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28 May 2014, Volume 21 Issue 3 Previous Issue    Next Issue
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Molecular Improvement of Grain Weight and Yield in Rice by Using GW6 Gene LI Yuan-yuan, TAO Hong-jian, ZHAO Xiang-qian, XU Jie, LI Geng-mi, HU Shi-kai, DONG Guo-jun, SHI Zheng-yuan, WU Li-wen, HU Jiang, YE Guo-you, GUO Long-biao 2014, 21(3): 127-132.  DOI: 10.1016/S1672-6308(13)60175-4 Abstract ( )   PDF (819KB) ( )   Molecular design breeding is one of straightforward approaches to break yield barriers in rice. In this study, GW6 gene for grain length and width from Baodali was transferred into an indica recurrent parent 9311 and a japonica variety Zhonghua 11 (ZH11) using marker-assisted backcross (MAB). One and three introgression lines were selected for phenotypic analysis from 9311 and ZH11 genetic backgrounds, respectively. SSL-1, an improved 9311 near isogenic line with GW6 performed 11%, 19% and 6.7% higher of grain length, 1000-grain weight and single plant yield, respectively, as compared with 9311. All the three improved ZH11-GW6 lines, R1, R2 and R3, had more than 30% increase in grain weight and about 7% higher in grain yield. Seed plumpness of R1, R2 and R3 was improved synchronously because the three ZH11-GW6 lines contained GIF1 (Grain Incomplete Filling 1), a dominant grain filling gene. Thus, GW6 has high potential in increasing the yield of inbred lines through MAB, making it an important genetic resource in super hybrid rice breeding. This study provides insights in the utilization of GW6 for large grain and high yield rice breeding via molecular design breeding.

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Genotype X Environment Interactions for Agronomic Traits of Rice Revealed by Association Mapping XU Fei-fei #, TANG Fu-fu #, SHAO Ya-fang, CHEN Ya-ling, TONG Chuan, BAO Jin-song 2014, 21(3): 133-141.  DOI: 10.1016/S1672-6308(13)60179-1 Abstract ( )   PDF (1188KB) ( )   Agronomic traits are important determinants to rice yield, which are controlled by complex genetic factors as well as genotype by environment (G ? E) interaction effects. The G ? E effects for agronomic traits of rice have been dissected with various approaches, but not with the current available approach, the association studies. In this study, a total of 32 655 single nucleotide polymorphisms were used to carry out associations with 14 agronomic traits among 20 rice accessions in two environments. The G ? E interaction effects for all the agronomic traits were at highly significant levels (P < 0.01), accounting for 3.4%–22.3% of the total sum of squares except for the length of brown rice. Twenty three putative quantitative trait loci (QTLs), including five previously known and several new promising associations, were identified for 10 of 14 traits. Analysis of the relationships between the traits for which QTLs and the genotype effects could be identified suggested that the higher the genotypic effect, the higher the possibility to identify QTLs for the given trait. The new QTLs detected in this study will facilitate dissection of the complex agronomic traits and may give insight into the G ? E effects with association mapping.

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Structural and Histochemical Characterization of Developing Rice Caryopsis YU Xu-run, ZHOU Liang, XIONG Fei, WANG Zhong 2014, 21(3): 142-149.  DOI: 10.1016/S1672-6308(13)60176-6 Abstract ( )   PDF (3274KB) ( )   The development of pericarp, seed coat, starchy endosperm and aleurone of the rice caryopsis was investigated, histochemically and structurally, from the time of flowering to maturity. The results showed that during its growth, the maximum length of the caryopsis was attained first, followed by width and then thickness. Histochemical examination of the caryopsis showed that starch was mainly accumulated in the endosperm, but the endosperm showed no metabolic activity, while embryo and pericarp contained a few starch grains, and embryo and aleurone were strongly active. Aleuronic cells contained many aleurone grains and spherosomes, and aleurone in the dorsal region developed earlier and contained more layers of cells. Amyloplasts in endosperm contained many starch granules and were spherical at early stages but polyhedric at late stages. The protein bodies appeared later than amyloplasts, and the number of protein bodies in subaleurone was greater than those in the starchy endosperm. The white-belly portion of endosperm might be relative to the status of amyloplast development.

