Groundnut leaf miner (GLM) is currently a threat to soybean production in Uganda due to the great yield losses as a result of the severe damage it causes on leaves leading to reduced photosynthetic area. GLM is a fairly new pest on soybean in Uganda, having initially been observed in soybean fields in 2011 in eastern Uganda. The objective of this study was to determine the yield loss caused by the groundnut leaf miner and effectiveness and profitability of commonly used pesticides for the control of the groundnut leaf miner (Aproaerema modicella Deventer) (GLM), when tested with popular soybean (Glycine max) genotypes grown in Uganda. In a split plot RCBD design, pesticide protection (treated vs. untreated) formed the main plots; and six commercial soybean varieties (Maksoy 1N, 2N, 3N, 4N, 5N; and Namsoy 4M) as subplots. The study was done in two locations in eastern Uganda (Iki Iki District Agricultural Training and Information Centre (Iki Iki DATIC) and National Semi-Arid Resources Research Institute, Serere (NaSARRI) with two planting rounds at Iki Iki. These sites were chosen because they are hot spots for GLM. GLM severity and soybean yield were significantly affected by the pesticide protection. Overall, percentage grain yield losses caused by GLM on the different soybean varieties ranged from 37.3% to 65.7% and the highest loss was displayed by Maksoy 5N. Grain yield loss recorded at Iki Iki DATIC (53.1%) was remarkably higher than that recorded at the NaSARRI (49.1%). Economic analysis showed marginal returns to be dependent on location, with the Iki Iki DATIC having 0.6 and NaSARRI 1.1. This study has shown that the groundnut leaf miner, a recently emergent pest of soybean is becoming a big threat to soybean production and that chemical control alone may not be economical in managing the pest.
Drought is a major constraint of common bean (Phaseolus vulgaris L.) production in Uganda where irrigation for the crop is very uncommon. This study aimed to identify quantitative trait loci (QTLs) underlying drought tolerance in 128 F5 RILs derived from an Andean intra-gene cross between droughttolerant SEQ 1027 and BRB 191. Eighteen traits were evaluated under drought stress and non-stress conditions in the field for 2 years and in the greenhouse for 1 year, respectively. A linkage map spanning 486.29 cM was constructed using 53 single nucleotide polymorphic markers (SNP) markers obtained from the KASP genotyping assay. Eleven consistent QTLs were detected on five linkage groups at a threshold of Logarithm of Odds (LOD) ≥ 3.0. Four QTLs were constitutive, seven were adaptive and were associated with 100 seed weight, grain yield, chlorophyll content, harvest index, dry weight of leaf and stem biomass and yield production efficiency. The QTL associated with a 100 seed weight (sw3.1 BS) was the most consistent with the highest percentage of variation explained (21%). Colocalization of five drought-related factors QTLs was detected on pv10 suggesting pleiotropic effects on this chromosome. Identification of molecular markers closely linked to the QTLs identified in this study will facilitate marker assisted breeding for drought tolerance.
Widespread adoption of quality protein maize (QPM), especially among tropical farming systems has been slow mainly due to the slow process of generating varieties with acceptable kernel quality and adaptability to different agroecological contexts. A molecular based foreground selection system for opaque 2 (o2), the cause of enhanced lysine content in maize exists. Background selection systems albeit, are poorly developed in spite of the mapping of putative loci associated with kernel modification and knowledge on causes of modification. The aim of this study was to develop background selection systems for o2 introgression into locally adapted genotypes. Experiments were conducted at Makerere University Agricultural Research Institute, Kabanyolo (MUARIK), in Uganda on backcross progeny (BC1F1) and BC2F2), derived from a locally adapted line 136R and a QPM donor CML176. We tested the use of zein proteins known to influence modification as well as DNA markers and phenotypic descriptors as tools for background selection for recurrent parent genome and modifier loci in locally adapted maize genotypes. Simply inherited traits such as maize streak virus disease resistance were suitable for background selection. Other traits include plant and ear heights. The simple sequence repeats markers mapped to chromosomes 3, 5, 7, respectively and associated with quantitative trait loci (QTL) conditioning resistance in maize to grey leaf spot and anthesis to silking interval were suitable for assay of recurrent parent genome. The 27-kDa γ zein protein levels was suitable for background selection for kernel modification. It should, however, be used along with other zeins such as the 22 kDa and 19 kDa zein proteins.
Considerable effort has been made to improve drought-stress tolerance in sorghum by incorporating the stay-green trait into drought-susceptible elite sorghum varieties. Keeping track of the several genes involved in the expression of this complex trait during the breeding program is an enormous task. In this study, the fidelity of recently identified SSR markers were tested for introgression of stay-green QTLs into elite sorghum lines. Of the 102 SSR loci tested, seventy-eight (78) markers were found to be polymorphic between the donor lines (B35 and E36-1) and the recipient lines (Sekedo and Seredo). In total, 25 polymorphisms were detected in SSR loci flanking key stay-green quantitative trait loci (QTLs) from the B35 donor line, and 6 in E36-1. In B35, 5 SSR markers were linked to the QTL StgA, 6 linked to StgB, 3 linked to Stg1, 2 linked to Stg2, 4 linked to Stg3 and 5 linked to Stg4. In contrast, only 6 polymorphic SSR markers were detected in the vicinity of key QTLs found in E36-1. Two were linked to LGA, 1 to LGJ and 3 to LGG. No markers were found linked to QTL LGD and LGH. Similar SSR polymorphisms were observed for markers needed to recover the recurrent parent genomes (RPG) in the subsequent backcross generations. These findings reveal the limitations of using E36-1 as a donor parent in marker-assisted selection (MAS) programmes for improvement of drought tolerance. Low hybridization efficiency (22.5%) was achieved using the anther dehiscence method. Such low hybridization efficiency requires use of molecular markers to easily identify plants harbouring the required genotypes.
Breeding for resistance to flower bud thrips (Megalurothrips sjostedti) in cowpea has been hindered by the quantitative nature of resistance. To identify simple sequence repeat (SSR) markers associated with resistance to flower bud thrips that could be used for marker-assisted breeding, a F 2 population was generated from a cross between genotypes TVU-123 (resistant) and WC36 (susceptible). The population was evaluated for thrips damage scores, thrips counts, and pods number per plant under artificial infestation. Sixty-six microsatellites markers were screened between the two parental lines and seven polymorphic markers were used for genotype 100 F 2 plants. Single marker analysis was used to evaluate an association between the markers and traits. Transgressive segregation among the F 2 plants for resistance to flower thrips was observed. A significant negative relationship was observed between thrips damage scores and pods number per plant. Markers CP37/38 and CP215/216 were significantly associated with thrips damage scores and thrips counts, respectively. The two markers explained 7 and 11.2% of the total variation in thrips damage scores and thrips counts with positive and negative effects, respectively. Mainly additive gene effects were observed. A more detailed study using more markers on these loci should provide better understanding of this complex trait.
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