Nebahat Sari

Rootstock resistance to Fusarium wilt and effect on watermelon fruit yield and quality

The potential of grafted watermelon for resistance toFusarium oxysporum f.sp.niveum on some Curcurbitaceae,Lagenaria, Luffa, Benincasa and commercial rootstocks was evaluated. Effects of grafting on yield and quality of diseased plants were evaluated. All grafted plants and rootstocks were resistant to the three known races (0, 1, and 2) ofF. oxysporum f.sp.niveum except watermelon cv. ‘Crimson Tide’, which was susceptible to race 2. Fruit yield was positively (21–112%) affected byLagenaria rootstocks but negatively affected (200–267%) byCucurbita rootstocks when compared with the control. While only minor differences in fruit quality were determined in control and grafted plants onLagenaria rootstocks, the quality parameters for watermelon grafted ontoCucurbita rootstocks were lower than in the control. The reasons for low yield and quality might be due to an incompatibility betweenCucurbita rootstocks and watermelon. These results showed that rootstock influence on disease resistance as well as yield and quality of scion fruit is important in determining the potential use of grafting applications in watermelon.

A new method for haploid muskmelon (Cucumis melo L.) dihaploidization

Three methods for dihaploidization of haploid melon (Cucumis melo L.) plants were evaluated. Ploidy level was determined morphologically and cytologically for plants treated with colchicine. Immersion of in vitro plantlets or single node explants was compared to immersion of soot tips of greenhouse grown plants in a colchicine solution. In addition, application of single drops of colchicine was applied to lateral buds of greenhouse grown plants. Dihaploidization rate by immersion of apical growing point was about 89%, a rate three times greater than in vitro application by immersion of plantlets or their cuttings into colchicine solution. Colchicine treatment of lateral buds by medicine dropper was found to be ineffective in dihaploid production.

Characterization of watermelon (Citrullus lanatus) accessions collected from Turkey for morphological traits

In this study, the Turkish watermelon genetic resources were collected in 2004 and morphologically characterized in 2005. The collection comprising of traditional cultivars and local accessions were collected from 15 different provinces of Southeastern Anatolia, Aegean, Marmara-Thrace, Middle Anatolia and Mediterranean regions of Turkey where local watermelon types are widely grown. A total of 134 accessions were characterized morphologically according to UPOV descriptor list for 56 qualitative characters (6 seedling, 4 plant, 11 leaf, 5 flower, 23 fruit and 7 seed) and morphologic relatedness were examined. Additionally, 22 quantitative characters were also measured. Our results indicated that the accessions studied have a great deal of variation for most of the morphological traits. The accessions were divided into five different groups according to principle component analysis. However, the geographical origin was not a great source for grouping.

The genetic characterization of Turkish watermelon ( Citrullus lanatus ) accessions using RAPD markers

Genetic diversity of the Turkish watermelon genetic resources was evaluated using different Citrullus species, wild relatives, foreign landraces, open pollinated (OP) and commercial hybrid cultivars by RAPD markers. The germplasm was consisted of 303 accessions collected from various geographical regions. Twenty-two of 35 RAPD primers generated a total of 241 reproducible bands, 146 (60.6%) of which were polymorphic. Based on the RAPD data the genetic similarity coefficients were calculated and the dendrogram was constructed using UPGMA (Unweighted pair-group method with arithmetic average). Cluster analysis of the 303 accessions employing RAPD data resulted in a multi-branched dendrogram indicating that most of the Turkish accessions belonging to var. lanatus of Citrullus lanatus (Thunb.) Matsum et Nakai were grouped together. Accessions of different Citrullus species and Praecitrullus fistulosus (Stocks) Pangalo formed distant clusters from C. lanatus var. lanatus. Among 303 accessions, a subset of 56 accessions was selected representing different groups and a second dendrogram was constructed. The genetic similarity coefficients (GS) within the Turkish accessions were ranged from 0.76 to 1.00 with 0.94 average indicating that they are closely related. Taken together, our results indicated that low genetic variability exist among the watermelon genetic resources collected from Turkey contrary to their remarkable phenotypic diversity.

Morphological characterization of Hungarian and Turkish watermelon (Citrullus lanatus (Thunb.) Matsum. et Nakai) genetic resources.

Thirty-nine Hungarian accessions either collected from different regions of Hungary or obtained from gene banks and 11 Turkish accessions representing particular regions of Turkey were evaluated and compared for morphological characteristics. Qualitative characters were obtained according to the modified UPOV descriptor list for 58 characters. Sixteen quantitative characters (hypocotyl length, cotyledon width and length, length of main stem, number of nodes, length and width of leaf, length of petiole, length and width of the ovary, fruit weight, size of pistil scar, diameter and length of fruit, thickness of outer layer of pericarp, total soluble solids) were also measured. Results of both qualitative and quantitative measurements indicated that Hungarian and Turkish germplasm resources present a wide range of diversity for morphological traits. Accessions of the two countries show many similarities, therefore cannot be separated clearly. Considering the historical background, the two countries might have varieties with similar phenotypes and genetically common backgrounds.

