DArTseq-based SNP markers reveal high genetic diversity among early generation fall armyworm tolerant maize inbred lines.

Diversity analysis using molecular markers serves as a powerful tool in unravelling the intricacies of inclusivity within various populations and is an initial step in the assessment of populations and the development of inbred lines for host plant resistance in maize. This study was conducted to assess the genetic diversity and population structure of 242 newly developed S3 inbred lines using 3,305 single nucleotide polymorphism (SNP) markers and to also assess the level of homozygosity achieved in each of the inbred lines. A total of 1,184 SNP markers were found highly informative, with a mean polymorphic information content (PIC) of 0.23. Gene diversity was high among the inbred lines, ranging from 0.04 to 0.50, with an average of 0.27. The residual heterozygosity of the 242 S3 inbred lines averaged 8.8%, indicating moderately low heterozygosity levels among the inbred lines. Eighty-four percent of the 58,322 pairwise kinship coefficients among the inbred lines were near zero (0.00-0.05), with only 0.3% of them above 0.50. These results revealed that many of the inbred lines were distantly related, but none were redundant, suggesting each inbred line had a unique genetic makeup with great potential to provide novel alleles for maize improvement. The admixture-based structure analysis, principal coordinate analysis, and neighbour-joining clustering were concordant in dividing the 242 inbred lines into three subgroups based on the pedigree and selection history of the inbred lines. These findings could guide the effective use of the newly developed inbred lines and their evaluation in quantitative genetics and molecular studies to identify candidate lines for breeding locally adapted fall armyworm tolerant varieties in Ghana and other countries in West and Central Africa.

The use of Beauveria bassiana for the control of the larger grain borer, Prostephanus truncatus, in stored maize: Semi-field trials in Ghana.

Laboratory research in Ghana demonstrated the effectiveness of an isolate of Beauveria bassiana (IMI 389521) from the United Kingdom against the larger grain borer Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae), a major pest of stored maize. The minimum effective concentration, following artificial infestation trials on maize, was between 109 and 1010 cfu/kg maize. Before moving out to village-level control, a major requirement was to determine if the product could effect control in artificially infested maize held under real environmental conditions in several locations in Ghana. Therefore, this study investigated the efficacy of formulated conidia of B. bassiana, IMI 389521, at two concentrations (1 × 109 and 3.16 × 109 cfu/kg maize) to control P. truncatus on stored maize kernels under semi-field conditions in Ghana. Maize ('Obatanpa' cultivar) kernels were treated with the formulated B. bassiana product and stored in polypropylene woven bags in cribs in Southern Ghana. After 24 h, one hundred adults of P. truncatus were placed into each bag containing the treated maize. Mortality and the percent of weight loss of kernels were assessed every two weeks for three months. The semi-field trials revealed the possibility of successfully controlling adult P. truncatus on maize kernels treated with B. bassiana at 3.16 × 109 cfu/kg maize. However, due to the minimal protection of kernels after four weeks, re-treating maize kernels after this period is recommended to ensure maximum protection during prolonged storage.

Characterization of Groundnut (Arachis hypogaea L.) Test Locations Using Representative Testing Environments With Farmer-Preferred Traits.

In this study, the differential rankings of 36 groundnut genotypes under varying environmental conditions were studied at various levels of phenotype. Locations that are generally accepted by the crop- and soil-based research community to represent the entire Guinea and Sudan Savanna agro-ecological zones in Ghana were characterized, this time using a crop. The characterization was done based on four farmer-preferred traits (early and late leaf spot disease ratings, and haulm and pod yields) using three models (i.e., AMMI, GGE, and Finlay-Wilkinson regression). These models were used to capture specific levels of phenotype, namely, genotype-by-environment interaction (GE), genotype main effect plus GE (G+GE), and environment and genotype main effects plus GE (E+G+GE), respectively. The effect of three major environmental covariables was also determined using factorial regression. Location main effect was found to be highly significant (p < 0.001), confirming its importance in cultivar placement. However, unlike genotypes where the best is usually adjudged through statistical ranking, locations are judged against a benchmark, particularly when phenotyping for disease severity. It was also found that the locations represent one complex mega-environment, justifying the need to test new technologies, including genotypes in all of them before they can be approved for adoption nationally. Again, depending on the phenotypic level considered, genotypic rankings may change, causing environmental groupings to change. For instance, all locations clustered to form one group in 2017 for early and late leaf spot diseases and pod yield when GE was considered, but the groupings changed when G+GE was considered for the same traits in the same year. As a result, assessing genotypic performance at the various levels to arrive at a consensus decision is suggested. Genotypes ICGV-IS 141120 and ICGV-IS 13937 were found to be the best performing.

