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The pollination and fertilization behavior of Fig plant Arbind Mani Tripathi Nepal [email protected]

1. Introduction: Fig is one of the oldest known fruit trees in the world and considered as sacred fruit in all holy books, as objects of worship and for their many practical uses. The Common Fig (Ficus carica L.) is a large, deciduous shrub or small tree , belongs to the family of Moraceae and probably originated in southern Arabia where Wildfig and Caprifig trees are still to be found (Condit, 1947; Zukovskij, 1950; Storey, 1975 cited by Mars, M.2003). Now a day, it is an important crop all over the world and the wild forms are found in Mediterranean, Arabia, Iran, and as well as in Central Asia and Transcaucasia (Mars, 2003). The height of fig plant is 6.9–10 metres, with smooth grey bark, leaves 12–25 cm. long and 10–18 cm. across, and deeply lobed with three or five lobes. The fruit is 3–5 cm. long, with a green skin, sometimes ripening towards purple or brown (Anonymous, 2009a). The genus Ficus has about 850 species and the somatic chromosome number is 2n = 2x = 26 (Storey, 1975; Jona & Gribaudo, 1991 cited by Mars, 2003). The fig plants not only an important crop for human beings but also they are extremely important food resources for wildlife. Several Ficus species are domesticated as ornamentals like F. elastica (India rubber plant), F. benjamina (weeping fig), F. religiosa (the sacred Bo-tree or Bodh-tree of the Buddhists, and sacred Pipal-tree of the Hindus) (Jona & Gribaudo, 1991 cited by Mars, M.2003). The only ones cultivated for their fruits are F. carica L. (the common fig). Figs are one of the highest plant sources of calcium and fiber. According to USDA, dried figs are richest in fibre, copper, manganese, magnesium, potassium, calcium, and vitamin K, relative to human needs. They have smaller amounts of many other nutrients. Figs have a laxative effect and contain many antioxidants. They are good source of flavonoids and polyphenols. Fig leaves are used as animal feed and the latex, dried and powdered, is used to coagulate milk. According to FAO reports of 2005, fig-production was 1,057,000 tonnes; Turkey was the top fig-producer (285,000 tonnes), followed by Egypt (170,000 tonnes) and other Mediterranean countries (Anonymous, 2009b).

2. Types of Fig There are 277 collections of figs originating from different Mediterranean areas (Roger and Khadari, 2003) and classify four different horticultural types such as Caprifigs, Smyrna (one crop), San Pedro (two crops) and Common (parthenocarpic) types (Lyons and Mceachern, 2009, Anonymous, 2009c) which are described in given below.

2.1. Capri Fig. The Caprifig produces a small non-edible fruit and produces both types of staminate and pistillate flowers. This pollen is essential for fertilizing fruit of the Smyrna and San Pedro types which pollen is transported by a Blastophaga wasp to the pollen-sterile types. Commercial growers hang baskets of Blastophaga-infested Caprifigs so they can effectively pollinate the fruit.

2.2. Smyrna Fig The Smyrna fig variety produces large edible fruit with true seeds but needs to pollination for fruit setting. The Blastophaga wasp (pollinator) and Caprifigs (pollinizer) are most important factors to require for normal fruit development. If the fertilization process

does not occur, fruit will not develop properly and will fall from the tree but one thing wasp does not oviposit in fruit due to very long styles. These types of figs are commonly sold as dried form.

2.3. San Pedro Fig These figs have combined characteristics of Smyrna and Common figs and they can bear two crops of fruit in one season. First crop on last season's growth called the Breba crop which is parthenocarpic no need to pollination and the second crop is the Smyrna type which requires to pollinator (Blastophaga wasp) and pollinizer (Caprifigs) for fruit development. It is rarely cultivated as a commercial purpose.

2.4. Common Fig These figs develop parthenocarpically without pollination so they do not have true seeds and produced on current season wood. The first crop of these figs bears on one year old wood while second crop borne on current season's growth. Most commercial cultivars are found in this group like Mission, Kadota, Magnolia, Brown Turkey, Celeste etc.

