 Sunchon National University  Department of Horticulture  Interspecific hybridization and hybrid seed yield of winter squash ( Cucurbita maxima Duch.) and pumpkin ( Cucurbita moschata Duch.) lines for rootstock breeding  Nematov Hasan  Master’s degree student

Interspecific hybridization and hybrid seed yield of winter squash (Cucurbita maxima Duch.) and pumpkin (Cucurbita moschata Duch.) lines for rootstock breeding BLACK SEA AGRICULTURAL RESEARCH INSTITUTE, SAMSUN, TURKEY ONDOKUZ MAYıS UNIVERSITY, FACULTY OF AGRICULTURE, DEPARTMENT OF HORTICULTURE, SAMSUN, TURKEY ARTICLE HISTORY: RECEIVED 21 OCTOBER 2011 RECEIVED IN REVISED FORM 23 OCTOBER 2012 ACCEPTED 24 OCTOBER 2012 Onur Karaağaç, Ahmet Balkaya

Abstract  In this study, different interspecific hybridization combinations were evaluated in order to obtain C. maxima × C. moschata rootstocks.  The field experiment of this study was carried out in the Çarşamba district of Samsun Province in The initial genetic materials were inbred and purified up to the S 5 generation.  A total of 234 pollinations of different combinations between twelve C. maxima lines and eleven C. moschata lines were performed.  79 interspecific hybrid fruits were obtained from these hybridizations.  The MA9 × MO8, MA12 × MO2 and MA4 × MO8 hybrid combinations were the most promising candidates for rootstock breeding.  selected combinations will be used in the development of promising new rootstock cultivars

Introduction  The most commonly used Cucurbita spp. rootstock is an interspecific C. maxima × C. moschata hybrid (Colla et al., 2010)  The use of rootstocks has been shown to enhance the vigor of the scion through the resistance to soil pathogens and tolerance to low soil temperatures and or salinity (Ruiz et al., 1997)  In the genus Cucurbita, several attempts have been made to produce interspecific hybrids between five cultivated species: (Korakot et al., 2010). Cucurbita pepo, C. maxima, C. moschata, Cucurbita argyrosperma and Cucurbita ficifoliaKorakot et al., 2010  The main objective of this study is to develop an inbred line from interspecific crosses between C. maxima and C. moschata using hybridization.  The developed inbred lines may be used for rootstock breeding in the future.

Materials and methods  This study was carried out cooperatively by the Black Sea Agricultural Research Institute and the Ondokuz Mayis University Agriculture Faculty.  In this experiment, the 12 inbred lines of C. maxima (MA1, MA3, MA4, MA5, MA8, MA9, MA11, MA12, MA13, MA14, MA15 and MA20) at the S5 generation, and 11 inbred lines of C. moschata (MO1, MO2, MO4, MO5, MO6, MO7, MO8, MO10, MO11 and MO13) at the S5 generation were used.  These genetic materials, consisting of winter squash and pumpkin populations collected from different parts of Turkey, were characterized and selfed by Balkaya et al., 2009, Balkaya et al.,  The C. maxima plants were used as the female parent and the C. moschata plants were used as the male parent in diallel crossing treatments.

Results and discussion Female parents (C. maxima)Number of crossNumber of fruit set Number of fruit set with normal seeds MA1 183 ± 0.38 MA3 160 ± 0.00 MA4 93 ± 0.50 MA5 150 ± 0.00 MA8 180 ± 0.00 MA ± 0.45 (75%) 6 ± 0.52 MA ± 0.44 MA ± 0.41 (80%) 6 ± 0.41 MA ± 0.46 (71%) 0 ± 0.00 MA ± 0.00 MA ± 0.20 MA ± ± 0.00 Total ± ± 3.11 Table 1. Results of interspecies hybridization in genotypes with C. maxima as the female parent in different combinations (mean ± standard deviation).

Results and discussion Table 2. Results of interspecies hybridization in genotypes with C. moschata as the male parent in different combinations (mean ± standard deviation). Male parents (C. moschata)Number of crossNumber of fruit set Number of fruit set with normal seeds MO1 80 ± 0.00 MO2 3 3 ± 0.00 (100%) 3 ± 0.00 MO4 126 ± ± 0.00 MO5 80 ± 0.00 MO ± ± 0.00 MO7 99 ± 0.00 (100%)0 ± 0.00 MO ± 0.50 MO10 31 ± 0.58 MO11 70 ± 0.00 MO ± ± 0.00 MO ± ± 0.00 Total ± ± 7.17

Results and discussion Table 3. A summary of the interspecific compatibility of the different interspecific cross- combinations (mean ± standard deviation). ♂♀ MA1MA4MA9MA11MA12MA13MA15MA20 MO2 × 25.0 y 75.0 z ×× 361 ± ± 4.1 ××× MO4 × 50 Ab 25.0 Ab × 76.4 ± 10.1 Ab 15.5 Ab × 18.0 Ab MO6 0.0 Ab × 15.0 ± 5.0 Ab × 24.0 ± 7.5 Ab 8.4 ± 2.2 Ab × 2.5±2.2 Ab MO7 ×××× 28.8 ± 18.9 Ab 18.1 ± 10.2 Ab × 7.0 ± 5.4 Ab MO8 116 ± ± ± ± ± ± ± ± ± ± ± 11.4 Ab × 5.4 ± 2.5 Ab MO10 ×××××× × MO12 ×× × 17. ± 4.5 Ab 3.0 Ab × 5.9 ± 1.1 Ab MO13 ×× 17.0 ± 6.7 Ab × 15.3 ± 5.0 Ab 4.5 ± 3.5 Ab × 6.8 ± 0.7 Ab x: Absence of fruit set; y: Seed number/fruit; z: Rate of abortive seed; Ab: All seeds were aborted.

Results and discussion Table 4. Seed characteristic of the promising interspecific hybrid combinations. CombinationsWidth (mm)Length (mm) Thickness (mm) Seed germination rate (%) 100 seed weight (g) Seed yield (g/fruit) Number of seeds (n./fruit) Seed abortion rate (%) MA1 × MO d21.24 b5.16 a25.00 e34.99 ab39.46 c d12.04 a MA11 × MO a20.25 c5.10 a a ab25.59 e d0.00 e MA9 × MO cd17.11 d4.24 b63.39 c a b b0.00 e MA12 × MO e19.90 c3.59 b f b b a6.01 c MA12 × MO c21.00 b4.96 a62.21 c34.35 ab36.04 d c3.00 d MA4 × MO e b5.00 a56.07 d39.75 ab a a 9.60 b MA15 × MO b23.23 a3.67 b65.06 b31.50 * * P <0.001 <0.01 <0.05<0.001 CV (%) These combinations gave only one fruit. For this reason, the statistical analysis was not reported.

Results and discussion -Gene transfer between C. maxima and C. moschata has been difficult. - Crosses between some cultigens of the two species yield neither seed nor fruit. -The successes of the presented interspecific hybridizations were, in general, comparable to the published data. -In the test of interspecific crosses, different cultivars within the species performed differently. -For this reason, these interspecific hybrids derived from crosses of C. maxima×C. moschata also will be utilized as bridge crosses with backcross programmes in future breeding work. -Thus, it will be increased both seed yield and seed viability of these combinations. Hybridization programs with these lines have been implemented.