Crop Adaptation to Climate Change (Yadav/Crop Adaptation to Climate Change) || Sorghum Genetic Enhancement for Climate Change Adaptation

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    Chapter 14

    Sorghum Genetic Enhancement for ClimateChange AdaptationBelum V.S. Reddy, A. Ashok Kumar, Sampangiramireddy Ramesh, and Pulluru S. Reddy

    Introduction

    Sorghum [Sorghum bicolor (L.) Moench] is thefifth most important cereal crop and is the dietarystaple of more than 500 million people in over90 countries, primarily in the developing world.It is grown on 47 m ha in 104 countries in Africa,Asia, Oceania, and the Americas (Table 14.1).The United States, Nigeria, India, Mexico, Su-dan, China, and Argentina are the major sorghumproducers globally (http://faostat.fao.org/site/567/default.aspx#ancor, accessed February 11,2010). Sorghum grain is mostly used directlyfor food (55%) and is consumed in the form ofporridges (thick or thin) and flat breads; how-ever, sorghum is also an important feed grain(33%), especially in Australia and the Americas.Stover (crop residue after grain harvest) is animportant source of dry matter to both milch anddraft animals in mixed crop-livestock systems.Sorghum is also an effective source of greenfodder due to its quick growth and high yieldand quality. Of late, sorghum with sugar-richjuicy stalks (called sweet sorghum) is emergingas an important biofuel crop. Thus, sorghum is

    a unique crop with multiple uses as food, feed,fodder, fuel, and fiber.

    Yield and quality of sorghum is influencedby a wide array of biotic and abiotic con-straints. Significant biotic constraints include theinsects, such as shoot fly, stem borer, midge,head bug, aphid, army worms, and locusts, andthe diseases, such as grain mold, charcoal rot,downy mildew, anthracnose, rust, and leaf blight.Striga (Striga asiatica, Striga densiflora, Strigahermonthica) is a devastating parasitic weedfound in many regions of Africa and India.Abiotic constraints include: problematic soils,drought, and temperature extremes. Climatic andedaphic changes including variable precipita-tion, higher soil and air temperatures, and in-creased soil alkalinity and acidity driven byincreasing anthropogenic activities are becom-ing major global concerns threatening sorghumproduction.

    This chapter examines the implications ofclimate change for major sorghum-growing ar-eas and production. Inherent characteristics ofsorghum to cope with climate change effects,the genetic options to mitigate climate change

    Crop Adaptation to Climate Change, First Edition. Edited by Shyam S. Yadav, Robert J. Redden, Jerry L. Hatfield,Hermann Lotze-Campen and Anthony E. Hall.c 2011 John Wiley & Sons, Ltd. Published 2011 by John Wiley & Sons, Ltd.

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    SORGHUM GENETIC ENHANCEMENT FOR CLIMATE CHANGE ADAPTATION 327

    Table 14.1. Sorghum area, production, and productivityin 2007 for countries with substantial area.

    Area Production Yield(m ha) (m t) (t ha1)

    World 46.9 63.4 1.4Africa 29.5 26.1 0.9Americas 6.5 24.6 3.8Asia 10.1 10.8 1.1Europe 0.2 0.7 3.6Oceania 0.6 1.3 2.1Sudan 9.0 5.8 0.7India 8.5 7.2 0.8Nigeria 7.8 9.1 1.2Niger 2.8 1.0 0.3USA 2.7 12.6 4.6Mexico 1.8 6.2 3.5Burkina Faso 1.6 1.6 1.0Ethiopia 1.5 2.2 1.5Mali 1.1 0.9 0.8

    Source: http://faostat.fao.org/site/567/default.aspx#ancor.

    effects and future strategies for genetic improve-ment are discussed.

    Climate change impacts onsorghum production

    Global warming due to climate change will affectgrain and stover yields in crops, more so in trop-ical Africa and Asia where sorghum is a majorfood crop. Most climate change models predictrises in air and soil temperatures and sea levels,and increased frequencies of extreme weatherevents leading to unprecedented changes in agri-cultural production in the years to come (IPCC2007). Although both developed and develop-ing countries will be affected, developing coun-tries with little adaptive capacity and limited re-sources are more vulnerable to climate changeeffects. Desertification, shortages of fresh wa-ter, soil erosion, increased salinity, changed pestand disease scenarios, and biodiversity loss aresome of the factors that adversely affect agricul-tural productivity. Detailed implications of cli-mate change effects, resilience of populations,and coping mechanisms are not fully understoodin most countries in the semiarid tropics (SAT) of

    Asia and Africa (Dar 2007; Cooper et al. 2008),which are traditional sorghum belts.

