability (Table 1). The result obtained almost agreed with Shifriss (4), but was somewhat different from the others (1,2,3).

In conclusion, the characteristic feature of the bush gene action was partial dominance. The degree of dominance lessened as the growth proceeded.

Table 1. Segregation of bush and vine types in the 3 different growth stages in the F2 and BC1F1 populations from the cross ‘Zucchini x PI 285611.

Date

Generation

No. of plants

Expected ratio

X2-value

P
Bush
Vine
June 10 F2 199 79 3:1 1.731 0.10 – 0.25
BC1F1 78 82 1:1 0.1 0.75 – 0.90
July 6 F2 201 77 3:1 1.079 0.25 – 0.50
BC1F1 77 81 1:1 0.101 0.75 – 0.90
August 5 F2 197 76 3:1 1.173 0.25 – 0.50
BC1F1 65 77 1:1 1.014 0.25 – 0.50

 

Figure 1. Frequency distribution of vine length at the 3 different growth stages in the F2 and backcross populations from the cross, Zucchini/PI 285611. The means of parents (P1, P2) and F1 populations are indicated as black and open circles, respectively.

Figure 1, 2, & 3

Literature Cited

  1. Denna, D.W. and H,M. Munger. 1963. Morphology of the bush and vine habits and the allelism of the bush genes in cucurbita maxima and C. pepo squash. Proc. Amer. Soc. Hort. Sci. 82:370-377.
  2. Singh, D. 1949. Inheritance of certain economic characters in the squash, Cucurbita maxima Duch. Minn. Expt. Sta. Tech. Bul. No. 186.
  3. Sinnott, E.W. and G.B. Durham. 1922. Inheritance in the summer squash. J. Heredity 13:177-186.
  4. Shifriss, O.W. 1947. Developmental reversal of dominance in Cucurbita pepo. Proc. Amer. Soc. Hort. Sci 50:330-346.