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.

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 Wxop 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.

The diversity of glutelin acidic polypeptides in rice cultivars collected from Northern Vietnam was characterized via sodium dodecyl sulphatepolyacrylamide gel electrophoresis (SDS-PAGE) and isoelectric focusing (IEF) electrophoresis. Glutelin acidic subunits were separated into four bands by molecular mass, as a-1 (39 kDa), a-2 (38 kDa), a-3 (37.5 or 37 kDa) and a-4 (34 or 33 kDa). One hundred and eighty-five Vietnamese rice cultivars were divided into three types, based on differences in staining intensity and the molecular size of the a-3 and a-4 polypeptides derived from SDS-PAGE analysis. Wide variation was also observed in the isoelectric point (pI) staining intensity, in addition to the absence/ presence of pI bands detected via IEF analysis. A total of 16 pI bands, ranging from pI 6.30 to pI 7.52, were identified in the various local rice cultivars. The maximum and minimum of IEF bands detected were 14 and 10, respectively. The genetic variability index (H′) ranged from 0.280 to 0.820, which confirms that local rice cultivars from Northern Vietnam have diverse glutelin seed storage units.

SummaryOne of the key aims of the Plantwise programme, led by CABI, is to reduce pesticide misuse. Through plant clinics, farmers are provided with a range of Integrated Pest Management (IPM) options by plant doctors who emphasize pest monitoring and prevention options before direct control measures. Country surveys carried out in Cambodia, Myanmar, Thailand and Vietnam in 2017 revealed that, after attending plant clinics, both men and women farmers had reduced the frequency of pesticide applications on their crops, replaced the most toxic chemicals with safer alternatives, increased the use of non-chemical options to tackle pests and diseases, stopped applying pesticides on the advice of friends and agrodealers, and reported a dramatic decrease in health problems. Key highlights Farmers have dramatically reduced the number of pesticide applications on their crops. While the number of farmers not spraying at all increased from 2.1% to 19.3% after visiting a plant clinic, the number of farmers who applied pesticides at least three times per crop dropped from 73.6% to 29.55%. After receiving advice from plant doctors to stop using the most toxic chemicals, farmers are using safer alternatives. With a greater understanding of the health and environmental costs of pesticides, increasing numbers of farmers have switched to non-chemical cultural methods (49.5%, up from 14.75%). After visiting a plant clinic, farmers are much less likely to rely on their own experiences or the advice of agro-dealers regarding pesticide use. After visiting a plant clinic, farmers reported a dramatic drop (81%) in health problems experienced as a result of pesticides. 100% of men and women stated that they were happy with the performance of plant clinics. CABI CASE STUDY 20 ContextPests and diseases are a major constraint to food security, income generation and world trade. Worldwide, an estimated 70,000 different pest species damage agricultural crops. Global potential losses due to pests has been estimated to vary from about 50% in wheat to more than 80% in cotton production, with weeds producing the highest potential losses overall (34%) compared to animal pests (18%) and pathogens (16%) (Oerke, 2006).To reduce and prevent crop losses, farmers have increasingly turned to pesticides. Yet, despite a significant increase in pesticide use, crop losses have not significantly decreased. About 3 billion tons of pesticides are applied each year across the world, yet pests, insects, weeds and plant pathogens destroy about 40% of all crops, valued at US$2 trillion (Pimentel, 2009). Pesticides are also being overused and used incorrectly, leading to human health and environmental concerns.