Browsing by Author "Tukamuhabwa, P."
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Item Agronomic qualities of genetic pyramids of common bean developed for multiple-disease-resistance(African Crop Science Journal, 2017-11-27) Okii, D.; Tukamuhabwa, P.; Tusiime, G.; Buah, S.; Gepts, P.Multiple co-infections by different pathogens on common bean (Phaseolus vulgaris L.) affect its productivity and cause complete crop loss in susceptible varieties. Therefore, gene pyramiding using marker assisted selection (MAS) and backcrossing, provide alternative cost-effective control measures to bean diseases. However, in the process of developing pyramids, linkage drags were likely to affect the qualities of progeny lines, hence, special attention was paid to this situation. The objective of this study was thus to assess the agronomic qualities of advanced genetic pyramids developed from a four-way cross for multiple disease resistance. The disease resistance genes (R) pyramided from four parents were: Co42 and Co-5 from G2333; Phg-2 from MEX54; Pythium ultimum Dennis from MLB49-89A and I & bc3 from MCM5001. The progeny lines were planted in an incomplete block design, and replicated thrice for two seasons (2015A and 2015B) in fields at CIAT, Kawanda in Uganda. Agronomic traits were highly heritable (0.6), except number of pods per plant (< 0.3). Backcrossing generated high-yielding bean lines, with 270 - 290 seed per plant and early maturity (95-100 days). Nine superior lines with desirable qualities, such as earliness (95 days), high seed rate (290 seeds per plant), and climbing ability, were obtained. Pyramiding R genes did not affect yield traits, except time to flowering and number of flower buds per plant due to transgressive segregation.Item Composition and variation of fatty acids among groundnut cultivars in Uganda(African Crop Science Journal, 2017-02-26) Achola, E.; Tukamuhabwa, P.; Adriko, J.; Michael, D.; Okello, D.K.Groundnuts (Arachis hypogaea L.) contain approximately 44-56% oil made up of fatty acids. Oleic and linoleic acids comprise about 80% of fatty acids in groundnuts. Groundnuts with >80% oleic are beneficial health-wise and also improve groundnut quality, flavour, and extended shelf-life, which is beneficial to traders. In Uganda, however, little is known about the fatty acids content of commercially available cultivars. This study was undertaken to determine the fatty acid composition of the most recently released commercially available groundnut cultivars in Uganda. Eleven groundnut genotypes were profiled for different fatty acids using gas chromatography (GC). Data were recorded in percentages from chromatographs and totaled up to about 100%. Oleic to linoleic ratios (O/L) and iodine values were calculated from fatty acid data. Groundnut genotypes tested differed significantly (P<0.05) in oleic, linoleic, palmitic, behenic, gadoleic, arachidic and palmitoleic acids. Oleic acid was highest in Lot 197 line, and linoleic acid was lowest in the same line. Oleic acid was lowest in Serenut 7 (43.19%) and linoleic acid was highest in the same line (33.45%). The lowest iodine value was observed in 197 (84.14); and the highest in Serenut 9T (96.59). Significant correlations (P<0.001) were observed between most of the fatty acids, except between arachidic versus gadoleic, stearic and gamma linoleic.Item Detection of cowpea aphid-borne mosaic virus (CABMV) in cowpea by reverse transcription polymerase chain reaction(African Crop Science Journal, 2018-08-30) Mbeyagala, E. K.; Tukamuhabwa, P.; Mukasa, S.B.The occurrence of CABMV on cowpea (Vigna unguiculata L. Walp) in Uganda was described recently in several studies. This study developed and optimised a reverse transcription polymerase chain reaction (RT-PCR) based assay for the detection of CABMV in leaf samples, and compared it to previous RT-PCR and ELISA assays. Use of the forward primer (CABFF1, 5'- GGT AAC AAY AGT GGR CAA CC-3') and the reverse primer (CABRR1, 5'- CTG AGC ACT CMA ACC GGG-3') yielded a product of ~ 1,642 bp. Amplicon sequencing and subsequent BLASTN analysis showed that Ugandan isolates were 89.3-94.3% identical indicating they belong to the same strain of CABMV. Phylogenetic analysis also placed the Ugandan isolates in the same cluster different from other isolates but closer to those from Burkina Faso. However, the previously reported RT-PCR assay (GF/GR primer pair) did not give the expected PCR fragment (221 bp) and gave no virus hits upon amplicon sequencing and sequence analysis. The ELISA assay did not differentiate between