Revealing Genetic Relationship and Prospecting of Novel Donors Among Upland Rice Genotypes Using qDTY-Linked SSR Markers

A total of 17 simple sequence repeat(SSR) markers linked to QTLs(qDTYs) governing grain yield under reproductive stage(RS) drought stress were used to assess the genetic relationship and prospecting new donors for q DTYs among 32 popular upland rice genotypes. These SSR markers generated a total of 36 alleles with an average allele count of 2.1 per locus. Polymorphic information content value of the markers ranged from 0.376 to 0.662 with an average value of 0.484. The expected heterozyogosity ranged from 0.381 to 0.632. STRUCTURE analysis divided the 32 genotypes into three sub-populations. Subsequent phenotyping revealed that all the tolerant genotypes were grouped into one sub-population, whereas the moderately tolerant and susceptible genotypes were grouped into separate sub-populations. Phylogenetic tree constructed by the unweighted neighbour-joining method also divided the genotypes into three clusters. The grouping pattern of genotypes into the clusters was similar to that into the STRUCTURE analysis, on the basis of drought tolerance level. The average value of genetic dissimilarity coefficient among the genotypes was observed to be 0.486. Furthermore, by combining genotyping data with phenotyping data, 16 new donors for 6 qDTYs were identified.

The differenee in protein content,MDH,POD and COD isozymes during root different developmental stages in lowland rice and upland rice

The difference in protein content, MDH,POD and COD isozymes have been seenbetween lowland rice roots and upland rice roots during root growth and development. High pro-tein content has been examined in upland rice roots,but isozyme bands in lowland rice roots aremore than that in upland rice roots.Total area of POD isozyme bands at seedling and tilleringstages of upland rice is larger than that of lowland rice.The POD isozymes zymogram in the rootof upland rice is more stable compared with that of lowland rice.More COD isozyme numbershave been showed in roots of upland rice,but the relative activity of COD isozyme in roots of up-land rice at the seedling and tillering stages is lower than that of lowland rice.COD7 band can beshown in upland rice root at flowering stage,but it is absent in lowland rice.Therefore,COD7,band can be taken as an index for resistance of the upland rice to drought environment.

A new method for evaluating the drought tolerance of upland rice cultivars

Worldwide, approximately 27 million ha of rice are grown in upland rather than paddy fields, and is subject to drought stress. To counter this stress, it is desirable to breed new rice cultivars with improved drought tolerance. For breeding purposes, especially for breeding upland rice, it is desirable to develop a simple and accurate method to evaluate rice drought tolerance. We describe a new method that can be used to evaluate efficiently the drought tolerance degree(DTD) of upland rice cultivars, and call it the DTD method.DTD is defined as the mean of the ratios of green leaf length to total leaf length of the top three leaves in every rice seedling after drought treatment, and thus takes values from zero to one. To test whether the DTD method works effectively to evaluate drought tolerance of upland rice cultivars, we determined the DTD values of 13 upland rice cultivars showing varying degrees of drought tolerance in drought-tolerance trials. The idrl-1 mutant, which displayed the strongest drought tolerance of the 13 cultivars as identified by drought-tolerance trials under severe drought stress, had the highest DTD value and297-28, displaying the weakest drought tolerance, had the lowest DTD value. Further analyses of water potential, survival rate, panicles per plant, spikelets per panicle, seed setting rate, yield per plant, and contents of proline, chlorophyll, and malondialdehyde(MDA) indicated that DTD values are in general correlated with the values of these traits,making this new method useful for assessing the drought tolerance of upland rice cultivars.These results show that the DTD method is a simple, direct and relatively accurate evaluation method for drought-tolerance breeding of upland rice.

Field identification of morphological and physiological traits in two special mutants with strong tolerance and high sensitivity to drought stress in upland rice(Oryza sativa L.)

