Wheat yellow rust (WYR), caused by Puccinia striiformis f. sp. tritici (PST), is a major disease of wheat, and deployment of a single cultivar often leads to disease epidemics. Effect of inoculum level, foliar fungicide spray, and wheat cultivar mixtures were evaluated on disease development in the field and greenhouse in Nepal. Treatments were arranged in a split–split plot design with three replications in both experiments. Two inoculum levels of PST (low and high) were main plot factors; nontreated control and foliar spray of fungicides (Mancozeb and Bayleton) were subplot factors; and two-component cultivar mixtures, composed of different ratios of a susceptible (S) and a resistant (R) cultivars (90:10, 80:20, and 50:50, 100:0, and 0:100) were sub–subplot factors. WYR severity was assessed at different time intervals, and disease development was calculated as area under the disease progress curve (AUDPC). Inoculum level did not cause significant differences in AUDPC in the field but did in the greenhouse. Foliar spray of fungicides reduced the AUDPC in the greenhouse and field. In both experiments, AUDPC values were low in cultivar mixtures compared with a pure stand of a susceptible cultivar. As the proportion of resistant cultivar increased compared with the susceptible cultivar in the S:R mixture component, disease severity decreased with a consequent increase in grain yield. The greater yield obtained with cultivar mixtures compared with only the susceptible cultivar, independent of inoculum level and fungicide spray in the field, revealed a promising strategy to manage WYR in Nepal. 相似文献
Inland fisheries underpin food security in many tropical countries. The most productive inland fisheries in tropical and subtropical developing countries occur in large river–floodplain systems that are often impacted by land cover changes. However, few studies to date have assessed the effects of changes in floodplain land cover on fishery yields. Here, we integrated fisheries and satellite‐mapped habitat data to evaluate the effects of floodplain deforestation on fishery yields in 68 floodplain lake systems of the lower Amazon River, representing a wide range in relative amounts of woody, herbaceous and non‐vegetated land cover. We modelled relative fish yields (fish capture per unit effort [CPUE]) in the floodplain lakes as a function of the relative amounts of forest, shrub, aquatic macrophyte and bare/herbaceous habitats surrounding them. We found that forest amount was positively related (p =.0003) to multispecies CPUE. The validity of these findings was supported by rejection of plausible alternative causative mechanisms involving habitat‐related differences in amount of piscivores, fishing effort, lake area, and habitat effects on CPUE of the nine taxa dominating multispecies yields. Our results provide support to the idea that removal of floodplain forests reduces fishery yields per unit effort. Increased protection of floodplain forests is necessary to maintain the food, income and livelihood security services provided by large river–floodplain fisheries. 相似文献
Leaf yellowing symptoms were observed on Acacia mangium in the Sipahijala district of Tripura, India, during June 2017. Symptomatic and asymptomatic leaf samples (three of each) were collected from roadside trees of A. mangium for DNA extraction using the CTAB method. Amplicons of ~1.25 kb and ~480 bp were detected in all the symptomatic samples using the phytoplasma‐specific universal 16S rRNA and secA gene primers. Pair wise sequence analysis of 16S rRNA gene sequences, virtual RFLP and phylogenetic analysis revealed that the phytoplasma strain associated with A. mangium belonged to phytoplasma subgroup 16SrII‐C. This is the first report of an association between the 16SrII‐C subgroup and A. mangium leaf yellowing. 相似文献
A questionnaire survey of 408 households explored the role of socio-economic and cultural factors in rice (Oryza sativa L.) varietal diversity management on-farm in two contrasting eco-sites in Nepal. Multiple regression outputs suggest that
number of parcels of land, livestock number, number of rice ecosystems, agro-ecology (altitude), and use of chemical fertilizer
have a significant positive influence on landrace diversity on-farm, while membership in farmers’ groups linked to extension
services has significant but negative influence on landrace diversity. Factors with significant positive influence on diversity
of modern varieties on-farm were number of parcels of land and of rice ecosystems, access to irrigation, membership in farmers’
groups, and use of insecticide. Within communities, resource-endowed households maintain significantly higher varietal diversity
on-farm than resource-poor households and play a significant role in conserving landraces that are vulnerable to genetic erosion
and those with socio-cultural and market-preferred traits. Resource-poor households also contribute to local diversity conservation
but at lower richness and area coverage levels than resource-endowed households. Households where a female had assumed the
role of head of household due to death or migrant work of her husband had less diversity due to lower labor availability.
Landraces with socio-cultural and market-preferred traits are few in number but have potential to be conserved on-farm.
Panicle architecture directly affects the grain yield of rice; meanwhile, crop domestication has increased the complexity of rice panicle size and branching pattern. Genome-wide association study (GWAS) was performed to investigate the genetic basis underlying panicle architecture using 183 rice accessions from around the world and a 7 K SNP array. Phenotyping was conducted at Texas A&M AgriLife Research Center in Beaumont, TX. GWAS was performed using MLM (Q?+?K) model using GAPIT software. At p-value?<?0.001, a total of 49 GWAS QTLs controlling various panicle architecture traits were mapped. Considering the recurring and linked SNPs across the panicle architecture traits, 42 independent QTL regions were identified. Among these, 27 QTL regions co-localized with known genes or previously reported QTLs or significant SNP markers, while 15 were potentially novel QTL regions. The results of our study offer useful information on genetic bases controlling panicle architecture in rice, which could be further validated and utilized for designing markers for use in markers assisted selection (MAS) in rice breeding programs.