High yield and nutritional quality of rice for animal feed achieved by continuous irrigation with treated municipal wastewater

Paddy and Water Environment - Two consecutive pilot-scale experiments were conducted to investigate the potential reuse of treated municipal wastewater (TWW) as an irrigation source for cultivating...     

Influence of single-nucleotide polymorphisms in the gene encoding granule-bound starch synthase I on amylose content in Vietnamese rice cultivars

Amylose content is one of the most important factors influencing the physical and chemical properties of starch in rice. Analysis of 352 Vietnamese rice cultivars revealed a wide range of variation in apparent amylose content and the expression level of granule-bound starch synthase. On the basis of single-nucleotide polymorphisms (SNP) at the splicing donor site of the first intron and in the coding region of the granule-bound starch synthase I gene, Waxy gene, alleles can be classified into seven groups that reflect differences in apparent amylose content. The very low and low apparent amylose content levels were tightly associated with a G to T in the first intron whereas intermediate and high amylose was associated with a T genotype at SNP in exon 10. The correlation between the combination of T genotype at SNP in the first intron, C in exon 6, or C in exon 10 was predominant among low amylose rice varieties. Our analysis confirmed the existence of Wx^op allele in Vietnamese rice germplasm. The results of this study suggest that the low amylose properties of Vietnamese local rice germplasm are attributable to spontaneous mutations at exons, and not at the splicing donor site.     

Diversity in Phenotypic Profiles in Landrace Populations of Vietnamese Rice: A Case Study of Agronomic Characters for Conserving Crop Genetic Diversity on Farm

Phenotypic variation of agronomic characters in aromatic rice (Oryza sativa L.) was analyzed in order to elucidate the genetic diversity of the populations of rice landraces. Thirteen populations in Namdinh province, in the Red River Delta of Vietnam, were studied in both of farmers fields and an experimental field. Only small differences were found in agronomic characters among the populations, including populations containing different varieties. Variations among the populations in the frequency distributions of several characters suggested different degrees of diversity among the populations even among populations with the same variety name. The phenotypic profiles of farmers fields were different from those in an experimental field suggesting the environmental differences between them. One variety cultivated in the Myloc district had different phenotypic characters from the other varieties in the Haihau district more clearly in the experimental field. Since the small phenotypic variation in each of farm might be due to the genetic drift and selection by the farmers, on farm conservation of the landraces of rice is considered to be under a force to decrease phenotypic diversity. The present study suggests that the targeting several farms with different phenotypic profiles contribute to the conservation of regional genetic diversity of the landraces of rice.     

Wet sieving versus dry crushing: Soil microaggregates reveal different physical structure,bacterial diversity and organic matter composition in a clay gradient

Soil microaggregates contain particles of different sizes, which may affect their potential to store organic carbon (OC). A variety of methods can be used to isolate microaggregates from the larger soil structures, among which wet sieving approaches are widely employed. We developed a novel dry crushing method that isolates microaggregates along failure planes due to mechanical stresses rather than hydraulic pressures and compared the mechanical stability, OC contents and microbial community composition between dry-crushed and wet-sieved samples with contrasting clay contents. Dry-crushed samples exhibited a higher stability and bacterial diversity compared to wet-sieved samples. As a result, the dry-crushed microaggregates had different size distributions when analysed dry and after wetting. In the dry state, dry-crushed microaggregates were larger and contained more sand-sized primary particles within the aggregate structures. The wetting of dry-crushed aggregates caused a disintegration of larger microaggregates and sand-sized primary particles into smaller microaggregates that contained finer particles. In the soils with lower clay contents, the diameter of dry-crushed microaggregates was 40 μm larger due to more sand-sized primary particles remaining within the aggregates. Depending on how much volume in microaggregates is occupied by large primary particles, the OC concentration increased in the soil with higher clay content. Wet-sieved size fractions also showed a similar pattern of OC distribution, whereas more primary particles were observed outside of aggregates. Wet sieving approaches disperse the soil into OC-rich aggregates and might be preferable if OC dynamics are investigated. Differences in bacterial community composition in dependence on clay content were more pronounced in dry-crushed microaggregates. If intact aggregate architectures are of interest for the isolation of soil structural units, the presented dry crushing method might provide an advantageous alternative that also better preserves bacterial diversity.     

Improved techniques for rearing mud crab Scylla paramamosain (Estampador 1949) larvae

A series of rearing trials in small 1 L cones and large tanks of 30–100 L were carried out to develop optimal rearing techniques for mud crab (Scylla paramamosain) larvae. Using water exchange (discontinuous partial water renewal or continuous treatment through biofiltration) and micro‐algae (Chlorella or Chaetoceros) supplementation (daily supplementation at 0.1–0.2 million cells mL⁻¹ or maintenance at 1–2 millions cells mL⁻¹), six different types of rearing systems were tried. The combination of a green‐water batch system for early stages and a recirculating system with micro‐algae supplementation for later stages resulted in the best overall performance of the crab larvae. No clear effects of crab stocking density (50–200 larvae L⁻¹) and rotifer (30–60 rotifers mL⁻¹) and Artemia density (10–20 L⁻¹) were observed. A stocking density of 100–150 zoea 1 (Z1) L⁻¹, combined with rotifer of 30–45 mL⁻¹ for early stages and Artemia feeding at 10–15 nauplii mL⁻¹ for Z3–Z5 seemed to produce the best performance of S. paramamosain larvae. Optimal rations for crab larvae should, however, be adjusted depending on the species, larval stage, larval status, prey size, rearing system and techniques. A practical feeding schedule could be to increase live food density from 30 to 45 rotifers mL⁻¹ from Z1 to Z2 and increase the number of Artemia nauplii mL⁻¹ from 10 to 15 from Z3 to Z5. Bacterial disease remains one of the key factors underlying the high mortality in the zoea stages. Further research to develop safe prophylactic treatments is therefore warranted. Combined with proper live food enrichment techniques, application of these findings has sustained a survival rate from Z1 to crab 1–2 stages in large rearing tanks of 10–15% (maximum 30%).