Browsing by Author "Paul Gibson"

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Combining ability and heritability analysis of sweetpotato weevil resistance, root yield, and dry matter content in sweetpotato
(Frontiers in Plant Science, 2022-09-07) Immaculate Mugisa; Jeninah Karungi; Paul Musana; Roy Odama; Agnes Alajo; Doreen M. Chelangat; Milton O. Anyanga; Bonny M. Oloka; Iara Gonçalves dos Santos; Herbert Talwana; Mildred Ochwo-Ssemakula; Richard Edema; Paul Gibson; Reuben Ssali; Hugo Campos; Bode A. Olukolu; Guilherme da Silva Pereira; Craig Yencho; Benard Yada
Efficient breeding and selection of superior genotypes requires a comprehensive understanding of the genetics of traits. This study was aimed at establishing the general combining ability (GCA), specific combining ability (SCA), and heritability of sweetpotato weevil (Cylas spp.) resistance, storage root yield, and dry matter content in a sweetpotato multi-parental breeding population. A population of 1,896 F1 clones obtained from an 8 × 8 North Carolina II design cross was evaluated with its parents in the field at two sweetpotato weevil hotspots in Uganda, using an augmented row-column design. Clone roots were further evaluated in three rounds of a no-choice feeding laboratory bioassay. Significant GCA effects for parents and SCA effects for families were observed for most traits and all variance components were highly significant (p ≤ 0.001). Narrow-sense heritability estimates for weevil severity, storage root yield, and dry matter content were 0.35, 0.36, and 0.45, respectively. Parental genotypes with superior GCA for weevil resistance included “Mugande,” NASPOT 5, “Dimbuka- bukulula,” and “Wagabolige.” On the other hand, families that displayed the highest levels of resistance to weevils included “Wagabolige” × NASPOT 10 O, NASPOT 5 × “Dimbuka-bukulula,” “Mugande” × “Dimbuka-bukulula,” and NASPOT 11 × NASPOT 7. The moderate levels of narrow-sense heritability observed for the traits, coupled with the significant GCA and SCA effects, suggest that there is potential for their improvement through conventional breeding via hybridization and progeny selection and advancement. Although selection for weevil resistance may, to some extent, be challenging for breeders, efforts could be boosted through applying genomics-assisted breeding. Superior parents and families identified through this study could be deployed in further research involving the genetic improvement of these traits.
Genetics of Drought tolerance in common bean genotypes adapted to Ugandan conditions
(J. Plant Breed. Crop Sci., 2015-01-21) Winnyfred Amongi; Stanley Tamusange Nkalubo; Paul Gibson; Richard Edema; Mildred Ochwo-Ssemakula
Common bean (Phaseolus vulgaris L.) is an important source of food and income for majority of households in Sub-Saharan Africa. However, bean production in Uganda is being affected by drought which has resulted from recent changes in climate. Developing high-yielding and drought-tolerant bean cultivars would significantly contribute to increased and stable yields in drought-prone environments. However, prior research was not focused on breeding for drought tolerance in bean in Uganda. Thus, this study sought to elucidate the genetics governing the inheritance of drought tolerance in Ugandan bean genotypes, through establishing the mechanism of inheritance of this trait in the genotypes relevant to Uganda. Five drought-tolerant and three drought-sensitive genotypes were hybridized using a NCII mating design. The findings of the study indicated that drought tolerance is controlled by both additive and non-additive gene action with more predominance of additive gene effects for seed yield, pod weight, seed and pod and number. Further findings also revealed that the genotypes SEN 99 and NABE 15 are good combiners for drought tolerance.
Heterotic gains, transgressive segregation and tness cost of sweetpotato weevil resistance expression in a partial diallel cross of sweetpotato
(Euphytica, 2023-08-27) Immaculate Mugisa; Jeninah Karungi; Paul Musana; Roy Odama; Milton O. Anyanga; Richard Edema; Paul Gibson; Reuben T. Ssali; Hugo Campos; Bonny M. Oloka; G. Craig Yencho; Benard Yada
Heterosis-exploiting breeding schemes are currently under consideration as a means of accelerating genetic gains in sweetpotato (Ipomoea batatas) breeding. This study was aimed at establishing heterotic gains, fitness costs and transgressive segregation associated with sweetpotato weevil (SPW) resistance in a partial diallel cross of sweetpotato. A total of 1896 clones were tested at two sites, for two seasons each in Uganda. Data on weevil severity (WED), weevil incidence (WI), storage root yield (SRY) and dry matter content (DM) were obtained. Best linear unbiased predictors (BLUPs) for each clone across environments were used to estimate het- erotic gains and for regression analyses to establish relationships between key traits. In general, low mid- parent heterotic gains were detected with the highest favorable levels recorded for SRY (14.7%) and WED (− 7.9%). About 25% of the crosses exhibited desirable and significant mid-parent heterosis for weevil resistance. Over 16% of the clones displayed superior transgressive segregation, with the highest percentages recorded for SRY (21%) and WED (18%). A yield penalty of 10% was observed to be associated with SPW resistance whereas no decline in DM was detected in relation to the same. Chances of improving sweetpotato through exploiting heterosis in controlled crosses using parents of mostly similar background are somewhat minimal, as revealed by the low heterotic gains. The yield penalty detected due to SPW resistance suggests that a trade-o may be necessary between maximizing yields and developing weevil-resistant cultivars if the current needs for this crop are to be met in weevil-prone areas.
