Flowers with a greater probability of transferring pollen to these high-quality recipients will have greater reproductive success as males, and because pollen transfer can only occur between flowers open at the same time, this advantage falls to first flowers . The optimal sex allocation of first flowers is therefore more male than that of last flowers, unless the female gain curve decelerates much more rapidly than the male . This scenario is similar to our numerical model, but where Brunet and Charlesworth assume an equal probability of fruit-set across flowers regardless of resource status, we instead assume that fruit-set probability decreases with resource status, and where Brunet and Charlesworth assume no variation in flowering onset, we allow onset to vary. We discuss these differences below. In some species, declining fruit-set within plants appears to be an outcome of decreasingly female sex allocation optima . In many others, resource shortage at least contributes to the low fruit set of last flowers . When we assumed that fruit-set probability decreases with resource status, we found that the drop in expected female reproductive success from first to last flowers outpaced the drop in expected male success . The average functional gender of first flowers on plants is therefore more female than that of last flowers , vertical aeroponic tower garden leading us to expect that optimal sex allocation is least female in the last flowers. This expectation contrasts with Brunet & Charlesworth’s prediction for optimal allocation under declining resources with constant fruit set probability.
Pinpointing the precise sex allocation optima of flower classes under declining fruit-set probability requires testing in an analytical ESS model. The numerical model con- firmed that declining fruit-set creates conditions that could lead to selection for variable pre-fertilization sex allocation within plants. An ESS model would help predict the long-term outcome of this selection. When flowering onset is variable and fruit-set declines, a shift occurs in the quality of male mating opportunity available to early- versus late-flowering plants. Consequently, expected male success decreases among plants across the season , and functional femaleness increases . Others have speculated that variation in the mating environment experienced by early- versus late-flowering plants in dichogamous species leads to variation in their optimal sex allocation. We similarly suggest that optimal sex allocation may be increasingly female from early- to late-flowering plants in adichogamous species whose fruit-set declines. This prediction again requires testing in an ESS model. The key finding of the numerical model was that declining fruit-set can drive temporal variation in functional gender both within and among plants. Within plants, the model revealed that the effect of declining resources among flower classes on optimal sex allocation may depend on whether resource status does or does not affect fruit-set probability. Among plants, the model presented here suggests that heterogeneity in the mating environment may lead to among-plant variation in sex allocation optima. This contrasts with past work emphasizing effects of heterogeneity in the physical environment .
These two factors may lead to mechanistically different responses: whereas heterogeneity in the physical environment selects for plasticity in sex allocation , temporal heterogeneity in the mating environment resulting from declining fruit-set might instead give rise to correlational selection on flowering time and sex allocation.Temporal trends in phenotypic femaleness in B. rapa con- flicted with trends in functional gender predicted by the numerical model. Before examining this discrepancy, we need to consider the relationship between phenotypic gender and sex allocation. Inclusion of equivalence factor E in calculating Gp means that Gp is influenced by the population, and is not an inherent property of a plant or flower . It therefore cannot be directly read as sex allocation. Unlike some other formulations of phenotypic gender , however, ours did not allow E to vary over time. Thus, the same inverse relationship between Gp and the pollen-to-ovule ratio holds for all flowers in our study, meaningGp is interpretable as an indicator of sex allocation. Varying costs per pollen grain and costs per ovule across species can complicate interpretation of p:o as sex allocation , but this concern does not apply when evaluating directions of change in sex allocation among flowers and plants of a single species. The expectation that our indicator of sex allocation, Gp, would mirror trends in functional gender predicted by the model rests on the assumption that variation in functional gender causes variation in sex allocation optima. As stated above, this assumption requires testing in an analytical ESS model.
Even if the assumption is correct, however, observed trends in phenotypic femaleness in B. rapa could oppose expectations for several reasons. We first consider our experimental design. Our indicator of sex allocation includes pre-fertilization investment only, but female investment continues through seed and fruit maturation . We restricted our focus to pre-fertilization investment because declining fruit-set cannot be both the cause and the consequence of among-flower variation in sex allocation optima, and because variation in pre-fertilization allocation often matches predicted variation in optima . Also related to the experiment, plants may have plastically adjusted their allocation to the relatively constant glasshouse environment, perhaps masking temporal variation that would be expressed in the field. Discrepancy in within-plant temporal trends in sex allocation across glasshouse and field environments in some Clarkia taxa lends credence to this possibility . Second, optimal allocation in Brassica rapa might be influenced by factors not considered in the model, such as prefertilization decline in resource status, unequal male and female gain curves, and competition among related pollen grains and seeds . Moreover, model results were sensitive to self-incompatibility, the relationship between flowers displayed and pollen export, and flower longevity . The first of these factors certainly applies to B. rapa, and the other two may. Because these factors affect mate availability, they interact with declining fruitset to shape the sex allocation optima of flowers and plants. Interaction between factors is supported by Brunet’s finding that when fruit-set declines, the estimated male success and functional gender of first versus last flowers depends on whether calculations take floral dichogamy into