Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Journal of Cell and Tissue Research Vol. 16(2) 5727-5732 (2016) (Available online at www. Tcrjournals.com) ISSN: 0973-0028; E-ISSN: 0974-0910 Review Article CONTRIBUTION OF BIOTECHNOLOGY TO HIGHER MAIZE PRODUCTIVITY: A MINI REVIEW ? MIR, S. D.,1 AHMAD, M.,1 ZAFFAR. G.,2 LONE, A. A.,2 RATHER. M. A.,3 DAR, Z. A.,2 MEHRAJ, U.1 AND MIR, M. A.4 Division of Genetics and Plant Breeding, Faculty of Agriculture Wadura; 2Dryland (Karewa) Agricultural Research Station, Budgam, Srinagar; 3Zeera Research Station, Gurez; 4Directorate of Sericulture, Srinagar. Sher-e-Kashmir University of Agricultural Sciences and Technology of Kashmir Shalimar campus, Srinagar 191 121. E. mail: [email protected], 1 Received: April 17, 2016; Accepted: May 18, 2016 Abstract: In the context of current climate variability, as well as predicted increases in mean temperature and annual precipitation, what do recent advances in agricultural biotechnology offer the genetic enhancement of agricultural crops so that they are better adapted to biotic and abiotic stresses, leading to higher crop productivity? Developing crops that are better adapted to abiotic stresses is important for food production in many parts of the world today. Anticipated changes in climate and its variability, particularly extreme temperatures and changes in rainfall, are expected to make crop improvement even more crucial for food production. Biotechnology approaches, molecular breeding and genetic engineering, and their integration with conventional breeding to develop verities for Maize, Sorghum and Barley crops that is more tolerant of abiotic stresses. In addition to a multidisciplinary approach, we also examine some constraints that need to be overcome to realize the full potential of agricultural biotechnology for sustainable crop production to meet the demands of a projected world population of nine billion in 2050. Key words : Biotechnology, Maize improvement INTRODUCTION In recent years biotechnology is emerging as one of the latest tools of agricultural research. In concert with traditional plant breeding practices, biotechnology is contributing towards the development of novel methods to genetically alter and control plant development, plant performance and plant products. Great progress has been made over the past decade with respect to the application of biotechnology to generate nutritionally improved food crops. Biofortified staple crops such as rice, maize and wheat harboring essential micronutrients to benefit the world’s poor are under development as well as new varieties of crops which have the ability to combat chronic disease. The accessibility of food crops that are high in nutritional content is granted for those who live in the industrialized world; however, this is not always the case for the rural poor who reside in developing countries. For such populations, a diet that is balanced in adequate levels of vitamins and minerals can be difficult to achieve and maintain. All too often, a monotonous diet in which a single crop such as rice predominates is all that is on hand and affordable [1]. Fortunately, due to recent developments in agricultural biotechnology, it is now possible to generate food crops which are nutritionally enhanced to improve the content and bioavailability of essential nutrients, such as iron and vitamin A [2,3]. A Similar technology has been used to fend off chronic illnesses including heart disease and cancer [4,5]. The term biotechnology is composed of two 5727 J. Cell Tissue Research words bio (Greek bios, means life) and technology (Greek technologia, means systematic treatment). Biotechnology involves the systematic application of biological processes for the beneficial use. One of the areas of plant biotechnology involves the delivery, integration and expression of defined genes into plant cells, which can be grown in artificial culture media to regenerate plants. Thus biotechnological approaches have the potential to complement conventional methods of breeding by reducing the time taken to produce cultivars with improved characteristics. Conventional breeding utilizes domestic crop cultivars and related genera as a source of genes for improvement of existing cultivars, and this process involves the transfer of a set of genes from the donor to the recipient. In contrast, biotechnological approaches can transfer defined genes from any organism, thereby increase the gene pool available for improvement. The improvement of wheat by biotechnological approaches primarily involves introduction of