Mechanism of rice variety resistance to the yellow stem borer,Scirpophaga incertulas (Walker)

Yellow stem borer(YSB),Scir-pophaga incertulas(Walker)has be-come the main rice insect pest onceagain along the Changjiang Riversince 1990s.Unfortunately,no ricevariety with resistance to YSB hasbeen reported so far.Japonica Zhen-dao 2 with moderate resistance toYSB was found.In 10 rice vari-eties with different resistance levels,YSB individuals showed distinct de-velopmental rates,and the asyn-chronous development even occurredin the same rice variety.In this

E164—A new indica rice variety

E164(Wandao 27)was bred from the crossMilyang 23//IR4412-164-3-6/IR4712-108-1by the pedigree method.It was admitted andnamed Wandao 27 in Anhui Province in 1990.E164 has been proved to be an excellentricevariety with superior grain quality,high yieldand multi-resistance.It has been cultivated in an

An early maturing rice variety of high quality—Zhefu 218

Early maturing rice variety of high quality "Zhefu 218" was developed by prof XIA Yingwu, Zhejiang Agricultural University, Hangzhou, China. The growth period of the new rice variety is 106 d and its average yield is about 5.25-7.08 t / ha. It has the speciality of early-maturing combined with good quality. Not only the grains of "Zhefu 218" are of excellent cooking, but also of nutritive quality. The flavour of the cooked rice of"Zhefu 218" is considerably better than those of the ordinary rice cultivars here.

Analysis of inheritance of scented rice variety Shenxiangjing 4

We analyzed the inheritance of fragrance bysoaking rice grains or leafblades in 17g/l KOHsolution, using scented rice (Shengxiangjing 4)and non-scented rice (Huxuan 19 and Lao-laiqing) as materials. The Fplants of various crosses did notpresent fragrance. In the Fthe segregating ra-tio of fragrance and non-fragrance plants and

A blast-resistant and high-yielding rice variety Shuangchao 25

Shuangchao 25 was derived from the cross ofShuanggui 36/Kang 2 in 1983.The female parentwas a panicle-number type with quick growth andstrong-tiUering ability.The male parent was apanicle-weight type with Bl and BB resistance.The segregated progenies were selected by the"Method of Combination and Population Selec-

High-yielding rice variety Zhong 83-49

The early season indica rice variety Zhong83-49 was developed in 1981 as one of theFbreeding lines by selections from IR24/Yuanfengzao(F)//Zhuke 2.After various tri-als and tests,Zhong 83-49 has been proved to be a

A rice variety with a high straw biomass retained nitrogen and phosphorus without affecting soil bacterial species

It is well documented that rice paddy fields act as agricultural wetlands that remove or retain nutrients;however,their associated effects on soil microbial communities are rarely reported.The present study evaluates the impact of rice variety on nutrient removal via plant uptake,nutrient retention in the soil,and bacterial associations in rice paddy fields,using a network analysis that compares the soil bacterial communities of two rice varieties.We found that the high-straw rice variety(YD-1)allows uptake of a high amount of nitrogen(N)and phosphorus(P)from paddy rice fields via harvesting,but causes less residual total N and P to remain in the soil.However,both rice varieties(YD-1 and XS-134(Xiushui-134))had non-significant effects on the dominant bacterial taxa.The short-term response of bacterial community diversity to rice variety is found to be mainly due to less frequently recovered species.A network analysis that incorporates soil nutrients as nodes,along with bacterial taxa,found that only one node representing the total P related to the non-dominant species had an indirect association with the rice straw biomass.The observed short-term impact of the two rice varieties(XS-134 and YD-1)on soil bacterial diversity and nutrient surplus in these agricultural wetlands is limited under a high level of fertilization.

