Citrus Anther Culture
Abstract
Oranges (Citrus sp) are a genus of the Rutaceae family that has the highest economic value. In general, people like oranges because they taste sweet, refreshing, the skin is easy to peel and contains lots of vitamin C which is very beneficial for the body. Our country is one of the orange producers which has quite large potential to meet consumer demand at home and abroad. Therefore, Indonesia is the second largest importing country in ASEAN after Malaysia because the availability of citrus fruit in the country is not sufficient for people's needs. Efforts to increase orange production, apart from expanding the planting area, are also carried out through plant breeding programs using hybrid seeds that have high yields and are of good quality both genetically and in terms of their growth capacity. Hybrid seeds can be obtained from crossing two pure lines used as parents. To obtain pure lines, this can be done through conventional crossing, namely by crossing between varieties followed by a selection process. However, the application of this technique still has several obstacles, including incompatibility problems, it is still influenced by climate and soil conditions, it requires a very long time, the use of extensive selection land, and the unavailability of the gene sources needed in cultivated germplasm. Apart from that, conventional crossing will produce progeny that will segregate. Therefore, a method is needed that can shorten the time to obtain pure strains without crossing. One alternative to overcome this is to use anther culture techniques. Anther culture is a tissue culture technique that can speed up the process of obtaining pure lines (homozygos) through multiplication. With anther culture a haploid callus will be produced which will later be regenerated into a haploid plant which has the same chromosomes as the gamete cells, and if the chromosomes are doubled it will produce a double haploid plant which can be used as a parent in conventional breeding to produce F1 hybrids. Apart from conventional breeding purposes, haploid callus can also be used as material (parents) for protoplast fusion to produce triploid fusion products which, when regenerated, will produce seedless orange plants. Anther culture has been successfully applied to many plants, including rice and tomatoes. Factors that need to be known so that induction of embryogenesis from anther culture can be successful include: 1) determining the development phase of responsive microspores, 2) temperature or carbon source stress treatment, 3) appropriate media composition, and 4) suitable culture incubation conditions. support. One important factor that influences the production of haploid plants through anther culture is the stage of microspore development. In most plant species, anthers are responsive only during the uninucleate phase of pollen development. In contrast, in tobacco plants the optimum response was found at some time before, during and after the first mitotic phase of pollen (the end of the uninucleate phase to the beginning of the binucleate phase of pollen). Another factor that determines the success of anther culture is pretreatment of the anthers before anther culture. Before being introduced to the in vitro environment, the anthers can be given stress pretreatment such as mannitol, temperature (low and high), osmotic, nitrogen and carbohydrate. With stress pretreatment, metabolic processes in the tissue will stop temporarily and after a certain period of time the tissue will begin to develop again with a new metabolic pathway if it is in supportive environmental conditions. Stress pretreatment also plays a role in diverting the gametophytic development pathway into the sporophytic direction to produce embryos. Without stress, microspores will develop into normal ripe pollen. Stress can be applied at the level of the whole plant, flower bud, anther, or directly on the microspores. The composition of the basic media and isolation techniques are very important for the success of anther culture. Optimization of selected media is generally carried out to increase the medium's ability to induce callus formation, embryos, and regeneration of cultured explants. The media in plant tissue culture generally consists of macro, micro nutrient components, vitamins, amino acids, sugars, complex organic materials, solidifying agents (agar), and growth regulators.
