Browsing by Author "Otim, Michael Hilary"

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    Evaluation of rice genotypes for resistance to the stalk-eyed fly (Diopsis longicornis) in rice in Uganda
    (International Journal of Agronomy and Agricultural Research (IJAAR), 2016) Ganteh Weelar, Charles; Otim, Michael Hilary; Lamo, Jimmy; Awio, Bruno; Ochwo-Ssemakula, Mildred
    Globally, rice production is limited by abiotic and biotic factors. Of the insect pests attacking rice, the stalk-eyed fly is the most abundant. Major rice growing districts in Uganda are affected, and varieties grown by farmers are susceptible. The objective of this study was to identify sources of resistance to stalk-eyed flies among improved rice genotypes in Uganda. Fifty genotypes from the Africa Rice Centre, IRRI, South Korea and the National Crops Resources Research Institute (NaCRRI) in Uganda were screened under cage and field conditions at NaCRRI. Trials were laid out in an alpha lattice design, with 3 replications, for both experiments. Natural infestation (D. longicornis or D. apicalis) was used in the field while cage trials utilized artificial infestation with D. longicornis. Data on deadhearts were collected from seedling to tillering stages, at 7, 14, 21 and 28 days. Analyses of variance were performed using restricted maximum likelihood. Infestation levels for 31 (62%) rice genotypes were the same under both field and cage conditions, 4 (8%) genotypes showed higher susceptibility in the cage than in the field and 15 (30%) were more resistant in the cage than in the field. Genotypes NERICA 4, TXD306, NM7-22-11- B-P-1-1 and K85 were identified as the most resistant varieties. F3 genotypes (GSR IR1- 5-S14-S2-Y1 x K85, Gigante x NERICA4, NERICA4 x Gigante, NERICA1x NERICA4, NERICA4 x NERICA6, and NERICA4 x SUPA) were also found resistant. These genotypes were recommended for release and further advancement, respectively.
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    Influence of Cassava Morphological Traits and Environmental Conditions on Field Populations of Bemisia tabaci
    (Insects, 2021) Katono, Kasifa; Macfadyen, Sarina; Omongo, Christopher Abu; Lapaka Odong, Thomas; Colvin, John; Karungi, Jeninah; Otim, Michael Hilary
    High populations of species in the whitefly complex Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) were reported to cause severe damage to cassava in East and Central Africa. However, reasons for B. tabaci population increases are not well understood. We investigated the effect of cassava morphological traits, temperature, rainfall and relative humidity (RH) on the abundance of B. tabaci. Five cassava genotypes with varying levels of resistance to cassava mosaic disease, cassava brown streak disease, and B. tabaci infestation were planted in three Ugandan agro-ecological zones. The experiment was conducted in 2016 and 2017 in a randomized complete block design. Across all locations, the tallest genotype Alado alado supported the lowest number of B. tabaci adults. In areas with high B. tabaci prevalence, leaf area, leaf lobe width, and leaf lobe number exhibited significant positive effects (p < 0.001) on B. tabaci adult count. Positive effects of relative humidity and negative effects of temperature and rainfall on B. tabaci adult and nymph counts were observed in 2016 and 2017, resulting in low populations in Lira. Evidently, temperatures of 28–30 C, rainfall of 30–150 mm and RH of 55–70%, and deployment of cassava genotypes of low plant height, large leaf area, and lobe width significantly enhanced B. tabaci population growth.
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    Mode of inheritance of resistance to the stalk-eyed fly (Diopsis longicornis) in rice
    (International Journal of Agronomy and Agricultural Research, 2017) Ganteh Weelar, Charles; Lamo, Jimmy; Otim, Michael Hilary; Awio, Bruno; Ochwo-Ssemakula, Mildred
    Stalk eyed flies (D. longicornis and D. apicalis) are pests of economic importance on rice. Of the two species of stalk- eyed fly, D. longicornis is the most prevalent and destructive. To determine the mode of inheritance for resistance to the stalk-eyed fly in rice in Uganda, crosses were made among eight parental lines (NERICA4, TXD306, K85, NM7-22-11-B-P-1-1, NERICA1, NERICA6, NAMCHE2 and PAKISTAN) selected on the basis of their response to the stalk-eyed fly, high yield and early maturity. Of the eight, four genotypes [NERICA4, TXD306, and NM7-22-11-B-P-1-1 and K85], exhibited lower levels of deadheart occurrence and were crossed using the North Carolina II mating design with four susceptible genotypes [NERICA1 and NERICA6, PAKISTAN, and NAMCHE2]. Studies on combining abilities were conducted on 16 F1 hybrids along with the eight parents. Narrow sense coefficients of genetic determination (NSCGD) were low to moderate (0.09 - 0.33) and broad sense coefficients of genetic determination (BSCGD) were moderate to high (0.38 - 0.89) for traits studied. Both GCA and SCA effects were significant for percentage of deadhearts. However, Baker’s ratio was less than 0.5 (0.37) for deadhearts, indicating that both additive and non-additive gene effects were involved in resistance to the stalkeyed fly, although non-additive gene effects were more important. NERICA4 andK85 were found to be good general combiners for increasing resistance. The crosses Pakistan × TXD306 and NERICA1× NM7-22-11-B-P-1-1 were identified as promising lines for advancement.