Adoption of Improved Rice Varieties in the Global South:A Review

Improved rice varieties(IRVs)play a significant role in establishing food security and improving livelihood in the Global South since its introduction in the 1960s.However,the adoption of new IRVs has remained relatively low.This low adoption poses a challenge to rice-producing and consuming countries as they are increasingly threatened by production shortages,malnutrition,and poor rice quality.Many empirical studies have attempted to identify the determinants influencing the adoption of IRVs by distinguishing the characteristics between adopters and non-adopters.This review showed a consensus on the important determinants influencing the adoption of IRVs in the Global South.Findings synthesized from 99 studies suggested that variables(farm size,education,information access and farm location)examined extensively are not necessarily the most important determinants of adoption when undertaking a weighted analysis.Terrain,source of seed and technology-related attributes(perceived yield,maturity,ease of use,marketability and technical efficiency)are more important determinants of adoption,with determinants changing according to adoption type(probability or intensity of adoption),variety type and region.The recommendations for future adoption studies include:incorporating more technology-specific variables,increasing research for overlooked regions and variety types,shifting away from predominant static analysis by capturing the dynamics of the adoption process,and considering the potential biases in analyses.This review will facilitate the development of targeted interventions and policies that promote IRV adoption in the Global South.

Differing responses of root morphology and physiology to nitrogen application rates and their relationships with grain yield in rice

Root morphology and physiology influence aboveground growth and yield formation in rice.However,root morphological and physiological differences among rice varieties with differing nitrogen(N)sensitivities and their relationship with grain yield are still unclear.In this study,rice varieties differing in N sensitivity over many years of experiments were used.A field experiment with multiple N rates(0,90,180,270,and 360 kg ha^(-1))was conducted to elucidate the effects of N application on root morphology,root physiology,and grain yield.A pot experiment with root excision and exogenous application of 6-benzyladenine(6-BA)at heading stage was used to further verify the above effects.The findings revealed that(1)under the same N application rate,N-insensitive varieties(NIV)had relatively large root biomass(root dry weight,length,and number).Grain yield was associated with root biomass in NIV.The oxidation activity and zeatin(Z)+zeatin riboside(ZR)contents in roots obviously and positively correlated with grain yield in N-sensitive varieties(NSV),and accounted for its higher grain yield than that of NIV at lower N application rates(90 and 180 kg ha^(-1)).(2)The root dry weight required for equal grain yield of NIV was greater than that of NSV.Excision of 1/10 and 1/8 of roots at heading stage had no discernible effect on the yield of Liangyoupeijiu(NIV),and it significantly reduced yield by 11.5%and 21.3%in Tianyouhuazhan(NSV),respectively,compared to the treatment without root excision.The decrease of filled kernels and grain weight after root excision was the primary cause for the yield reduction.Root excision and exogenous 6-BA application after root excision had little influence on the root activity of NIV.The oxidation activity and Z+ZR contents in roots of NSV decreased under root excision,and the increase in the proportion of excised roots aggravated these effects.The application of exogenous 6-BA increased the root activity of NSV and increased filled kernels and grain weight,thereby reducing yield loss after root excision.Thus,the root biomass of NIV was large,and there may be a phenomenon of"root growth redundancy."Vigorous root activity was an essential feature of NSV.Selecting rice varieties with high root activity or increasing root activity by cultivation measures could lead to higher grain yield under lower N application rates.

Super Rice Cropping Will Enhance Rice Yield and Reduce CH_4 Emission:A Case Study in Nanjing,China

A pot experiment was performed to learn the differences in plant productivity and OH4 emission between two rice cultivars, super rice variety Ningjing 1 and traditional variety Zhendao 11, which were currently commercially appUed in Nanjing, China. Similar seasonal changes of CH4 emission fluxes and soil solution CH4 contents were found between the tested cultivars. Although there was no significant difference in plant biomass production between the cultivars, the grain yield of Ningjing 1 was significantly higher by 35.0% （P 〈 0.05） than that of Zhendao 11, whereas the total CH4 emission from Ningjing 1 was 35.2% lower （P 〈 0.05）. The main difference in the amounts of CH4 emission between the cultivars occurred in the period from the tillering stage to the heading stage. The biomass-scaled and yield-scaled CH4 emissions were respectively 3.8 and 5.2 mg/g for Ningjing 1, significantly lower than those for Zhendao 11 （7.4 and 12.8 mg/g, respectively）. According to the relationships between the plant growth characteristics and the CH4 emission, a stronger root system contributed mainly to the lower CH4 emission of Ningjing 1, as compared with Zhendao 11. Our results demonstrated that super rice has advantages not only in grain productivity but also in CH4 emission mitigation. Further expansion of super rice cropping will enhance rice yield and reduce greenhouse gas emission in China.

