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«Biotechnology-Assisted Participatory Plant Breeding: Complement or Contradiction? PPB Monograph No. 3 Ann Mane Thro and Charlie Spillane 1 7 ...»

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Prolongation or, or delay in, the ripening or sensescence pf the fruits or flowers of sorne crops could benefi t resource-poor farmers, especially those farthe s t from markets. Transgenic manipula tion of hormones (ethylene) and enzymes (e.g., polygalaeurona se) h as resulted in the development of a range·of transgenic plants with delayed ripening and seneseence (Newbigin et al, 1995). In addition, the use of inducible promoters and repressors is bein g explored. Work on d elayed d eterioration of eassava is under way at th e University of Bath, UK (Li et al, 1998).

Nutritional Quality and Processing Characteristics

Much ge netie engineering research is under way on the manipul a tion of biosynthetic pa thways so t ha t plan ts produce higher levels of compounds or n ew phenoty pes useful to humans. Genes from the biosynthetic pathways of one species (a bacterium or a plan t) can often be successfully used as transgen es in another lo increase the le veis of desirable compounds such as lipids (Gibson et al, 1994).

It can be argued that resource-poor farmers have as much interest in the functional properties of crops as industria l food proeessors do.

80th groups are interes ted in manipulating lhe proteins and carbohydrates in foods, which affeet traits su eh as cooking time, texture, dough elasticity, digestibility, gelling, foaming, and emulsification (Altpeter et al, 1996; Barro et al, 1997). For instance, it might be possible to d evelop varieties that req uire less fuel for eooking or that provide dough with greater elasticity. Farmer preferences for the functional characteristics of landraces are often considered a major RelevanJ. Products from Biotechnology Research reason for non-adoption of high -yielding varieties (FAO, 1996). While k.nowledge of how to modify functional properties lS rapidly growing in the food processing sector (e.g., Barro et al, 1997; Mazur et al, 1999), little or none of this knowledge has been transferred to those who could use it to broaden lhe range of options available to resource-poor farmers.

The nutritional value oí plant protein is often limited by the laek of essenlial amino aeids, especialIy lysine, threonine, and methionine (Bright and Shewry, 1983). Most plants are deficient in one or more oí these critica! protein components, whereas milk, meat, and eggs tend to eontain them in adequate amounts. In sorne crops this nutritional deficiency applies ¡rrespective oí whether the variety is a landrace or a modern variety. Among lhe eereals, maize is low in lhe amino aeid Iysine. Grain legumes such as soybean and peanut, which serve as valuable SOUTces of protein in the diets of human beings and livestock, are especially deficient in the sulfur-containing antino acids methionine and cysteine.

Conventional plant breeding has had little success in altering the essential amino acid composition of plants. Major eITorts have been devoted to increasing the quantity and quality of maize protein through the breeding of high-Iysine varieties, but this has led to a trade-off between yield and protein quality/quantity (Gilbert, 1995). Transgenic approaches may offer routes round such trade-offs, and a range of such approaches has now been developed. These improve the amino acid profile of crop protein either by transferring genes encoding more nutritious proteins from other species le.g., Molvig et al, 1997) or by manipulating crop biosynthetic pathways to in crease the nutritional profile of endogenous proteins (Karchi et al, 1993). The use oC artificial genes has also been attempted (J. Jaynes, pers. comm.). Where transformation protocols have been developed, important legumes such as peanut and phaseolus beans can now be improved nutritional1y through the transfer of methionine-rich protein genes from species such as sunflower (Molvig et al, 1997).

Micronutrient deficiency is a major problem amongst the poor worldwide and is often reCerred to as 'hidden hunger'. Lack of micronutrients such as vitamin A and iron not only causes suffering and death but also has adverse afIects on labor productivity. Poor nutrition, especially during peak labor periods, can lead to low output, triggering a spiral of decline in which poverty, ill health, and hunger reinforce one another. The knock-on eITects oC micronutrient deficiency are immense. For instance, the correct levels of zinc in diets can reduce the incidence of malaria in children by 40% (Graham et al, 1999).

