Correlations Among Yield Components in Exotic Cucumber Germplasm

Cucurbit Genetics Cooperative Report 21:21-24 (article 8) 1998

Jinsheng Liu
Agricultural Division, Jiangsu State Farms Group Corporation, No. 1 Zhu Jiang Road, Nanjing 210008, P.R. China

Jack E. Staub
Vegetable Crops Research Unit, USDA/ARS, Department of Horticulture, University of Wisconsin, Madison, WI 53706, U.S.A.

Introduction. The genetic relationships among 13 botanical varieties of Cucumis savitus L. are presented in a companion paper in this issue. It is evident from that study that the botanical varieties examined differ in their morphology. Phenotypic correlations among morphological characteristics (fruit number, lateral branch number, fruit length and diameter and number of female nodes) of C. sativus var. hardwickii accessions has been documented Kupper and Staub, 1988). Such correlations have also been examined in lines derived from var. hardwickii (Fredrick and Staub, 1989). Since C. sativus var. hardwickii differs considerably from var. sativus (commercial cucumber), it has been used as an outgroup in various diversity assessments in cucumber (Dijkhuizen et al., 1996; Meglic et al, 1996). Correlations between yield components can be important in breeding of cucumber using exotic germplasm. Therefore, a study was designed to investigate the association of yield components observed in a study of putative botanical varieties (companion article) and relate them to previous studies using C. sativus var. hardwickii and its derived inbred lines. This was done in order to determine whether the correlations for yield components observed among botanical varieties could be used in developing strategies for cucumber improvement.

Material and Methods. Parents and F1 progeny are those given in a companion article in this issue. Phenotypic correlation coefficients were calculated for each character according to Becker (1992) and Steel and Torrie (1980). These were compared to data from Kupper and Staub (1988) and Fredrick and Staub (1989).

Results and Discussion. Cross-progeny in this study exhibited different values for all variables measured when compared to their parents (companion article) and themselves (Table 1). Many parents and progeny exhibited similarities with the var. sativus accessions examined. Although flowering dates were close to the common var. sativus parent, the values of the variables were generally closer to the var. sativus inbred parent (WI 2780) than the botanical variety used in a particular cross. Values were higher in cross-progeny where the botanical variety was extreme for a particular trait (e.g., var. falcatus for L:D ratio, var. sikkimensis for lateral branch number).

Significant positive correlations were detected between lateral branch number and three-harvest yield, lateral branch number and three-harvest yield, lateral branch number and three-harvest fruit weight, days to anthesis and three-harvest fruit weight, and three-harvest yield and fruit weight (Table 2). In studies by Kupper and Staub (1988) using var. hardwickii accessions crossed to var. sativus elite lines,moderate to large positive correlations were observed between fruit number and lateral branch number (Table 2). The positive relationship found between these two characters confirmed other studies (Horst and Lower,m 1978; Hutchins, 1940). In that study, large numbers of fruit tended to occur on plants with considerable lateral branching, but the size of the fruit borne on those plants were relatively small. In a study using var. hardwickii-derived lines mated with var. sativus lines, Fredrick and Staub (1989) found that correlation coefficients were moderate to large between three-harvest yield and lateral branch number (Table 2). A high positive correlation was detected between fruit length and fruit L:D ratio. Negative correlations of intermediate range were detected between L:D ratio and three-harvest yields and lateral branch number.

Data from these studies and the present study indicate that positive correlations exist between yield and lateral branch number, and negative correlations exist between days to anthesis, lateral branch number and yield and L”D ratio in exotic germplasm (i.e. using documented and putative botanical varieties of C. sativus). We suggest that these relationships be considered when developing germplasm enhancement strategies using exotic germplasm in cucumber.