exogenous genes in a heritable manner, and secondarily, the availability of genes that confer positive traits when genetically transferred into considerable attention over the years from plant breeders with the purpose of increasing the grain yield and to minimize crop loss due to unfavourable environmental conditions, and attack by various pests and pathogens. In the early 60’s, conventional breeding coupled with improved farm management practices led to a significant increase in world wheat production thereby ushering in the green revolution. Subsequently, the targets of genetic improvement shifted to reducing yield variability caused by various biotic and abiotic stresses and increasing the inputuse efficiency [6]. With this change in the global food policy in the last few decades, biotechnology offered a possible solution firstly, by lowering the farm level production costs by making plants resistant to various abiotic and biotic stresses, and secondly, by enhancing the product quality (i.e. by increasing the appearance of end product, nutritional content or processing or storage characteristics). The introduction of foreign genes encoding for useful agronomic traits into commercial cultivars has resulted in saving precious time required for introgression of the desired trait from the wild relatives by conventional practices and alleviating the degradation of the environment due to the use of hazardous biocides. In recent years, wheat improvement efforts have therefore focussed on raising the yield potential, quality characteristics and resistance to biotic stresses and tolerance to abiotic stresses depending on the regional requirement of the crop. Role of biotechnology in maize improvement: Biote-chnology has contributed tremendous advances in maize production via different avenues, including application of effective bio fertilizers, plant growth promoter and more importantly development of transgenic traits resistant to herbicides and/or pests [7]. QTL for BSLB resistance in maize: Banded leaf and sheath blight (BLSB) caused by Rhizoctoniasolani Kühn in maize (Zea mays L.) is an important disease in China as well as South and Southeast Asia. The identification of quantitative trait loci (QTL) for resistance to this disease would facilitate the development of disease resistant maize hybrids. BLSB is an enormously destructive disease on susceptible maize. So it is desirable to exploit additional sources of resistance against BLSB to improve the disease resistance of present maize hybrids. Moreover, BLSB does not occur every year, so general resistance genes could easily be lost in the absence of selection pressure in conventional breeding programs. Marker-assisted selection (MAS) promises to be superior to conventional phenotypic selection if the trait is severely affected by environmental conditions or is difficult to evaluate [8]. Localization of genes controlling disease resistance via DNA markers could allow introgression of these genes into elite materials, even in areas where the disease is not common. Significant QTL were located on 11 chromosomal regions. Two major QTL (qBLSB-2a at Ya’an and qBLSB-6c at Chongqing) explaining phenotypic variation of 10.35 and 9.26% were only identified in one environment. Four other QTL (qBLSB-2c, qBLSB-6a, qBLSB-6b, and qBLSB-10) with genetic distances away from the closest linkage markers of 0.01 to 10.00 cM were found in both environments. QTL qBLSB-6b and qBLSB-10 were located to two chromosomal regions between bnlg 1600 and umc 1818 and mmc 0501 and phi 054. The QTL detected in this region each in two environments had same closest linkage markers bnlg 1538 and phi 054, respectively. They may be used for MAS [9]. QTL for DM resistance in maize: Progress has been made in mapping agriculturally important genes with molecular makers, which forms the foundation for marker-aided selection (MAS). The use of MAS can expedite such difficult screening procedures such as the testing for disease or insect 5728 Mir et al. resistance. However, when several resistance genes are initially present in a donor parent, some of them may be lost during the breeding programs. The chance of losing resistance genes can be reduced if they are detected early. This is particularly useful when the breeding process is time consuming, e.g. when exotic germplasm is used as the resistant parent. QTLs for resistance to P. sorghiin maize is based on RFLP mapping a population derived from 94 RILs. [10] identied tight linkage of the RFLP markers umc11, umc23a, and umc113 to genes conferring resistance to P. sorghiin