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Gametophytic Selection: a Simple Technique for Thermo Tolerance Genotypes Identification in Maize

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Gametophytic Selection: a Simple Technique for Thermo Tolerance Genotypes Identification in Maize Int.J.Curr.Microbiol.App.Sci (2017) 6(8): 1649-1655 International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 6 Number 8 (2017) pp. 1649-1655 Journal homepage: http://www.ijcmas.com Review Article https://doi.org/10.20546/ijcmas.2017.608.198 Gametophytic Selection: A Simple Technique for Thermo Tolerance Genotypes Identification in Maize Ashutosh Singh1*, Rajen Chowdhury2 and Ratan Das3 1Department of Plant Biotechnology UAS GKVK Bengaluru, India 2Department of Biotechnology, CPMB&B, Tamil Nadu Agricultural University, India 3Department of Horticulture and Post Harvest Technology Visva-Bharati, India *Corresponding author: ABSTRACT K e yw or ds Temperature of environment increase day by day so present time identification of Thermo tolerance heat tolerant genotypes is great challenge. Because tolerance to high temperature Genotypes, is a multi-genic character and also many screenable traits are available. But there no single techniques available which give holistic idea about plant level heat Gametophytic selection . tolerance. Gametophytic selection could be one of the alternative strategies. There are many successful attempt have been made to improve the crop plants by Article Info gametophytic selection. In this review discuss the advantages of gametophytic Accepted: selection over sporophytic selection, the effect of high temperature on maize and 17 June 2017 how gametophytic selection is a potential option for high temperature screening in Available Online: 10 August 2017 maize. Introduction The main goal of any plant breeding program are developed a small but growing resurgence is the improvement of all characteristics that of research focused on male gamete selection contribute to economic value. These has developed (McCormick, 2004). The life characteristics may be increased yield, ability cycle of angiosperms are consist of two parts of tolerant to biotic and abiotic stresses (Fehr (Gametophytic and sporophytic) and it 1991). Traditional selection has mainly provide opportunity to introduce early focused on the sporophytic phase of a plant’s selection into breeding program via life cycle. But sporophytic selection has many gametophytic selection (Fig. 1). The most limitations. With the improvement of prominent phase of angiosperm life cycle is breeding techniques and biotechnological the sporophytic generation and it develops advances, now many options available to from zygote followed by the fertilization. plant scientists interested in improving an array of plant responses and characteristics. Constrains of sporophytic selection In recent time information available from Traditional selection has mainly focused on plant genome and many advance techniques the sporophytic phase of a plant’s life cycle. 1649 Int.J.Curr.Microbiol.App.Sci (2017) 6(8): 1649-1655 But sporophytic selection has many Gamete selection limitations. It is extremely time consuming, labor intensive and can occupy vast quantities Gametophytic selection could be either male of space. Sporophytic selection also requires or female gametophytic selection. But the large population sizes in order to obtain the male gametes are more susceptible for stress essential combination of attributes needed to so crop improvement mainly focuses on male improve a crop. gametophytic selection. Male gametophytic development is a very complex process that Many woody perennial species especially requires the coordinated participation of have lagged behind in new cultivar various cell and tissue types and their development due to larger physical size and associated specific gene expression patterns. long juvenile phases (Hormaza and Herrero, In this process both sporophyitc (anther, 1996). Sporophytic selection needs to repeat tapetum) and gametophytic (pollen) tissues several seasons that increase the cost of participate in this process. Gametophytic selection. The environment changes day by selection is highly reduced system as day so it is very difficult to screen the crops at compared with the sporophyte and therefore it the field. provides opportunities to study the developmental regulation of gene expression The life cycle of angiosperms offers the and functional interactions between different opportunity to introduce early selection into cell types (Honys et al., 2004). breeding programs via gametophytic selection. The alternation of generations that Male gametophytic selection can occur in two occurs in angiosperms is a conserved attribute styles: selection for pollen competitive ability of the plant kingdom. The most prominent or selection for tolerance to environmental phase of the angiosperm life cycle is