Available Online at http://www.recentscientific.com International Journal of CODEN: IJRSFP (USA) Recent Scientific International Journal of Recent Scientific Research Research Vol. 11, Issue, 01(D), pp. 36941-36949, January, 2020 ISSN: 0976-3031 DOI: 10.24327/IJRSR RESEARCH ARTICLE DOUBLED HAPLOIDS IN GENETIC IMPROVEMENT: A REVIEW 1Seeja, G and 2*Sreekumar, S 1Department of Plant Breeding and Genetics, College of Agriculture, Kerala Agricultural University, Ambalavayal, Wayanad Pin 673593 2Saraswathy Thangavelu Extension Centre, Jawaharlal Nehru Tropical Botanic Garden and Research Institute, Puthenthope, Thiruvananthapuram, Pin 695586 DOI: http://dx.doi.org/10.24327/ijrsr.2020.1101.5029 ARTICLE INFO ABSTRACT Article History: Doubled haploidy is a powerful tool to induce genetic improvement leading to economic Received 6th October, 2019 benefits especially among perennial crops with critical breeding duration. It represents Received in revised form 15th recombinant products of parental genomes in a completely homozygous state which have November, 2019 more relevance in horticultural crops that are either perennial in nature or out crossing Accepted 12th December, 2019 plants with severe inbreeding depression. The efficiency of doubled haploid recovery in Published online 28th January, 2020 various horticultural crops is one of the best breeding techniques which has to be explored extensively. Now-a-days, it can be efficiently combined with other plant biotechnological Key Words: techniques, enabling several novel breeding achievements, such as improved mutation Double haploidy, Polyploid, breeding, backcrossing, hybrid breeding and genetic transformation. The present reviews focussed on the genesis and application of doubled haploids in plant breeding. Population, Genetics, Crop, Breeding Copyright © Seeja, G and Sreekumar, S, 2020, this is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited. INTRODUCTION depression. Selection can be expected for traits caused by recessive deleterious genes that are associated with vegetative Genetic improvement is the basis of plant breeding, which growth. Induction of doubled haploidy and its relevance in actually expect some desirable variability in plant traits either plant breeding are briefly reviewed here. by utilization of existing natural variability or by creating artificial variability via conventional methods such as heterosis Origin of Doubled Haploids breeding, recombination breeding, mutation breeding, Haploids are plants with a gametic chromosome number (n) polyploidy breeding and non-conventional methods like and produced from diploid species (2n=2x), known as somatic hybridization, genetic engineering etc. Polyploidy is monoploids, contain only one set of chromosome in the one of the best options to induce genetic variability with sporophytic phase (2n=x). They are smaller, exhibit lesser plant desirable character especially among perennial crops. Based on vigour and are sterile due to the inability of their chromosomes the variation in chromosome number polyploidy can be to pair during meiosis. Therefore, to propagate through seed classified into different types such as haploids, diploids, and to include in breeding programs, their fertility has to be triplods etc,. Haploids can be modified into doubled haploids restored. A plant or line obtained by doubling the chromosome (DHs ) in which have homozygous alleles at all loci. Hence, it number of a haploid plant or individual is doubled haploid. can be represented as new varieties (self-pollinated crops) or as Doubled haploid technique is a valuable method for genetic parental inbred line for the production of hybrid varieties cartography of complex traits. (cross-pollinated crops). In fact, cross pollinated species often express a high degree of inbreeding depression due to The best method to shortcut breeding technology is induction heterozygosity and hence the induction of doubled haploids of haploid lines. Haploid plants are intensively utilized for process per se can serve not only as a fast method for the investigation and improvement of many agricultural crops. production of homozygous lines but also as a selection tool for Haploids are unique plants and can provide researchers with the elimination of genotypes expressing strong inbreeding *Corresponding author: Sreekumar, S Saraswathy Thangavelu Extension Centre, Jawaharlal Nehru Tropical Botanic Garden and Research Institute, Puthenthope, Thiruvananthapuram, Pin 695586 Seeja, G and Sreekumar, S., Doubled Haploids in Genetic Improvement: A Review genetic information not possible with normal diploid is needed, since kernels containing haploid embryos exhibit a individuals. normal