maize. Twoof the three QTLs were not always constant across seasons. However, only one QTL was stable in both seasons. These results suggest that one major gene and two minor genes control SDM resistance. These markers should bevery useful in breeding programs in facilitating the introgression of the resistance genes into commercial varieties. DNA markers in genomic regions of interest enable breeders to select on the basis of genotype rather than phenotype, which can be especially helpful if a target trait is time-consuming to score. Markerbased breeding will revolutionize the process of cultivar development [11]. Another interesting application of these results would be the use of these linked markers as a starting point for molecular approaches, such as chromosome walking, to clone the resistance genes [12]. Marker-assisted selection for these loci should be productive for Resistance QTL clusters in maize: The distribution of the QTL in the genome showed a high concentration of QTL in a few chromosomal regions. Such a concentration in the distribution of QTL has already been observed in previous studies by a number of workers. Many resistance genes and QTL in maize have been located in 3.04 and 6.01 regions of chromosomes [13]. For example, in 3.04 region, four resistance genes for rust disease (rp3, wsm2, mv1, and scm2) were located within 5 cM by RFLP markers UMC102 and UMC10 [14,15]. The resistance QTL for European corn borer (Ostrinianubilalis Hübner) was located in the 3.04 region. And in the 6.01 region, resistance genes for Cochliobolus heterostrophus (Drechs.) Drechs. Helminthosporiummaydis (Nisikado & Miyake) rhm1 and scm1 [14,16] were found. These results indicated that 3.04 and 6.01 regions were important for disease and insect resistance in maize. In this study, only five QTL of qBLSB-1, qBLSB-3, qBLSB-4, qBLSB-5, and qBLSB-6c were not mapped close to other QTL. The remaining 6 QTL were located in three chromosomal regions 2.06 to 2.08, 6.01 to 6.02, and 10.02 to 10.03, forming three groups of QTL. These results corroborated previous findings and supported the concept that resistance QTL to diseases and insects in maize were not randomly distributed across the genome but clustered in specific regions [17]. QTL for resistance to GRS in maize: Fusarium graminearum Schwabe, the conidial form of Gibberellazeae, is the causal fungal pathogen responsible for Gibberella stalk rot of maize. Using a BC (1) F(1) backcross mapping population derived from a cross between ‘1145’ (donor parent, completely resistant) and ‘Y331’ (recurrent parent, highly susceptible), two quantitative trait loci (QTLs), qRfg1 and qRfg2, conferring resistance to Gibberella stalk rot have been detected. The major QTL qRfg1 was further confirmed in the double haploid, F(2), BC(2)F(1), and BC(3)F(1) populations. Within a qRfg1 confidence interval, single/low-copy bacterial artificial chromosome sequences, anchored expressed sequence tags, and insertion/deletion polymorphisms, were exploited to develop 59 markers to saturate the qRfg1 region. A step by step narrowing-down strategy was adopted to pursue fine mapping of the qRfg1 locus. Recombinants within the qRfg1 region, screened from each backcross generation, were backcrossed to ‘Y331’ to produce the next backcross progenies. These progenies were individually genotyped and evaluated for resistance to Gibberella stalk rot. Significant (or no significant) difference in resistance reactions between homozygous and heterozygous genotypes in backcross progeny suggested presence (or absence) of qRfg1 in ‘1145’ donor fragments. The phenotypes were compared to sizes of donor fragments among recombinants to delimit the qRfg1 region. Sequential fine mapping of BC(4)F(1) to BC(6)F(1) generations enabled us to progressively refine the qRfg1 locus to a ~500-kb interval flanked by the markers SSR334 and SSR58. Meanwhile, resistance of qRfg1 to Gibberella stalk rot was also investigated in BC(3)F(1) to BC(6) F(1) generations. Once introgressed into the ‘Y331’ genome, the qRfg1 locus could steadily enhance the frequency of resistant plants by 32-43%. Hence, the qRfg1 locus was capable of improving maize resistance to Gibberella stalk rot [9]. Strategies for disease control: The smut fungi Ustilagomaydis and Sporisoriumreilianum are parasites that attack maize plants. Ustilagomaydis 5729 J. Cell Tissue Research causes a disease known as boil smut or common smut, which is characterized by large tumour-like structures on the leaves, cobs and male flowers in which the fungus proliferates and produces spores. Sporisoriumreilianum