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<p>  </p> <p>Rice (<em>Oryza sativa</em> L.) is a staple crop consumed globally. Increased variability in rainfall in much of the world is a predicted consequence of climate change and drought is predicted to be a major cause for concern for rice production. One approach to mitigating water-deficit stress is integrating beneficial (drought-tolerance) loci from wild rice donors into elite rice cultivars. Bi-parental interspecific chromosome segment substitution lines (CSSLs) and near introgression lines (NILs) are genetic resources that contain genetic introgressions from wild rice but are otherwise genetically identical to the cultivated parent, known as the recurrent parent. For this study, 12 CSSLs and NILs were selected for having wild rice introgressions on chromosomes two and five, previously shown to be beneficial under field conditions. In the current work, these lines were evaluated under water-deficit conditions for their potential of serving as future pre-breeding material. The recurrent parents, Cybonnet and Jefferson, two U.S. cultivars adapted to the Southern Rice Belt, were additionally included in this study as controls. In total, three trials took place: two at Purdue University under controlled environments (West Lafayette, Indiana) and one in the field at the Dale Bumpers Rice Research Center (Stuttgart, Arkansas). Traits such as yield components, gas exchange, leaf water content, leaf water potential and chlorophyll fluorescence were measured during predawn and midday timepoints. Results from the three trials did not show consistent genotype rankings in yield component traits, which was expected due to the different ways in which water-deficit treatments were approached (continuous water-deficit application versus transient drought and recovery). While many of the CSSLs outranked Cybonnet in mean values, none were significantly different, likely due to low replication. Despite not having identified superior genotypes, the yield component, physiology, and high-throughput phenotyping datasets published here can provide the foundation to address future questions about physiological linkages and methodology development associating high-throughput data with ground-truth measurements. All data associated with this work are publicly available through Purdue University Research Repository.</p>

The African Rice Gall Midge (AfRGM), Orseolia oryzivora Harris and Gagné (Diptera: Cecidomyiidae), is an endemic rice pest found throughout Africa. The failure of most other control methods imposes the need to use crop resistance. This study was initiated: (1) to develop an accurate method for assessing damage caused by AfRGM; (2) to determine AfRGM resistance genes’ modes of action, the heritability estimates of their resistance to AfRGM and the behavioural pattern of progenies with resistance to AfRGM attack; (3) to reveal convergent evolution of same or similar resistance gene(s) in geographically distinct landraces, or divergent evolution of genotypes carrying the same gene, by analysing the genetic diversity among five AfRGM parental lines; (4) to build a core sample of progenies to be used as a reduced mapping population, largely reflecting the entire genome of the whole population, after an estimate of the heritability of 15 agro-morphological descriptors and; (5) determine Simple Sequence Repeat (SSR) markers flanking genes or quantitative trait loci (QTLs) linked to resistance to AfRGM. A method of accurately assessing damage caused by AfRGM was determined by comparing four methods of assessment including the International Rice Research Institute’s (IRRI) Standard Evaluation System (SES) for rice and three methods based on resistance index (RI) assessments differing in the computing of the percentage of tillers with galls on a resistant check variety. The RI-based assessment (RI-BA) methods consistently provided a better evaluation of AfRGM damage than the SES, regardless of the trial size. Within RI-BA methods, RI-BA2 was always more accurate than RI-BA1 and RI-BA3 when the plot was large. RI-BA2 and RI-BA3 were equally accurate when the plot size was small, and they provided better estimates than RI-BA1. When the plot was of medium size, RI-BA2 was more accurate than RI-BA3; RI-BA3 also surpassed RI-BA1. Overall, the best method of assessing AfRGM damage was RI-BA2, regardless of the plot size. Five rice populations including F1, F2 and F3 generations involving ITA306, a susceptible variety of Oryza sativa subsp. indica, and four varieties having different reactions against AfRGM were used to determine the genetic basis of resistance and estimate the heritability of resistance to AfRGM. All the F1s were susceptible, suggesting recessive gene inheritance. The F2 generations’ segregation pattern of 1R:15S in both ITA306-TOS14519 and ITA306-TOG7106 crosses as well as the segregation of 1R:8Seg:7S in ITA306-TOS7106 F3 families indicated that the AfRGM resistance expression being studied is governed by two genes. The deviation of the segregation patterns of crosses involving ITA306 and the tolerant parental lines from Mendelian segregation ratios suggests that the tolerance to AfRGM shown by BW348-1 and Cisadane is under complex mechanisms of control rather than under simple genetic control. The narrow-sense heritability estimates of resistance to AfRGM were low in populations involving tolerant varieties and were high in populations