The two mutants idr1-1 and 297-28, which were obtained from the radiation mutation of HD297 and IAPAR9, were used as experimental materials in this study for a 2-year(2012 and 2013) experiment about field drought resistance identification in Beijing, China. Key agronomic traits and water-related physiological indexes were observed and measured, including the leaf anti-dead level(LADL), days to heading, plant height, setting percentage, aboveground biomass, leaf water potential(LWP), net photosynthetic rate(Pn) and transpiration rate. The results showed that the mutant idr1-1 that was under drought stress(DS) conditions for 2 years had the highest LADL grades(1.3 and 2.0) among all the materials, and they were 2–3 grades stronger than the wild-type IAPAR9 with an average that was 21.4% higher for the setting percentage than the wild type. Compared with the IAPAR9 for the 2-year average delay in the days to heading and the reduction rates in the plant height, setting percentage, and aboveground biomass under DS compared with the well-watered(WW) treatment, idr1-1 showed 3.2% less delay and 19.1, 16.4, and 6.1% less reduction, respectively. The idr1-1 in the LWP always exhibited the highest performance among all the materials. The Pn of idr1-1 under severe and mild DS comparing with that under WW was slightly decreased and even slightly increased, respectively, leading to an average reduction rate of only 0.92%, which was 26.93% less than that of IAPAR9. Under the severe DS, idr1-1 still showed the highest value of 16.88 μmol CO2 m–2 s–1 among all the materials and was significantly higher than that of IAPAR9(11.66 μmol CO2 m–2 s–1). Furthermore, only idr1-1 had the increased and the highest transpiration rate values(7.6 and 6.04 mmol H2 O m–2 s–1) under both mild and severe DS compared with the values under WW, when the transpiration rate of all the other materials significantly decreased. By contrast, the 297-28 in terms of the LADL grade under DS was the lowest(7.0), and it was four grades weaker than its wildtype HD297 and even one grade weaker than the drought-sensitive paddy rice SN265. For the 2-year average reduction rates in aboveground biomass and plant heights under DS compared with those under the WW, 297-28 was 31.6 and 31.8% higher than HD297, respectively. Meanwhile, 297-28 showed the worst performance for the LWP, Pn, and transpiration rate. These results suggest that idr1-1 might be a superior drought tolerant mutant of upland rice found in China. It has a strong ability to maintain and even enhance leaf transpiration while maintaining a high plant water potential under DS, thus supporting a high Pn and alleviating the delay in agronomic trait development and yield loss effectively. 297-28 is a much more highly drought-sensitive mutant that is even more sensitive than paddy rice varieties. The two mutants could be used as drought tolerance controls for rice germplasm identification and the drought resistant mechanism studies in the future. idr1-1 is also suitable for breeding drought-tolerant and lodging-resistant high-yield rice varieties.

Variation in Grain Quality of Upland Rice from Luang Prabang Province, Lao PDR

Luang Prabang Province is located within the area recognized as the center of rice(Oryza sativa L.) diversity in Lao PDR. This study reported on grain quality characteristics of 60 upland rice seed samples sharing 49 variety names collected from 6 villages in Luang Prabang in 2015. Most of the samples has non-pigmented pericarp, while red pericarp was found in four samples and purple in five samples. Almost all of the samples were of large grain type, with glutinous endosperm in 70% and non-glutinous endosperm in 30%. The brown(unpolished) rice was found with a wide range of grain nutritional quality, including protein(9.2% ± 0.9%), Fe(15.9 ± 6.9 mg/kg), Zn(19.6 ± 2.1 mg/kg), anthocyanin(0.774 ± 0.880 mg/g), and anti-oxidative capacity(2.071 ± 1.373 mg/g). The varieties sharing similar names had similar morphological characteristics but varied in nutritional concentration, with required confirmation in genetic variation analysis. This study found that some rice varieties with high grain quality may benefit the farmers directly or could be used in varietal improvement programs.