positive and negative samples. The newly developed RT-PCR assay for detecting CABMV, described in this study, has important applications for plant quarantine, resistance breeding, host range studies as well as epidemiological studies for the control of CABMV in the country.Item Development of a hot pepper root rot and wilt disease management strategy through genetic resistance, chemical application and proper choice of rotational crops(RUFORUM, 2010-09-24) Tusiime, G.; Tukamuhabwa, P.; Nkalubo, S.; Awori, E.; Tumwekwase, S.This study seeks to contribute to increased productivity of hot pepper (Capsicum chinense) by incorporating an integrated pest management (IPM) package for root rot/wilt disease (Phytophthora capsici). Pathogen host diversity will be determined to guide the use of crop rotation in managing the disease. Oomycete fungicides will be screened for effectiveness in managing P. capsici. Additionally, resistance introgression will be carried out with resistant donors. The contribution of the Phyto 5.2 QTL disease resistance will also be determined in order to assess its usability in resistance breeding. The study will be carried out in collaboration with pepper farmers in Kasese, UgandaItem Enhancing Soybean Rust resistance through Rpp2, Rpp3 and Rpp4 pair wise Gene Pyramiding(African Journal of Agricultural Research, 2012-08-07) Maphosa, M.; Talwana, H.; Tukamuhabwa, P.The threat posed by soybean rust (Phakopsora pachyrhizi) on soybean production is worsened by resistance breakdown associated with single gene resistance present in most cultivars. Few studies have however been undertaken to use mapped simple sequence markers for gene pyramiding to enhance rust resistance. This study validated use of identified simple sequence repeat markers for gene pyramiding, and determined the most effective pairwise gene combination for three independent soybean rust resistance genes, Rpp2, Rpp3 and Rpp4. Markers Satt460 and AF162283 were polymorphic for the three resistance genes among the parents and were therefore used in selections made in the F2 and F3 families. In the F2 generation, soybean plants (homozygous dominant or heterozygous at both loci) with two gene combinations had relatively lower disease severity and sporulation than the parents, suggesting complementary epistatic gene action for resistance. Similarly, homozygous F3 families showed lower severity, lesion density and sporulation. Gene Rpp3 contributed positively to resistance with various genetic backgrounds for most parameters measured, compared to Rpp2 and Rpp4 resistance genes. Overall, the results suggest that marker gene pyramiding is feasible and can substantially increase resistance to soybean rust through reduced severity and reduced sporulating lesions.Item Fruit Traits associated with Resistance to Fruit Pests of Hot Pepper(MUJAES, 2021-07-03) Ssekkadde, P.; Ribeiro, C.S.C.; Ochwo-Ssemakula, M.N.; Tukamuhabwa, P.; Karungi, J.Thirty-seven local and fourteen exotic hot pepper (Capsicum spp.) genotypes were screened under natural field conditions for resistance to two quarantine fruit pests; the fruit fly (Diptera: Tephritidae) and the false coddling moth (Lepidoptera: Tortricidae) at Makerere University Research Institute Kabanyolo for two seasons. The genotypes were grown in a randomised complete block design with three replications. Data on pest occurrence and damage; and fruit traits (fruit weight, length, width, flesh penetrability, and fruit wall thickness) were subjected to analysis of variance. The 51 genotypes showed variation in pest infestation and fruit traits. Five local genotypes (UG-WE02-1014, UG-WE02-0711, UG-EA06-0515 and UG-WE02-1608) and one exotic (CAP0408-12) showed resistance to fruit fly infestation. Fruit fly infestation correlated highly with fruit weight (r=0.59, p<0.001) and width (r=0.63, p<.001), among others. Similarly, FCM infestation positively correlated to fruit weight (r=0.50, p<0.001) and width (r=0.50, p<0.001). The identified hot pepper genotypes with resistance to fruit fly and FCM can be used in hot pepper improvement programsItem Genetic analysis of resistance to soybean rust disease(African Crop Science Journal, 2008-08-06) Kiryowa, M.; Tukamuhabwa, P.; Adipala, E.Soybean rust (Phakopsora pachyrhizi Sydow.) causes the most damage of all the pathogens known to attack soybean (Glycine max. Merril). A study was conducted in Uganda to estimate the magnitude of genetic parameters controlling soybean rust resistance and to estimate narrow sense heritability of the resistance. Soybean crosses were made