involving resistant varieties. They ranged from 0.086 in the ITA306-Cisadane population, to 0.4 in the ITA306-TOG7106 population. Conversely, the broad-sense heritability estimates ranged from 0.23 (ITA306-Cisadane) to 0.63 (ITA306-TOS14519). The behavioural patterns of progenies against AfRGM attack were evaluated for 532, 413 and 479 F2 progenies from ITA306-BW348-1, ITA306-Cisadane and ITA306-TOS14519 crosses, respectively, in addition to 90 BC1F2 progenies from the ITA306 and TOG7106 cross. One F3 generation of 649 families from a cross between ITA306 and TOS14519 was also tested. Four types of behavioural pattern categories were observed: (1) progenies were more resistant than the resistant check entry at 45 DAT and 70 DAT; (2) progenies were more resistant at 45 DAT and became susceptible at 70 DAT; (3) progenies were susceptible at both 45 DAT and 70 DAT; (4) progenies were susceptible at 45 DAT but reverted to resistant at 70 DAT. The first three categories were the most frequently observed and occurred in all cross combinations. The last category was observed only for a few progenies from the ITA306-TOS14519 F2 and F3 generations and, surprisingly, many from the ITA306 and BW348-1 cross. Heritability estimates were calculated for 15 major traits in an F3 population in order to predict the genetic gain associated with each trait, together with the resistance to AfRGM and to estimate the influence of the environment on phenotypic values. Broad-sense heritability (H2) estimates were high for the penultimate leaf length (PLL) - 0.99, penultimate leaf width (PLW) – 1.0, flag leaf length (FLL) - 0.99, flag leaf width (FLW) – 1.0, ligule length (LigL) - 0.99, tillering ability (Til) - 0.99, number of days to booting (DB) - 0.95, number of days to first heading (DFH) - 0.96, number of days to heading (DH) - 0.89, number of days to maturity (DM) - 0.98, culm length (CL) - 0.99, plant height (PH) - 0.99, panicle length (PanL) - 0.95, secondary branching (SB) - 0.95 and the thousand grains weight (TGW) - 0.71. Conversely, narrow-sense heritability estimates were very low (nearly 0) in PLL, FLL, Lig, DB, DFH, DM and SB or low (at most 0.267) in PLW, FLW, DH and PH, with a high value of 0.727 for TGW. Inheritance of the traits studied was therefore under non-additive gene effects rather than additive genetic effects and can therefore be improved using pedigree breeding schemes along with breeding for AfRGM resistance. Fine genetic evaluation of five AfRGM parental lines was studied in terms of polymorphisms using 303 SSR primers covering the rice genome. Of the 178 polymorphic primers identified, 60 were highly polymorphic and informative. The number of alleles amplified by these primers ranged from one to five for a total of 1,041 alleles. The polymorphism rate was globally high, ranging from 45.2% to 66.8%. The mean of the polymorphism information content (PIC) was 0.553. Factorial analysis, based on the allelic diversity, demarcated the parental lines into Oryza glaberrima Steud, Oryza sativa subsp. japonica and O. sativa subsp. indica groups, while a cluster analysis distinguished them into four groups: AfRGM resistant, susceptible, moderately resistant and tolerant. BW348-1 and Cisadane showed the least diversity, despite their distant geographical origins. TOS14519 and TOG7106 showed more divergence to ITA306 despite their common West African origin. This variability amongst the genotypes tested is the result of farmer-based selection for AfRGM resistance rather than direct breeding efforts through breeder intervention. A method of selecting individuals for a mapping population, based on a core sample, was developed in order to speed up the mapping procedure. A diversity study amongst F2 and F3 generations involving 15 quantitative and 26 qualitative agro-morphological characters was carried out and led to the dropping of seven non-discriminant descriptors. The diversity index (H) was calculated for each remaining character and the discriminant descriptors were selected based on a diversity index threshold value above 0.4. Four descriptors of H values less than 0.35 were therefore dropped. The sizing of the core collection of 64 individuals and the selection of these individuals were done using MSTRAT version 4.1 package in redundancy mode, a construction run of 100 times with an iteration number of 500. The core sample was similar to the whole population for clustering pattern, minimum and maximum quantitative values and diversity index, while mean values and coefficient of variation distinguished them. The core sample, which represents 10% of the whole population, also revealed the same phenotypic variation and the same genotypic segregation according to two SSR markers. It can therefore efficiently reflect the whole population as a mapping population. Finally, a study was undertaken to identify flanking markers to the gene/QTL involved in the resistance against AfRGM using bulked segregant analysis (BSA). A polymorphism study between ITA306 and TOS14519 displayed 145 polymorphic SSR markers, which were used to screen the bulks that originated from the two tails, and depicted only two SSRs as candidate markers linked to gall midge resistance. These markers included RM317 and RM17303 which displayed strong significance after an analysis of variance using an F test, meaning that they were segregating with the resistant alleles. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.