also attacks maize plants; however, it infects the entire plant and its symptoms become manifested only in the male and female flowers. For this reason, it is also referred to as maize head smut. Little has been known up to now as to how these pathogens cause disease. Four years ago, a team of scientists headed by the Marburg group succeeded in decoding the genome sequence of Ustilagomaydis. They demonstrated that the genes, for a large number of completely new proteins secreted by the fungus, are arranged in groups on the chromosomes in so-called gene clusters. These proteins control the colonisation of the host plant. The researchers were initially only able to demonstrate the presence of these proteins in Ustilagomaydis. “However, they found it hard to imagine that these proteins, which play such a crucial role in maize infestation, should only be present in the genome of a single smut fungus. For this reason, they also sequenced the genome of Sporisoriumreilianum,” explains RegineKahmann from the Max Planck Institute in Marburg. Over 90 percent of the proteins secreted by Ustilagomaydis also exist in Sporisoriumreilianum. However, many of these proteins differ significantly between the two species and are therefore difficult to detect at the gene level. “Surprisingly, however, almost all of the genes of the two organisms are arranged in the same order. As a result, they were able to superimpose the two genomes like blueprints and display the differences in this way,” says Kahmann. The scientists discovered 43 so-called divergence regions, in which the differences in the two sets of genes are particularly significant. These included all of the gene clusters identified four years ago, whose genes play an important role in the infection of the host plant. In addition to this, four out of six randomly selected divergence regions influence the strength of Ustilago maydis infection, and surprisingly, one of these does not contain genes for secreted proteins. “This shows that additional, thus far undiscovered molecules control the relationship between the fungus and the plant,” comments Jan Schirawski. Therefore, the genes that differ most strongly between the two fungi are in all likelihood those that play an important role in the infestation of the maize plant. The different life styles of Ustilagomaydis and Sporisoriumreilianum presumably resulted in the development of species-specific gene variants in these fungi over the course of evolution, e. g. to suppress the plant’s immune response. The maize plants, in turn, modified the target molecules of these fungal proteins. Maize plants apparently form at least one protein to counteract each of the proteins released by the fungi. “What they see that the signs of an ongoing struggle between the defending plant and attacking parasite. The variety of the weapons of attack and defence used is the product of an arms race between the plant and the fungus. Each modification on one side is countered by an adaptation on the other,” explains Schirawski. With the help of the molecules they discovered on the basis of the differences between the two fungi, the Marburg-based researchers have the long term hope that it will be possible to develop new strategies for disease control of these and related plant parasites. Transgenic maize: Maize has also been biofortified with β-carotene as well as other essential micronutrients necessary to maintain one’s health. [18] measured the triglycerol-rich lipoprotein fraction of blood from North American female volunteers who consumed biofortified maize porridge. In this case, the authors found a vitamin A equivalence value of β-carotene in biofortified maize to be 3.1-fold higher than in conventional white porridge maize. A similar study using Zimbabwean men found biofortified yellow maize porridge to provide an equivalence of 40%–50% of the US recommended Dietary Allowance of vitamin A. Another study using Mongolian gerbils who were fed biofortified maize containing β-cryptoxanthin resulted in a more efficient bioconversion than the use of a β-carotene supplement. The results of these studies indicate that the biofortification of maize via biotechnology can be a useful strategy to improve vitamin A status. A triple-vitamin fortified maize which expresses high amounts of β-carotene, ascorbate, and folate has been developed in the endosperm through metabolic engineering. The transgenic kernels contained 169fold the normal amount of β-carotene, 6-fold the normal amount of ascorbate, and double the normal amount of folate as conventionally-bred