Cover Crops as Affecting Soil Chemical and Physical Properties and Development of Upland Rice and Soybean Cultivated in Rotation

Cover crops can provide changes in soil chemical and physical properties, which could allow a sustainable development of soybean and upland rice rotation in Brazilian Cerrado. The objective of this study was to determine the effects of cover crops(cultivated in the offseason) in the soybean-upland rice rotation(cultivated in the summer season) on the soil chemical and physical properties, yield components and grain yield of the cash crops. The experimental design was a randomized block design in factorial scheme 4 × 2 with six replications. Treatments were composed by four cover crops: fallow, millet(Pennisetum glaucum) + Crotalaria ochroleuca, millet + pigeon pea(Cajanus cajans), and millet + pigeon pea + Urochola ruziziensis in the offseason with one or two cycles of cover crops, with rice(Oryza sativa)or soybean(Glycine max) in the summer season. Cover crops alone provided no changes in soil chemical properties. However, the rotation cover crops/cash crops/cover crops/cash crops reduced p H, Al and H + Al and increased Ca, Mg, K and Fe contents in the soil. The cover crops millet + pigeon pea and millet + pigeon pea + U. ruziziensis improved soil physical properties in relation to fallow,especially in the 0–0.10 m soil layer. In spite of the improvement of the soil physical properties after two years of rotation with cover crops and cash crops, the soil physical quality was still below the recommended level, showing values of macroporosity, S index and soil aeration capacity lower than 0.10 m3/m3, 0.035 and 0.34, respectively. Upland rice production was higher under mixtures of cover crops than under fallow, mainly because of soil physical changes done by these mixtures of cover crops.Soybean grain yield was similar under all cover crops tested, but was higher after the rotation cover crops/upland rice/cover crops than after only one cycle of cover crops.

The ABA synthesis enzyme allele OsNCED2^(T)promotes dryland adaptation in upland rice

Upland rice shows dryland adaptation in the form of a deeper and denser root system and greater drought resistance than its counterpart,irrigated rice.Our previous study revealed a difference in the frequency of the OsNCED2 gene between upland and irrigated populations.A nonsynonymous mutation(C to T,from irrigated to upland rice)may have led to functional variation fixed by artificial selection,but the exact biological function in dryland adaptation is unclear.In this study,transgenic and association analysis indicated that the domesticated fixed mutation caused functional variation in OsNCED2,increasing ABA levels,root development,and drought tolerance in upland rice under dryland conditions.OsNCED2-overexpressing rice showed increased reactive oxygen species-scavenging abilities and transcription levels of many genes functioning in stress response and development that may regulate root development and drought tolerance.OsNCED2^(T)-NILs showed a denser root system and drought resistance,promoting the yield of rice under dryland conditions.OsNCED2^(T)may confer dryland adaptation in upland rice and may find use in breeding dryland-adapted,water-saving rice.

Artificial selection of the Green Revolution gene Semidwarf 1 is implicated in upland rice breeding

Semidwarf breeding has boosted crop production and is a well-known outcome from the first Green Revolution. The Green Revolution gene Semidwarf 1(SD1), which modulates gibberellic acid(GA) biosynthesis, plays a principal role in determining rice plant height. Mutations in SD1 reduce rice plant height and promote lodging resistance and fertilizer tolerance to increase grain production. The plant height mediated by SD1 also favors grain yield under certain conditions. However, it is not yet known whether the function of SD1 in upland rice promotes adaptation and grain production. In this study, the plant height and grain yield of irrigated and upland rice were comparatively analyzed under paddy and dryland conditions. In response to dryland environments, rice requires a reduction in plant height to cope with water deficits. Upland rice accessions had greater plant heights than their irrigated counterparts under both paddy and dryland conditions, and appropriately reducing plant height could improve adaptability to dryland environments and maintain high grain yield formation. Moreover, upland rice cultivars with thicker stem diameters had stronger lodging resistance, which addresses the lodging problem. Knockout of SD1 in the upland rice cultivar IRAT104 reduced the plant height and grain yield, demonstrating that the adjustment of plant height mediated by SD1 could increase grain production in dryland fields. In addition, an SD1 genetic diversity analysis verified that haplotype variation causes phenotypic variation in plant height. During the breeding history of rice, SD1 allelic mutations were selected from landraces to improve the grain yield of irrigated rice cultivars, and this selection was accompanied by a reduction in plant height. Thus, five known mutant alleles were analyzed to verify that functional SD1 is required for upland rice production. All these results suggest that SD1 might have undergone artificial positive selection in upland rice, which provides further insights concerning greater plant height in upland rice breeding.

