Anther Culture Tool for rice breeding
It is urgent that biotechnology and related tools be used to support traditional breeding strategies. This will allow rice producers to overcome the production limitations and improve the quality and climatic tolerance of the crop. Culture is a method that allows homozygosity to be fixed immediately by diploidizing regenerated haploid plant stems. This makes it an efficient way to develop inbred lines. The successful use of Anther culture in the acceleration of breeding programs for many crop species, including rice, has been proven to be a success. Unfortunately, there are still many limitations that prevent it from reaching its full potential. Although culture has proven effective in Japonica rice breeding, it is not applicable to Indica rice due to its inherent recalcitrant genetic background.
Indica rice is subject to a number of limitations, including early anther necrosis and poor callus induction, proliferation, low green plant regeneration, frequent albinism, and poor callus recruitment and proliferation. Factors such as the genotype, physiological condition of donor plants, pollen development stage at cultivation, composition and physical state of culture media, incubation conditions, and anther pretreatments all play a role in androgenesis. This chapter outlines the possibilities for improving the application of anther culture techniques on rice to create a supplementary breeding tool. Rice has been a staple food since ancient times. Rice growers must increase their production due to an increase in the human population. Due to limited resources, this has been more challenging. It is imperative to use biotechnology and other related tools in order to not only overcome the productivity barrier, but also increase the quality and production efficiency of the product and reduce biotic and biotic stress tolerance. Culture is one of the many modern biotechnological methods to improve rice crop.
culture is a method for rapid development of fully homozygous lineages. Anther culture is an alternative to traditional inbred line generation which usually requires several cycles of inbreeding. Although anther culture can be used to supplement the breeding of Japonica rice varieties, its use for Indica varieties is restricted due to their genetic background. Indica rice has limited androgenic potential due to early anther necrosis and poor callus induction. Also, there is a low rate of green plant regeneration and albinism. Many factors affect the success of the technique, including genotype, physiological status, stage of pollen development at culture, composition of culture media (including nutritional sources and growth regulators), physical condition of culture media and anther pretreatments.
This chapter provides an overview of the practical aspects and uses of anther cultivation techniques for rice breeding.
Technique of culture
In order for androgenesis success, microspores must be directed towards sporophyte growth. Pretreatments are usually required to disrupt the normal process of pollen development and trigger the androgenic response. There are many pretreatments that are needed for androgenesis. These pretreatments can be different for different species, as well as variations within species. There is no single method that can be used for all species and varieties of androgenesis. There are however, well-documented protocols that can be used during anther cultivation.
Rice culture involves two steps. The first is to incite embryogenic calluses using microspores, followed by green plant regeneration with the induced calluses. Rice anther culture protocol includes pretreatment of panicles, surface sterilization, excision of anthers (from panicles), and in vitro cultivation of anthers using a specific medium under aseptic conditions. Anthers respond to culture by a gradual browning of the anther wall tissues and the breaking or splitting of the the anther to expose their pollen callus. After 3-8 weeks of cultivation, anthers will develop pollen callus. The second stage is to use appropriate regeneration media to regenerate the green plants from calluses. The plants that have been regenerated are then transplanted into the desired environment and can then be acclimatized to ensure they become haploids.
Histories of another culture
Reference first reported the possibility of altering the gametophytic pathway in microspores to facilitate haploid plant growth through in vitro cultivation. This was done by culturing immature Anthers from the Solanaceous species Datura Innoxia. Reference obtained haploid plants by culturing Nicotiana isolated anthers. In vitro cultivation of anthers and isolated Pollen has proven successful in haploid growth with many other crops, including rice, wheat, maize and Brassica. Microspore embryogenesis is effective for model species like barley, rapeseed and tobacco. However, other species that are economically or scientifically important such as Arabidopsis and woody plants and legume crops are less responsive to the technique. This important technique for creating haploids or dihaploids has undergone extensive research. The technique should be practical and can be used in breeding programs. Anther or microspore cultivation must be capable of producing haploids in large quantities from virtually any genotype or species.
Reference first reported haploloid plant production in rice using anther culture. Many studies have been done to improve various aspects of rice-culture. Not only can culture be used for dihaploid production, but applications have also been developed to allow for gene transformation and other biotechnological methods. The Japonica rice varieties are most popular in Japan and China. Culture has been widely used to improve the rice crop because they can be grown in vitro. This technique is not suitable for Indica rice breeding because of the inherent resistance to Indica varieties. The potential for Indica rice breeding has yet to be fully explored.