crops. Crops such as these can offer far more nutritionally complete meals for Africa’s malnourished [19,20]. Transgenic maize (corn) has been deliberately genetically modified (GM) to have agronomically desirable traits. Traits that have been engineered 5730 Mir et al. into corn include resistance to herbicides and resistance to insect pests, the latter being achieved by incorporation of a gene that codes for the Bacillus thuringiensis (Bt) toxin. Hybrids with both herbicide and pest resistance have also been produced. In 2009, transgenic maize was grown commercially in 11 countries, including the United States (where 85% of the maize crop was genetically modified), Brazil (36% GM), Argentina (83% GM), South Africa (57% GM), Canada (84% GM), the Philippines (19% GM) and Spain (20% GM). Corn varieties resistant to glyphosate herbicides have been produced. There are also corn hybrids with tolerance to imidazoline herbicides, but in these, the herbicide-tolerance trait was bred without the use of genetic engineering. Herbicide-resistant GM corn is grown in the United States. A variation of herbicideresistant GM corn was approved for import into the European Union in 2004, but such imports remain highly controversial. Bt corn: The European corn borer, Ostrinianubilalis, destroys corn crops by burrowing into the stem, causing the plant to fall over. Bt corn is a variant of maize, genetically altered to express the bacterial Bt toxin, which is poisonous to insect pests. In the case of corn, the pest is the European corn borer. Expressing the toxin was achieved by inserting a gene from the microorganism Bacillus thuringiensis into the corn genome. This gene codes for a toxin that causes the formation of pores in the Lepidoptera larval digestive tract. These pores allow naturally occurring enteric bacteria, such as E. coli and Enterobacter, to enter the hemocoel, where they multiply and cause sepsis [21]. This is contrary to the common misconception that Bt toxin kills the larvae by starvation. The fertilizers impact, growth and yield of maize grain are highly responsive to nitrogen fertilization, where maize fields, worldwide, receive around 10 million metric tons of N fertilizer per year [22]. However, nitrogen use efficiency (NUE), i.e. ratio of grain yield to N fertilizer supplied, of maize globally falls between 25-50%, indicating that more than half the N fertilizer applied to maize field is lost to the environment. On the other hand, hybrids developed with transgenic resistance to root feeding by corn rootworm (Diabrotica spp.) have led to larger and healthier root system and consequently greater N uptake. Similarly, transgenic maize hybrids with enhanced drought tolerance could also, indirectly, increase N uptake and utilization [23]. Application of bio fertilizers containing Azospirillumbrasilense and yeast Rhodotorulaglutinis at low rate of NKP (50%) mineral fertil¬izers, plus sulfur at recommended dose, gave comparable results for growth parameters of maize compared with 100% NPK [24]. Genetic engineering also helped developed Maize cultivars with resistance to herbicides, including genetically modified transgenic (glyphosate and glufosinate) and non-transgenic (sethoxydim and imidazolinone) hybrids. One example is Maize cultivar with an hra transgene confer 1000-fold cross-resistance to ALS (acetolactate synthase)-inhibiting herbicides and the adoption of transgenic herbi¬cide-resistant maize hybrids is ever increasing [25]. Finally, the contribution of biotechnology to maize advances is reflected in the production of nearly 75% of the maize in the United States containing biotech traits [26]. Furthermore, continuing to discover and develop new technologies in the agricultural sciences will greatly contribute to the food security. Development of second and third generation herbicide-resistant and insect-resistant traits that stack multiple modes of action will insure the beneficial aspects of this technology for years to come. Also, development of drought-tolerant maize is becoming a reality [27]. CONCLUSIONS Biotechnology has contributed tremendous advances in maize production via different avenues, including application of effective biofertilizers, plant growth promoter and more importantly development of transgenic traits resistant to herbicides and/or pests. Maize is the premier monocotyledonous species for biotech research based on its transformation characteristics, conventional and molecular breeding advances and monetary value in the agronomic marketplace. However, there are major factors that greatly limiting maize