Identification of the key morphological sweetpotato weevil resistance predictors in Ugandan sweetpotato genotypes using correlation and path-coefficient analysis
(Crop Science, 2023-03-16) Florence Osaru; Jeninah Karungi; Roy Odama; Doreen Murenju Chelangat; Paul Musana; Milton Anyanga Otema; Bonny Oloka; Paul Gibson; Richard Edema; Reuben Tendo Ssali; George Craig Yencho; Benard Yada
Sweetpotato weevils (SPWs) can cause up to 100% yield losses in sweetpotato (Ipomoea batatas). Nevertheless, there has been limited success in breeding for SPW resistance globally. This is attributed partly to difficulty in screening for resistance because resistance to the SPW is complex and is mediated by several resistance indicators. Measuring all these resistance indicators is costly and time consuming. To enhance efficiency in selection for SPW resistance, there is need to profile and identify key resistance indicators. Potentially, this will better enable breeders to timely and precisely select for SPW resistance. The objective of this study was to identify the most efficient morphological resistance indicators against SPW. Thirty sweetpotato genotypes that varied in resistance to SPW comprising local collections, released varieties, and breeding lines were evaluated at three locations for two seasons in Uganda using an alpha lattice design. Data were collected on storage root yield, SPW root and stem damage, and weevil resistance indicators such as vine vigor (VV), ground cover (GC), vine weight (VW), storage root neck length (NL), latex content, cortex thickness (CT), and dry matter content (DM). Genotype means for all mea- sured traits varied significantly except for CT. Negative relationships were observed between SPW root damage and GC, VW, CT, VV, NL, and DM. However, path coefficient analysis showed storage root NL (direct effect of −0.43, p < 0.001) as the most important morphological resistance indicator. Therefore, NL could be the most
Inheritance of resistance to common bacterial blight in four selected common bean (Phaseolus vulgaris L.) genotypes
(2017-06-09) Boris M. E. Alladassi; Stanley T. Nkalubo; Clare Mukankusi; Eric S.Mwale; Paul Gibson; Richard Edema; Carlos A. Urrea; James D. Kelly; Patrick R. Rubaihayo
Common bacterial blight (CBB) is the most serious bacterial disease of common bean in Uganda. It causes severe yield losses of up to 62%. Genetic resistance is the most effective option for controlling CBB in smallholder common bean production systems. This study was carried out to determine the inheritance pattern of CBB resistance in leaf and pod of four new resistance sources. The four resistant and four susceptible genotypes were crossed in a half-diallel mating design. F1 individuals were advanced to F2 and evaluated with the parents, in a randomized complete block design replicated twice. Combining ability analysis was performed according to Griffing's (1956) method IV and model 1 using Genstat 12th. General combining ability effects were significant whereas specific combining ability was not suggesting that resistance to CBB in leaf and pod was primarily controlled by additive genes effects. The estimated narrow sense coefficient of genetic determination was moderately high (0.65) for the resistance in leaf and high (0.83) for resistance in pod suggesting that early-generation selection would be effective. Baker’s ratio estimates were relatively high for resistance in leaf (0.79) and pod (0.9) suggesting that hybrids’ performance can be predicted based on the parents’ general combining ability (GCA) effects.
NIRS Predictions, Phenotypic Variability and Optimization of Cooking Time for Evaluation of the Root Softness of Boiled Cassava
(National Agricultural Research Organisation, 2023-09-01) Babirye Fatumah Namakula; Ephraim Nuwamanya; Michael Kanaabi; Paul Gibson; Enoch Wembabazi; Iragaba Paula; Robert Sezi Kawuki
This study aimed at quantifying the extent of genetic variability of softness in cassava germplasm across varied cooking times and root sections. It also examined the possibility of using Near Infrared Spectroscopy (NIRS) for measurement of cassava root softness. Softness was evaluated using a penetrometer. This was done at 15, 30 and 45minutes cooking time, all across proximal, middle and distal root sections. These measurements were done on 57 accessions. For each sample, spectra were acquired using NIRS Benchtop (FOSS DS2500) on a composite of each root section of mashed fresh cassava sample. Modified Partial Least Squares regression (MPLS) was used for NIRS calibration development using WINISI software. Significant (P < 0.001) variability in softness was established. Cooking time significantly influenced softness and there were significant accession and root part interaction (P < 0.001). Wide variability and high heritability (H = 0.8) were found for softness at 30 minutes cooking time. Highest association was found with 30- and 45-minutes cooking time (r = 0.58). Strong association was observed between middle root section with distal (r = 0.74) and proximal (r = 0.73). NIRS softness calibration (R2c) were 0.445, 0.413 and 0.521 for 15-, 30-, and 45-minutes cooking time respectively. NIRS prediction (R2p) were 0.322, 0.192, and 0.390 for 15-, 30-, and 45-minutes cooking time respectively. These results suggest that 30 minutes cooking time and middle root section are optimum for softness phenotyping.