Rootstock potential of Turkish Lagenaria siceraria germplasm for watermelon: plant growth, yield and quality

* Correspondence: huseyinayhan44@yahoo.com

Effect of mycorrhizae inoculation on plant growth, yield, and phosphorus uptake in garlic under field conditions

The effect of mycorrhizae species and phosphorus (P) fertilizer on garlic (Allium sativum L.) growth, yield–quality, and P uptake under high P accumulated non-sterile field conditions were studied. Experiments were conducted for two successive years under field conditions of Menzilat soil series (Typic xerofluvent) at the Research Farm of the University of Cukurova (Turkey). Glomus mosseae arbuscular mycorrhizae (AM) were tested on local Urfa genotype of garlic at 0, 40, 80, and 120 kg phosphorus (P2O5) ha−1. In the first year, garlic was inoculated with 1,000 spores per plant, but in the second year, garlic was inoculated with either 1,000 or 2,000 spores per plant. Emergence, plant growth, yield, bulb size, root mycorrhizal infection, and phosphorus uptake of plants were examined. Neither mycorrhizal inoculation nor P2O5 supply increased garlic growth and yield. However, at 0 level of P2O5 application, mycorrhizal inoculation slightly increased plant P uptake. In the second year of the experiment, mycorrhizae significantly increased clove yield. The results revealed that although garlic is mycorrhizal dependent, mycorrhizal inoculation did not contribute to the plant growth and nutrient uptake.

Physiologic races ofFusarium oxysporum f.sp.melonis in the southeastern anatolia region of turkey and varietal reactions to races of the pathogen

Thirty-four isolates ofFusarium oxysporum f.sp.melonis (F.o.m.) obtained from 205 fields in melon-producing areas in the southeastern Anatolia Region of Turkey were identified on the basis of colony morphology and pathogenicity by the root dip method. In this region the mean prevalence of wilt disease was 88.1% and the mean incidence of disease was 47.5%. Physiologic races 0, 1, 2, and 1,2 of the pathogen were determined by their reactions on differential melon cultivars ‘Charentais T,’ ‘Isoblon’, ‘Isovac’ and ‘Margot’ in the greenhouse. Race 1,2, representating 58.8% (20/34) of all isolates, was widely distributed. Of the other pathogenic isolates, eight were identified as race 0, five as race 1, and one as race 2. This is the first report of physiologic races ofF.o.m. in Turkey. Of 44 melon cultivars tested in the greenhouse for resistance toF.o.m. races, 36 were found to be moderately resistant to race 0, 17 were susceptible to race 1,2, 34.1% were highly resistant to race 1, and 52.2% had moderate resistance to race 2.

The Andromonoecious Sex Determination Gene Predates the Separation of Cucumis and Citrullus Genera

Understanding the evolution of sex determination in plants requires the cloning and the characterization of sex determination genes. Monoecy is characterized by the presence of both male and female flowers on the same plant. Andromonoecy is characterized by plants carrying both male and bisexual flowers. In watermelon, the transition between these two sexual forms is controlled by the identity of the alleles at the A locus. We previously showed, in two Cucumis species, melon and cucumber, that the transition from monoecy to andromonoecy results from mutations in 1-aminocyclopropane-1-carboxylic acid synthase (ACS) gene, ACS-7/ACS2. To test whether the ACS-7/ACS2 function is conserved in cucurbits, we cloned and characterized ClACS7 in watermelon. We demonstrated co-segregation of ClACS7, the homolog of CmACS-7/CsACS2, with the A locus. Sequence analysis of ClACS7 in watermelon accessions identified three ClACS7 isoforms, two in andromonoecious and one in monoecious lines. To determine whether the andromonoecious phenotype is due to a loss of ACS enzymatic activity, we expressed and assayed the activity of the three protein isoforms. Like in melon and cucumber, the isoforms from the andromonoecious lines showed reduced to no enzymatic activity and the isoform from the monoecious line was active. Consistent with this, the mutations leading andromonoecy were clustered in the active site of the enzyme. Based on this, we concluded that active ClACS7 enzyme leads to the development of female flowers in monoecious lines, whereas a reduction of enzymatic activity yields hermaphrodite flowers. ClACS7, like CmACS-7/CsACS2 in melon and cucumber, is highly expressed in carpel primordia of buds determined to develop carpels and not in male flowers. Based on this finding and previous investigations, we concluded that the monoecy gene, ACS7, likely predated the separation of the Cucumis and Citrullus genera.

Genetic Characterization of Turkish Snake Melon (Cucumis melo L. subsp. melo flexuosus Group) Accessions Revealed by SSR Markers

Snake melon is an important cucurbit crop especially in the Southeastern and the Mediterranean region of Turkey. It is consumed as fresh or pickled. The production is mainly done with the local landraces in the country. Turkey is one of the secondary diversification centers of melon and possesses valuable genetic resources which have different morphological characteristics in case of snake melon. Genetic diversity of snake melon genotypes collected from different regions of Turkey and reference genotypes obtained from World Melon Gene Bank in Avignon-France was examined using 13 simple sequence repeat (SSR) markers. A total of 69 alleles were detected, with an average of 5.31 alleles per locus. The polymorphism information content of SSR markers ranged from 0.19 to 0.57 (average 0.38). Based on cluster analysis, two major groups were defined. The first major group included only one accession (61), while the rest of all accessions grouped in the second major group and separated into different sub-clusters. Based on SSR markers, cluster analysis indicated that considerably high genetic variability exists among the examined accessions; however, Turkish snake melon accessions were grouped together with the reference snake melon accessions.