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implementing a project to select germp lasm which is high in mieronutrients from geneban ks (see h ttp://www.idre.caf). Tms ger mplasm cou ld be fed directly in to PPB or PVS p r ojects in areas where mi cr onutrie nt deficiency is a problem. lt may also be possible to unravel the genetics oC high- and low· m.icronutri en t phenotypes using molecular m a rkers and QTL analysis (DellaPenna, 1999 ) and henee to d evelop popu lations of germplasm 'enriched'w ilh m icronutrien ts.

Transge nic approaches to increasing nu tritio nal valu e co uld have a vcry great impaet by add ing micronu trients 5u ch as vitamin A to incxpensive staple roods sueh as rice (Ye et al, 2000) and eassaya (Iglesias et al, 1997 ).

Many erop specics contain high levels of anti-nutritional factors.

These inelude co mpound s such as tannins, erucie aeid, allergen s, cyanogen s, and mtrates. Increased processin g and cooking are typically necessary to redu ce the active levels of these compounds so that the resultin g food is safe for con sumption. Th e r eduction of anti-nutritional factors has long been an objective of con vention a l breeding, with variab le success. Often selections having low levels of the antinutri tional factor are unproductive, suggesting an ecologicaJ role C the or eompound or eompound s involved. MAS can reduce the levels of antinutrients more efTiciently than the m ethod s used previously. Rapeseed lo\V in erucie aeíd is one produet oC research using MAS. Transgenic a pproach es are now being used to develop plants in which the antinutrient is not synthesized at all. Besides improving human nu trition, this r esearch will allow the roles of these compounds to be studied- an avenue oC r esearch tha t eould lead to the iden tification oC alternative plant proteetion s trategies that are less damagin g to human nu trition.





Labor-Saving Biotechnologies

Many resource-poor farmers are interested in saving labor, partieularly d urin g peak periods, rather than solely in increasing r eturn s to land (Gilbert. 1995)_ Henee, yield pcr heetare m ay nOl be the m ost app rop ria te criterion for assessing the impaet of researeh on farmers {Chambers, 1983J. Resource-poor farmers assess tcehnologies in terms of the extent to which they may enable them te rcalloeate exis ting land and labor to other productive aetivities, while maintaining current levels of prod u ction. The other aetivity may be agricultural (e.g., s hifting good-quality land out of maize ioto a more valuable crop) or off-rarm (e. g., sendin g ehildren to school) (Gilbert, 1995).

Afforda ble biotechnologies that reduce the labor and other r esources dcvoted to crop man agem e n t are likely to benefit m any resource-poo r farmers. Examples include h erbieide- and pes t- or disease- resista n t eultivars, early-m a turing cultivars, and eultiva rs th a t require less post-harvest proeessing. Converscly, technologies that increase the la bo r burden may not prove popular, even if they raise yie lds. Som e farm -level inducible promoters may Call into this category.

Releuant Products from Biotechnology Research Participatory research often reveals that women or children bear the brunt of labor-intensive activities such as weeding and post-harvest processing. It may also reveal the periods when labor intensity is at its highest and lowest. Such information could be factored into the setting of biotechnology and breeding research priorities. The subsequent research could have a major impact if it led to products that reduced the drudgery ofunderprivileged household members or cornmunity groups al peak labor periods.

Post-harvest processing is an area in which labor-saving technologies might prove especially beneficial. Many plant-derived foods require a great deal of processing, such as shelling, pealing, cooking, and fermentation, before consumption. The biological basis of many traditional food processing practices is well known (e.g., NAS, 1992). Genetic engineering to improve the functional properties of crops for specific industrial or domestic processing purposes could help reduce gender-specific labor constraints in many environments (e.g., Barro et al, 1997).

Labor-saving technolQgies may not always be beneficial. While positive impacts may be felt in one social context it is possible that the same technology could have negative impacts in another. For instance, herbicide-tolerant plants (especially if the secd is treated) can be expected to be very valuable to maize farmers threatened by striga in western Kenya, but could displace labor if deployed in the Kenyan maize belt in Trans Nzoia (J. Lynam, pers. conun.). Herbicide-tolerant crops in general tcnd to displace labor, especially where they also allow no-till farming (Naylor, 1994). However, this technology also has highly positive implications, especially foc women and children, who often provide the bulk of labor for weeding (Box 14).