<i>Sitophilus</i>Weevil Reaction in Upland Rice Elite Lines

Insects of the genus Sitophilus are among the most destructive pests in rice storage, and the best strategy to control it is to use resistant genotypes. In this study, 26 upland rice elite lines were evaluated for Sitophilus weevil reaction on grain weight. The seeds were placed in plastic recipients stored in a room with temperature and lightning simulating a warehouse environment. The number of living weevils and the grain weight were obtained in two evaluations, one 35 days after storage, and the other 35 days after infestation. The lines differed statistically for number of living weevils and for grain weight in both evaluations. The correlations between these two characters were -?0.99 and -?0.47 for the first and the second evaluation (P < 0.05), respectively. The lines BRS Pepita, AB 112089 and AB 112090 were the most susceptible. Seventeen of the twenty-six elite lines were resistant in both evaluations and could be successfully used in upland rice breeding programs.

Effect of Inoculation with Arbuscular Mycorrhizal Fungus on Nitrogen and Phosphorus Utilization in Upland Rice-Mungbean Intercropping System

The effect of arbuscular mycorrhiza fungi （AMF） on plant growth and nutrition utilization in upland rice and mungbean intercropping system was studied. A pot experiment was conducted in the greenhouse and AMF colonization rates of rice and mungbean roots, plant nutrient contents, the ability of nitrogen fixation, and nutrient contents changed in the soil were analyzed. The results were obtained as follows： the rates of AMF colonization of rice and mungbean roots were reached to 14.47 and 92.2% in intercopping system, and increased by 4.11 and 11.95% compared with that of in monocropping; the nirtrogen contents of mungbean and rice were increased by 83.72 and 64.83% in shoots, and 53.76 and 41.29% in roots, respectively, while the contents of iron in shoot and root of mungbean were increased by 223.08 and 60.19%, respectively. In the intercropping system with inoculation of AMF, the biomass of mungbean increased by 288.8%. However, the biomass of rice was not significantly changed among all treatments with or without inoculation of AMF recorded. The number and dry weight of nodules were significantly increased either when mungbean was intercropped with rice or inoculated with AMF. When compared with that of monocropping without AMF inoculation, the contents of nitrogen, phosphorus and iron in nodules of intercropping mungbean with inoculation increased by 80.14, 69.54 and 39.62%, respectively. Additionally, intercropping with AMF inoculation significantly increased soil nitrogen content, but reduced soil phosphorus content. We concluded that upland rice-mungbean intercropping system and inoculation with AMF improved the nutrient uptake, the ability of nitrogen fixation and the growth of mungbean.

Screening for Drought-Tolerant and Low-Input Responsive Upland Rice Landraces

Productivity potentials of upland rice landraces (URLs) are continuously compromised by scanty water supply due to competing priorities for irrigations and fluctuations in agro-ecological conditions peculiar to low-input farming systems. A growing demand for rice amidst decline in productive agricultural areas plunges into an urgent contribution of marginal areas critical in attaining food sufficiency among Filipino households. Agronomic performances of URLs locally found in Catanduanes province, Philippines were evaluated in a replicated trial utilizing three URLs: Kamanang [1], Kadari [2] and Bulaw [3]. The experimental set-up was closely monitored for consistent dry moisture content and zero fertilizer application. Results were significant for traditional upland landraces: Kamanang and Kadari, scored in terms of higher germination rate, increment plant height and the number of tillers during the vegetative stage. Leaf color gradations, although statistically not significant across cultivars, were suggestive of varying adaptive performance between traditional cultivars subjected to low-input system. Putative low-input responsive lines indicated by the higher survival percentage and overall agronomic responses were selected from the study site. Screened lines took part of the advance population which would be potentially able to tolerate poor soil conditions (i.e. poor storehouse of water and nutrients) especially in areas with edaphological constraints and changing rainfall distribution pattern. The development of putative drought tolerant lines among URLs forms the most economical solution implicated to areas with limited access to agricultural interventions.

