This study was conducted in Department of Horticulture, Faculty of Agriculture, University of Cukurova in 1999 and 2000. Watermelon [Citrullus lanatus (Thunb.) Matsum and Nakai] cultivar Crimson Tide was grafted onto 10 different rootstocks. Cucurbita moschata, Cucurbita maxima and Lagenaria siceraria were open pollinated cultivars, and Strong Tosa, Gold Tosa, P360 (Cucurbita maxima × Cucurbita moschata), Skopje, Emphasis, 216 and FRG (Lagenaria spp.) were hybrid cultivars. The ungrafted Crimson Tide watermelon cultivar was used as the control. Plants were grown under low tunnel conditions until the outdoor temperature was suitable (22-25°C) for watermelon growth. Our results showed that while survival rate was low (65%) in Cucurbita type rootstocks, it was high (95%) in Lagenaria type rootstocks. Grafted plants flowered about 10 days earlier and showed more vigorous vegetative growth than the control plants. Grafted plants had up to 148% higher fresh weights than control plants. Similarly, grafted plants showed 42-180% higher dry weight, 58-100% more leaves and larger leaf area as compared with the control. In total yield, Lagenaria type rootstocks produced a higher yield but Cucurbita type rootstocks produced a lower yield than the control. While control plants had 6.43 kg/m 2 yield, Lagenaria type rootstocks produced 27-106% higher yield than the control. In contrast, Cucurbita type rootstocks had 127-240% less yield than the control. This could be attributed to incompatibility of Cucurbita rootstocks because some of the plants died before harvest. The study showed that rootstock choices influence plant growth as well as yield and quality of scion fruit, suggesting an important consideration in the potential use of grafting applications in watermelon.

The landraces of Lagenaria siceraria in Turkey show great diversity for morphologic traits, particularly in fruit size and shape even though Turkey is not centre of genetic diversity for L. siceraria. In Turkey, L. siceraria is used as food, musical instruments and containers, according to the type and shape of their fruits. Its diversity has been gradually declining over the last 25 years. With the aim of assessing variations in plant, fruit and seed morphology among the L. siceraria landraces, 15 field trips for collection of germplasm to southern parts of Turkey (Mediterranean region) were carried out in the period of 2003-2004. The study also aimed at developing a representative core collection of the material to guide future studies and uses concerning its existing genetic diversity in Turkey. A total of 182 accessions (fruits and/or seeds) were collected. The seeds from all the sample material were sown in green house conditions at the experimental station of the Faculty of Agriculture of the Mustafa Kemal University in Hatay (Antakya), (36°18 0 22 00 N, 36°13 0 33 00 E, 82 m). In the spring of 2004, 162 out of the 182 sown seeds germinated and developed into viable seedlings. These were further transplanted in the field in 10 replicates. The morpho-agronomic characterization was carried out following the international standards for crop descriptors set by Bioversity International. The data were subject to both descriptive statistics and multivariate analysis by Principle Component Analysis. The descriptive statistics revealed that the whole collection exhibits a great deal of morphological diversity and that the subset core collection represents most of the variability. The first three principle components, calculated by using six quantitative traits, explained 26%, 21% and 17% (a total of 64%) of the total variation. Among the studied accessions, no apparently distinct patterns such as geographical origin were detected. This may suggest that the accessions have been introduced to Turkey from multiple locations and/or their diversity had been distributed almost evenly across the Mediterranean region of this country. Based on our results from the morphological characterization, 30 genotypes were selected to develop a subgroup (core) collection in order to represent most of the genetic diversity of all accessions. The work presented here is the first report about morphological characterization of Turkish L. siceraria germplasm.

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