Development of lepidopteran pest-resistant transgenic japonica rice harboring a synthetic cry2A* gene

A synthetic cry2A^＊ gene enco ding Bacillus thuringiensis（Bt） δ-endotoxi n that resi st ance to lepidopteran pest was transformed into japonica rice variety Jijing 88, which is the most widely cultivated variety in Jilin Province, Northeast China, by Agrobacterium-mediated transformation. A total of 106 independent transformants overexpressing cry2A^＊ gene driven by ubiquitin（Ubi） promoter was produced. Three single-copy homozygous transgenic lines were finally selected based on the results of PCR analysis, se gregation ratio of Bast a resistance, and Southern hybridiza tion analyse s. RT-PCR and enzyme linke dimmune sorbent assay（ELISA） revealed that cry2A^＊ transcripts and protein were highly expressed in these lines. The high level of Cry2A^＊ protein expression resulted in high resistance to rice striped stem borer as evidence d by insect feeding bioassays. Our results demonst rate that cry2A^＊ transgenic japonica rice confers resistance to the rice striped stem borer in the laboratory conditions.

Factors Affecting Adoption of Improved Rice Varieties among Rural Farm Households in Central Nepal

The use of improved high yielding crop varieties is an important avenue for reducing hunger and food insecurity in developing countries. Using cross-sectional data obtained from a survey conducted during 2013 crop season, we performed a probit model （plot-level analysis） to determine the probability of adopting new improved rice varieties （NIRVs） by smallholder farmers particularly from two main agro-ecological regions （hills and tropical plain terai regions） of Central Nepal. The results revealed that education, extension services and seed access play significant roles in adoption decisions. Additionally, farm and field characteristic variables such as farm size, endowment of favorable land type （e.g. lowlands）, and animal power （e.g. oxen） are the key factors influencing the probability of adopting NIRVs. The results showed that technology specific variables （e.g. yield potential and acceptability） are significant for explaining adoption behavior, implying that it is important to take farmers＇ preferences to varietal characteristics into consideration in the design of a research and development program. Given the significant role played by extension and access related variables, increased emphasis on information dissemination, field demonstration, and farmers＇ participatory research and training programs to popularize new rice varieties and enhance their adoption rate are required. This also suggests that policy intervention should be made on improving the educational status of farming households, and developing programs on varietal package of rice seed which offer farmers a variety of choices among the appropriate pools of germplasm. Such programs ultimately help farmers develop more profit-oriented behavior which are necessary to enhance adoption rate, production and food security in the long run.

Development of a Highly Informative Microsatellite (SSR) Marker Framework for Rice (Oryza sativa L.) Genotyping

To select highly informative microsatellite markers （SSRs） and establish a useful genetic SSR framework for rice genotyping, 15 rice （Oryza sativa L.） cultivars including six indica varieties and nine japonica varieties were used to analyze the polymorphism information content （PIC） value of 489 SSR markers. A total of 1 296 alleles were detected by 405 polymorphic markers with an average of 3.2 per locus. The PIC value of each chromosome was ranged from 0.4039 （chromosome 2） to 0.5840 （chromosome 11）. Among the two rice subspecies, indica （0.3685-0.4952） gave a higher PIC value than japonica （0.1326-0.3164） and displayed a higher genetic diversity. Genetic diversity of indica was high on chromosome 12 （0.4952） and low on chromosome 8 （0.3685）, while that for japonica was high on chromosome 11 （0.3164） and low on chromosome 2 （0.1326）. A SSR framework including 141 highly informative markers for genotyping was selected from 199 SSR markers （PIC〉0.50）. Ninety-three SSR markers distributed on 12 chromosomes were found to be related to indica-japonica differentiation. Of these 93 pairs of SSR primers, 17 pairs were considered as core primers （all the japonica varieties have the same specific alleles, while the indica varieties have another specific alleles）, 48 pairs as the second classic primers （all the japonica or indica varieties have the same specific alleles, while the indica or japanica varieties have two or more other specific alleles ） and 28 pairs as the third classic primers （all the japonica and indica varieties have two or more alleles, but the specific alleles are different between japonica and indica）. Thirty-two SSR markers were selected to be highly informative and useful for genetic diversity analysis of japonica varieties. This work provides a lot of useful information of SSR markers for rice breeding programs, especially for genotyping, diversity analysis and genetic mapping.