Effects of Arbuscular Mycorrhizal Fungi(AMF) on Growth of Upland Rice under Soil Pb Contamination

[Objective] This study aimed to investigate the effects of arbuscular mycor-rhizal fungi （AMF） on growth of upland rice under soil Pb contamination. [Method] Using potting method, the effects of Glomus mosseae on the growth of Oryzal sati-va L. under different soil Pb concentrations （0, 300, 600 mg/kg） were investigated. [Result] According to the results, the mycorrhizal colonization rate of upland rice in-oculated with Glomus mosseae was significantly reduced （P〈0.05） with the increase of Pb concentration in soil. Compared with non-inoculation treatment, inoculation of arbuscular mycorrhizal fungi significantly improved the biomass of upland rice and Pb concentration of upland rice roots with addition of 300 mg/kg Pb but significantly reduced Pb concentration of upland rice shoots, which was consistent with the re-duced R/S （P〈0.05）; with addition of 600 mg/kg Pb, inoculation of arbuscular mycor-rhizal fungi significantly improved the biomass of upland rice roots （P〈0.05） but sig-nificantly reduced Pb concentration of upland rice shoots and roots （P〈0.05）; there was no significant difference in R/S between inoculation treatment and non-inocula-tion treatment. [Conclusion] This study indicated that inoculating Glomus mosseae under certain Pb concentrations could to some extent al eviate the toxic effects of Pb on Oryzal sativa L.

Effects of Arbuscular Mycorrhizal Fungi on Upland Rice Oxidative Stress Induced by Cu and Pb Contamination in Soil

[Objective] This study aimed to investigate the effect of arbuscular mycor-rhizal fungi on upland rice oxidative stress induced by Cu and Pb contamination in soil. [Method] The upland rice seeds were sowed in pots, in which the soil was previously mixed with a certain amount of Glomus mosseae and 0, 100 and 200 mg/kg Cu, or 0, 300 and 600 mg/kg Pb. In the control treatment, Glomus mosseae was inactivated before mixed into the soil. Then, the physiological and chemical properties of the aboveground parts of rice plants were measured at mature stage. [Result] Compared with the control treatment （NM）, Glomus mosseae （GM） treat-ment inhibited the POD, CAT and SOD activity while increased the soluble protein content under 100 mg/kg Cu and 300 mg/kg Pb treatment, improved the POD and CAT activity and soluble protein content while decreased SOD activity under 200 mg/kg Cu. SOD and POD activity showed no significant difference between NM and GM treatment under 600 mg/kg Pb, but the CAT activity was enhanced and soluble protein content was decreased. [Conclusion] This study wil provide theoretical refer-ence for bioremediation of soil heavy metal pol ution.

Insight to the Mode of Action of <i>Allium sativum</i>Leaf Agglutinin (ASAL) Expressing in T₃Rice Lines on Brown Planthopper

Brown planthopper, the sap sucking hemipteran pest, is one of the major contributors to the yield loss of rice through the world. To combat the situation researchers are interested identifying genes from plant origin having potentiality to develop hemipteran pest resistance. Interestingly, it was observed that rice plants expressing ASAL, a monocot mannose binding lectin, showed significant resistance to brown planthopper and green leafhopper. Additionally, antibiotic resistant marker gene free ASAL expressing rice lines were developed to overcome the biosafety issues. However, the basis behind the resistance against planthoppers is still not clearly understood. Ligand blot assay was performed with total BBMV protein from BPH and a ~56 kDa receptor protein was detected. LC MS/MS analysis revealed that the receptor protein is NADH quinone oxidoreductase (NQO), a key player in electron transport chain, insect defense response and male/female gametogenesis. Presumably interaction of ASAL with NQO may lead to toxicity and loss of fecundity among BPH feeding on ASAL expressing transgenic rice plants. These findings provide a stable scientific basis for considering these transgenic ASAL expressing rice plants as significant product for combating BPH attack associated yield loss of rice.

