First report of Bipolaris secalis causing leaf spot disease on Brachiaria (syn. Urochloa) grass

Brachiaria (syn. Urochloa) grass is rapidly gaining popularity as a new forage option in sub-Saharan Africa including Rwanda. During disease surveillance in Rwanda in 2018–2019, Brachiaria foliage was found with necrotic purple spots with a whitish centre on the upper surface of leaves (Figure 1). Diseased leaves were collected from farmers' fields in Bugesera (02°08'33.4'' S, 030°09'08.8'' E), Huye (02°28'54.8˝ S, 29°46'.56.9˝ E), Nyagatare (01°18'56.16˝ S, 030°18'18.24˝ E) and Rwamagana (01°58'49.62˝ S, 030°27'29.82˝ E) districts. Pathogen isolation and identification was done in the Plant Pathology Laboratory of the Rwanda Agriculture and Animal Resources Development Board in Rubona, Rwanda. The pathogen was isolated and grown on commercial potato dextrose agar (PDA) amended with ampicillin (100 μg ml−1) and incubated at 24°C for two weeks (Ghimire et al., 2011)

Influence on plant density on variability of soil fertility and nutrient budgets in low input East African highland banana (Musa spp. AAA-EA) cropping systems

The productivity of East African highland (EAH) banana cropping systems is declining, particularly in areas with low inherent soil fertility. Soil fertility management requires knowledge of nutrient flows at the interface between the soil surface and the soil system. The magnitude of soil fertility dynamics and nutrient depletion was studied for a short-term banana plant density trial in three contrasting agro-ecological sites of Rwanda (Kibungo low rainfall with medium soil fertility, Rubona high rainfall with low soil fertility and Ruhengeri high rainfall with high soil fertility) using nutrient stock and partial nutrient balance calculations. Plant density did not influence significantly nutrient mass fractions in plant parts (fruit, leaves and pseudostems) but nutrients contained through shredded leaves and pseudostems and those removed through bunch dry matter increased with plant density. Plant density responses to variation in soil fertility and partial nutrient balances seemed to depend on diversity in climate and soil type. Partial N and K balances (kg ha -1 year -1 ) were estimated to be strongly negative at Rubona and Ruhengeri while Ca and Mg were positive at Kibungo and Ruhengeri but negative at Rubona. This study showed that partial nutrient balances associated with soil nutrient stocks can provide the first order of magnitude of nutrient depletion in low input EAH banana cropping systems. This brings attention from agricultural researchers and farmers to develop options that can improve the productivity of these systems, where resource availability for improved nutrient management is scarce. © 2013 Springer Science+Business Media Dordrecht.status: publishe

Synthesis of ultrathin and compact Au@MnO2 nanoparticles for shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS)

973 Program [2009CB930703, 2007CB815303]; NSF of China [20703032, 11074210, 21021002]Shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) based on Au@SiO2 or Au@Al2O3 nanoparticles (NPs) shows great potential to break the long-standing limitations of substrate and surface generality of surface-enhanced Raman scattering (SERS). However, the shell of SiO2 or Al2O3 can easily be dissolved in alkaline media, which limits the applications of SHINERS in alkaline systems. Besides that, the synthesis of Au@SiO2 NPs can be further simplified and Au@Al2O3 NPs be replaced by other NPs that are more amenable for mass production. In an attempt to make SHINERS NPs available in any systems practically, we report the synthesis of ultrathin and compact Au@MnO2 NPs. The shell thickness of MnO2 can be controlled down to about 1.2 nm without any pinhole. SHINERS based on such Au@MnO2 NPs exhibits much higher Raman enhancement effect than Au@SiO2 NPs and can be applied in alkaline systems in which Au@SiO2 or Au@Al2O3 NPs cannot be applied. Copyright (c) 2011 John Wiley & Sons, Ltd