and progenies analysed according to the North Carolina II mating design with three resistant parents acting as males namely Maksoy 1N, UG5 and GC00138-29; and three susceptible parents acting as females namely Nam 1, Kabanyolo 1 and Wondersoya. F1s and F2s were planted in the field during two rainy seasons (2004 - 2005). Rust severity was scored using a scale of 0 – 10. Genetic parameter estimates were VE = 0.86186, VD = 0.30145, VA = 0.4616, VP = 1.6248 and VG = 0.763. Resistance gene for rust expressed complete dominance with ..4VD/ 2VA = 1.1. Broad sense heritability (hb2) was 0.5, while narrow sense heritability, hn2, derived from parameter estimates as a ratio of Additive Variation to Phenotypic variation (VA/VP), was 0.3. Environmental variation contributed most (53%) to total variation (VP) due to high “within families component of variance, VE” at F2 generation, which accounts for the low heritability estimates. General Combining Ability (GCA) and Specific Combining Ability (SCA) were significant with the parent GC00138-29 having the lowest GCA value (-0.488) making it the best combiner that can be used in breeding programs for resistance to soybean rust. The cross GC00138-29 x Wondersoya had the lowest SCA value (-0.18) suggesting that it would produce the most highly resistant hybrid offsprings.Item Genetic Components of Pod Shattering in Soybean(Euphytica, 2002-05-16) Tukamuhabwa, P.; Rubaihayo, P.; Dashiell, K.E.Half diallel crosses among ten pure breeding lines of soybean were made in 1997 and 1998 to study the inheritance of pod shattering in soybean. Evaluation for pod shattering among F2 segregating populations was carried out in an oven set at 80 °C for 12 hours. Diallel analysis was carried out to estimate genetic parameters and detect presence of non allelic interaction of genes affecting pod shattering. Hayman's diallel analysis indicated significant variation of Wr + Vr and Wr – Vr over arrays, suggesting epistatic gene action. Similarly results from a joint regression coefficient over replications were significantly (p < 0.05) different from unity and zero, suggesting presence of non allelic interaction of genes. The intercept was positive, suggesting partial dominance for the shattering trait. Both general combining ability (GCA) and specific combining ability (SCA) effects were significant (p < 0.05).Item Genotypic variation for maize weevil resistance in eastern and southern Africa maize inbred lines(Uganda Journal of Agricultural Sciences, 2016-03-27) Kasozi, L.C.; Derera, J.; Tongoona, P.; Tukamuhabwa, P.; Muwonge, A.; Asea, G.The maize weevil (Sitophilus zeamais Motschulsky) is the most destructive storage insect pest of maize (Zea mays L.) worldwide, especially among susceptible varieties. Breeding for grain resistance against the weevil is a major component of an integrated pest management strategy in maize production. The objective of this study was to identify diverse sources of weevil resistance for introgression in breeding programmes. A total of 180 inbred lines from three geographical areas were screened for maize weevil resistance. Screening was executed by infesting 50 g of maize grain with 32 newly emerged adult weevils, placed in 250 cm3 glass jars in a “no-choice” laboratory test. The grain susceptibility parameters used were F1 weevil progeny emergence, percent grain damage, median development period, Dobie’s index of susceptibility, and parental weevil mortality. New sources of weevil resistance for maize breeding were identified. Eight inbred lines were consistently resistant and, therefore, selected as potential donors for weevil resistance in the maize improvement programmes. There was significant genetic variation, and high levels of heritability (89 – 96%) for weevil resistance that suggested high potential for germplasm improvement through selection. No significant association was observed between maize weevil resistance and grain yield, suggesting that breeding for maize weevil resistance can be achieved without compromising grain yield.Item Morphological Characterization of Ugandan Sweetpotato Germplasm(Crop Science, 2010-11-01) Yada, B.; Tukamuhabwa, P.; Alajo, A.; Mwanga, R. O. M.Sweetpotato [Ipomoea batatas (L.) Lam] is a widely grown and consumed root crop in Uganda. A total of 1303 accessions of sweetpotato germplasm collected from 21 districts of Uganda were planted for morphological characterization. Forty morphological descriptors were scored on 1256 accessions 90 to 100 d after planting. Stepwise discriminant analysis showed that the discriminating power