Relationship Between the B Genes of Two Cucurbita Species, IV.

Cucurbit Genetics Cooperative Report 13:55-57 (article 22) 1990

Oved Shifriss
21 Walter Avenue, Highland Park, NJ 08904

Raymond B. Volin and Tom V. Williams
Northrup King Co., 10290 Greenway Rd., Naples, FL 33962

This report provides data on the inheritance of precocious depletion of chlorophyll in C. moschata based on the cross NJ-B x IL-B (see Table 1 in the preceding report). The data were obtained in Naples, Florida, during the past three growing seasons. The spring and fall data of 1989 are presented in Tables 1 and 2 respectively. The combined data for the three seasons, including fall of 1988, are presented in Table 3.

The focus in classification is on the effects of two “precocious” genes on ovaries and stems. The genetic basis for the myriad effects of these genes on leaves, in response to environmental variations, requires a separate analysis.

With the exception of one baffling case (F₂ from clone NOMP, Table 1; see also Table 3, test #5), the data agree with the hypothesis that the two “precocious” genes are non-linked (see Table 2 as well as Table 3, tests #4 and 6).

In addition to the total of 306 F₂ plants in Table 2, there were 12 F₂ individuals of doubtful phenotypes. These were listed in our notebook as unclassified. Of the 12, one plant, 807-34, was tentatively described as having green stems and bicolor fruits. The bicolor fruits were of the type we usually associate with plants heterozygous for the “precocious” gene of C. maxima. Nevertheless, there was a lingering doubt about the genetic basis for the bicolor fruits.

Breeding tests of plant 807-34 (or tests of other similar plants) should reveal its genotype. Any one of the following three answers is conceivable. (a) Plant 807-34 was heterogygous for the “precocious” gene of C. pepo. (b) It was a cross-over product involving the “precosious” gene of C. maxima. (c) It was heterozygous for the “precocious” gene of C. maxima, but carried elements that selectively switch one of the dual effects of this gene from dominant to recessive expression. At present we incline to believe that the third answer (c) is the correct one.

Table 1. Inheritance of chlorophyll depletion in C. moschata. Field data, spring 1989, Naples, Florida.

	Phenotypic Classes				X²
	PDC-O or GOTy	PDC-O	GO		F2
	PDC-S	GS	GS		12:3:1
	PDC-P or GB	GP	GP		Testcross
Breeding Materialsz	PDC-B or GB	GB	GB	Total	2:1:1	P
P1, NJ-B	0	5	0	5	–	–
P2, IL-B	5	0	0	5	–	–
F1, P1 x P2	20	0	0	20	–	–
F2
from clone MP	167	37	15	219	0.5738	0.70-0.80
from clone NOMP	124	47	4	175	10.9353	0.001-0.01
Testcross
F1 x Black Line	74	27	49	150	6.4800	0.02-0.05
F1 x ‘Butterbush’	54	26	30	110	0.3273	0.80-0.90

^z The description of the breeding materials is given in Table 1 of the preceding report.
^y The key to phenotypic symbols is given in the text of the preceding report.

Table 2. Inheritance of precocious depletion of chlorophyll in C. moschata. Field data, fall 1989. Naples, Florida.

	Phenotypic Classes				X²
	PDC-O or GOTy	PDC-O	GO		F2
	PDC-S	GS	GS		12:3:1
	PDC-P or GP	GP	GP		Testcross
Breeding materialsz	PDC-B or GB	GB	GB	Total	2:1:1	P
P1, NJ-B	0	5	0	5	–	–
P2, IL-B	5	0	0	5	–	–
F1, P1xP2	10	0	0	10	–	–
F2
(a) from F1 plant 153-2	88	18	9	115	1.0812	0.50-0.70
(b) from F1 plant 153-8	75	15	8	98	1.2245	0.50-0.70
(c) from F1 plant 154-1	65	19	9	93	2.2115	0.30-0.50
F2 pooled	228	52	26	306	3.0729	0.20-0.30
			Heterogeneity		1.44	0.80-0.90
Testcrosses
(a) 153-2x Black Line	24	9	15	48	1.5000	0.30-0.50
(b) 153-8x Black Line	31	9	9	49	3.4489	0.10-0.20
(c) 154-1x Black Line	27	14	9	50	1.3200	0.50-0.70
Testcrosses pooled	82	32	33	147	1.9796	0.30-0.50
			Heterogeneity		4.29	0.30-0.50

^zThe description of the breeding materials is given in Table 1 of the preceding report.
^yThe key to phenotypic symbols is given in the text of the preceding report.

Table 3. Inheritance of precocious chlorophyll depletion in C. moschata. Summary of field data from fall 1988 to fall 1989, Naples, Florida.

		Phenotypic Classes
		PDC-O or GOTy	PDC-O	GO
		PDC-S	GS	GS
	Breeding materialsz	PDC-P or GP	GP	GP
Test	Generations & growing seasons	PDC-B or GB	GB	GB	Total
1.	P1, NJ-B: Fall ’88, Spring ’89, Fall ’89	0	22	0	22
2.	P2, IL-B: Fall ’88, Spring ’89, Fall ’89	22	0	0	22
3.	F1, P1xP2: Fall ’88, Spring ’89, Fall ’89	48	0	0	48
4.	F2:
	(a) from clone MP, Fall ’88	162	34	18	214
	(b) from clone MP, Spring ’89	167	37	15	219
	(c) from new F1 plants, Fall ’89	228	52	26	306
	F2 of test 4 pooled	557	123	59	739
		X2	df	P
	Deviation (12:3:1)	5.32	2	0.05-0.10
	Heterogeneity	1.00	4	0.90-0.95
5.	F2 :
	(a) from clone NOMP, Fall ’88	96	25	1	122
	(b) from clone NOMP, Spring ’89	124	47	4	175
	F2 of test 5 pooled	220	72	5	297
		X2	df	P
	Deviation (12:3:1)	14.72	2	<0.001
	Heterogeneity	2.39	2	0.30-0.50
6.	Testcrosses:
	(a) F1 x Black Line, Spring ’89	74	27	49	150
	(b) F1 x ‘Butterbush’, Spring ’89	54	26	30	110
	(c) F1 x Black Line, Fall ’89	82	32	33	147
	Testcrosses pooled	210	85	112	407
		X2	df	P
	Deviation (2:1:1)	4.00	2	0.10-0.20
	Heterogeneity	4.79	4	0.30-0.50
7.	BC1, F1 x P1:
	(a) Clone MP x NJ-B, Fall ’88	47	43	0	90
	(b) Clone NOMP x NJ-B, Fall ’88	50	52	0	102
	BC1 of test 7 pooled	97	95	0	192

^zThe description of the breeding materials is given in Table 1 of the preceding report. The F₁ seed was produced in small samples in New Brunswick, NJ, between 1983 and 1985. Most of the F₂ seed (test 4, a and b; test 5, a and b) and all the BC₁ seed (test 7) was also prodiced in New Brunswick, NJ. Other F₂ seed (test 4, c) and all testcross seed (test 6) was produced in Naples Florida.
^yThe key to phenotypic symbols is given in the text of the preceding report.
^xThe data for fall 1988 were taken from Table 1 in reference 2. The data for spring and fall 1989 are in Tables 1 and 2 of the present report.