Records of Arthropod Species Sampled from Avocado Plant (Persea americana Mill) in Smallscale Agro-ecosystems at Taita Hills and Mount Kilimanjaro

Avocado, Persea americana Mill, plays a central role in distribution of both beneficial and detrimental arthropods thereby influencing local species diversity in agro-ecosystems adjacent to Afromontane forests at Mount Kilimanjaro in North-eastern Tanzania and Taita Hills in South-eastern Kenya. However, little is known about arthropod species that inhabit avocado trees in the two study areas despite the fact that the crop forms the major part of agro-ecosystem in the East African highlands. A novel survey was, therefore, carried out for two years between August 2012 and July 2014 to establish arthropod species in avocado orchards along South-eastern slopes of both Mount Kilimanjaro and Taita Hills. A total of sixty one species of arthropods were recorded from the avocado crop through fruit observation and canopy sampling. The present arthropod checklist provides baseline knowledge for scientists in evaluating beneficial and pest status of each species inhabiting avocado plant in the East African agro-ecosystems.Peer reviewe

Maturity indices of specific mango varieties produced at medium altitude agro-ecological zone in Kenya

The high postharvest losses (40 – 50%) reported in the mango value chain are partly attributed to lack of reliable maturity indices. Harvest maturity is dictated by the intended use and the target market for the fruits. The aim of this study was to establish maturity indices of three commercial mango varieties namely ‘Van dyke,’ ‘Kent’ and ‘Tommy Atkins’ in Embu County of Kenya. At least eighteen mango trees (six per variety) were randomly tagged at 50% flowering in each of the three selected small-scale farms in Embu County. Number of days from flowering to different maturity stages were recorded (computational method). For each variety and maturity stage, five fruits were randomly sampled from the pool and analysed for physical (size, density, firmness, colour), physiological (ethylene evolution and respiration rate) and biochemical (obrix/Total Soluble Solids (TSS), total titratable acidity (TTA) and their ratio) indices of maturity. The results showed that although size increased as the fruits developed, it was not a reliable index of maturity since some small-sized fruits attained advanced maturity earlier than others that were large-sized. The weight of the fruits fluctuated as the fruits developed and similar trend was observed on the specific gravity. Flesh firmness decreased gradually with maturity from a mean firmness of 40.54 N to 6.84 N. Tommy Atkins exhibited the lowest firmness levels at stage 4. Kent variety had the lowest ethylene at all stages while Tommy Atkins variety had the highest respiration rate of 21.40 ml/kg/hr at stage 1, which increased gradually to 32.10 ml/kg/hr at stage 4. The highest TSS: TTA values were reported in Kent variety. The results revealed significant differences in maturity indices of the three mango varieties despite similar physical indices. This study confirms the unreliability of physical maturity indices such as size and shape in establishing the right harvest stage of mango fruits. Computational, physiological and biochemical maturity indices should be incorporated in determination of accurate harvest maturity for mango

Datasets on abundance of common blossom thrips and weather variables in small-scale avocado orchards at Taita Hills and Mount Kilimanjaro

Avocado, Persea americana Miller (Lauraceae), is an important fruit crop cultivated by small-holder farmers along Afrotropical highlands of Taita Hills in South-eastern Kenya and Mount Kilimanjaro in Northern Tanzania. The small-holder farmers in these East African regions generate substantial food and cash from avocado fruits. However, the avocado crop is faced with challenges of infestation by insect pests such as the common blossom thrips (Frankliniella schultzei Trybom) which feeds on pollen and floral tissue thereby reducing productivity of the trees. Moreover, there is no information describing distribution patterns of Frankliniella schultzei and associated weather in East African avocado orchards despite the fact that small-scale farming is dependent on rainfall. This article was, therefore, initiated to provide dataset on abundance of Frankliniella schultzei from the avocado plants that relates with monthly rainfall and air temperatures at Taita Hills and Mount Kilimanjaro. Frankliniella schultzei was collected using white coloured beating tray and camel brush whereas air temperatures (°C) and rainfall (mm) was recorded daily using automatic data loggers and rain gauge, respectively. The survey at the two transects commenced during peak flowering season of avocado crop in August up to end of harvesting period in July of the following year. Temporal datasets were generated by Kruskal-Wallis Chi-square test. Current temporal datasets presents strong baseline information specifically for Kenya and Tanzania government agencies to develop further agricultural strategies aimed at improving avocado farming within Taita Hills and Mount Kilimanjaro agro-ecosystems.Peer reviewe

Spatial characterization of common blossom thrips (Frankliniella schultzei) in smallholder avocado orchards along slopes of Taita Hills and Mount Kilimanjaro

Frankliniella schultzei Trybom (Thysanoptera:Thripidae) is an important flower pest of avocado crop (Persea americana Mill) at Taita Hills in South-eastern Kenya and Mount Kilimanjaro in North-eastern Tanzania. However, its geographical distribution is not known in the East African avocado cropping systems. In order to generate the spatial data of the common blossom thrips (Frankliniella schultzei), a survey was carried out in smallholder avocado orchards along altitudinal gradient (900 -1800m.a.s.l.) of Taita Hills and Mount Kilimanjaro using a white coloured beating tray and camel brush. Once the specimens of thrips were taxonomically verified, the abundance data was tabulated into three altitudinal zones, namely; lowland (900-1199m.a.s.l.), sub-montane (1200-1499m.a.s.l.) and montane (1500-1799m.a.s.l.). Frankliniella schultzei was recorded in all altitudinal zones of both transects with mean abundance being highest at Taita Hills (5.4) compared to Mount Kilimanjaro (0.9). However, abundance of the pest was greater in cooler highlands (>1200m.a.s.l.) than warmer lowland areas (<1200m.a.s.l.) of both transects. The findings of this study contributes significantly towards spatial mapping of Frankliniella schultzei in East Africa and this information is important in developing strategies aimed at controling infestation of avocado flowers by the insect pest at the two study transects.Peer reviewe

Genetic analysis of early-maturing maize (<i>Zea Mays</i> L.) inbred lines under stress and nonstress conditions

<p>Early-maturing maize (<i>Zea Mays</i> L.) germplasm developed from diverse sources has the potential for use in developing maize hybrids suitable for increasing maize production in the dry ecologies of eastern Africa. A diallel study was conducted to estimate general combining ability (GCA) of 12 early-maturing maize inbred lines, identify potential single-cross hybrids for use as parents, assess genetic diversity among the inbred lines, and relate genetic distance to specific combining ability (SCA) and hybrid performance. Sixty-six F₁ diallel hybrids were evaluated under optimal and drought stress conditions at four locations in Kenya and Uganda. The parental inbred lines were genotyped using 94 single nucleotide polymorphism (SNP) markers. Additive gene action was more important than nonadditive gene action for inheritance of grain yield (GY) under optimal conditions. However, nonadditive gene effects were more important in the inheritance of GY under drought and across all environments. Inbred lines CKL0722, VL058014, and CZL0724 were among the best with positive GCA effects for GY across both optimal and drought stress conditions. The correlation between SCA and both genetic distance and F₁ GY was significant under both drought stress and across all environments. Inbred lines with desirable GCA effects for GY and other agronomic traits and hybrids with good performance under both optimal and drought stress conditions are potential parents for development of various types of high-yielding, stress-tolerant, and early-maturing hybrids.</p