of 20 morphological traits was sufficient to differentiate the accessions. The level of morphological variation for the 40 traits estimated using the Shannon Weaver diversity index (H') ranged from 0.10 to 0.99, with an overall mean of 0.71 ±0.03, suggesting a highly diverse collection. Cluster analysis using the unweighted pair-group method using arithmetic averages grouped the 1256 accessions into 20 major clusters, with the number of accessions per cluster ranging from 15 to 166. The general leaf outline was highly correlated with leaf lobe type (r = 0.79) and leaf lobe number (r = 0.80) and were the predominant characters in grouping the accessions to clusters. No grouping of accessions based on region of origin was observed, suggesting movement of germplasm between regions. Approximately 70% of the accessions were morphologically distinct and a collection of 946 accessions was selected to represent Ugandan sweetpotato landrace diversity. The complete passport data for this collection is available at: http://www.viazivitamu.org/ugasp_db/gis.htmItem Morphological diversity of tropical common bean germplasm(African Crop Science Journal, 2014-02-21) Okii, D.; Tukamuhabwa, P.; Odong, T.; Namayanja ,A.; Mukabaranga, J.; Gepts, P.Common bean (Phaseolus vulgaris L.) landraces and varieties grown by farmers in the tropics are a major source of genes and genetic diversity for bean improvement. These materials are, however, threatened by genetic erosion. In this study, we sought to understand the current state of genetic diversity of common bean in Uganda, using the available collection consisting of 284 bean accessions. A field experiment was conducted at the National Crops Resources Research Institute in Namulonge, Uganda. The level of morphological variation estimated with the Shannon Weaver diversity index (H), ranged from 0.47 to 0.58, with an overall mean of 0.56±0.19, an indicator of moderate genetic diversity. Principal component analysis (PCA) clustered the germplasm into three major groups (G1, G2 and G3). The genotypes differed mostly for growth habit, pod cross-section, pod curvature, hypocotyl colour, days to flowering, node number on the main stem, number of flower buds, and 100 seed weight.Item Next-Generation Sequencing Reveals the First Complete Genome Sequence of Cowpea aphid-borne mosaic virus from Uganda(Genome Announcements, 2018-08-15) Mbeyagala, E. K.; Tukamuhabwa, P.; Bisikwa,J.; Mukasa, S. B.We present here the first complete genome sequence of Cowpea aphid-borne mosaic virus (CABMV) isolated from cowpea in Uganda and compare it with five CABMV complete genome sequences from Brazil (2), India (2), and Zimbabwe (1). It most resembled the genomes of two Brazilian isolates (MG-Avr and BR1) and one Indian isolate (RR3).Item Potential for soybean rust tolerance among elite soybean lines in Uganda(Crop protection, 2009) Oloka, Herbert K.; Tukamuhabwa, P.; Sengooba, T.; Adipala, E.; Kabayi, P.Soybean rust, (Phakopsora pachyrhizi), currently the most devastating disease of soybeans worldwide, is known to challenge single resistance genes deployed against it and therefore, disease tolerance is indisputably the most viable measure in controlling the pathogen. Studies were conducted at Namulonge in Central Uganda to assess the level of tolerance to soybean rust among selected elite soybean lines. Seven elite lines together with three local checks were tested in a split-plot design where some plots were protected with fungicide to estimate the level of tolerance to soybean rust. The experimentwas conducted for three cropping seasons beginning second rains of 2005. A rust tolerance index (RTI) was computed for each test line as the ratio of yield from unprotected plots to yield from protected plots. The study showed that high levels of tolerance to soybean rust were present in the test lines. The soybean lines that showed high levels of tolerance included MNG 10.3 and MNG 3.26 all showing RTIs higher than 0.93. These lines also out-yielded the local checks by about 400 kg ha 1 and are recommended for multi-location testing.Item Potential for yield loss reduction and profitability assessment of pesticide control of groundnut leaf miner among soybean genotypes(African Journals Online (AJOL), 2019-05-17) Namara, M.; Karungi, J.; Edema, R.; Gibson, P.; Tukamuhabwa, P.