Hybrid breeding for fall armyworm resistance: Combining ability and hybrid prediction

Fall armyworm (FAW, Spodoptera frugiperda) emerged as a major lepidopteran pest destroying maize in sub-Saharan Africa. A diallel mating design was used to generate 210 experimental hybrids from 21 lines. Experimental hybrids and four checks were evaluated in two locations. Commercial checks suffered higher foliar and ear damage compared to the top 15 hybrids. Mean squares associated with the genotypic variation were higher than genotype-by-environment interactions for foliar and ear damage traits. Heritabilities were moderate to high. Significant correlations were observed between grain yield (GY) with ear rot (−0.54) and ear damage (−0.45). Positive and significant GCA effects were observed for GY in seven parental lines, which were developed from multiple insect resistance breeding programmes. CKSBL10153 has the highest GCA value for GY and shows significant GCA effects for foliar and ear damage traits. These lines were identified as the ideal combiners for GY and FAW resistance and are therefore recommended for utilization as testers in the development of FAW-resistant three-way cross-hybrid maize with correlated response for increased GY. GCA and marker-based prediction correlations of GY were 0.79 and 0.96, respectively. Both GCA effects and marker-based models were effective in predicting hybrid performance for FAW resistance.     

The metal silo: An effective grain storage technology for reducing post-harvest insect and pathogen losses in maize while improving smallholder farmers’ food security in developing countries

Traditional storage practices in developing countries cannot guarantee protection against major storage pests of staple food crops like maize, leading to 20-30% grain losses, particularly due to post-harvest insect pests and grain pathogens. As a result, smallholder farmers end up selling their grain soon after harvest, only to buy it back at an expensive price just a few months after harvest, falling in a poverty trap. The potential impact on poverty reduction and greater livelihood security will not be realized, however, if farmers are unable to store grains and sell surplus production at attractive prices. Apart from causing quantitative losses, pests in stored grain are also linked to aflatoxin contamination and poisoning. To address this problem, a metal silo was developed as a valid option and proven effective in protecting stored grains from attack by storage insect pests. A metal silo is a cylindrical structure, constructed from a galvanized iron sheet and hermetically sealed, killing any insect pests that may be present. The impact of metal silo technology in Africa, Asia and Latin America includes, improving food security, empowering smallholder farmers, enhancing income opportunities and job creation, and safeguarding the agro-ecosystems. The metal silo can be fabricated in different sizes, 100 kg-3000 kg holding capacity by trained local artisans, with the corresponding prices of $35 to $375. The use of metal silo, therefore, should be encouraged in order to prevent storage losses and enhance food security in developing countries.     

Genetic differentiation among selected tepary bean collections revealed by morphological traits and simple sequence repeat markers

Understanding the genetic relationship of crop ideotypes is essential for genetic analysis and breeding. The objective of this study was to determine genetic differentiation present among 20 selected tepary bean (Phaseolus acutifolius A. Gray) genotypes using morphological traits and simple sequence repeat (SSR) markers in order to identify genetically unique parental lines to develop breeding populations. Phenotypic diversity was estimated using Shannon-Weaver diversity index (H’), principal component analysis (PCA) and cluster analysis (CA). Genotypic diversity was estimated using Jaccard's genetic distances and CA. Shannon-Weaver diversity index values for the studied morphological traits ranged from 0.89 to 0.99, with a mean of 0.95 revealing high phenotypic differences among test genotypes. PCA identified four useful principal components (PC's) which contributed to 73% of the total phenotypic variation of collections. PC1 accounted for 28% of the total variation correlated to dry shoot mass and number of pods per plant. PC2 correlated with number of seeds per pod, grain yield and harvest index and contributed to 21% of total variation. The mean observed (H_o) and expected (H_e) heterozygosity values were 0.45 and 0.51, respectively revealing moderate genetic differentiation among genotypes. The mean polymorphic information content was 0.52, suggesting efficient discriminatory power of the SSR loci useful in future tepary bean genetic diversity analysis. The current study revealed moderate genetic differentiation among the studied tepary bean genotypes. Morphological traits and SSR markers well-correlated in allocating the tepary bean genotypes. The following genotypes were genetically distinct: G40201, G40237, G40068, G40033 and G40063 which are recommended for further crosses, selection and population development.     