    Predicted climate change effectson crop growth and yield in majorsorghum growing areas

    The world climate is continuing to change atrates that are projected to be unprecedented inrecent human history. Global average surfacetemperature increased by about 0.6C duringthe twentieth century (IPCC 2007). Accordingto the Fourth Assessment Report (IPCC 2007),most of the observed increase in the global av-erage temperature since the mid-twentieth cen-tury has been attributed to the observed increasein anthropogenic greenhouse gas concentrations.The Intergovernmental Panel on Climate Change(IPCC) climate models predict an increase inglobal average surface temperature of between1.4C and 5.8C from 2001 to 2100, the rangedepending largely on the scale of fossil fuel burn-ing between now and then and on the differentmodels used. At the lower range of tempera-ture rise (13C), global food production mightactually increase, but above this range, it wouldprobably decrease (IPCC 2007). However, broadtrends will be overshadowed by local differ-ences, as the impacts of climate change are likelyto be highly spatially variable (Cooper et al.2008). Table 14.2 describes predicted changes in

    Table 14.2. Predicted changes in temperature and rainfallin the major sorghum growing areas (based on regionalpredictions for A1B scenario for the end of the twenty-firstcentury).

    Region Season

    Temperatureresponse

    (C)

    Precipitationresponse

    (%)

    East Africa OctDec +3.1 +11MarMay +3.2 +6

    Southern Africa OctMar +3.1 10West Africa JulOct +3.2 +2South Asia JunFeb +3.3 +11

    Source: IPCC 2007.

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    328 CROP ADAPTATION TO CLIMATE CHANGE

    temperature and rainfall in major sorghum-growing areas.

    Disaggregated effects of predictedchanges in temperatures andrainfall on sorghum yields

    Preliminary cropping simulations exercises wereconducted at ICRISAT to assess the impacts ofclimate change on sorghum yields in SAT areasof Africa and Asia. The following four scenarioswere examined: potential grain yield with currentcropping constrained only by climate; percentchange in yield with current climate modified forpredicted changes in rainfall; percent change inyield with current climate modified for predictedchanges in temperature; and percent change inyield with current climate modified for pre-dicted changes in both temperature and rainfall(Table 14.3).

    Initial simulations predicted that for any givenclimate change scenario, the impact of climatechange could vary both in nature and in mag-nitude from location to location, from crop tocrop, from cultivar to cultivar, and from sea-son to season. In general, the sorghum matu-rity period of current varieties decreases withincreased temperatures. Climate change effectsin terms of high temperatures and erratic rainfallmay drastically reduce sorghum yields in SouthAsia, Southern Africa, and West Africa (Cooperet al. 2008; Table 14.3).

    The impact of climate change on insectpests will be felt in terms of increased produc-tion losses and reduced efficacy of management

    strategies (Chakraborty et al. 2000). For all insectspecies, higher temperatures below the speciesupper lethal limit could result in faster develop-ment rates, leading to rapid increase of pest pop-ulations as the time to reproductive maturity is re-duced. For example, an increase of 1C and 2Cin daily maxima and minima will cause codlingmoth (Cydia pomonella) to become active about1020 days earlier than expected. Overwinter-ing of pests will increase as a result of climatechange, producing larger spring populations as abase for a build-up in numbers in the followingseason. There will be increased dispersal of air-borne pest species in response to atmosphericdisturbances. Many insects are migratory andtherefore may be well adapted to exploit new op-portunities by moving rapidly into those areas,which becomes increasingly favorable as a resultof climate change (Hill and Dymock 1989). Allthese possibilities have a significant bearing oncrop productivity.

    Characteristics of sorghumthat help in coping withclimate change

    Sorghum is a C4 plant with an extensive andfibrous root system enabling it to draw mois-ture from deep layers of soil. Sorghum requiresless moisture for growth compared to other ma-jor cereal crops; for example, in some studies,sorghum required 332 kg of water per kg of ac-cumulated dry matter, whereas maize required368 kg of water, barley required 434 kg, andwheat required 514 kg. Sorghum has the capacity

    Table 14.3. Disaggregated effects of climate change on sorghum yields.

    RegionPotential grainyield (kg ha1)

    Rainfalleffect on yield

    Temperatureeffect on yield

    Climate changeeffect on yield

    East Africa short rains 3244 +10% +11% +21%East Africa long rains 2232 +6% +42% +48%Southern Africa 2753 6% 16% 22%West Africa 1896 +6% 20% 14%South Asia 2800 +1% 38% 37%

    Source: Cooper et al. 2008.

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    SORGHUM GENETIC ENHANCEMENT FOR CLIMATE CHANGE ADAPTATION 329

    to survive some dry periods and resume growthupon receipt of rain (House 1985). Sorghum alsowithstands wet extremes better than many othercereal crops, especially maize. Sorghum contin-ues to grow, though not well, in flooded condi-tions; maize, by contrast, will die. Sorghum pro-duces grain even when temperatures are high.Inflorescence development and seed-set are nor-mal at temperatures of 4043C and at 1530%relative humidity, if soil moisture is available.Sorghum is not as tolerant of cool weather assome maize cultivars. Sorghum grows slowly be-low 20C, but germination and growth will occurin some varieties at temperature as low as 12C(House 1985).