Weed Management in Rainfed Upland Rice Fields under Varied Agro-Ecologies in Nigeria

The demand for rice to meet the dietary need in low-income countries is expected to witness an exponential rise as the population increases.Meeting the rice demand domestically has remained challenging due to significant yield loss caused by several biotic and abiotic factors.Among these factors,one of the most important is the high weed pressure that ravages the upland rice ecology.In Nigeria,several independent weed control techniques,such as physical,chemical and cultural methods,have been recommended and adopted for weed control across varying rice upland ecologies.However,outcomes of these approaches when used independently have not consistently led to an increase in yield.There remains an outstanding deficit between the actual yield and the potential rice yield.This review aimed to identify potential research gaps,and quest effective and sustainable weed management strategies in smallholder upland rice farming systems in Nigeria.A critical analysis of studies suggests the potential of sustainable weed management practices if adopted and adapted smartly in different upland ecologies in Nigeria.Competitiveness of upland rice against weeds can be enhanced through strategic integration of weed competitive cultivars,optimum nitrogen application timings(within weed-free periods),uniform plant spacing,and high seeding rates,with conventional herbicide/manual weed control practices.However,such management practices can only be engaged where inputs are supplied on time and the technical know-how is extended to farmers.The review equally highlights potential research gaps for further studies.

晚粳稻籽粒中砷、镉、铬、镍、铅等重金属含量的品种和粒位效应

选用籽粒着粒密度差异较大的密穗型品种秀水63和散穗型品种秀水11,种植于受重金属轻度污染的土壤,研究了晚粳稻籽粒中有毒重金属As、Cd、Cr、Ni、Pb含量的品种与粒位效应。结果表明,重金属含量的粒位间差异秀水63明显大于秀水11,As、Cd、Cr、Pb含量粒位间差异显著,Ni含量差异较小。穗上部籽粒As、Cd、Ni含量高于中部籽粒,穗下部籽粒最低,而Cr、Pb则正好相反。稻米中几种重金属含量与粒重的关系因重金属种类不同存在着差异,籽粒As、Cd、Ni含量与粒重呈正相关,而Cr和Pb含量与粒重呈负相关。秀水63和秀水11不同粒位的籽粒灌浆模式存在差异,下位粒灌浆速率较低,使粒重较上、中位粒低,导致粒重有较大的粒位差异,而这种差异也与穗部着粒密度有关,秀水63明显大于秀水11。籽粒As、Cd、Ni含量与最大灌浆速率(GRm)呈正相关,与到达最大灌浆速率时间(Tpoi)呈负相关,而Cr和Pb含量与以上两个籽粒灌浆特性参数分别呈负相关和正相关,说明籽粒As、Cd、Ni的积累与碳水化合物的积累具有相同或相近的模式,而Cr和Pb表现为不同的积累模式。

Extent of Reduction of the Fallow Period and Its Impact on Upland Rice Production in the Nongowa Chiefdom of Kenema District in Eastern Sierra Leone