Effects of Varieties and Cooking Methods on Physical and Chemical Characteristics of Cooked Rice

To analyze the effect of different lowland rice varieties and different cooking methods on physical and chemical characteristics of cooked rice. A factorial randomized block design with two factors was used and each combination of the factors was repeated three times. The first factor was rice variety（Ciherang and Ciliwung） and the second factor was the cooking method（stovetop, boiling and steaming, and rice cooker）. Results showed that Ciherang and Ciliwung varieties were classified into slender grain rice type with yellowred color. The amylose content of Ciherang was classified as moderate, while the amylose content of Ciliwung classified as low. The most abundant amino acid contained in Ciherang and Ciliwung varieties was glutamic acid. Statistical analysis showed that cooking method had significant effects on texture, lightness, chroma, hue and moisture content of cooked rice. Rice cooked with liwet method had the lowest texture value, lowest lightness value, highest chroma value, and highest moisture content.

Susceptibility to Insecticides and Ecological Fitness in Resistant Rice Varieties of Field Nilaparvata lugens Stl Population Free from Insecticides in Laboratory

A population of rice brown planthopper （BPH） Nilaparvata lugens collected from a paddy field in Hangzhou was successively reared on susceptible rice Taichung Native 1 （TN1） in a laboratory free from insecticides for more than 14 generations. The changes in susceptibility to insecticides and ecological fitness on different resistant rice varieties were monitored in each generation. The resistance ratio to imidacloprid sharply declined with the succession of rearing generations without insecticides from 359.94-fold at F1 to 6.50-fold at F14 compared with the susceptible strain, and the resistance ratio to chlorpyrifos was from 9.90-fold at F1 to 5.94-fold at F14. Nymphal duration and weights of newly hatched female adults were significantly affected by rice variety, generation and their interactions, but nymphal survival was significantly affected by the generation only. The ratio of brachypterous adults in males was affected by the generation and generation × variety interaction, whereas no difference was found in females. Nymphal duration extended with increasing generations, and the female nymphal duration was shorter in the susceptible variety TN1 than those in the resistant varieties IR26 and IR36. In addition, the female adult weight in TN1 was higher than those in IR26 and IR36. These results indicated that the resistance of field BPH population to insecticides was reversed after several generations of no-exposure to insecticides, and the ecological fitness in TN1 was higher than those in IR26 and IR36. These findings suggested the rational and reduced use of insecticides in combination with the manipulation of resistant rice varieties would be effective for BPH management.

Amylose Content and Starch Granule Size in Rice Grains are Affected By Growing Season

Amylose content and starch granule size in grains influence rice quality,which differs between the early(ES)and late season(LS).The objective of this study was to determine the variation of amylose content and starch granule size between seasons and find the main reasons(e.g.,temperature and solar radiation)for the observed variation.Field experiments with six rice varieties(three high and three low amylose content rice)planted in the ES and LS were conducted in 2016 and 2017,respectively.The mean temperatures during the filling stage were higher in ES,however,the daily temperatures at 7-10 days after flowering(DAF)in 2016,and at 5-10,13-14 DAF in 2017 were higher in LS.The results showed that amylose content in LS was lower than in ES with high amylose content rice varieties(HACV);the opposite trend occurred with low amylose content rice varieties(LACV).The mean starch granule diameter was higher in LS than ES in 2016,but the opposite result occurred in 2017 with all rice.Our results suggest that higher temperatures increased and decreased the amylose content in HACV and LACV,respectively.Temperatures at 5-15 DAF were important for the formation of starch granules:lower temperatures during 10-14 DAF increased the proportion of larger starch granules(d>6.21μm,some with d>13.3μm),and higher temperatures at 5-6 DAF increased the proportion of starch granules with diameter 4.24-6.21μm.

Analysis of Genetic Similarity for Improved Japonica Rice Varieties from Different Provinces and Cities in China

