can then develop into an embryo within the emerging seed. Repeated fertilizations within the ovary are accompanied by maturation of the ovary to form the tomato fruit. Homologs of the recA gene, including rad51, play a key role in homologous recombinational repair of DNA during meiosis. A rad51 homolog is present in the anther of tomato (Lycopersicon esculentum), suggesting that recombinational repair occurs during meiosis in tomato. Hydroponic and greenhouse cultivation Tomatoes are often grown in greenhouses in cooler climates, and cultivars such as the British 'Moneymaker' and a number of cultivars grown in Siberia are specifically bred for indoor growing. In more temperate climates, it is not uncommon to start seeds in greenhouses during the late winter for future transplant. Greenhouse tomato production in large-acreage commercial greenhouses and owner-operator stand-alone or multiple-bay greenhouses is on the increase, providing fruit during those times of the year when field-grown fruit is not readily available. Smaller sized fruit (cherry and grape), or cluster tomatoes (fruit-on-the-vine) are the fruit of choice for the large commercial greenhouse operators while the beefsteak varieties are the choice of owner-operator growers. Hydroponic technique is often used in hostile growing environments, as well as high-density plantings. Picking and ripening To facilitate transportation and storage, tomatoes are often picked unripe (green) and ripened in storage with ethylene. A machine-harvestable variety of tomato (the "square tomato") was developed in the 1950s by University of California, Davis's Gordie C. Hanna, which, in combination with the development of a suitable harvester, revolutionized the tomato-growing industry. This type of tomato is grown commercially near plants that process and can tomatoes, tomato sauce, and tomato paste. They are harvested when ripe and are flavorful when picked. They are harvested 24 hours a day, seven days a week during a 12- to 14-week season, and immediately transported to packing plants, which operate on the same schedule. California is a center of this sort of commercial tomato production and produces about a third of the processed tomatoes produced in the world. In 1994, Calgene introduced a genetically modified tomato called the FlavrSavr, which could be vine ripened without compromising shelf life. However, the product was not commercially successful, and was sold only until 1997. Yield The world dedicated 4.8 million hectares in 2012 for tomato cultivation and the total production was about 161.8 million tonnes. The average world farm yield for tomato was 33.6 tonnes per