production. One of these factors is drought stress, to which Maize is highly sensitive, especially at critical times of the growing season, discouraging smallholder farmers from risking investment in best management practices including quality hybrid seed and fertilizer. Therefore, drought tolerant hybrids are being developed for maize through conventional breeding, markerassisted breeding, and biotechnology and will be licensed to local seed companies producing and selling hybrids for local farmers to help reduce smallholder farmer’s risk from drought and provide better food security. In spite of opposition groups, GM crops now acco- 5731 J. Cell Tissue Research unt for more than 300 million acres worldwide and are grown by over 17 million farmers in more than 25 countries. The vast majority of the increase in farming of GM crops is in developing countries. In 2012, the World Health Assembly (WHA) agreed on a set of global targets to hold the world accountable for reducing malnutrition. It is unlikely that these targets will be met within the timeframe set and new sustainable development goals are now being set up with the target date of 2030. To achieve the goal of providing crops with additional health benefits on a global scale, much work is required and will involve interactions between many disciplines including plant breeders, molecular biologists, nutritionists and even social scientists. It is not worthwhile to spend the effort generating a biofortified crop for a given population if they are knowledgeable, prepared and not already willing to accept the technology or any changes in appearance of the biofortified crop. New crop varieties with enhanced nutritional qualities must be evaluated by clinical trials and select populations who can benefit most from them must be educated so that they understand how these advantages can make a difference in their community’s overall health. REFERENCES [1] Hefferon, K.L.: Int. J. Mol. Sci. (16): 3895-3914 (2015). [2] Pérez-Massot, E., Banakar, R., GómezGalera, S., Zorrilla-López, U., Sanahuja, G.,Arjó, G., Miralpeix, B., Vamvaka, E., Farré, G., Rivera, S.M..: Genes Nutr. 8: 29-41 (2013). [3] Gilani, G.S., Nasim, A.: J. AOAC Int. (90) 14401444 (2007). [4] Glenn, K.C.: Asia Pac. J. Clin. Nutr. (17): 229-232 (2008). [5] Stoger, E., Fischer, R., Moloney, M., Ma, J.K.: Annu. Rev. Plant Biol., (65): 743-768 (2014). [6] Rajaram, S., Singh, R.P., and Torres, E.: CIMMYT, Mexico. 101-118 (1988). [7] Ahmed a. Abdelhafez.: EC Agriculture. 2(4): 374376 (2015). [8] Visscher, P.M., Haley, C.S. and Thompson, R.: Genetics. (144):1923-1932 (1996). [9] Yang, Q., Yin, G., Guo, Y., Zhang, D., Chen, S. and Xu, M.L: Epub. 121(4): 673-687 (2010). [10] Agrama, H. A., Dahleen, L., Wentz, M., Jin, Y., and Steffenson, B.: Phytopathology, (94): 858-861 (2004). [11] Young, N.D.: Phytopathology (30): 479-501(1996). [12] Bentolila, S., Guitton, C., Bouvet, N., Nykaza, S., Freyssinet, G.: Theor. Appl. Genet., (82): 393-398 (1991). [13] Wang, Y.G., Xing, Q.H., Deng, Q.Y., Liang, F.S., Yuan, L.P., Weng, M.L. and Wang, B.:Appl. Genet. 107(5): 917-921 (2003). [14] Ming, R., Brewbaker, J.L., Pratt, R.C., Musket, T. and McMullen, M.D.: Theor. Appl. Genet. 95:271-275 (1997). [15] Chaba, J., McMullen, M.D., Barry, B.D., Darrah, L.L., Byrne P.F. and Kross, H.: Crop S c i . 4 2 : 584-593 (2002). [16] Chen, H.K., Zhao, B.Z. and Robert, D.: Genetics. (152): 1203-1216 (1999). [17] Bohn, M., Schulz, B., Kreps, R., Klein D. and Melchinger, A.E.: Theor. Appl. Genet. (101): 907917 (2000). [18] Leyva-Guerrero, E., Narayanan, N.N., Ihemere, U. and Sayre, R.T.: Curr. Opin. Biotechnol., (23): 257264 (2012). [19] Jeong, J., Guerinot, M.L.: Proc. Natl. Acad. Sci. (105):1777-1778 (2008). [20] Mugode, L., Há, B., Kaunda, A., Sikombe, T., Phiri, S., Mutale, R., Davis, C., Tanumihardjo, S., de Moura, F.F.: J. Agric. Food Chem. (62): 6317-6325 (2014). [21] Bradbury, L.M.T., Henry, R.J., Quingsheng, J., Reinke, R.F. and Waters, D.L.E.: Mol. Breed., (16): 279-283 (2006). [22] Norton, R.: J. Crop Improv., (28): 575-618 (2014). [23] Chikelu Mba., Guimaraes, E.P., Ghosh, K.: Agricul. Food Security. 1: 7 (2012). [24] Kimani-Murage.: PLoS ONE. 10(6): 943-950 (2015). [25] Li, Z., Yang, P., Tang, H., Wu, W., Yin, H., Liu, Z., Zhang, L.: Reg Environ Change. (10): 1007-1013 (year ) [26] VonGrebmer,K.,Saltzman,A.,Birol, E., Wiesmann, D., Prasai, N., Yin, S., Yohannes, Y., Menon, P., Thompson, J. and Sonntag, A.: International Food Policy Research Institute: Washington, DC, USA, (2014). [27] Ahmed a. Abdelhafez.:. EC Agriculture. 2(4): 374376 (2015). 5732