The Efficacy of Alternative, Environmentally Friendly Plant Protection Measures for Control of Fall Armyworm, Spodoptera Frugiperda, in Maize.

The invasive fall armyworm (FAW) is threatening maize production and the livelihoods of millions of smallholder farmers in the newly invaded areas in Africa and Asia. To control this new key pest and to overcome health, environmental, and resistance problems related to the indiscriminate use of insecticides, effective and sustainable alternative pest control approaches are needed. Here, we report on field trials that tested maltodextrin, neem-based products, ash, and soil, as well as the locally produced alata samina soap, in the Upper West and Greater Accra regions, Ghana. Significant reductions of larval numbers and crop damage, together with increased yields, were mostly achieved by applying the insecticide emamectin benzoate, which was considered the positive control in this set of trials. However, high efficiency and cost-benefit ratios were also achieved with two neem-based products. Maltodextrin was only efficient at one of the two sites, with a clear dose-dependent effect, while the higher dosage was nearly as effective as emamectin benzoate. Due to its relatively high product cost, maltodextrin is generally less cost-efficient. Ash and soil, as well as alata samina soap treatments, did not efficiently reduce FAW larval numbers or crop damage at the dosages tested; thus, they also did not significantly increase maize yields.

Agroecological management of a soil-dwelling orthopteran pest in vineyards.

The efficacy of different combinations of undervine and inter-row treatments for managing a soil-dwelling orthopteran pest, weta (Hemiandrus sp.), in vineyards was investigated over 2 seasons. This insect damages vine buds, thus reducing subsequent grape yield. The undervine treatments comprised pea straw mulch, mussel shells, tick beans [Vicia faba Linn. var minor (Fab)], plastic sleeves on vine trunks (treated control) and control (no intervention), while inter-rows contained either the existing vegetation or tick beans. Treatments were arranged in a randomized complete block design with 10 replicates. Data were collected on weta densities, damage to beans and components of yield. The latter were numbers of bud laid down per vine, shoots per bud, clusters per shoot, grape bunches per vine, bunch weight and yield. The undervine treatments significantly affected all variables except the number of shoots per bud. In contrast, none of the variables was significantly affected by the inter-row treatments or their interaction with undervine treatments, apart from weta density. At the end of the experiment, weta density in the shell treatment was about 58% lower than in the control. As a result, there was about 39% significant yield increase in that treatment compared to the control. Although the undervine beans and sleeves treatments increased yield, there were no reductions in weta density. With undervine beans, the insect fed on the bean plants instead of vine buds. Thus, yield in that treatment was approximately 28% higher than in the control. These results demonstrate that simple agroecological management approaches can reduce above-ground damage by soil-dwelling insects.

Ecological and pest-management implications of sex differences in scarab landing patterns on grape vines.

BACKGROUND: Melolonthinae beetles, comprising different white grub species, are a globally-distributed pest group. Their larvae feed on roots of several crop and forestry species, and adults can cause severe defoliation. In New Zealand, the endemic scarab pest Costelytra zealandica (White) causes severe defoliation on different horticultural crops, including grape vines (Vitis vinifera). Understanding flight and landing behaviours of this pest can help inform pest management decisions. METHODS: Adult beetles were counted and then removed from 96 grape vine plants from 21:30 until 23:00 h, every day from October 26 until December 2, during 2014 and 2015. Also, adults were removed from the grape vine foliage at dusk 5, 10, 15, 20 and 25 min after flight started on 2015. Statistical analyses were performed using generalised linear models with a beta-binomial distribution to analyse proportions and with a negative binomial distribution for beetle abundance. RESULTS: By analysing C. zealandica sex ratios during its entire flight season, it is clear that the proportion of males is higher at the beginning of the season, gradually declining towards its end. When adults were successively removed from the grape vines at 5-min intervals after flight activity begun, the mean proportion of males ranged from 6-28%. The male proportion suggests males were attracted to females that had already landed on grape vines, probably through pheromone release. DISCUSSION: The seasonal and daily changes in adult C. zealandica sex ratio throughout its flight season are presented for the first time. Although seasonal changes in sex ratio have been reported for other melolonthines, changes during their daily flight activity have not been analysed so far. Sex-ratio changes can have important consequences for the management of this pest species, and possibly for other melolonthines, as it has been previously suggested that C. zealandica females land on plants that produce a silhouette against the sky. Therefore, long-term management might evaluate the effect of different plant heights and architecture on female melolonthine landing patterns, with consequences for male distribution, and subsequently overall damage within horticultural areas.