account. Finally, some model assumptions might not apply to the study population. For example, the model assumed resource limitation of fruit production. Most species exhibit pollen limitation in at least some populations in some years . If pollen were limiting, fruit-set probability might not decrease within plants. Predicted temporal trends in functional gender may therefore occur only in populations or years where female fitness is resource-limited. The model also assumed that flowers varied in their quality as pollen recipients, but plants did not. Selection tends to favour early flowering through female fitness , suggesting that among-plant variation in female quality may alter male mating opportunity. TheB. rapa data reported here are, to our knowledge, one of just three datasets reporting temporalvariation in pollen and ovule production both within and among plants, and the only such dataset for an adichogamous species . Data describing within-plant temporal trends are, however, available for some other adichogamous species. These reveal increasing , decreasing and constant p:o from first to last flowers, suggesting multiple influences on sex allocation optima. Further data on temporal trends in adichogamous species, particularly at the among-plant level, might help resolve the potential role of declining fruit-set in shaping allocation optima.Citrus is a genus, which is evergreen trees, that belongs to the Rutaceae family, and is grown in tropical and subtropical countries in a belt from 40 0 North Latitude to 40 0 South Latitude . Citrus is generally thought to have originated in South Asia’s tropical and subtropical areas, including China, India, and the Malay Archipelago. After domestication, it was distributed from these regions to the rest of the world as well . Before giving a scientific name to Citrus or before Linnaeus’s classification, it was named “Kedros.” The word “Citrus” emanates from “Kedros,” the Latin form. Kedros is originally a Greek word for fragrant trees such as cedar, cypress, and pine. Citrus leaves and fruits had their specific fragrance, vertical gardening in greenhouse and the smell of Citrus leaves and fruits resembled cedar. For this reason, Citrus fruits were named “Kedros” . Although the history and geographical origin of Citrus remain unclear, there are different opinions about that .
The earliest known reference about the Citrus origin is the myth of Hesperides’s Golden Apples in Greek mythology. According to the legend, golden-colored apples were hidden in Hesperides’ garden. The son of Heracles, Greek Herakles, Roman Hercules, Zeus , and the mortal Alcmene had to labor to take three golden apples from the Hesperides’ garden. A dragon guarded this garden. Hercules killed the dragon and took the apples. It was believed that if anyone ate these apples, they could give immortal life to the person. There was a rumor that Gaia gavethese apples or Citrus fruits at Hera and Zeus’s wedding. Due to the Hesperides’ golden apples legend, the Greek botanical name of Citruses is “πορτοκάλι,” which is “Hesperidoeidē.” Therefore, there was doubt whether these golden apples represent today’s apples or other fruits. In those times, the word “apple” used to be given as a name to all fruits except for berries. Although there is a rumor that these apples were quinces, most opinions are that these mentioned golden apples may be Citrus fruits . Even if its origin is not known exactly, Citrus fruits are one of the most grown fruits in the world today, with production exceeding 113 million tons year -1 from about 10 million ha in 2020 . Sweet oranges Osb., mandarins , satsumas Marc, Clementines , lemons Burn and grapefruits are cultivars that have commercial importance in the world ; Ma et. al, 2020, FAOSTAT, 2020. China, Brazil, and the US are generally among the leading Citrus-producing countries , but this differs slightly when we look at the Citrus species separately in terms of their production quantity. According to FAOSTAT values, sweet oranges and sour oranges were categorized within the orange group by indicating the production amount of orange. The most produced Citrus fruits in the world, measured by quantity, were oranges with 75 million tons. Mandarins are the second most-produced among Citrus cultivars following orange production, with 38 million tons.Tangerine, mandarin, Clementine, and Satsuma were evaluated in mandarin groups. Brazil, India, and China are the leader countries in total orange production. China, Spain, and Turkey are the places where the most mandarin is produced around the world. It is seen that the production amount of mandarin has increased since 2016. Even though the mandarin production area decreased in 2020 compared to the previous year , there was an increase in mandarin production in 2020. For the last five years, China, Spain, and Turkey have maintained their leadership in mandarin production, respectively . Thanks to the taste and aroma that Citrus fruits have, Citrus fruits are consumed as food such as fresh fruit, juice, and jam. Furthermore, Citrus varieties are used in food, cosmetics, perfumery, and chemoprophylactic drug production in the pharmaceutical industry. In addition, Citrus species are beneficial for human health due to their phytochemicals and nutrients. The peel and pulp of Citrus cultivars contain ascorbic acid , alkaloids, coumarins, limonoids, carotenoids, and flavonoids such as anthocyanins. These phytochemicals with biological activities are essential for human health, and they help to prevent human degenerative diseases, including cancer, aging, cardiovascular diseases, inflammation, and diabetes II . Citrus fruits are among the most consumed fruits in the world due to their beneficial properties for health and their taste and aroma components. For this reason, it is important to develop new varieties with higher fruit quality and meet consumer demands with Citrus breeding. One of the most important goals of Citrus breeding is to produce and improve Citrus species with desired properties for global marketing. To obtain the selected properties, fruit quality characteristics must be improved. In Citrus fruits, especially mandarins, fruit size, taste, seedlessness, peelability, and color are critical fruit quality traits. These fruit characteristics are complex, and they can be affected by genetics , environment , genetics and environment interaction . To develop new varieties with desired properties for mandarin breeding, the genetic basis of fruit quality characteristics should be well understood. Modern genetics and modern biology tools such as molecular markers, linkage mapping, and quantitative trait locus analyses are performed for genetic studies in mandarins .