Entity

Time filter

Source Type


Ghaley B.B.,Renewable Natural Resources Research Center | Ghaley B.B.,Copenhagen University | Christiansen J.L.,Copenhagen University | Andersen S.B.,Copenhagen University
Euphytica | Year: 2012

With an objective to evaluate the Bhutan rice (Oryza sativa L.) landraces for genetic diversity in blast resistance, 402 accessions viz. 352 landraces, a differential set of 32 R gene lines and 18 modern cultivars were field-evaluated in three blast 'hotspot' sites followed by genetic analysis of the 352 landraces with 27 microsatellite markers. Across the sites, 19 landraces (5.4%) exhibited complete resistance with zero disease score and 203 (58%) and 163 (46%) landraces showed high partial resistance for early leaf and panicle blast, respectively, with disease score of four to six. Field evaluation for leaf and panicle blast at three experimental sites in Bhutan showed best cultivar discrimination in early leaf blast at the tillering stage (heritability, h 2 = 0. 32) and in the panicle blast at maturity (h 2 = 0.44). Subdivision of the genetic variation into cultivar groups revealed the most variation for blast severity within the 352 landraces with h 2 of 0. 31 and 0. 46 for early leaf and panicle blast, respectively. Cluster analysis of the landraces revealed two distinct rice cultivar groups, which separated at dissimilarity of 0.84 according to origin of the cultivars from low, mid and high altitude zones in Bhutan. All microsatellites were polymorphic with two to 21 different alleles per marker and a high polymorphic information content value of 0.61. The identified blast resistant landraces were genetically diverse originating from different rice cultivation zones. Further investigation of the resistant and partial resistant material may reveal specific blast resistance genes, which could be useful to mitigate blast incidence in rice-producing countries. © 2011 Springer Science+Business Media B.V. Source


Ghaley B.B.,Renewable Natural Resources Research Center | Ghaley B.B.,Copenhagen University
Experimental Agriculture | Year: 2012

The uptake of urea fertilizer (NDFF), applied with 150kg nitrogen (N) ha-1, topdressed in five splits of 30kg N ha-1 (30 N) each at 7, 26, 45, 70 and 83 days after transplanting (DAT) of rice (Oryza sativa L.), was investigated in an improved (Khangma Maap, KM) and a traditional (Janam, JN) cultivar in Bhutan highlands, using enriched 15N stable isotope. The treatments were arranged in a split-split plot design, with N fertilizer levels as main plots, cultivars as subplots and topdressing treatments as sub-subplots, with all the sub-subplots receiving the same dose except different timing of one split of enriched 15N to determine partial N fertilize use efficiency at each split dose. Although cultivar differences were not recorded in soil N accumulation and in total dry matter N, KM produced 21% higher grain yields compared to JN due to higher grain harvest index and partial factor productivity of N. Irrespective of the cultivars, topdressing timing had significant effects on NDFF, with highest mean N recovery (REN) of 29% of applied 30 N at 45 DAT during active tillering stage, resulting in mean NDFF total (grain + straw) uptake of 8.71kg N ha-1 compared to least effective topdressing timing at 7 DAT with mean REN of 12% and NDFF total of 3.51kg N ha-1. In similarity to topdressing at 45 DAT, topdressing at 70 DAT (panicle initiation stage) was equally effective with mean REN of 27% across the cultivars. Hence, fertilizer N topdressing recommendations that combine use of improved cultivars with N applications timed to coincide with maximum crop demand at 45 and 70 DAT, could enhance N fertilizer use efficiency for increased rice yields as well as reduce N losses downstream, which can cause adverse off-site environmental effects. © 2012 Cambridge University Press. Source


Dorji T.,Renewable Natural Resources Research Center | Jianlin H.,Kenya International Livestock Research Institute | Wafula P.,Kenya International Livestock Research Institute | Yamamoto Y.,Hiroshima University | And 5 more authors.
Animal Science Journal | Year: 2010

Genotype data from eight microsatellite markers were used to assess genetic diversity and relationships among five indigenous Bhutanese sheep populations, Sakten, Jakar, Sarpang, Sipsu and Tsirang. Estimates of mean observed and expected heterozygosities, mean number of alleles per locus/population were obtained. The highest observed heterozygosities were found in Jakar (0.657) and Sakten (0.647), while the lowest one was found in Tsirang (0.539). Genetic distances, pairwise proportion of different alleles, UPGMA tree, and principal component analysis indicate close relationship among Tsirang, Sipsu and Sarpang populations, while Jakar and Sakten populations are located in one cluster. These two clusters are separated geographically, and show distinct phenotypic as well as molecular characters. We therefore recommend that the Bhutanese native sheep populations be classified into at least two distinct breeds, Jakar-Sakten sheep and Sipsu sheep. Since Jakar and Sakten sheep have different morphological phenotypes, further analyses will be required to understand the genetic differences between these two sheep populations. © 2010 The Authors. Journal compilation © 2010 Japanese Society of Animal Science. Source


Ghaley B.B.,Renewable Natural Resources Research Center | Ghaley B.B.,Copenhagen University | Hogh-Jensen H.,University of Aarhus | Christiansen J.L.,Copenhagen University
Plant and Soil | Year: 2010

The recovery of soil derived nitrogen (NDFS) and fertilizer N (NDFF) was investigated in highland rice (Oryza sativa L.) fields in Bhutan, characterized by high inputs of farmyard manure (FYM). The effect of 60 kg N ha-1 (60 N) applied in two splits to a traditional and an improved cultivar, popular among the farmers, was investigated using the 15N isotope dilution technique. No differences were found between cultivars with respect to the uptake of NDFS and NDFF, but the improved cultivar yielded 27% more (P ≤ 0.05) grain compared with the traditional cultivar. This was largely due to its greater harvest index (HI). The mean percentage recovery of fertilizer N (REN) applied at 45 days after transplanting (DAT) was 34% compared to 22% at 7 DAT, resulting in 56% greater uptake of NDFF at 45 DAT. The overall REN for both the improved and the traditional cultivars were 25.7% and 30% respectively, with no difference between cultivars, but REN decreased with increasing FYM inputs. Fertilizer N recommendations that allow for previous FYM inputs combined with applications timed to coincide with maximum crop demand (45 DAT), and the use of improved cultivars, could enhance N fertilizer recoveries (REN) and increase rice yields in the Bhutan Highlands. © 2010 Springer Science+Business Media B.V. Source


Tsunoda K.,Showa University | Namikawa T.,Nagoya University | Sato K.,Showa University | Hasnath M.A.,Bangladesh Agricultural University | And 7 more authors.
Biochemical Genetics | Year: 2010

Allele and genotype frequency distributions of prion protein (PrP) polymorphisms at three codons, 136, 154, and 171, in East Asian sheep were determined by PCR-RFLP analysis using 553 animals from nine local breeds of the northern group and four local breeds of the southern group. Based on the genotype distribution, the risk score for scrapie was estimated. Among the local breeds, ARQ appeared predominantly (0.7701-1), followed by ARH and ARR. From such a biased allele distribution, it was difficult to ascertain the prevalent genetic relationships. A marked difference in allele frequencies between the northern and southern groups was seen (P < 0.0001). The East Asian sheep had ARQ at the highest frequency (0.8834); in European sheep it was 0.5317. According to an assessment of scrapie risk in the PrP genotype classes, the predominant ARQ/ARQ in East Asian sheep corresponded to the risk score of R4. This finding suggests that East Asian sheep have a high level of genetic susceptibility to scrapie. © 2009 Springer Science+Business Media, LLC. Source

Discover hidden collaborations