Table 1. Comparisons among F1 progeny of putative Cucumis sativus L. botanical varieties mated with a C. sativus line (WI 2870) for sex expression days to anthesis, lateral branch number (primary) and fruit number, weight and length:diameter ratio (L:D)

F1 hybrid/line1	Origin	Sex2	Days to anthesis	Lateral branch number	Three harvest yield	Three harvest weight (kg)	L:D ratio
var. anatolicus	Russia	G	23.5	1.3	88.3	47.0	2.5
var. cilicicus	Russia	G	23.8	0.0	82.3	50.1	2.5
var. europaeus	Russia	G	27.0	1.8	99.0	41.1	2.6
var. falcatus	Japan	PF	27.5	1.0	72.0	32.5	4.3
var. indo-europaeus	Russia	PF	26.5	1.5	93.3	38.3	2.1
var. irano-turanieus	Russia	PF	24.3	1.5	92.5	40.6	2.0
var. izmir	Russia	G	24.3	10.	90.8	52.7	1.8
var. sikkimensis	Russia	PF	30.8	2.8	79.8	18.2	2.7
var. squamosus	Russia	PF	30.3	1.0	51.0	24.3	2.3
var. testudaceus	Russia	G	25.8	0.3	85.5	44.5	2.1
var. tubercullatus	China	G	23.8	0.0	79.3	58.7	2.2
var. vulgatus	India	PF	35.3	1.8	108.3	37.3	2.4
var. hardwickii	India	PF	35.3	3.5	188.3	29.1	1.9
var.sativus (Gy14)	USA	G	31.3	1.0	69.0	27.8	2.3
var. sativus (WI 2870)3	USA	G	24.3	0.0	76.5	47.0	2.4
LSD			2.7	0.6	16.3	6.9	0.3
C.V.(%)			25	25	15	17	10

1 Hybrid made by crossing each botanical variety with the USDA picking cucumber line WI 2870.
2 M = monoecious, PF = predominantly female, and G = gynoecious.
3 WI 2870 observed as a line.

Table 2. Correlation coefficients of morphological traits of F1 hybrids of Cucumis sativus botanical varieties and Cucumis sativus var. sativus lines in three studies.

Study	Trait	Days to anthesis	Lateral branch number	Three harvest yield	Three harvest weight (kg)	L:D ratio
Kupper & Staub (1988)1)	Days to anthesis Lateral branch no. Three harvest yield L:D ratio		-0.2	-0.15 0.74**	— — —	-0.12 -0.48** -0.38** —
Fredrick & Staub (1989)2	Days to anthesis Lateral branch no. Three harvest yield L:D ratio		0.34	0.27 0.57*	— — —	-0.33** -0.47* -0.65*
Present Study 3	Days to anthesis Lateral branch no. Three harvest yield L:D ratio		0.41	0.41 0.68**	0.68** 0.67** 0.50**	— — — —

1 Cross-progeny derived from matings between six var. hardwickii accessions and three inbred lines of var. sativus.
2 Cross-progeny derived from matings between five var. hardwickii x var. sativus-derived lines and four var. sativus lines.
3 Cross-progeny derived from matings between 13 botanical varieties of C. sativus and a var. sativus line WI 2870.

Literature Cited

1. Becker, W.A. 1992. Manual of quantitative genetics. Academic Enterprises, New York, USA.
2. Dijkhuizen, A., W.C. Kennard, M.J. Havey and J.E. Staub. 1996. RFLP variability and genetic relationships in cultivated cucumber. Euphytica 90:79-80.
3. Fredrick, L.R., and J.E. Staub. 1989. Combining ability analysis and evaluation of nearly homozygous lines derived from Cucumis sativus var. hardwickii (R.) Alef. J. Amer. Soc. Hort. Sci. 114:332-338.
4. Horst, E.K., and R.L. Lower. 1978. Cucumis hardwickii: A source of germplasm for the cucumber breeder. Cucurbit Genetics Coop. Rpt. 1:5.
5. Hutchins, A.E. 1940. Inheritance in the cucumber., J. Agric. Res. 60: 117-128.
6. Kupper, R.S. and J.E. Staub. 1988/ Combining ability between lines of Cucumis sativus L. and Cucumis sativus var. hardwickii (R.) Alef. Euphytica 38:197-120.
7. Steel, R., and J.H. Torrie. 1980. Principles and procedures of statistics. 2nd ed. McGraw-Hill, New York.