Flooding cycle in wetland rice (Oryza sativa L.) production systems is often subject to seasonal and cultural variations which may affect the availability and uptake of nitrogen in different ways. These factors may more or less influence the physiological and growth responses of the plant. In an effort to improve productivity in rice cropping systems, two controlled environment studies and a field trial were conducted to evaluate the growth and yield responses of rice to different flooding regimes and nitrogen fertilizer management strategies. In the first glasshouse trial, an upland cultivar (GM-1) was used to study the effects of four flooding regimes and three nitrogen application rates on the tillering, yield components and grain yield of rice. The field study determined the applicability of the results of the glasshouse trial to out-door environmental conditions, with the aim of gaining further insight into the impact of nitrogen application strategy on tiller and grain qualities. Two wetland cultivars (FKR-19 and N-19) and GM-1 were used to evaluate the effects of two flooding regimes and two nitrogen topdressing patterns. The second glasshouse trial determined the effect of hydro-priming on the establishment of direct seeded rice, and the effect of flooding on aerenchyma formation in rice roots. Results of the studies showed that flooding with standing water of 5 cm above the soil surface, irrespective of when it occurred, and nitrogen application increased the number of tillers and panicles, above ground dry matter, nitrogen uptake and grain yield of rice. However, late flooding and high nitrogen application rate of 220 kg ha-1 were found to encourage the production of late tillers, thereby reducing the efficiency of nitrogen use for grain production. Nitrogen application in three split doses tended to increase plant nitrogen content at heading; it slightly increased the protein content of the grains at maturity, but reduced the amylose content of the starch granules. Nitrogen application in two split doses led to increased grain yield in non-flooded plants, while the three-split treatment increased nitrogen uptake and grain yield in the flooded plants. Flooding significantly increased aerenchyma formation in the cortical tissues of rice roots, particularly at 50 mm behind the root tips. Hydro-priming seeds for 48 h improved plant establishment by shortening the germination and emergence times, and increasing the height and dry matter accumulation of seedlings, thereby ameliorating the susceptibility of rice to flooding stress. Overall, the thesis affirmed that controlled flooding is beneficial to rice production since it enhanced the growth and yield of the plant. It further revealed that early flooding and appropriate timing of moderate nitrogen application can ensure the conservation of water and nitrogen resources, including the quality of the environment, with no significant consequence for yield and productivity of the crop. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Two field trials were conducted to determine the impact of water management on the efficacy of insecticide seed treatments against rice water weevil, Lissorhoptrus oryzophilus Kuschel, in rice at the Delta Research and Extension Center during 2011 and 2012. The performance of thiamethoxam, chlorantraniliprole, and clothianidin was evaluated when the permanent flood was established at different timings (6 and 8 weeks after planting) and the effect of flush number (0, 1, or 2) on seed treatment performance was evaluated. Seed treatment efficacy was not impacted by delayed flooding, but 2 flushes reduced efficacy of some seed treatments. Experiments were also conducted to determine the impact of reduced seeding rates found in hybrid rice production on the efficacy of insecticide seed treatments targeting rice water weevil. Efficacy was similar when comparing currently labeled rates of thiamethoxam, chlorantraniliprole, and clothianidin with higher rates of these products.

