玉米致死性坏死病研究进展

玉米致死性坏死病(MLND或CLND)先后在美洲和非洲严重暴发成灾,造成重大经济损失,该病在我国存在着巨大的潜在隐患。作者根据近年来国内外有关MLND(或CLND)的研究报道,对其病原种类、地理分布、发病症状、检测方法、生物学特性和防治技术等进行了综述,并就我国对于该重大潜在病害的预防和控制提出了建议。

肯尼亚杂交玉米新品种高效栽培技术规程

根据肯尼亚的玉米致死性坏死病(MLN)的发生规律,选用适宜的玉米品种,采用适合当地的田间管理,制定了符合当地的高效栽培技术规程,目的是提高肯尼亚玉米产量,并对病害的预防和控制提出了建议。

Enhancing Maize Grain Yield in Acid Soils of Western Kenya Using Aluminium Tolerant Germplasm

Maize （Zea mays L.） is one of the world＇s most important cereals and is a staple food for many people in developing countries. However, in acid soils （pH 〈 5.5）, its productivity is limited by aluminium （AI） toxicity, besides other factors. The objectives of this study were to： develop AI tolerant maize inbred lines for a maize breeding program in Kenya, develop single cross hybrids （SCHs） from some of the tolerant inbred lines and determine AI tolerance levels of the SCHs. One hundred and seventy five inbreds and 49 SCHs were developed and screened in nutrient culture containing 0 or 222μM using Relative Net Root Growth （RNRG）, hematoxylin staining （HS） and under AI saturated field conditions （44%-45.6%） at Sega and Chepkoilel. Seedling root growth was inhibited in 95% of the inbreds. F hybrids obtained from inbreds varying in A1 tolerance, exhibited tolerance equal to or greater than that of the more tolerant parent indicating a positive transgressive inheritance to AI toxicity. Fifty eight percent of the F SCHs were heterotic for tolerance to AI toxicity. AI tolerance estimated by RNRG was well correlated to that of HS （r2 = 0.88, P 〈 0.005） but minimally correlated with the field estimates （r2 = 0.24-0.35）, implying that RNRG can predict field selection under AI toxic soils by between 24% and 35%. Plant breeders should therefore employ both approaches in selecting cultivars under AI stress. This study has developed and identified A1 tolerant inbreds and SCHs for use in the acid soils of Kenya and similar regions.

Kenya and the Emerging Power-Shift in Global Political-Economy: Right-Wing Populism and Social Media Activism

A potential global power transition characterized by emerging economies of BRICS where China is the likely leading contender against the United States as the only global hegemon seems inevitable.The increasingly multipolar world is evidenced by the attention given to right-wing populism in Europe and USA attributed to China’s aggressive approach to international trade through its stealth entry and subsequent investments in global political-economy.China’s presence in Africa and Trump’s America first policy’s attempt to open“new business frontiers”in emerging economies of Asia and Africa in order to contain Chinese influence and threat in global hegemony are interesting happenstances that require closer scrutiny.Kenya,the biggest economy in East Africa,which is among the fastest growing regions globally,is the gateway to the East African Common Market.Historically,Kenya has a policy of non-alignment in international relations making it possible to receive FDI from both China and the US but with highly contested elections.Therefore,Kenya presents a perfect laboratory for examining the emerging power-shift in global political-economy as the country grapples with traditionally chaotic electoral power transitions and the two biggest economies in the world compete for business in Nairobi.The 2017 elections not only betrayed the international community’s commitment to Western values of human rights and democracy,but also revealed the challenges of governance in post-World War II global liberalism characterized by sophisticated media institutional spaces.

South Africa＇s Press Representation of Zimbabwe＇s Economic Crisis and Fears of a Regional Bubble, 2000-2008

This article examines the representation of the Zimbabwean economic crisis by The Sunday Times, The Sunday Independent and The Mail ＆ Guardian. The article uses critical political-economy theories of the media in the context of cultural studies, theories of news production, and discourse analysis to inspect how the South African press represented the economic situation.

Mapping Qtls for Grain Yield and Yield Components in Kenyan Maize (<i>Zea mays</i>L.) Under Low Phosphorus Using Single Nucleotide Polymorphism (SNPS)

Selection for tolerance to low phosphorus (P) using morphological traits alone is slow and often confounded by environmental effects. This study identified some Quantitative Trait Loci (QTLs) associated with grain yield (GYLD), Plant (PHT) and Ear heights (EHT) under low P in maize using single nucleotide polymorphic markers. 228 F2:3 individuals derived from a cross between two contrasting maize inbred lines together with 239 SNPs were mapped onto ten linkage groups (LGs) spanning 2255 centiMorgans (cM) with an average inter-marker distance of 9.44 cM. Majority of the SNP markers (63%) followed the Mendelian segregation and were fairly distributed in all the LGs. Mean performance for all the traits in the F3 population was higher than the parental values, which suggested transgressive segregation for all traits. Low to moderate broad sense heritability (0.35 - 0.50) in the F3 population for GYLD, PHT and EHT indicated that tolerance to low P is controlled by complex multi genetic factors. A full multi-QTL model analysis suggested six QTLs (2 QTLs each for GYLD, PHT and EHT) located on chromosomes 1, 3, 4 and 8. The two QTLs for GYLD increased maize yield under low P soils by 173 kg/ha while the 2 QTLs for PHT increased plant growth by 18.14 cm. The % phenotypic variance explained by these QTLs under low P environments had a wide range (0.242% - 53.34%) and was much lower for GYLD compared to plant growth. Both additive and dominance gene actions contributed differentially to the observed phenotypic variance for tolerance to low P soils with dominance contributing more genetic effects compared additive effects for majority of the QTLs. The findings of this study will provide some basis for marker-assisted selection for yield improvement and further guide breeding strategies under low P soils of western Kenya.

Influence of Constituent Materials Properties on the Compressive Strength of in Situ Concrete in Kenya

The poor quality of Kenyan in situ concrete has necessitated research to establish the properties of the ingredient materials and their influence on the troubling rate of failure of reinforced concrete structures in the country during construction and usage. The compressive strength of concrete relies on the properties of the constituent materials, proportions of the mixture, workmanship, compaction method and curing conditions. This paper outlines findings of an experimental investigation on the properties of Kenyan concrete ingredient materials and their influence on the compressive strength of concrete in Kenya. Three types of cements (42.5N, 32.5R, 32.5N) from six different cement manufacturers and fine aggregates from three different regions in the country were used during the study. Cements and aggregates chemical analysis was done using the Atomic Absorption Spectrometer machine while the physical and the mechanical properties were checked based on the British Standards. The British DOE concrete mix design method was used to generate the concrete mix proportion and concrete was tested for early and ultimate compressive strengths at 7, 14 and 28 days. It was observed that the different cement brands have varying properties with CEM A having the highest ultimate compressive and flexural strengths. It was further noted that aggregates from the coastal region produced concrete of higher compressive strengths. When the commonly used mix design method was adopted, blended Portland cements produced concrete with ultimate compressive strengths lower than the designed target strengths. The study therefore recommends the development of a concrete mix design procedure for blended cement concrete production in Kenya.