Infectious bursal disease: outbreak investigation,molecular characterization,and vaccine immunogenicity trial in Ethiopia

Tropical Animal Health and Production - The study was conducted with the objective of isolation and molecular characterization of infectious bursal disease virus (IBDV) circulating in Ethiopia and...     

Genetic distance among doubled haploid maize lines and their testcross performance under drought stress and non-stress conditions

In contrast to conventional inbreeding that takes up to seven generations to develop inbred lines, the doubled haploid (DH) technology allows production of inbred lines in two generations. The objectives of the present study were to: (a) evaluate testcross performance of 45 doubled haploid lines under drought stress and non-stress conditions (b) estimate heritabilities for grain yield and other traits and (c) to assess the genetic distance and relationship among the DH lines using 163,080 SNPs generated using genotyping-by-sequencing (GBS). The 45 hybrid and five checks were evaluated using a 10 × 5 alpha lattice in six drought stress and nine well-watered environments in Kenya, Uganda, and Tanzania. Differences in trait means between the drought stress and well-watered conditions were significant for all measured traits except for anthesis date. Genetic variances for grain yield, grain moisture, plant height and ear height were high under well-watered environments while genetic variance for anthesis date, root lodging and stalk lodging were high under drought stress environments. Combined analyses across drought stress and well-watered environments showed that ten top hybrids produced 1.6–2.2 t/ha grain yield under well-watered condition and 1–1.4 t/ha under drought stress condition higher than the mean of the commercial checks. Genetic distance between pairwise comparisons of the 38 of the 45 DH lines ranged from 0.07 to 0.48, and the overall average distance was 0.36. Both cluster and principal coordinate analysis using the genetic distance matrix calculated from 163,080 SNPs showed two major groups and the patterns of group was in agreement with their pedigree. Thirteen (13) of the best hybrids are currently in National Performance Trials testing, an important step towards commercialization in Kenya, Tanzania and Uganda.     

Risk factors for foot and mouth disease seroprevalence in indigenous cattle in Southern Ethiopia: the effect of production system

A serological survey to investigate risk factors for Foot and Mouth Disease (FMD) occurrence was conducted between October 2007 and March 2008 in Southern Ethiopia. Antibodies against non-structural protein of FMD virus (using 3abc ELISA) were measured as indicator of exposure to the virus. The seroprevalence of FMD was 9.5% (95%CI = 7.7 – 11.3, n = 1020) and 48.1% (95% CI = 36.8 – 59.4%, n = 79), respectively at animal and herd levels. Within herd seropositivity was ranged from 6.7 to 46.7% with 18.6% (95%CI = 14.6 – 22.5%) risk of being seropositive for an animal in positive herds. The most important herd level risk factors identified were pastoral system (OR = 16.3, 95% CI = 2.0 -133.7) compared to sedentary, low altitude (OR = 7.5, 95% CI 1.4 -40.7) compared to high altitude, keeping cattle with small ruminants (OR = 5.1, 95% CI 1.0 -25.2) when compared to one species or alone. Seroprevalence was significantly higher (P <0.05) in South Omo than Sidama and Gamo Gofa areas. The odds of seropositivity were 2.8 and 2.3 times higher in the adult (>4 years) and maturing animals (3–4 years) compared to young age category (<3 years). Both multivariable logistic and negative binomial regressions depicted that production system was the major risk factor for FMD seropositivity. Consequently, higher prevalence of FMD in pastoral system where animals are an integral part of life has substantial livelihood and economic implications, which signifies the need for devising control measures.