    Climate change adaptation andgenetic options

    Climate change being a threat multiplier, suit-able strategies need to be urgently integratedinto national and regional sorghum improve-ment programs. Some of the adaptation strate-gies to address climate change impacts includedevelopment of better weather forecasting sys-tems, crop husbandry technologies and pest fore-casting and pest management technologies, andchanges in land use and water management sys-tems. Mitigation strategies may also include de-velopment of technologies to achieve improvedinput use efficiencies (such as fertilizer micro-dosing and need-based application of pesticidesfor pest management) but these involve recur-ring costs. Genetic management is considered asthe most cost-effective and eco-friendly optionto mitigate the adverse impact of climate changeon sorghum production. Unlike other adaptationstrategies, genetic options do not involve recur-ring costs. Genetic options should focus on rede-ployment of trait-specific germplasm and breed-ing for plant defense traits.

    Redeployment of germplasm

    Climate change will cause changes in the lengthof the growing period (LGP) in some regions.

    The LGP is defined as the number of days inany given rainfall season, when there is suffi-cient water stored in the soil profile to supportcrop growth. The impact of climate change onthe likely change in the average LGP acrossAfrica has been comprehensively mapped byICRISAT using the General Circulation ModelHadCM3.B1 for the period 20002050 (Cooperet al. 2009). The study showed that the extentof global SAT areas will be changed through (1)SAT areas being lost from their driest mar-gins and become arid zones due to LGPs becom-ing too short or (2) SAT areas being gainedon their wetter margins from subhumid regionsthrough the reduction in the current LGPs inthose zones. It means sorghum could be grown innew areas of the currently humid tropics wheresorghum is not grown at present. Large-scaleadaptation studies will be required to under-stand soil and climate conditions, pest scenar-ios, cropping systems, consumptions patterns,and markets in the new areas. International agri-cultural research centers (IARCs), agriculturalresearch institutes (ARIs), and national agricul-tural research system (NARS) with large reser-voirs of sorghum germplasm, breeding material,and commercial cultivars could play a significantrole in deploying suitable germplasm to the newareas. Several trait-specific, non-milo, and high-yielding female lines developed at ICRISAT, in arange of plant heights and maturities can be uti-lized in producing the hybrids that are of valueto different agroecological zones (Table 14.4).Development of crop cultivars with a maturityduration that matches the prevailing LGP will beone of the best strategies to cope with changesin LGP. Retargeting of traits of local importanceshould be undertaken by the NARS with the helpof other partners.

    Drought tolerance

    Four growth stages in sorghum have been con-sidered as vulnerable to drought: germinationand seedling emergence, postemergence or earlyseedling stage, midseason or preflowering, and

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    330 CROP ADAPTATION TO CLIMATE CHANGE

    Table 14.4. Details of the sorghum trait-specific (milo) and non-milo A-/B-pairs developed atICRISAT-Patancheru.

    S. No. ICSA numbers Traits Total lines

    1 1103 High yielding 772 88,00188,026 High yielding 153 89,00189,004 High yielding 44 90,00190,004 High yielding 45 91,00191,010 High yielding 106 94,00194,012 High yielding 127 201259 Downy mildew resistant 598 260295 Anthracnose resistant 369 296328 Leaf blight resistant 33

    10 329350 Rust resistant 2211 351408 Grain mold resistant 5812 409436 Shoot fly resistant (rainy) 2813 437463 Shoot fly resistant (postrainy) 2714 464474 Stem borer resistant (rainy) 1115 475487 Stem borer resistant (postrainy) 1316 488545 Midge resistant 5817 546565 Head bug resistant 2018 566599 Striga resistant 3419 600614 Acid soil tolerant lines 1520 615637 Early maturity lines 2321 638670 Durra (large grain) lines 3322 671687 Tillering and stay-green lines 1723 688738 Non-milo (A2) cytoplasmic lines 5124 739755 Non-milo (A3) cytoplasmic lines 1725 756767 Non-milo (A4) cytoplasmic lines 12

    Total 689

    Source: Reddy et al. 2006.The number of lines being maintained.

    terminal or postflowering. Terminal drought isthe most limiting factor for sorghum productionworldwide. In sub-Saharan Africa, drought atboth seedling establishment and terminal stagesis very common. In India, sorghum is grown dur-ing both rainy and postrainy seasons. The vari-able moisture availability at both prefloweringand postflowering stages during the rainy seasoncan have severe impact on grain and biomassyield. Climatic variability and associated ge...

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