Rice (Oryza sativa L.) is the second most important cereal crop in Malawi. Rice productivity in the dominant (85%) rainfed ecosystem is very low, with mean yield of only 1.4 t ha-1. Farmers plant traditional landraces that have low yield potential and are susceptible to various stresses such as drought and diseases. Development and introduction of improved rice varieties, with stress tolerance traits from introduced varieties, such as the New Rice for Africa (NERICAs), could significantly increase productivity. Previous attempts to introduce high yielding irrigated varieties into the dominant rainfed ecosystem in Malawi have not been successful because farmers basically did not adopt the varieties, claiming that the varieties were lacking in grain traits that they preferred but that the traits were present in their landraces. The notable traits mentioned, through previous informal surveys, were long grains, medium to slender shape and aromatic grain with intermediate gelatinization temperature. No formal study has been conducted to ascertain the preferences, and the genetic control of the traits, including yield and yield related traits, have not been studied. The objectives of this study were to: 1) confirm farmers’ preferences for grain traits using participatory rural appraisal; 2) determine amount of genetic variability for yield and yield related traits in Malawi rice landraces, 3) determine the genetic control and correlations of grain length, grain shape and 1000-grain weight, 4) determine the inheritance of aroma and gelatinization temperature and, 5) determine the genetic control, correlations and path coefficients of yield and yield related traits, in F2 generations of Malawi rice landraces and NERICA varieties crosses. To confirm the farmers’ preferences for grain traits, a participatory rural appraisal was conducted in 2006 in two villages that were representative of rainfed rice growing areas in Malawi. The villages were Liundi and Nawanga in Machinga and Salima Districts, respectively. Qualitative and quantitative data were collected through questionnaires and discussions with 190 respondents, as well as through observations. To determine variability among Malawi rice landraces, 19 landraces were planted at Lifuwu in a Randomized Complete Block Design with three replicates in 2006. Data on plant height, days to 50% flowering, number of panicles per hill, panicle length, number of filled grains per panicle, 1000-grain weight, panicle weight, grain length and grain yield were collected and analyzed. Four Malawi rice landraces were crossed to four NERICA varieties in 2006 in a North Carolina Design II mating scheme to determine the genetic control of grain size. F1 plants were raised in 2007 and in 2008, 16 F2 populations together with their parents were planted in a Randomized Complete Block Design with three replicates at Lifuwu. Data on grain length, grain shape and 1000-grain weight were collected and analyzed. To determine the inheritance of aroma and gelatinization temperature, four Malawi rice landraces were crossed to four NERICA varieties in 2006 and F1 plants were raised in 2007. In 2008, 16 F2 populations together with their parents were planted in a Randomized Complete Block Design with three replicates at Lifuwu. Aroma and gelatinization temperature were evaluated. To determine the gene action of yield and yield related traits, four Malawi rice landraces were crossed to four NERICA varieties in 2006 in a North Carolina Design II mating scheme and F1 plants were raised in 2007. In 2008, 16 F2 populations together with their parents were planted in a Randomized Complete Block Design with three replicates at Lifuwu. Data on grain yield, the number of panicles per hill, days to 50% flowering, panicle length, panicle weight and 1000-grain weight were collected and analyzed The participatory rural appraisal confirmed that that long, slender or medium shape grains, with aroma and intermediate gelatinization temperature were the key traits preferred by farmers. Therefore the farmer preferred traits of long, slender grains, with aroma and medium gelatinization temperature, must be selected for in any high yielding varieties to be developed for the rainfed rice ecosystem. Results showed that differences were significant (P=0.05) for all the traits that were studied. Heritability estimates were low to moderate: 18.3% for panicle weight, 40.0% for panicles per hill and 56.3% for days to 50% flowering date. The high genetic variability among the landraces could be used in a breeding programme to develop improved varieties for various morphological traits. The number of panicles per hill and 1000-grain weight combined moderate heritabilities with relatively high genetic advance and therefore could be reliable traits for yield improvement. Genetic analysis of grain size showed that Malawi rice landraces were variable for all three grain size characteristics, namely grain length, grain shape and 1000-grain weight. NERICA varieties were variable for 