Bilge Yildirim

Evaluation of Genetic Diversity in Lemons and Some of Their Relatives Based on SRAP and SSR Markers

Genetic diversity was evaluated by sequence-related amplified polymorphism (SRAP) and simple sequence repeat (SSR) markers among 45 lemons (Citrus limon (L.) Burm. f.), five citrons (Citrus medica L.), four rough lemons (Citrus jambhiri Lush), and two Citrus volkameriana accessions. Twenty-one SRAP primer combinations produced a total of 141 (77%) polymorphic fragments with an average of 6.7 fragments per primer combinations whereas 13 SSR primers produced a total of 26 (76%) polymorphic fragments with an average of 2.0 per primer. The unweighted pair-group method arithmetic average analysis as assessed with combined SRAP and SSR data demonstrated that the accessions had a similarity range from 0.65 to 1.00. Rough lemons and C. volkameriana accessions were relatively closely related. In lemon group, accessions from hybrid origin were distant from the others. We also applied principal components analysis (PCA) for a better presentation of relation among the accessions studies. Using PCA, 88.7% of the total variation in the original dimensions could be represented by just the two dimensions defined by the first two PCs. Although nearly all accessions could be distinguished, there was a low level of genetic diversity detected among lemon cultivars.

Effects of 2,4-DP (2,4-dichlorophenoxypropionic acid) plant growth regulator on fruit size and yield of Valencia oranges (Citrus sinensis Osb.)

The Valencia orange is a high-quality fruit grown in Turkey; however, small fruit sizes and high fruit discard percentages are common in Valencia oranges. Small fruit size is the main factor limiting the marketing of Valencia oranges; thus, synthetic auxins are commonly used to enhance the size of citrus fruit. The objective of the present study was to observe the effects of 2,4-dichlorophenoxypropionic acid (2,4-DP) on the fruit size, yield and quality of Valencia oranges from 29-year-old trees budded on sour orange rootstock in Adana, Turkey during 2005–06. Three concentrations (50, 100 and 150 ppm) of 2,4-DP were applied during the June drop, when the mean fruit diameter was 13–15 mm. The results indicated that the application of 2,4-DP increased the fruit size of Valencia oranges without reducing yield. The application had a significant effect on fruit yield. Compared with the control trees, applications of 2,4-DP increased the number of large, commercially valuable Valencia oranges (75–80 mm). Moreover, an increase in the concentration of 2,4-DP increased the yield and weight of the fruits. As a result, fruit retention was highest in trees sprayed with 150 ppm 2,4-DP. Except for the titratable acid content (TA), which increased with an increase in the 2,4-DP concentration, the internal characteristics of the fruit were not affected by treatment with 2,4-DP. Thus, the results of the present study revealed that 2,4-DP can be used to improve the fruit size of Valencia fruitlets during the June drop.