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Association and Heritability Studies for Drought Resistance under Varied Moisture Stress Regimes in Backcross Inbred Population of Rice R. SELLAMMAL, S. ROBIN, M. RAVEENDRAN 2014, 21(3): 150-161.  DOI: 10.1016/S1672-6308(13)60177-8 Abstract ( )   PDF (192KB) ( )   Drought stress is one of the major constraints affecting rice production and yield stability in the rainfed regions. To understand the physiological basis of drought resistance related component traits, we used a backcross inbred population of rice under three kinds of moisture regimes viz., non-stress, moderate (24.48%) and severe stress (73.97%) conditions which reflect the differential responses of the genotypes to varying stress intensities. The plot yield, 1000-grain weight, panicle exsertion and canopy air temperature difference exhibited high heritability under the control conditions, whereas spikelet sterility and single plant yield exhibited high heritability under the moderate stress conditions. Traits such as days to 50% flowering, plant height and osmotic potential showed high heritability under the severe stress conditions. Plot yield under stress was significantly and positively correlated with harvest index and 1000-grain weight, but negatively associated with leaf rolling score and days to 50% flowering. The drought susceptibility index and drought response index were negatively correlated between each other both under the moderate and severe stress conditions. The derived traits viz., difference in panicle length between the control and the severe stress was associated with osmotic adjustment measured under field conditions. Difference in plant height and panicle length was negatively associated with plot yield under stress.

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Germplasm Innovation of Heat Tolerance in Rice for Irrigated Lowland Conditions in the Philippines Norvie L. MANIGBAS, Leslie Angela F. LAMBIO, Luvina B. MADRID, Corazon C. CARDENAS 2014, 21(3): 162-169.  DOI: 10.1016/S1672-6308(13)60180-8 Abstract ( )   PDF (1662KB) ( )   Heat-tolerant varieties, such as N22 and Dular, which were used in this study, usually have low yield potential and undesirable plant characteristics but combining them with high yielding and improved rice varieties, new heat-tolerant rice genotypes with high yield potential can be achieved. In this study, phenotyping and selecting desirable materials from various crosses were performed under high temperature conditions during the reproductive stage. Screening was performed in the field and glasshouse to select individuals with heat tolerance and high yield potential. Several advanced breeding lines from Gayabyeo/N22 cross produced desirable individuals with heat tolerance, resistance to pests and diseases, and high yield potential. The genetic variation in percent sterility among the selected backcross populations grown in high temperature environments showed that large number of plants can be identified and selected with lower percent sterility.

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Experiences with Rice Grown on Permanent Raised Beds: Effect of Crop Establishment Techniques on Water Use, Productivity, Profitability and Soil Physical Properties R. K. NARESH, S. S. TOMAR, Dipender KUMAR, Samsher, Purushottam, S. P. SINGH, Ashish DWIVEDI, Vineet KUMARVineet KUMAR 2014, 21(3): 170-180.  DOI: 10.1016/S1672-6308(13)60185-7 Abstract ( )   PDF (645KB) ( )   In recent years, conventional rice production technologies have been leading to deterioration of soil health and declining farm profitability due to high inputs of water and labor. Conservation agriculture (CA) based resource-conserving technologies i.e. zero-tillage (ZT), raised-bed planting and direct-seeded rice (DSR) have shown promise as alternatives to conventional production technologies to overcome these problems. Present study was undertaken during 2009–2012 to establish an understanding of how permanent raised bed cropping system could be practiced to save water at the field application level to improve water productivity and also have the capability to enhance productivity, profitability and soil physical quality. The results showed that among different crop establishment techniques, conventional-tilled puddle transplanted rice (CT-TPR) required 14%?25% more water than other techniques. Compared with the CT-TPR system, zero till direct-seeded rice (ZT-DSR) consumed 6%–10% less water with almost equal system productivity and demonstrated higher water productivity. Wide raised beds saved about 15%–24% water and grain yield decrease of about 8%. Direct-seeded rice after ZT or reduced tillage or on unpuddled soil provided more net income than CT-TPR. The CT-TPR system had higher bulk density and penetration resistance due to compaction caused by the repeated wet tillage in rice. The steady-state infiltration rate and soil aggregation (> 0.25 mm) were higher under permanent beds and ZT and lower in the CT-TPR system. Under CT-TPR, soil aggregation was static across seasons, whereas it improved under no-till and permanent beds. Similarly, mean weight diameter of aggregates was higher under ZT and permanent beds and increased over time. The study reveals that to sustain the rice productivity, CA-based planting techniques can be more viable options. However, the long-term effects of these alternative technologies need to be studied under varying agro-ecologies in western Uttar Pradesh, India.

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Susceptibility to Insecticides and Ecological Fitness in Resistant Rice Varieties of Field Nilaparvata lugens St?l Population Free from Insecticides in Laboratory YANG Ya-jun, DONG Bi-qin, XU Hong-xing, ZHENG Xu-song, K.L. HEONG, LU Zhong-xian 2014, 21(3): 181-186.  DOI: 10.1016/S1672-6308(13)60181-X Abstract ( )   PDF (174KB) ( )   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.