3. Flowering and fertilization behaviour Fig is widely distributed in the tropics and subtropics regions where its numerous variations found. The flower biology and fertilization process play a crucial role in the fig. The grower often faced difficulties for obtaining sufficient yield because exactly they do not know local figs fertilization behaviour. The Ficus genus is characterized by hundreds to thousands of tiny flowers occurring in the inside of a fleshy, fruit-like body. The fruit-like body or receptacle is commonly thought as a fruit, but it is properly a false fruit or multiple fruit, in which the flowers and seeds grow together to form a single mass. So, the fig "fruit" is derived from a specially adapted type of inflorescence and technically called a syconium (Anonymous, 2009d). The syconium often has a bulbous shape with a small opening (the ostiole) at the outward end that allows access to pollinators. The flowers are pollinated by very small wasps that crawl through the opening in search of a suitable place to lay eggs. Without this pollinator service fig trees cannot reproduce by seed. The small opening visible at the apex of the synconium, is a narrow passage, which allows entering specialised wasp for pollination. At least 1000 species of figs occur in both bisexual and unisexual forms and with significant variation within those two types. About half of the species are monoicous (with both male and female flowers occurring inside each of their fruit-bodies), and about half are dioicous (having separate male dominant flowering and female-flowering trees). The flower is invisible and blooming inside the fruit. The Common fig flowers are female type and its syconia contains only long-styled pistillate flowers. The Caprifig which has male and female flowers requiring visits by a tiny wasp (Blastophaga grossorum) and its syconium contain short styled pistillate flowers distributed inner wall and staminate flowers massed around the interior of the ostiole. The Smyrna fig is requiring cross-pollination by caprifigs in order to develop normal. The San Pedro fig is intermediate and its first crop independent like the common fig while second crop dependent on pollination. Floral scents often act as pollinator attractants. In the case of obligate and specific plant–pollinator relationships, the role of floral signals may be crucial in allowing the encounter of the partners. About 750 Ficus species (Moraceae) are involved in such interactions, each with a distinct species of pollinating wasp (Pige, et al. 2002). The receptive female phase of individual syconia may last more than two weeks, being marked by the

production of long distance attracting volatile substances which are detectable to fig wasps for several days (Kjellberg et al., 1983; Kjellberg et al., 1988). The wasps that pollinate Ficus inflorescences can be active or passive pollinators. They lay their eggs in fig flowers, so that a proportion of flowers will host a wasp larva instead of a seed. Jousselin, et al. (2003) showed, an actively pollinated monoecious fig that lack of pollination does not induce fig abortion, compared the locations of eggs and fertilised flowers of three actively pollinated Ficus species and one passively pollinated species. And found that more flowers containing wasp eggs were fertilised in the actively pollinated species relative to those of the passively pollinated one.