Participatory needs assessments with farmers may be necessary to darify the full impact oC changes in labor use. The situation can be extremely complex and difficult for 'outsiders' to understand. In the case of cassava, [or example, women farmers in unsta.ble parts of Africa feel that eliminating toxic compounds from the plant-to reduce the heavy demands on their labor for removing the toxin after harvest-could put food security at risk by making the growing oc stored crop more liable to theft (Chiwona-Karltun et al, 1997) (see Box S).

Conservation

Many of the biotechnologies that can be used to enhance plant production and productivity can also be used to meet conservation objectives. One example is tissue culture, whose use in rapidly propagating materials threatened by genetic erasion has already been discussed. Another is the use of the techniques oC molecular analysis to understand the diversity of plant populations. These techniques can Biotechnology-Assisled PPB: Comple ment or Corttradiction ?

BOJe 14 Herblclde-reslstant crop varletles ror weed control Weed control is a major problem fo c nearly a1l resource -poor fanners. The introduction of herbicide-resistant crop varieties would release much of the labor spent on weeding for othec, more produetive and profitable activities.

Fanners in Brazil and Thailand have actually requested the development and intcodu ction of such varieties because they re cognize their advantages.

Sorne cornmen tators express concem that the use of h erbicide-resistant erops in developing eountries will unwisely add to the 'chemical armoury' of agriculture. The technology makes the use of herbicides more a ttractive wh ere, up to now, no herbicides at all have been used. AJthough overall herbicide use is low in developing countries, sorne ehemicals have been over-used or used without proper safety preeautions in sorne regions.

Few data exist to assess the validity of this concem. Howe ver. a recent survey found that th e adoptíon of herbicide-resistant soybean in 19 states of the USA ha d led to significant decreases in lOtal he rbicide use, while the cu ltivatíon of he rbicide-resistant cotton was associated with no change in total herbicide u se.

As cates of USe are higher i.n the developed than in the developing world, these resulta suggest that trends in developing countries a dopting herbicide- resis tant crops might a t fLrSt continue upward, then level off at a lower usage level than would ha ve occurred if they had gone on using non-herbicide resistant crops. A more ruverse range of herbicides available to farmers could, in conj unction with the development of herbicide-resistant crops. form the basis of an integrated approach to weed control.

Among the barriers to the use of transgenic herbicide-resistant varieties in developing cou ntries is aecesa to the genes for herbicide tolerance. As patenta on wide ly uscd h erbicides such as glyphosate (Round-up) expire. reducing the cost of the he rbicide, so the value of the ge nes confening herbicide resistance increases. Discussion on this ¡ssue is under way between pubLic-sector researchers and sorne of the companies concemed. The chemical industry is interested in developing herbicides for major world crops such as maize, s oybean, wheat, rice, and cotton. But the re are many minor crops and non-eommercial market situations in which it has Hule interest. Sorne companies might be willing to faci litate access lo herbicide resistance transgenes for introduction into crops or varieties in which they h ave no comme rciaJ stake, particularly in situations where they are the manufacturer of the h erbicide.

Two further problems deserve a mention. Given the current difficulties with regard to biosafety regulations, it is unlikely that clearance would be given to use herbicide-resistant transgenic varíeties in sorne developing countries. And the use of this technology would also require measures to ensure that resistance to the herbicide would not evolve in weeds. This is less likely to happen when the ge n es foc resistance are derived fro m bacteria rather lhan plants.

Fanners in developing countries face many weed problems for which no effec tive control measures have yet been developed. These ¡nelude the parasitic broomrapes and witchweeds ($triga spp.). The areas infested with such weeds are

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vast and expanding. For example. a survey in Nigeria found that 70% oC fields were infested with witchweed sccds. Witchweeds infest the graio crops of more thanrl00 million people in sub-Saharan Arrica and Asia, reducing yields by 50% and more in drought years. Labor-intensive weeding is largely ineCCective against such weeds.

Recent research has shown that it is possible to control Striga spp. using imadizoline-resistant maize. Herbicide-resistant seed is treated with a systemic irnadizoline, resulting in excellent control. Because oC the small amounts of herbicide required, this weed control technology ia Iikely lo be accessible to resource-poor Cannen.



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