Theses and Dissertations Collection

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Browsing Theses and Dissertations Collection by Subject "Agro-ecologies"

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    Occurrence of rice blast in two agro-ecologies of Burundi and assessment of varietal resistance and diversity of pyricularia oryzae strains
    (Sokoine University of Agriculture, 2022) Niyonkuru, Estella
    In Burundi, rice is a very important staple food, generating income for smallholder farmers and the business community. Unfortunally constrained by rice blast disease cause by fungus Pyricularia oryzae, which can cause up to 100% loss if not managed. The present study was conducted in middle and high altitudes agro-ecologies of Burundi with an overall objective to increase rice productivity by identifying resistant rice cultivars for management of the disease. Occurrence of blast disease on rice cultivars was caary out in a triplicated split plot experiment in a Randomized Complete Block Design (RCBD) in middle and high altitudes zones. Rice blast disease incidence and severity were significant different between locations (P =0.000). The high altitude agro ecological zone had the higher disease incidence (68.68%) and severity (77.53%), than the disease incidence (3.42%) and severity (20.74%) recorded in Middle altitude agro- ecological zone. When compared between rice growth stages, the disease occurrence and severity were significantly different (p < 0.05). In high altitude, rice blast incidence (74.12 - 90.89%) and severity (48.15 - 100%) were recorded at the booting stage and dough stage. In middle altitude, incidence of disease was recorded at tillering (2.49 - 9.67%), booting (3.07 - 9.83%) and dough (0.49 - 1.68%) stages and blast severity was observed at tillering (11.11 - 33.33%) and booting stage (11.11- 48.155%). The Area Under the Disease Progress Curve (AUDPC) showed that the disease progress in all cultivars increased exponentially from tillering to the dough stage, but at this dough stage the disease progress plateaued in some cultivars. Another study was conducted in the both laboratories in IRRI-Burundi and Plant Molecular Biology at Sokoine University of Agriculture to establish genetic relatedness of rice blast (Pyricularia oryzae) isolates from two agro ecologies of Burundi. For the thirty five (35) Pyricularia oryzae isolates for two AEZ, a set of five primers were used for molecular markers targeting the International Transcribed Spacer (ITS) and Translation Elongation Factor (EF) regions by using polymerase chain reaction (PCR) followed with Sanger sequencing. The results showed differences in banding patterns between isolates: ITS1 and 2R, ITS3F and 4R, ITS1F and 4R, ITS4F and 5R and EF1- 983F and EF1-2218R showed bands size of 220bp, 350bp, 390bp, 550bp and 1235bp respectively. Phylogenetic analysis confirmed the narrow genetic diversity between Pyricularia oryzae isolates collected in high and middle altitudes regions of Burundi. Phylogenetic analysis showed that the isolates used from Burundi belong to Pyricularia oryzae and that the isolates vary considerably depending on the specific hosts. Some isolates were from hosts other than rice, Ryegrass, millet, wheat and Graminis-tritici for different locations. A screen house experiment in a Complete Randomized Design (CRD) with three repetitions was conducted in IRRI-Burundi to evaluate 10 cultivars for resistance to a particular artificially inoculated Pyricularia oryzae isolates. The results indicated a significant difference between isolates and cultivars in incidence and severity. Of the ten rice cultivars, only three were resistant (R) (Mugwiza, Rufutamadeni and V18) to all isolates of Pyricularia oryzae. Rice blast disease is distributed in middle and high altitudes agroecologies of Burundi. The study recommends more studies in different season to evaluate the incidence and severity of rice blast in relation to paddy yield and the genetic diversity of isolates for other locations in Burundi, not yet covered by the current study.
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    Performance of elite cereal and legume genotypes in varying potential agro-ecologies in Central Tanzania
    (Sokoine University of Agriculture, 2021) Wabwire, Simon
    Grain legumes and cereals are widely grown in many semi-arid areas of the tropics by smallholder farmers who derive from the crops multiple benefits such as nutritious food, soil fertility, and household income. Communities in these areas are highly vulnerable to weather and other natural disaster-related challenges thus facing a problem of low crop productivity. Field experiments were conducted during the 2019-2020 cropping season in different sub agro-ecologies of central Tanzania aiming to: - (i) identify legume and cereal genotypes of higher productivity in varying potential agro-ecologies (ii) determine the stability and GxE interaction of the legume and cereal genotypes in the different agro-ecologies (iii) identify relatively more efficient and productive cropping system in varying potential agro-ecologies of central Tanzania. Methods Experiments were laid down in two villages of each potential agro-ecology following an incomplete randomized block design with farmers as replications. Grain yield, yield components and growth data on fourteen genotypes in total of the four crops (groundnut, pigeon pea, sorghum and pearl millet) were collected and Land equivalent ratios (LERs) calculated for intercrops amongst the crops. Findings Results from the experiments generally revealed that G x M x E interactions were insignificant (p ≤ 0.05) in terms of grain yield for all the crop genotypes studied. For groundnut and pigeon pea genotypes, significant differences (p ≤ 0.05) were observed across the sub-ecologies while significant genotypic effects were observed in both sorghum and pearl millet genotypes. Genotype ICGV-SM 05650 of groundnut had the highest grain yield of 2105.08 kg ha-1, while ICGV-SM 02724 recorded the lowest grain yield of 1538.87 kg ha-1 in the high potential sub-ecology. Pearl millet genotype IP 8774 had the highest yield of 1049.4 kg ha-1 and the local check had the lowest yield of 388.9 kg ha-1. Though non-significant differences (P ≤ 0.05) among genotypes tested for grain yield were observed in pigeon pea and sorghum genotypes however, pigeon pea genotype ICEAP 00040 had a slightly higher grain yield of 779.17 kg ha-1 compared to ICEAP 00557 with 770.83 kg ha-1 grain yield and sorghum genotype GAMBELLA 1107 outperformed the other genotypes with grain yield of 1420.8 kg ha-1 followed by IESV 23010 DL of 1038.0 kg ha-1. Early planting outperformed late planting for the crop genotypes tested however, non-significant differences (p ≤ 0.05) in planting dates were observed. Furthermore, crop genotypes in the high potential generally out performed those under the moderate and low potential sub-ecologies. In terms of LERs, pigeon pea - sorghum, pigeon pea - groundnut and pigeon pea - pearl millet intercrops had higher LER values of 1.59 (high), 1.65 (moderate) and 2.36 (low potential agro-ecologies), respectively compared to LERs of 1.00 in their respective sole crops. Conclusion Findings of the study revealed that generally elite materials outperformed the local landraces. Furthermore, intercropping systems proved to be more efficient and productive compared to sole cropping systems. From the above findings, ICGV-SM 05650 (groundnut), ICEAP 00040 (pigeon pea), GAMBELLA 1107 (sorghum) and IP8774 (pearl millet) were recommended for deployment in these varying potential agro-ecologies due to their stable and superior performance in terms of grain yield. Intercrops Pigeon pea - Sorghum, Pigeon pea - Groundnut and Pigeon pea - Pearl millet were the more efficient and productive cropping systems therefore recommended for deployment in the high, moderate and low potential agro-ecologies respectively.