Effect of Seedling Raising Methods on Leaf Photosynthesis and Grain Yield of Mechanically-transplanted Japonica Rice

This study was conducted to investigate the effects of seedling raising modes on photosynthetic charactedsticsand grain yield under wheat straw returning. Four representative cultivars in Huaibei area were selected as test materials. By setting potted seedlings and carpet seedlings, the effects of different nursery meth- ods on the photosynthesis of rice at different growth stages in Huaibei area were investigated. Compared with carpet seedlings, the leaf area index of potted seedlings decreased at the maturation stage, but the dry weight of leaf shewed no significant difference.The SPAD of potted seedlings had an increasing trend after transplanting, but the SPAD increased differently according to cultivars. The net photosynthetic rate, stomatal conductance and transpiration rate of the leaves of pot seeding rice were significantly higher than those of carpet seedling rice on the 85^th d after transplanting. However, theintracellular CO2 concentration and water use efficiency of leaves had no significant differences between different ＇treatments. The results indicate that the photosynthetic capacity of flag leaves of pot seedling rice is stronger in early and middle stages, but the decay rate of photosynthetic function is slightly faster than carpet seedling rice, which might be the main reason for the rice yield of potted seedlings having no remarkable difference from carpet seedlings.

Effects of soilless substrates on seedling quality and the growth of transplanted super japonica rice

This study was conducted to investigate the effects of soilless substrates of hydroponically grown long-mat seedlings （HLMS） on seedling quality and field growth characteristics of transplanted super japonica rice. A widely grown conventional super japonica rice cultivar （Wuyunjing 23） was selected as the test material. The effect of HLMS on seedling quality, mechanical transplantation quality, field growth characteristics, yield, and benefit-cost ratio were compared with seedlings grown in organic substrates and traditional nutritive soil, whJch was selected as the control. Root number, root twJstJng power and root activity of seedlings cultivated by HLMS were decreased compared to that of the organic substrates andcontrol. However, seedling root length as well as aboveground growth were increased compared to the organic substrates and control seed- lings. In the HLMS, the content of gibberellin acid （GA3） decreased while abscisic acid （ABA） content increased compared to that of the organic substrates and control seedlings. During the early stages after transplanting, the re-greening of HLMS was delayed compared to that of the organic substrates and control seedlings. Nevertheless, there were no significant differences in tiller dynamics and crop yield among the HLMS, organic substrates and control treatments. The effects of HLMS on seedling production were similar to those of the organic substrates and traditional nutritive soil in the present study, suggesting that HLMS have the potential to replace traditional nutritive soil in seedling production without decreasing crop yield. Finally, it is important to reduce organic substrates and topsoil dependence during rice seedling production and worthwhile to consider HLMS popularization and its application on a larger scale.

Early Screening of Rice Varieties with High Essential Amino Acids by Aseptic Seedling Method

With 5 rice varieties( Yifeng 3321,Yifeng 3315,Yifeng 3317,Yifeng 45,Yifeng 14-24) as the experimental objects,the aseptic seedling method was used to culture the rice seeds,and the HPLC was used to determine the content of amino acids in aseptic rice seedlings as well as the total content of 8 kinds of essential amino acids and the content of protein. And the content of protein and amino acids in the polished rice of 5 varieties was detected,and the analysis of variance was performed for screening of the varieties containing high essential amino acids. The rice with high essential amino acids could be produced to meet people's rice quality requirements. The analysis of variance indicated that there were significant differences( F = 39. 262,p = 0. 01) in the content of essential amino acids among 5 kinds of rice varieties. By the Duncan's multiple comparison,the differences among rice varieties were calculated to obtain screening results. The aseptic seedlings:Yifeng 3321(7. 268),Yifeng 3315(6. 395),Yifeng 3317(5. 698),Yifeng 45(5. 567),Yifeng 14-24(5. 190). Rice: Yifeng 3321(2.998),Yifeng 14-24(2. 627),Yifeng 3317(2. 611),Yifeng 3315(2. 503),Yifeng 45(2. 281). Based on the estimated human daily requirement of essential amino acids and amino acids requirement pattern,it was found that the polished rice of 5 varieties was up to standard.The variety with the highest content of essential amino acids was Yifeng 3317(3830 mg/100g),followed by Yifeng 3321(3770 mg/100 g).The results showed that the high quality rice variety in this experiment was Yifeng 3321.

In-vitro vs in-vivo Inoculation: Screening for Resistance of Australian Rice Genotypes Against Blast Fungus

To assist with rapid screening for rice blast resistance as a precursor in a breeding program, the susceptibility to rice blast of 13 rice genotypes from Australia was evaluated in May to June 2013 using three distinct inoculation methods（spot, filter paper and standard methods） at seedling, vegetative and reproductive stages. The results revealed that the spot and filter paper inoculation methods were successful in discerning susceptibility to the rice blast disease（P ≤ 0.05）. Disease susceptibility declined significantly from the vegetative to reproductive stages. The standard method was conducted at three different stages for pot plants grown inside the mist house. However, low temperatures did not produce disease symptoms except in a few genotypes. Among the 13 rice genotypes screened, AAT9 expressed a highly resistant response, and AAT4, AAT6, AAT10, AAT11, AAT13, AAT17 and AAT18 expressed resistance at various stages. The results will be useful for selecting elite genotypes for disease tolerance where rice blast is prevalent. In addition, the resistant genotypes can serve as a gene pool used in breeding programmes to develop new resistant genotypes.