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.Item Progression of Cassava Brown Streak Disease (CBSD) in infected cassava roots in Uganda(Uganda Journal of Agricultural Sciences, 2012-11-20) Abaca, A.; Kawuki, S.R.; Tukamuhabwa, P.; Baguma, Y.; Bua, A.; Omongo, C.A.Cassava Brown Streak disease (CBSD) has and continues to be a major threat to the cassava industry in Uganda. The most economically damaging symptom of CBSD occurs on the roots as a yellow/brown, corky necrosis. However, the onset and development of this necrosis is not known. Therefore, this study was conducted to understand the progression of CBSD root necrosis.The experiment was conducted at Namulonge (central Uganda), where the CBSD pressure and whitefly population is high. Four CBSD susceptible genotypes (TME204, TMSI92/0067, MH97/2961, and Bamunanika) and five CBSD tolerant genotypes (TME14, NASE 3, NASE 1, MM96/0686 and 28- TME 14) were used. The experiment was laid out in a split-plot factorial experiment with three replicates. CBSD root necrosis was assessed at 4 months after planting (MAP) and, thereafter, at monthly intervals until 12 MAP. Results indicated significant differences (P<0.001)among reaction grades (susceptible and tolerant), genotypes and sampling times. CBSD root necrosis commences as early as 4 MAP in susceptible genotypes with a severity of 2 and incidence of 16.67%. These findings have important implications for CBSD breeding particularly when evaluating seedlings and/or clonal plants that often have different number of roots.Item Reaction of Exotic Soybean Germplasm to Phakopsora pachyrhizi in Uganda(Plant Disease, 2008) Oloka, H. K.; Tukamuhabwa, P.; Sengooba, T.; Shanmugasundram, S.Host plant resistance is the best long-term strategy for managing soybean rust (Phakopsora pachyrhizi) in endemic areas. Resistance breeding efforts are hampered by the presence of several races of the pathogen that often overcome single resistance genes deployed against them. In Uganda, only two soybean cultivars show moderate resistance to Phakopsora pachyrhizi, but this is likely to break down given the aggressive nature of the pathogen. A total of 25 rust tolerant or resistant accessions were imported from the Asian Vegetable Research and Development Centre and screened at Namulonge, in central Uganda. Only 10 accessions, G 33, G 8527, G8586, G 8587, GC 60020-8-7-7-18, GC 87016-11-B-2, GC 87021-26-B-1, SRE-D-14A, SRE-D-14B, and SS 86045-23-2, showed no rust symptoms at growth stage R6 during the three seasons of testing. Soybean rust resistance genes Rpp1, Rpp3, and Rpp4 did not confer resistance at Namulonge; gene Rpp2 was effective.Item Regeneration Procedure for Three Arachis hypogaea L. Botanicals in Uganda through Embryogenesis(Br Biotechnol J, 2015-05-06) Okello, D. K.; Akello, L. B.; Tukamuhabwa, P.; Odong, T. L.; Deom, C. M.A procedure was developed for embryogenesis from embryo explants derived from mature seeds of freshly harvested Serenut 4T, Serenut 1R and Acholi-white groundnut cultivars representing the three broad groundnut botanical classifications. This study explored the use of mature embryo axes as explants for somaticembryogenesis, and determined the factors that affect regeneration of three Ugandan groundnut cultivars. Freshly harvested mature seeds of the three groundnut cultivars were collected and the embryo explants were initiated on 3 media namely; Murashige and Skoog (MS) basal media with varying concentrations of the growth regulator 2,4-Dichlorophenoxy acetic acid (2,4-D); Chu N6 basal medium with vitamins (N6); and Callus Induction Medium (CIM). The shoot formation and elongation medium contained MS basal medium supplemented with indolebutyric acid (IBA) and 6- Benzylamminopurine (BAP) in isolation, and BAP in combination with a-naphthaleneacetic acid (NAA) and indoleacetic acid (IAA). For root induction, elongated shoots were transferred to MS medium supplemented with various combinations of NAA with IBA, BAP and a combination of IBA and Kinetin. Different concentrations of 2,4-D elicited different callogenesis responses in the cultivars with Acholi white (Valencia botanical) and Serenut 4T (Spanish botanical) giving the optimal response at 5mg/l whereas Serenut 1R (Virginia botanical) showed best response at a concentration of 30 mg/l. N6 and CIM supported callogenesis in Acholi white (AW) and Serenut 4T only. In all cultivars, maximum root production was gained when using MS medium supplemented with NAA- 1 mg/l and IBA -2.0 mg/l. On the other hand, for Serenut 1R and Serenut 4T, BAP 2.5 mg/l; NAA 0.5 mg/l combination yielded higher shoot regeneration percentage whereas for AW BAP 3 mg/l; NAA 0.5 mg/l supported maximum shoot production.This is the first ever report of successful regeneration of the three groundnuts botanicals in Uganda. These