Comparative study of endophytic and endophytic diazotrophic bacterial communities across rice landraces grown in the highlands of northern Thailand

Communities of bacterial endophytes within the rice landraces cultivated in the highlands of northern Thailand were studied using fingerprinting data of 16S rRNA and nifH genes profiling by polymerase chain reaction–denaturing gradient gel electrophoresis. The bacterial communities’ richness, diversity index, evenness, and stability were varied depending on the plant tissues, stages of growth, and rice cultivars. These indices for the endophytic diazotrophic bacteria within the landrace rice Bue Wah Bo were significantly the lowest. The endophytic bacteria revealed greater diversity by cluster analysis with seven clusters compared to the endophytic diazotrophic bacteria (three clusters). Principal component analysis suggested that the endophytic bacteria showed that the community structures across the rice landraces had a higher stability than those of the endophytic diazotrophic bacteria. Uncultured bacteria were found dominantly in both bacterial communities, while higher generic varieties were observed in the endophytic diazotrophic bacterial community. These differences in bacterial communities might be influenced either by genetic variation in the rice landraces or the rice cultivation system, where the nitrogen input affects the endophytic diazotrophic bacterial community

Effects of arbuscular mycorrhizal fungi on resistance to Phytophthora parasitica of citrus seedlings and on growth of Thai honey tangerine scions on citrus rootstocks

Thai honey tangerine (Sainamphueng tangerine) is generally grown by grafting on rootstocks of another variety of tangerine or citrus species which may differ in their reaction to beneficial and pathogenic soil organisms. The objectives of this study were to evaluate responses to arbuscular mycorrhizal (AM) fungi and Phytophthora parasitica of different citrus genotypes and the effect of AM fungi on the growth of scions of Thai honey tangerine grafted on different citrus rootstocks including Cleopatra tangerine, lime, pomelo, Swingle citrumelo and Troyer citrange. Significant differences were found among citrus species in the percentage of root colonization by the AM fungi and in the severity of root rot disease when inoculated with P. parasitica alone. Thai honey tangerine was most susceptible and Cleopatra tangerine was most resistant to P. parasitica. Inoculation with AM fungi could reduce disease severity of all the citrus plants from P. parasitica. AM fungi enhanced the growth of seedling to the greatest extent in lime. Variation in the response to AM fungi was found among the scions of Thai honey tangerine on different citrus rootstocks. The scion of Thai honey tangerine grew best on the lime rootstock inoculated with AM fungi.Key words: Phytophthora parasitica, citrus, rootstock, arbuscular mycorrhizal (AM) fungi, root rot

Iron and zinc variation along the grain length of different Thai rice varieties

ABSTRACT: This study examined the distribution of iron (Fe) and zinc (Zn) along the grain length of seven rice varieties. The experiment was conducted in a completely randomized design with two factors (variety and grain fraction) and three independent replications. Samples of brown and white rice of six common Thai rice varieties and a high Fe and Zn variety, IR68144, were transversely cut into three fractions per grain (basal, middle, and distal) with approximately the same length in each fraction. The concentration of Fe and Zn was determined by the dry ashing method and quantified using atomic absorption spectrometry. The middle grain fraction of brown rice was found to have the lowest Fe and Zn with greater concentration of Fe and Zn in the basal (embryo end) than the other fractions. The rice varieties differed in the amount of Fe and Zn allocated to different fractions of the endosperm (white rice). The potential for loss of Fe and Zn during milling due to their uneven distribution along the grain length will become more significant when higher nutrient concentrations are involved, such as those achieved by biofortification efforts. Micronutrient distribution needs to be taken into consideration to ensure that rice consumers benefit from Fe and Zn biofortification

Application of Silicon Influencing Grain Yield and Some Grain Quality Features in Thai Fragrant Rice

Silicon (Si) is a beneficial nutrient that has been shown to increase rice productivity and grain quality. Fragrant rice occupies the high end of the rice market with prices at twice to more than three times those of non-fragrant rice. Thus, this study evaluated the effects of increasing Si on the yield and quality of fragrant rice. Also measured were the content of proline and the expression of the genes associated with 2AP synthesis and Si transport. The fragrant rice varieties were found to differ markedly in the effect of Si on their quality, as measured by the grain 2AP concentration, while there were only slight differences in their yield response to Si. The varieties with low 2AP when the Si supply is limited are represented by either PTT1 or BNM4 with only slight increases in 2AP when Si was increased. Si affects the gene expression levels of the genes associated with 2AP synthesis, and the accumulation of 2AP in fragrant rice mainly occurred through the upregulation of Badh2, DAO, OAT, ProDH, and P5CS genes. The findings suggest that Si is a potential micronutrient that can be utilized for improving 2AP and grain yield in further aromatic rice breeding programs.</p

The impact of foliar applied zinc fertilizer on zinc and phytate accumulation in dorsal and ventral grain sections of four thai rice varieties with different grain zinc

© 2017 Elsevier Ltd. This manuscript version is made available under the CC-BY-NC-ND 4.0 license: http://creativecommons.org/licenses/by-nc-nd/4.This study investigated the effect of foliar applied zinc (Zn) on the distribution of Zn and phytate in rice grain between four Thai rice varieties that differ in grain Zn. Foliar Zn application at 0.5% ZnSO4 was applied at flowering and the early milky stage compared with non-foliar applied Zn. Among the high-yielding, low grain Zn varieties (CNT1 and RD21), foliar applied Zn increased Zn concentration in both dorsal and ventral sections of unpolished rice by up to 17.7 and 14.3%. In the low-yielding, high grain Zn varieties (KPK and NR), Zn concentration increased by 11% in the dorsal section of NR, but no effect was found in both sections of KPK. In polished rice, the Zn concentration increased by 20% in both sections but it was increased only in the ventral section of KPK and CNT1 by 21.0% and 25.0% respectively, while there was an increase of 12.5% in the dorsal section of RD21. The phytate in the seed fractions was measured as an indication for Zn bioavailability within humans. A lower phytate concentration was observed after foliar Zn application in both unpolished and polished rice, indicating the potential for a higher bioavailability of Zn in the rice grain

Transforming Subsistence Cropping in Asia

The Green Revolution has benefited many people in Asia, but not everyone. This paper examines how many farmers have increased their productivity with more intensive cropping systems of fruit, vegetables, and in some cases, flowers. Total area under these crops more than tripled between 1977 and 2003. Case studies to highlight the transformation include vegetable production to feed Asia’s booming cities, diversification of export crops in Thailand, vegetable production in Malaysia’s Cameron Highlands, flower production in Yunnan Province of China and opium replacement in the Golden Triangle. Access to the market is necessary for transformation, but changes are also driven by farmers’ own innovations combined with contributions from last century’s crop science, from phytohormones to hybrid technology. Other inputs are irrigation, fertilizers and pesticides, with overuse of the last two a serious threat to the environment as well as to human health. Concerns have also been raised regarding soil erosion caused by cropping on steep slopes. In addition to building roads and airports, government support has also come in the form of cheap credit for orchard establishment and more efficient quarantine procedures to facilitate exports. Cross-border trade that brings opportunities to inaccessible border regions will be further enhanced by regional free trade policy, particularly when liberalization of trade in fruit and vegetables is specified such as that just signed by ASEAN and China. Finally, a case is made for the need to improve cropping systems in less favorable environment with limited access to the market and the means through which crop scientists can work with farmers to bring this about