Methane emission from different rice cultivation systems in Bangladesh: A model based approach

Globally, a large amount of methane (CH4) emission is generated from agricultural systems including rice farming in many Asian countries including Bangladesh. However, a reliable estimate of CH4 emission from rice cultivation is not available, particularly considering the different rice types (i.e., local land races, high yielding varieties (HYV), and hybrid varieties) grown under diverse conditions. Here, we estimated current and future CH4 emission (both rate and amount) from different rice farming systems in Bangladesh using the IPCC Tier1 method. Model based estimates were validated with a pilot survey and with other studies. Across all rice types grown in different seasons, (i.e., Aus from March to August, Aman from July to December and Boro from December to June), the estimated CH4 emission in 2020 was at 2348 Gg CH4 yr− 1 (95% CIs of 799–5628 Gg CH4 yr− 1) while a slightly higher CH4 emission was estimated at 2376 Gg CH4 yr− 1 for the year 2060 after considering a 0.5 % cultivable rice land migration to non-agricultural activities. We also found significant differences in CH4 emission rates among types of rice cultivation and growing season. Average across all seasons, the highest CH4 emission was from hybrid varieties (225 kg CH4 ha− 1 yr− 1), while the lowest (128 kg CH4 ha− 1 yr− 1) from local land races. In contrast, the same local land races showed the highest emission rates when normalized against yield. Across all rice types, the largest CH4 emission was during Aman season accounting 61% of the total annual emission. Our model-based estimates reasonably compare with survey-based estimates (r2 = 0.94, p < 0.01) and fall within one standard deviation of a log-normal distribution of measurement based CH4 emissions. Our findings, therefore, provide a deeper insight into CH4 emissions from rice cultivation systems.

Evaluation of indigenous land races of deep-water paddy of North East India for nutraceutical value

Deep water paddy is a nature’s marvel for many ethnic communities living in flood prone river basins of some Asian and African countries. In recent times there is resurgence in interest on local land races in view of alarming depletion of agro-biodiversity and the urgency to preserve them. In Assam, the north eastern state of India, deep water paddy is being cultivated since time immemorial by several ethnic communities living in the Brahmaputra river basin. Although not properly enumerated, it is known that more than 70 land races of Bao Dhanexists. Moreover, recent works have revealed that contrary to general perception deep water paddy are rich in nutritional and nutraceutical values with 9% to 13% protein. Further interest on deep water paddy got a boost with the report that land races with red kernel (red rice) are rich in dietary antioxidant anthocyanin and study showed that they have impressive anti-oxidative activity in vitro. Deep water paddy or floating paddy popularly referred to as Bao dhan in Assam, represent a unique crop capable of withstanding diverse stress and man’s ingenuity to co-exist with hostile nature and weather condition. Owing to their antioxidant capacity and the associated health benefits, anthocyanins have gained increased attention in recent years, hence the study was initiated.

Analyses of Genetic Diversity, Differentiation and Geographic Origin of Natural Provenances and Land Races of Casuarina equisetifolia Based on EST-SSR Markers

Research Highlights: High variation of genetic diversity and differentiation among 27 seed sources within 14 natural provenances and 13 land race samples of Casuarina equisetifolia were found. High proportions of monoecious individuals may be present in some populations, as indicated by severe heterozytote deficiency and inbreeding found in many provenances and land races. The most probable origins of the land races were inferred according to the values of pairwise provenance differentiation and Nei’s genetic distances. Targeted introductions and testing of unrelated new accessions of C. equisetifolia from the Pacific and Philippines was proposed to identify Ralstonia-resistant genotypes. Background and Objectives: Casuarina equisetifolia was introduced to China a hundred years ago and has become a critically important tree species in coastal protection since the 1950s. Despite its importance, patterns of genetic variation, genetic relationships among natural provenances and probable origins of the land races remain unresolved. This has become a concern in China where Ralstonia solanacearum bacterial wilt has devastated plantations that are known to be from a narrow genetic base that urgently needs to be broadened. Materials and Methods: Fourteen natural provenances from Australia, Pacific islands and Southeast Asia, and 13 land race samples from parts of Asia and Africa outside the natural range were genotyped using 13 SSR (Simple Sequence Repeats) markers to characterize their allelic variation and genetic relationship. Results: Significant genetic diversity and differentiation among 27 seed sources within 14 provenances and 13 land race samples of C. equisetifolia was indicated. Significant heterozygote deficiency and inbreeding was indicated for a number of provenances, perhaps indicating a high proportion of monoecious parents in these populations. The most probable origins of the land races of the introduced countries were suggested according to the values of pairwise provenance differentiation (FST) and Nei’s genetic distances. Conclusions: We found significant genetic diversity and genetic differentiation among seed sources of C. equisetifolia. While individual land races do not appear to lack diversity, we were able to infer the origins of some, allowing targeted introductions of unrelated material to be made. In the case of the Chinese land race, targeting and testing new accessions from the Pacific and the Philippines may be a good strategy to identify Ralstonia-resistant genotypes.