Seedless in fruit crops: Parthenocarpic fruits

Parthenocarpy in fruits

1. Seedless fruits can occur when the ovary develops directly without fertilization (parthenocarpy) or when pollination and fertilization trigger ovary development , but the ovule/embryo aborts without producing mature seed (stenospermocarpy). ‘Parthenocarpy is the natural or artificially induced production of fruit without fertilization of ovules. The fruit is therefore seedless (Noll, 1902)’ Parthenogenesis refers to production of egg cells without fertilization Eg : Mangosteen INTRODUCTION

2. Seedlessness can contribute to increase the quality of the fruits when seeds are hard or have a bad taste. In the case of eggplant, the absence of seeds prevents browning and texture reduction of the pulp . Seeds can produce substances that accelerate the deterioration of the fruit, as in watermelon and eggplant. In this regard, the absence of seeds can increase the shelf life of the fruits, allowing a better conservation IMPORTANCE

3. In most plants, early fruit development can be divided into three phases. Development of the ovary with cell division, differentiation and fruit development which is generally referred to as fruit set . In second phase, fruit growth is primarily due to cell division. The third phase begins after cell division ceases. During this phase, fruit growth continues, mostly by cell expansion, until the fruit reaches its final size Mechanism of fruit development and seedless fruit formation

4. Genetic factors:  Some plant varieties have natural tendency to produce parthenocarpic fruits due to their genetic composition. For example plants like banana, pineapple, eggplant, etc. Hormones:  Certain plant hormones like auxins , gibberellins, etc. play an important role in development and maturation of fruit. Failed pollination:  Sometimes pollination fails but the chemical mechanism that get triggered due to the act of pollination leads to fruit development even if the fertilization fails. Stress:  Sometimes environmental stress can result in induction of parthenocarpy . For example, low temperature condition can result in production of parthenocarpic fruits in members of Cucurbitaceae Chemical inductions and mutation:  Sometimes plants are treated with certain chemicals that trigger fruiting without fertilization. Apart from this, spontaneous or induced mutations can also result in parthenocarpic fruit production. Causes of Parthenocarpy

5. Vegetative Parthenocarpy When parthenocarpic develop without pollination and from an unfertilized ovule, the parthenocarpy is said to be vegetative parthenocarpy Ex: Banana and Washington Navel Orange Stimulative Pathenocarpy Stimulative parthenocarpy occurs when parthenocarpy is induced by external factors like chemicals. Such parthenocarpy can be classified as hormone induced parthenocarpy or mutation induced parthenocarpy Ex: Black Corinth grapes Stenospermocarpy This is a unique type of parthenocarpy where fertilization does take place and the seed begins to develop but it eventually aborts Ex: Black Monukka and Sultania grapes Types of Parthenocarpy

6. Some plants that exhibit natural parthenocarpy are bananas, pineapples, cucumbers, grapes, and eggplants.

7. Changes occur during seedless fruit development

8. The seedlessness can be induced by the following methods . Use of growth regulators Application of GA at 8000 ppm in lanolin paste on the cut end of the style of the emasculated flowers of  guava  resulted in the development of seedless fruits. Similarly, seedlessness in loquat was induced by spraying GA 100 to 200 ppm on the emasculated flowers. Changing the ploidy level It was first demonstrated in Japan that by developing a triploid water melon 2n= 33 by crossing tetraploids x diploid varieties, seedlessness could be achieved. Naturally available seedless  guava  varieties are due to auto  polyploidy  (triploid) and not due to parthenocarpic fruit development.

9. Parthenogenesis In some plants, fruits develop parthenocarpically , still they produce viable seeds. (e.g. Mangosteen and Strawberry). This phenomenon is referred to as parthenogenesis. The seedlings of such fruits are genetically uniform. In certain cases, seeds develop partenogentically but they are non-viable (e.g.  Apple ) When female flowers of jack are pollinated with the pollen grains of bread fruit, seeds do form in jack but they did not germinate as they are non-viable.

10. Advantages Less messy and more enjoyable to eat. Eliminating cucumber seeds eases digestion issues for many people. Seedlessness lengthens shelf life since seeds tend to encourage the fruits' deterioration to hasten their dispersal into the world. Drawbacks They have to be propagated by cloning They have fewer vitamins and minerals They reduce the biodiversity of fruits