germination rate and lead to viable haploid seedlings. In general, haploids are classified into three types. Maternal Haploid embryos can be selected early in the breeding process, based on morphological and physiological markers. haploids contain only nuclear material and cytoplasm from the maternal parent. In vitro androgenic haploid obtained through In vitro induction of maternal haploids is gynogenesis.i.e., the anther or microspore culture and contain both the through in vitro culture of un-pollinated flower parts, such as cytoplasm and nucleus of the developing microsporophyte. The ovules, placenta attached to ovules, ovaries or whole flower microspore developed haploids are better and accurate. In vivo buds. Regenerants show higher genetic stability and lower rate androgenic haploid develop from an egg cell or any other cell of albino plants compared to androgenetic ones. It is used in of the embryo sac and later chromosomes of the maternal plants in which other induction techniques, such as androgensis parent being lost during embryogenesis. It contains the and the pollination methods are unsuccessful. Gynogenesis is cytoplasm of maternal plant and only the chromosomes of the successful in several species10, such as onion, sugar beet, paternal parent. cucumber, squash, gerbera, sunflower, wheat, barley etc., History however, the success is greatly influenced by several biotic and abiotic factors. The genotype of donor plants, combined with The first report of the haploid plant was published in 1992 by growth conditions, is the crucial factor. In onion, marked 1 Blakeslee et al. in Datura stramonium. Subsequently, haploids differences in embryo yields have been recorded among 2 were reported in many other species . In 1964 Guha and accessions and among plants within accessions. The average 3 Maheshwari developed an anther culture technique for the frequencies of induced embryos (calculated from ovaries production of haploids in the laboratory. Haploid production by possessing 6 ovules) varied between 0% in non-responding 4 5 wide crossing was reported in barley and tobacco . Tobacco, accessions to 18.6-22.6% in extremely responsive accessions, rapeseed and barley are the most responsive species for with individual donor plants producing up to 51.7% embryos. doubled haploid production. Doubled haploid methodologies The high haploid production frequency was tested in two have now been applied to over 250 species. Haploids can consecutive years and showed to be stable over years11. originate spontaneously in nature or as a result of various Induction rates were even higher in preselected onion induction techniques like chromosome doubling. Spontaneous genotypes, achieving frequencies of 196.5% embryos from a haploid plants are reported in several crop species, like tomato, doubled haploid line12 or 82.2% for an inbred line13. potato, soybean, maize, barley, wheat, rice, rye etc. Androgenic haploid embryos are produced by parthenogenesis or Chromosome elimination after wide hybridization is an pseudogamy. In 1969 Kermicle6reported the possibility of alternative method for producing haploids which is commonly obtaining androgenic haploids in maize. Pollination of plants utilized in wheat. In this approach, pollen from either Hordeum containing the homozygous gene ig1 (indeterminate bulbosum or maize is applied to the silks of an emasculated gametophyte 1) produced 1-3% of seeds with an androgenic wheat spike. The application of maize pollen has proven to be haploid embryo. In vitro androgenesis is a process of induction the most successful approach by providing the highest and regeneration of haploids and doubled haploids originating frequency of haploids. It was discovered that haploid plants of from male gametic cells. Due to its high effectiveness and Hordeum vulgare could be obtained on a large scale following the hybridization of Hordeum vulgare with Hordeum applicability in numerous plant species, it has outstanding 14 potential for plant breeding and commercial exploitation. It is bulbosum . When H. vulgare and H. bulbosum are crossed, a well established for plant breeding, genetic studies and/or normal double fertilization event occurs. However, during seed induced mutations of many plant species, including barley, development, chromosomes of H. bulbosum are eliminated in wheat, maize, rice, triticale, rye, tobacco, rapeseed and both the embryo and endosperm. At approximately 10 days cabbage7.Gynogenesis is production of haploid embryos post-fertilization, most dividing cells in the embryo are haploid. exclusively from a female gametophyte. In situ induction of Colchicine, a mitotic inhibitor is applied to the haploid