Turgut Yesiloglu

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.

Genetic Diversity in Citrus

The genus Citrus L. belongs to the subtribe Citrineae, the tribe Citreae within the subfamily Aurantioideae of the Rutaceae family (Webber, 1967). The Aurantioideae is one of seven subfamilies of Rutaceae which consists of two tribes and 33 genera. Each of tribes Clauseneae and Citreae is composed of three subtribes. Clauseneae includes Micromelinae, Clauseninae and Merrillinae, and Citreae has Triphasiinae, Citrinae and Balsamocitrinae. The Citrinae is distinct from all the other subtribes in the subfamily by having pulp vesicles in the fruit. This subtribe contains three groups; primitive citrus fruit, near citrus fruit, and true citrus fruit trees. True citrus fruits have six genera: Clymenia, Eremocitrus, Microcitrus, Poncirus, Fortunella and Citrus (Swingle & Reece, 1967).

Peroxidase gene-based estimation of genetic relationships and population structure among Citrus spp. and their relatives

Many stress-related interactions such as pathogen infection, insect tolerance, salt tolerance, auxin degradation, cell wall lignification, tissue suberization, and plant senescence involve various isoforms of peroxidases. Peroxidase gene polymorphism (POGP) markers have been used to estimate diversity, relationships and population structure among 80 Citrus and their relatives in Aurantioideae by using unweighted pair group method arithmetic average (UPGMA) and bayesian substructuring analysis. Fourteen primers produced a total of 148 fragments and 147 of them were polymorphic. The UPGMA analysis demonstrated that the accessions had a similarity range from 0.27 to 0.98 and were distinguished. The results of this study were mostly consistent with previous reports of different marker systems, but few different findings were also detected. The subtribe Clauseninae (tribe Clauseneae) did not clearly separate from the subtribes of the tribe Citreae. Substructuring analysis indicated that there were six subpopulations among the accessions studied. This study revealed that the POGP markers can be utilized to estimate genetic diversity, relationships and population structure in Citrus and related species in the Aurantioideae subfamily.

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.

Growth and photosynthetic response of young ‘Navelina’ trees budded on to eight citrus rootstocks in response to iron deficiency

Citrus trees growing in the Mediterranean region suffer from iron (Fe) deficiency because of the presence of high levels of carbonate ions in calcareous soils. In this context we have evaluated the effects of different citrus rootstocks on photosynthetic capacity and plant development of young ‘Navelina’ orange trees under Fe deprived conditions. Leaf number, shoot length, plant dry mass, leaf chlorophyll (Chl) concentration, net photosynthetic rate (P N), stomatal conductance (gS), leaf transpiration rate (E), intercellular CO2 concentration (Ci) and photosynthetic water use efficiency (WUE) of ‘Navelina’ orange scion budded on to eight citrus rootstocks with different agronomic characteristics were investigated. Significant decreases in leaf number, shoot length and plant dry mass under high pH conditions were observed. Plants on Tuzcu 31 31 and Gou Tou sour orange rootstocks were the least affected in terms of plant growth. The highest reduction in the leaf Chl content was observed in (-)Fe plants of Navelina on local trifoliate and C-35 citrange. These rootstocks also had significantly reduced PN, gS and E rates in the (-)Fe treatment. Shoots budded on Tuzcu 31 31 and Gou Tou sour oranges were the least affected by the induced Fe deficiency.

Rootstock Breeding for Abiotic Stress Tolerance in Citrus

Citrus species are the most widely produced fruit crops in the world. Citrus fruits are mainly produced in coastal areas in several countries as well as Mediterranean region, and production in these regions is affected by both biotic and abiotic stresses, including drought, extreme temperature, salinity, citrus canker, citrus tristeza virus, citrus green‐ ing, and others. The use of rootstocks in fruit production includes not only stronger re‐ sistance against pathogens but also a higher tolerance to abiotic stress conditions such as salinity, heavy metals, nutrient stress, water stress, and alkalinity. There is extensive ge‐ netic diversity in citrus which provides several materials to be used as rootstocks against abiotic stress. In this work, we tried to provide an overview of the abiotic stresses in cit‐ rus by combining literature with our studies, role of citrus rootstocks commercially used against abiotic stresses and rootstock breeding in citrus.

INFLUENCE OF GIRDLING ON THE SEASONAL LEAF NUTRITION STATUS AND FRUIT SIZE OF ROBINSON MANDARIN (CITRUS RETICULATA BLANCO)

This study was undertaken to investigate the effects of single and double girdling applications on the fruit yield, commercial size, quality, photosystem II (PSII), leaf chlorophyll and leaf nutrition content of 22-year-old Robinson mandarin (Citrus reticulata). Girdling treatments were performed at anthesis (when 60% of the flowers were opened) with approximately 5 mm trunk diameter in 2014. The fruit was harvested in 2014 at the optimum harvest time (in December) for fruit yield, properties and size. Evaluations of leaf mineral content, chlorophyll concentration and fluorescence measurements were performed at monthly intervals. Leaf samples were taken in eight periods for analysis of plant nutri-elements. It was determined that double girdling was the best application in terms of fruit yield and percentage of marketable fruit. The treatments did not significantly affect fruit internal quality. Girdling reduced PSII and leaf chlorophyll concentration but did not affect leaf mineral content. However, we observed a tendency toward a decrease in nitrogen levels in the girdled trees. According to the results of the present study, girdling treatments significantly affected fruit yield and size together with several macro-micro plant nutri-elements.

The Influence of Different Interstock Lengths of Minneola Tanjelo on Photosynthetic Parameters and Fruit Yield of Star Ruby Grapefruit

In this study, Minneola Tangelo hybrid, a cross of grapefruit and mandarin (Duncan grapefruit x Dancy mandarin), used as interstock to Star Ruby grapefruit with different lengths. Effects of different interstock lengths on fruit yield and quality, plant development and photosynthetic parameters were investigated. According to the results, different interstock lengths significantly affected fruit yield and size. The highest fruit yield was determined in T-M20-S whereas the lowest was on T-M5-S. The highest fruit size were determined in Star Ruby fruits on T-M5-S and T-M40-S whereas the lowest on T-M20-S and T-S (control). T-M40-S and T-M20-S treatments markedly reduced stem diameter and tree canopy in comparison to other treatments and control. Usage of different interstock lengths did not significantly affected some of fruit quality traits, net photosynthetic rate, stomatal conductance, leaf transpiration rate, leaf water usage efficiency and leaf chlorophyll concentration. In regards to seasonal changes, net photosynthetic rate were higher in spring and summer seasons then winter and fall seasons.