Slash-and-burn agriculture is the common practice for upland rice intercropping system in Sierra Leone and it has been blamed for the loss of forest vegetation across the country. Shortening of the fallow period in the Eastern region of Sierra Leone has implications on agricultural food production and the persistence of the remaining tropical rainforest. This study was therefore undertaken to assess: 1) the extent of reduction of the fallow period in the Nongowa Chiefdom of Kenema District;2) the causes of reduction in the fallow period;3) farmers’ perception of the relevance of fallow period and the implications of reduction of fallow period on crop production. The study revealed a drastic reduction of the fallow period in the chiefdom with a mean of 3.8 years which falls far below the country mean fallow period of 8.8 years as estimated by FAO. Farmers pointed out that the reduction of the fallow period was as a result of land scarcity due to competing land uses such as large scale commercial agriculture, logging, mining, charcoal burning and expansion of settlements. Farmers agreed that a fallow period of at least 10 years is necessary for upland rice production. Farmers were aware of the impact of reduction of the fallow period on upland rice production and were able to estimate rice yields based on the age of the fallow. Also, farmers have attempted to adapt to the constraints posed by shorter fallow periods by selection of rice varieties to suit the length of the fallow periods.

Effects of Arbuscular Mycorrhizal Fungi (AMF) on Distribution of Pb Forms in Rhizosphere of Upland Rice

[Objective] The aim was to study the effects of AMF on distribution of Pb in different chemical forms in rhizosphere soil of upland rice. [Method] A pot experiment was conducted to explore effects of AMF inoculation on distribution of Pb in different forms in rhizosphere of rice (Oryzal sativa L.) with Pb in different concentrations (0, 300 and 600 mg/kg). [Result] With inoculation adopted, mycorrzhial colonization rate of upland rice under Pb pdlution root declined substantially with Pb increasing in soils (P<0.05). Compared with non-inoculation, rhizosphere pH significantly enhanced by inoculation; when Pb was at 300 mg/kg, glomalin content in soils improved significantly by inoculation; when Pb was at 600 mg/kg, glomalin content in soils declined substantially (P<0.05). In addition, inoculation significantly improved contents of Pb in exchangeable and organic forms, but lowered Pb in carbonate bound and Fe-Mn oxides bound forms (P<0.05). [Conclusion] The research indicated that AMF inoculation would change distribution of Pb in different forms in rhizosphere soils of upland rice.

Effects of Mulching Mode on Canopy Physiological, Ecological Characteristics and Yield of Upland Rice

The effects of mulching mode on population physiology and ecology of rice were studied using a combination P88S/1128 as the material under three mulching cultivation modes including plastic film mulching, straw mulching and liquid film mulching, as well as bare cultivation (control). The results indicated that mulching mode had significant effects on micro-meteorological factors and individual growth of rice, as shown by an increase of relative humidity, a better internal micro-meteorological environment of rice population, a significant reduction under the rice canopy temperature, especially during high-temperature periods. Rice plants under mulching cultivation conditions displayed a stronger transpiration and lower leaf temperature, thereby improving the ability of anti-high temperature stress and markedly increasing the photosynthetic rate. Furthermore, the yield components of rice were significantly optimized under mulching cultivation, of which with plastic film mulching displayed the highest grain number per panicle and seed-setting rate, and a yield increase of 16.81% compared with the control; and with straw mulching displayed an increase of effective panicle number and a 9.59% increase of total yield compared to the control.

Molecular Variation and Application from Aerospace Mutagenesis in Upland Rice Huhan 3 and Huhan 7

To further improve upland rice varieties Huhan 3 and Huhan 7, seed samples were sent to outer space with two recoverable spaceships for approximately 1 and 5 d and were propagated for 7 and 5 generations, respectively. Phenotypic analysis revealed that the morphological traits and the protein and amylose contents of grains changed. Characterization of genomic mutations by the gene-associated simple sequence repeat （SSR） and insertion-delete （InDel） markers indicated that the mutation pattern was very complex. Most of the mutations occurred at the 3＇- or 5＇-end of the fragments in the simple sequence repeat fragment. Reverse transcription-polymerase chain reaction （RT-PCR） assay showed that mutations in those parts of the SSR affected their gene expression, indicating that gene associated markers would be helpful to isolate functional genes. Field survey for breeding also revealed that more lines with high yield, high quality and drought-tolerance could be selected through aerospace breeding. The results indicate that aerospace mutagenesis resulted in molecular variation, as well as physiological and morphological changes for rice breeding.