To provide a genetic basis for japonica rice breeding, the genetic similarity and cluster of 139 accessions of improved japonica rice varieties from 12 provinces and cities of China were analyzed using 34 SSR markers. Totally 198 alleles were detected among these improved japonica rice varieties with the average number of alleles per pair of primers was 5.3235. RM320, RM531, RM1, RM286, and RM336 showed more alleles, which were 15, 12, 11, 9, and 9, respectively. RM320, RM336, RM286 and RM531 showed higher genetic diversity indexes; which were 2.3324, 2.0292, 1.8996, and 1.7820, respectively. The range of genetic similar index among improved japonica rice varieties from different provinces was from 0.321 to 0.914, with the average of 0.686. There was a high genetic similarity among improved japonica rice varieties from Heilongjiang, Jilin, Liaoning, Ningxia, and Yunnan, which were located in similar latitude or similar ecological environment, while there was a low genetic similarity between improved japonica rice varieties from Guizhou and Jiangsu, and other provinces which were located in more different latitudes and ecological environments. The markers of RM320, RM531, RM1, RM286, and RM336 fit to be used in analysis of genetic diversity for improved japonica rice variety. The genetic similarity among improved japonica rice varieties from different provinces was closely associated with genetic basis of parents, and was also correlated with latitude and ecological environment where the varieties were bred.

Field Evaluation of Growth and Yield of Two Local Rice Varieties (Tox-728-1 and Madjitolngar) in Response to Indogenous Mycorrhizal Inoculation in South-Chad

This study was carried out to find out how dependent are two local rice varieties (Magitolngar and Tox-728-1) to inoculation with selected endogenous arbuscular mycorrhizal fungi (AMF) in a field where they were isolated. The multi-indigenous endomycorrhiza spores previously isolated and identified were the active ingredient in the production of bioinoculants used for this purpose. Spores massively multiplied from the rhizosphere of each rice variety in each of the four locally collected soils substrates were harvested to constitute 08 AMF inoculants (Kema = T1;Lama = T2;Latox = T3;Ndjatox = T4;Koloma = T5;Kolotox = T6;Ndjama = T7;Ketox = T8). These inoculants were field tested on the two rice varieties at Kelo, under a complete randomized block design, comprising 10 treatments (8 inoculants, 01 positive control = T9, 01 negative control = T10), each of which was repeated thrice. The analysis of data indicates that AMF-inoculated plants were taller, developed more tillers/plant, and produced more rice grains/panicle than non-AMF-inoculated plants for both studied rice varieties. The rice variety Madjitolngar yielded more grains (7.5 t/ha) than the Tox-728-1 variety (5.8 t/ha). Moreover, inoculants Koloma (T1), Latox (T3) and Kolotox (T6) on the one hand, Koloma (T1) and Ketox (T8) on the other hand, were best suited for the improvement of growth and yield of the rice varieties Madjitolngar and Tox-728-1 respectively, tested under field conditions at Kelo. In this study, the two rice varieties have shown a dependency to endomycorrhizal symbiosis at Kelo, and therefore, an industrial-scale production of efficient endomycorrhal inoculants is necessary to sustainably boost the productivity of this important crop in Chad.

Effect of Combined Application of Subsurface Drainage and Mineral Fertilization on Iron-Reducing Bacterial Populations’ Developments and Fe2+ Uptake by Two Rice Varieties in an Iron Toxic Paddy Soil of Burkina Faso (West Africa)

Rice is one of the staple crops in Burkina Faso. However, the local production covers only 47% of the population demands. One of the main reasons of the poor productivity in Burkina Faso is iron toxicity which is related mainly to the activity of Iron Reducing Bacteria in the rice field’s ecosystems. In order to control the harmful effects of Iron Reducing Bacterial populations and to improve rice productivity, a pots experiment was conducted at the experimental site of the University Ouaga I Pr. Joseph KI-ZERBO. An iron toxic soil from Kou Valley (West of Burkina Faso) and two rice varieties, BOUAKE-189 and ROK-5, sensitive and tolerant to iron toxicity, respectively, were used for the experiment. The pots were drained for 14 days (D2) and amended with chemical fertilizers (NPK + Urea and NPK + Urea + Ca + Mg + Zn complexes). Control pots without drainage and fertilization (D0/NF) were prepared similarly. The kinetics of Iron Reducing Bacterial populations and ferrous iron content in soil near rice roots were monitored throughout the cultural cycle using MPN and colorimetric methods, respectively. The total iron content was evaluated in rice plant using a spectrometric method. Data obtained were analyzed in relation to drainage and fertilization mode, rice growth stage and rice yield using the Student’s t-test and XLSTAT 2014 statistical software. The experiment showed that the combined application of subsurface drainage and NPK + Urea + Ca + Mg + Zn fertilization, reduced significantly the number of IRB in the soil near rice roots for both rice varieties (p = 0.050 and p = 0.020) increased the leaf tissue tolerance to excess amounts of Fe, and rice yield.