Fig wasps and Figs Fig wasp is the common name of wasps belongs to the family Agaonidae, which pollinate the flowers of fig trees. Adult fig wasps are commonly no larger than 5 millimetres in length. Fig wasps are members of the order Hymenoptera, comprising the ants, bees, wasps, and sawflies etc. Among the Agaonidae, the female is the more typically appearing insect, while the males are mostly wingless. In many cases the males' are mating females while still within the fig syconium and die inside the syconium after they mate. Inside the monoicous species of fig fruits have three kinds of flowers such as male, short female, and long female. Female fig wasps can reach the ovaries of short female flowers with their ovipositors, but cannot reach the ovaries of long female flowers. Thus, the short female flowers grow wasps and the long female flowers grow seeds, if they are pollinated. In the half of the fig species that are dioecious the female trees bear only female flowers while the fruit bodies of the male trees often are bisexual (hermaphrodite) but functionally male. The bisexual or hermaphrodite common figs are called Capri fig. The other one is female, as the male flower parts fail to develop; this produces the "edible" fig. Fig wasps grow in Caprifigs but not in the female syconiums because the female flower is too long for the wasp to successfully lay her eggs in them. However, the wasp pollinates the flower with pollen from the fig. In turn, the flowers provide a safe haven and nourishment for the next generation of wasps. Figs and fig wasps depend on each other to complete their reproduction (Jin-yan, 2005). The close company between fig species and their wasp pollinators proved clear example of co-evolution (Anonymous, 2009e, Kjellberg & Valdeyron, 1984 cited by Mars, 2003).When the wasp dies, it is broken down by enzymes inside the fig. Fig wasps are not known to transmit any diseases harmful to humans. There are typically only one species of wasp (Blastophaga psene) capable of fertilizing the flowers of each species of fig (Anonymous, 2009f). References: Anonymous, 2009a. Ficus [Online]. Available: http://en.wikipedia.org/wiki/Ficus (2009-081). Anonymous,2009b.Common fig[Online]. Available: http://en. wikipedia. org/wiki/ Common _fig (2009-7-28) Anonymous,2009c. Fig - Ficus carica L. [Online]. Available: http:/ /www. uga.edu /fruit /fig.html#taxonomy (2009-07-30). Anonymous,2009d. FIG [Online]. Available: http://www.crfg.org/pubs/ff/fig.html(2009-7-28) Anonymous,2009e. [Online]. Available: http://en.wikipedia.org/wiki/Ficus

Anonymous, 2009f. [Online]. Available: http://www. newworldencyclopedia.org/ entry/ Fig_ wasp (2009-8-2). Condit, I.J. 1947. The fig. Waltham, Chronica Botanica. Jin-yan Y., Z. Nan-xian, C, Yi-zhu, J. Xiao-cheng, D. Yua and Y. Hui, 2005.Seed and Wasp Production in the Mutualism of Figs and Fig Wasps. Forestry Studies in China, Vol.7 (1). Jona B. and I. Gribaudo, 1991. Ficus spp. In : Biotechnology in Agriculture and Forestry, Vol. 16, trees III (ed. by Y.P.S. Bajaj) : 76 - 93. Jousselin, E., M. H. Mckey. E. A. Herre and F. Kjellberg, 2003.Why do fig wasps actively pollinate monoecious figs? Oecologia 134: 381–387 Kjellberg, F., A. Aljibouri et G. Valdeyron, 1983. Observations récentes sur la pollinisation du figuier. Fruits, (38) 7 - 8: 567 - 569. Kjellberg, F. and G. Valdeyron, 1984. The pollination of the fig tree (Ficus carica L.) and its control in horticulture. Acta Oecologica , Oecol. Gener., (5) 4 : 407 - 412. Kjellberg, F., B. Doumesche and J.L. Bronstein, 1988 : Longevity of a fig wasp (Blastophaga psenes L.). Ecology 91 (2), :117 - 122. Lyons C. G. and G. R. Mceachern, 2009. Home fruit production - figs. [Online]. Available: https://aggie-horticulture.tamu.edu/extension/homefruit/fig/fig.html (2009-7-28). Mars, M.2003. Fig (Ficus carica L.) Genetic Resources and Breeding. Acta Hort., ISHS,605: 19-27. Pige, L. G., J. M. Ere, and M. H. Mckey, 2002. Specific attraction of fig pollinating wasps: Role of volatile compounds released by tropical figs. Journal of Chemical Ecology, Vol. 28(2). Roger J.P. and B. Khadari, 2003. Fig Germplasm of (1)CBNM Porquerolles Displays An Important Genetic Variability : Evidence from Pomological Descriptors. Acta Hort. ISHS 605: 51-59. Storey, W.B., 1975: Figs. In Janick J. and J. Moore (eds.), Advances in fruit breeding. Purdue Univ. Press. Indiana, pp. 568 - 589. Zukovskij, P.M. 1950. Ficus. In: Cultivated plants and their wild relatives., State Publishing House Soviet Science, Moscow, 1950, pp. 58 - 59.