results are likely to facilitate genetic transformation of three preferred Ugandan groundnut varietiesItem Responding to the soybean rust epidemic in sub-Saharan Africa: A review(African Crop Science Journal, 2003-04-16) Kawuki, R.S.; Adipala, E.; Lamo, J.; Tukamuhabwa, P.Soybean rust (Phakopsora pachyrhizi Sydow), a major threat to soybean production, is a new pathogen on the African continent, where it is increasingly threatening soybean production. The fungus is highly variable, and this complicates most disease management strategies. Most research on soybean rust, its epidemiology and management has been in the Orient, and only limited work has been done in Africa. However, experiences in the Orient will be important for soybean rust researchers in Africa, who are currently combating the epidemic. This approach will be necessary to design and implement rust management strategies in the African countries already affected, and those as yet unaffected. Because there is little information on distribution, epidemiology, and management of soybean rust from Africa, this paper provides an overview on 1) soybean rust epidemiology, disease assessments and management, as experienced in the endemic areas, 2) the distribution of soybean rust in Africa, 3) on-going research activities in the African countries most affected, and 4) discusses priority research activities. This review is intended to stimulate future research activities, leading to a better understanding of the pathogen, its biology and ecology, and management.Item Screening soybean genotypes for promiscuous symbiotic association with Bradyrhizobium strains(African Crop Science Journal, 2016-02-29) Agoyi, E. E.; Afutu, E.; Tumuhairwe,J.B.; Odong,T.L.; Tukamuhabwa, P.The current low soybean (Glycine max L. Merrill) yields in Sub-Saharan Africa can be alleviated by developing promiscuous genotypes. The research trend in Africa is towards developing promiscuous varieties for less labour and high yields in soybean production. A greenhouse experiment was conducted at Makerere University Agricultural Research Institute, Kabanyolo (MUARIK) with the aim of screening of soybean germplasm for promiscuous symbiotic association with Bradyrhizobium sp. in order to identify genotypes with potential to be used as parents to initiate a breeding programme focusing on promiscuous nodulation. The response of 65 soybean genotypes from different origins to cowpea-type inoculant, Bradyrhizobium sp. strain USDA 3456 were evaluated. Soybean seeds inoculated with both Bradyrhizobium sp. strain USDA 3456 and Bradyrhizobium japonicum strain USDA 110 were planted in buckets filled with steam-sterilised soil. Significant differences in the number of nodules, effective nodules, fresh and dry weight of nodules were observed among genotypes (P<0.001). Twelve of the 65 genotypes were highly responsive to Bradyrhizobium sp., with over 10 nodules per plant, over 50 mg dry weight of nodules, and 50% effective nodules. A highly positive correlation was shown between dry weight of nodules and nodule number. This study proposes the soybean genotypes NamII, WonderSoya, Bulindi 48C, NamSoy 4M, MakSoy 3N, NamSoy 3, K-Local, Kabanyolo 1, UG 5, Soprano, MakSoy 2N, and MakSoy 5N as potential parental materials for subsequent breeding work.Item Soybean rust severity, rate of rust development, and tolerance as influenced by maturity period and season(Crop Protection, 2004-05-15) Kawuki, R.S.; Tukamuhabwa, P.; Adipala, E.Studies were conducted in Uganda for three consecutive seasons to evaluate soybean lines of different maturation periods against rust. All the lines were highly susceptible to rust with only two lines graded as moderately resistant: TGx 1835-10E (early maturing) and TGx 1838-5E (late maturing). These two lines were consistently associated with non-sporulating lesions. Within each maturation group, soybean lines differed significantly in rates of rust development (RRDs), rust severities at R6 growth stage, and yielding ability under rust stress. Most of the lines had RRDs higher than the local check. However, it was only the early maturing lines that yielded higher than the local check. Higher levels of rust tolerance were observed in the early maturing lines (yields >1000 kg/ha), and lowest in late maturing lines (yields<500 kg/ha). Most variation in yields was due to differences among soybean lines, except the late and medium maturing lines were it was due to seasonal variation. Most variation in RRDs was due to the seasons and not soybean lines, and rust severity increased with crop age.