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Makerere University (2013)

Physiological and morphological responses of farmer preferred cassava (Manihot esculenta Crantz) cultivars to drought stress in Uganda

Chemayek, Bosco

Titre : Physiological and morphological responses of farmer preferred cassava (Manihot esculenta Crantz) cultivars to drought stress in Uganda

Auteur : Chemayek, Bosco

Université de soutenance : Makerere University

Grade : Masters of Science Degree in Crop Science 2013

Résumé partiel
Cassava is the most important staple food crop in the tropics feeding over 800 million people, mainly resource poor small scale-farmers. In Uganda, cassava ranks 2nd to bananas in terms of total production and per capita consumption but ranks 2nd to maize in production area, (UCA, 2010) and it is the leading food security crop. Cassava is commonly cultivated in areas considered marginal for most other crops, with low-fertility soils and annual rainfall of less than 600 mm in semi-arid environments thus making it vulnerable to drought stress. Drought tolerance mechanisms in cassava and strategies for its management developed elsewhere, but no such information was available in Uganda. The main objective of this study was to assess the physiological and morphological responses of cassava cultivars in Uganda to drought. A total of 56 cassava cultivars were collected from 17 districts in Uganda covering the major agro-ecological zones of the country. One check MM96/0686 known to be drought tolerant was acquired from International Institute for Tropical Agriculture (IITA) and included in the collections. The 56 cultivars were evaluated in the field in a randomized complete block design (RCBD) with two replicates in two drought prone areas of Nakasogola and Bullisa and one location with normal rainfall regime at Makerere University Agricultural Research Institute Kabanyolo (MUARIK). Based on their performance 5 month after planting (MAP), 15 cultivars were identified for rain-out shade study at MUARIK. Cultivars contrasting in their response to drought stress were selected based on number of surviving plants after three month of constant drought stress for detailed studies. In the rain-out shade, plants were established in a RCBD with 2 replicates in large polythene bags of 80 cm deep and 60 cm diameter. All experiments received adequate water supply by adding 5L of water once every two days for 1 MAP and thereafter adjusted to two watering regimes 1) stressed treatment (5L of water once every three weeks) and 2) non-stressed treatment (5L of water twice every week). Data was collected on crop establishment, plant height, leaf area and leaf retention, number of fibrous roots, fibrous root length, number of storage roots, fresh storage root weight, stomatal conductance, xylem pressure potential, shoot weight and harvest index. These assessments were done on five plants per cultivar per treatment starting one MAP at a month interval except for root data, shoot weight and harvest index that were collected at harvest. Results from field experiments indicated significant differences among cultivars as evaluated across locations for the number of plants that survived and degree of wilting. Genotype by environment (GxE) interaction was highly significant for number of surviving plants and leaf wilting. The cultivars which had the highest number of plants surviving in Bullisa and Nakasongola until end of the experiment (5 MAP) were considered drought tolerant, while those which had no surviving plant where considered most susceptible to drought stress. In the rain-out shade, cultivars showed significant reductions in morphological traits

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Page publiée le 15 mars 2018