1000-grain weight. Sixteen F2 progenies were variable for all three characteristics, and the variability was significant (P=0.05). Heritability estimates were high (45.4%) for grain length and low for grain shape (12.3%) and for 1000-grain weight (14.3%) suggesting that early generation selection would be effective for grain length. Predominance of additive gene action for grain length and grain shape suggested that early generation selection would be effective for these traits. Selection for 1000-grain weight would be more effective in later generations because of preponderance of non-additive gene action in the control of this trait. The correlation between grain length and grain shape was positive (r=0.769) and highly significant (P=0.01) suggesting that breeders would choose to select for both traits simultaneously, or they would choose one of the traits to develop varieties with long grains and medium shape. Crosses between aromatic and non-aromatic varieties had non-aromatic F1. The F2 progenies segregated into 3:1 ratio for non-aromatic: aromatic suggesting that, in the Malawi rice landraces, aroma was probably simply inherited through a single recessive gene. F1 progenies, between parents with high and intermediate gelatinization temperatures had intermediate gelatinization temperature. F2 progenies segregated into 1:3 ratios for high; intermediate gelatinization temperature in three out of four crosses suggesting control by one dominant gene. The segregation pattern in one cross was not significantly different from 3:13 ratio for high: intermediate suggesting that two dominant genes, one an inhibitor, were controlling the trait. Breeding and selecting for aroma and intermediate gelatinization temperature could be accomplished relatively easily because the traits are simply inherited. The genetic variability for yield and yield related traits was wide and significant (P=0.05) in the F2 populations of Malawi rice landraces and NERICA varieties crosses indicating that the populations would be valuable sources to develop varieties with improved yield. Panicle weight and the number of panicles per hill were positively correlated with, and had high direct effects on grain yield, therefore they could be used to indirectly select for high yield. Grain yield, the number of panicles per hill and plant height were predominantly controlled by additive gene action suggesting that bulk breeding methods would be adopted for these traits. The days to 50% flowering, panicle weight and 1000-grain weight were predominantly under the control of nonadditive gene action suggesting that hybrid development would be profitable for these traits. Faya Mpata, Faya Zidyana and NERICA 3 could be the best parents for improving yield and yield related traits because they had high general combining abilities for the traits. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Digitized by Kansas Correctional Industries

Call number: LD2668 .T4 1979 S94 / Master of Science

Call number: LD2668 .T4 1966 R829 / Master of Science

Thesis (MScAgric)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: As agriculture remains the economic engine of rural Africa, reducing poverty in Africa will depend largely on stimulating agricultural growth. To realize this growth, the efficient allocation of a country’s scarce natural resources becomes a prerequisite. Rwanda is endowed with extensive wetlands with a high potential for rice production due to its hilly topography, abundant rainfall, and warm temperatures. However, many of these wetlands remain uncultivated despite the prevailing rice deficit in the domestic and regional markets. Over the past decade, Rwanda has increasingly become dependent on regional and global markets for rice, as domestic supply is unable to keep pace with the growing domestic demand. This production deficit has limited the potential gains that farmers and the nation could realize in the form of income and foreign exchange earnings. The main objective of this study is to determine Rwanda’s comparative advantage in rice and to identify constraints limiting efficiency. To achieve this objective, this study utilizes the Policy Analysis Matrix (PAM) to measure the comparative advantage in rice production and the level of inefficiencies within the rice subsector in the Eastern Province of Rwanda. The key findings of the analysis demonstrate that this province has a comparative advantage in rice. However, within the sample, 68 % of rice farmers’ cooperatives, cultivating rice on 25% of the total area under study, have no comparative advantage. In terms of net welfare gains, due to market distortions, domestic rice prices are artificially high, which creates a deadweight loss in the rice market. In particular, the protectionist policies (i.e. rice import tariffs and farm inputs subsidization) induce the private farm profit to outweigh the social farm profit. This abnormal profit allows rice production to become financially profitable even where there is a comparative disadvantage. On