the stresses. The concept of selecting for pollen sporophytic generation. Sporophytes develop competitive ability relies on the assumption after fertilization of male and female gametes. that the most vigorous pollen grains will But gametophyte generation develops after confer vigour to the sporophyte (Ottaviano et meiosis of spores (Hormaza and Herrero, al., 1991). The main components of pollen 1996). These two different generations gives competitive ability are faster pollen idea for early selection pressure and it can be germination and pollen tube growth rates applied to both male and female which were shown to give rise to positive gametophytes. It is reported that male responses in kernel weight, because gametes are more sensitive for biotic and germinated pollen which have large pollen abiotic stresses so identification of pollen tube length can easily fertilize female gametes which are more resistance to these stress can (Ottaviano et al., 1983). Selective pressure be produce more resistant crop plants. And, can be most effectively applied at two times: competition between the large numbers of during pollen development or during pollen male gametophytes during development in the germination and tube growth (Hormaza and anther, pollen germination and tube growth in Herrero, 1996). Selection for such traits as the style, as well the independent phase that herbicide resistance is effective during the pollen experiences between shedding and quiescent stage, although for many stylar deposition, create an opportunity for environmental stresses it is important to apply easier manipulation using the male the selection pressure when genetic gametophyte (Ottaviano and Sari Gorla, differences are fully expressed. 1993). 1650 Int.J.Curr.Microbiol.App.Sci (2017) 6(8): 1649-1655 Temperature tolerance in maize attributed to both a direct effect of high temperature (Carberry et al., 1989) and pollen The global temperature increase day by day desiccation (Schoper et al., 1986; Lonnquist and different climate models predict that the and Jugenheimer, 1943). High temperature global mean temperature will continue this affects pollen fertility directly, since the crop trend, increasing by 1–4ºC by the end of the showed no visible symptoms of water stress twenty-first century, additionally (Schoper et al., 1987). climatological extremes such as heat waves leads to increase temperature more frequently Pollination is critical process for corn seed set (IPCC, 2013; Tebaldi et al., 2006; Hansen et and yield. For kernels to develop, silks must al., 2015). Above data suggested that average emerge and be fertilized by viable pollen. global temperature increases and it also Silks grow about 1 to 1.5 inches per day and significant different between seasonal and will continue to elongate until fertilized. also varies regional that leads to potential Temperatures greater than 35°C with low impact on the agriculture (IPCC, 2007). Most relative humidity will desiccate exposed silks, of the area under maize crop is in the warmer but not greater on impact silk elongation rates parts of temperate regions and in humid greatly. Pollen is no longer viable once subtropical climate. Highest production is in temperatures reach the more than optimum, areas having the temperature 21°C to 27°C. especially with low relative humidity. Maize production and productivity are prone Fortunately, pollen shed usually occurs from to rapid and constant changes due to global early to mid-morning when temperatures are warming related environmental changes lower. (Porter, 2005; Wahid et al., 2007). In india also 10-20% maize yield loss because of The temperature stress induces slow temperature fluctuation. desiccation of silks and result in low seeds set. Historically, this has been the most High temperature stresses affects all stages of important problem leading to yield reduction, crop. Among all stages reproductive stage of particularly in stressful years. Once silks maize is most sensitive. As the majority of begin to desiccate, they lose their capacity for our food supply is a product of sexual pollen tube growth and fertilization reproduction in flowering plants, (Madhiyazhagan Ramados et al., 2005). Heat understanding how different plants cope with also affects pollen production and viability. stress during their reproductive First, temperature more than 35°C depresses (gametophytic) phase is critical to managing pollen production. Even continuous heat, over the future of agricultural productivity. During several days before and during pollen-shed, the short time surrounding fertilization, even a results in only a fraction of fertile pollen single hot day cause fatal to reproductive being formed, probably because of the success for many plant species. Thus, it is reduced sugar available. In addition, high important to consider what aspects of plant temperature reduces
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