the demand side, although the domestic price of imported rice in Rwanda is slightly higher than the local rice price, the majority of consumers prefer imported rice to local rice, due to its long grain shape, aroma, and good quality. The low domestic demand for bold and short grain rice, which is cultivated by 70 % of Rwandan rice farmers, limits domestic rice producers’ market share. Given the study’s findings, the policy recommendations are threefold. The first involves technology dissemination and adoption. In order to improve the domestic rice production capacity and competitiveness, without compromising efficiency, it is imperative for rice farmers to adopt labour saving technologies. This technology adoption would allow for an increase in the area on which rice can be grown efficiently, due to a reduced social production cost. The second recommendation is that government should encourage research on the identification of aromatic and long grain rice varieties that can adapt to Rwanda’s agroecology, thereby meeting consumers’ demand preferences. Finally, though rice import tariffs protect domestic farmers against foreign competition, these policies decrease consumers’ welfare due to a reduction in the range of rice consumed in the domestic market. This study recommends the government to facilitate exportation of local rice in regional markets, and reduce rice import barriers. This intervention would benefit both farmers and consumers, while stabilizing the trade balance. / AFRIKAANSE OPSOMMING: Aangesien landbou steeds die ekonomiese enjin van landelik Afrika is, sal die vermindering van armoede grootliks afhang van die stimulering van groei binne landbou. Die doeltreffende toedeling van ‘n land se skaars hulpbronne is ‘n voorvereiste om hierdie groei te verwesenlik. Rwanda het ekstensiewe vleilande met ‘n hoë potensiaal vir rysproduksie as gevolg van die heuwelagtige topografie, oorvloedige reënval en warm temperature. Baie van die grond is egter steeds onbewerk desnieteenstaande die heersende rystekort in die plaaslike en streeksmarkte. Oor die afgelope dekade het Rwanda toemend afhanklik geraak van streeks- en globale markte vir rys aangesien plaaslike aanbod nie kan byhou met die toemane in plaaslike vraag nie. Die produksietekort het die potensiële voordele wat boere en die volk kan realiseer in die vorm van inkomste en buitelandse valuta, beperk. Die hoofdoelwit van die studie is om Rwanda se vergelykende voordeel in rys te bepaal en om die beperkings ten opsigte van doeltreffendheid te identifiseer. Om hierdie doelwit te bereik, het die studie die Beleidsanalise Matriks gebruik om die vergelykende voordeel in rysproduksie en die vlak van ondoeltreffendheid in die ryssubsektor van die Oostelike Provinsie van Rwanda, te meet. Die kern bevindinge van die analise dui daarop dat die Oostelike Provinsie van Rwanda ‘n mededingende voordeel in rys het. In die steekproef is daar egter 68% van die rysprodusente koöperasies wat geen mededingende voordeel het nie. In terme van netto welvaartsvoordele, as gevolg van verwringing in die mark, is die plaaslike prys van rys onnatuurlik hoog, wat ‘n dooieverlies skep in die rysmark. Spesifiek, die beskermende beleide (d.i. rys invoertariewe en plaas insetsubsidies) het tot gevolg dat private boerdery wins groter gewig dra as die sosiale boerdery wins. Die abnormale wins laat toe dat rysproduksie finansiëel winsgewend word selfs al is daar ‘n vergelykende nadeel. Aan die vraagkant, al is die plaaslike prys van ingevoerde rys in Rwanda ‘n klein bietjie hoër as die plaaslike rysprys, verkies die meeste verbruikers die ingevoerde rys eerder as die plaaslike rys, as gevolg van die lang korrel vorm, aroma en goeie kwaliteit. Die lae plaaslike verbruik vir vet kort korrel rys, wat verbou word deur 70% van die Rwandese rysboere, beperk die plaaslike rys produsente se markaandeel. Gegewe die studie se bevindings, is die beleidsaanbevelings drieledig. Die eerste behels tegnologie oordrag en aanvaarding. Om plaaslike rysproduksie kapasiteit en mededingendheid te verbeter sonder om doeltreffendheid af te skeep, is dit noodsaaklik vir rysboere om arbeidsbesparende tegnologie te aanvaar. Die tegnologie aanvaarding sal die area wat doeltreffend onder rys verbou word, vergroot as gevolg van verminderde sosiale produksiekoste. Die tweede aanbeveling is dat regering navorsing oor die identifisering van aromaties en lang korrel rys varieteite moet aanmoedig om aan te pas by Rwanda se agro-ekologie; om sodoende verbruikers tegemoet te kom met hulle vraagvoorkeure. Laastens, al beskerm invoertariewe van rys die plaaslike boere teen internasionale mededinging, verlaag hierdie beleide die verbruikerswelvaart as gevolg van ‘n verlaging in die verskeidenheid rys wat in die plaaslike mark verbruik word. Die studie beveel aan dat die regering die uitvoer van plaaslike rys in streeksmarkte fasiliteer en die invoerbeperkings op rys verminder. Die ingryping sal beide boere en verbruikers bevoordeel, terwyl die handelsbalans gestabiliseer word.