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Addis Ababa University (2017)

Genetic Improvement of Adapted Ethiopian Chickpea (Cicer Arietinum L.) Cultivar for Drought Tolerance Through Conventional and Marker-Assisted Backcross Breeding Methods

Jarso, Mussa

Titre : Genetic Improvement of Adapted Ethiopian Chickpea (Cicer Arietinum L.) Cultivar for Drought Tolerance Through Conventional and Marker-Assisted Backcross Breeding Methods

Auteur : Jarso, Mussa

Université de soutenance : Addis Ababa University

Grade : Doctor of Philosophy in Biology (Applied Genetics) 2017

Résumé partiel
Chickpea (Cicer arietinum L.) is the world’s third most important food legume both in area and production next to common bean (Phaseolus vulgaris L.) and field pea (Pisum sativum L.), grown mainly by small-scale farmers in the semi-arid tropics, West Asia and North Africa, and sub-Saharan regions, including Ethiopia. It an affordable cheap source of protein, one of the export commodities for cash and plays important role in soil amelioration. However, currently its average national yield is 1.91 t/ha when its potential could reach 5.5 t/ha. The low productivity is attributed to biotic and abiotic stresses, of which drought is accounting for 40-50% globally. Genetic manipulation of the crops through breeding for drought tolerance is among the ways to combat this problem. In recent years, tremendous progresses have been made in the development of novel genetic tools such as DNA molecular markers, dense genetic maps, and whole-genome transcription profiling techniques to identify genomic regions and genes underlying plant stress responses. The root traits such as root length-density have been also proposed as the main drought avoidance traits that contribute to yield under terminal drought environments in chickpea. Major genomic region containing QTL for drought related traits contributing up to 36% phenotypic variation have been identified by the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT). However, these markers have not yet been validated and been deployed into the Ethiopian chickpea breeding program. Even the already released Ethiopian chickpea cultivars for optimum environment have never been systematically evaluated for their response to drought tolerance. Ethiopia has vast area coverge under drought-prone zones and smallholder farmers are growing chichpea under this sub-optimal environment, but not specific breeding program in place for drougt tolerance. In this study, therefore, I have conducted two set of experiments : (1) introgression of drought tolerance genes from a drought tolerant donor parent (ICC 4958 obtained from ICRISAT, India) to the adapted high yielder Ethiopian chickpea cultivar, Ejere and (2) screening the improved cultivars for drought tolrance. A totao of 208 BC3F4 isogenic lines (ILs) were developed through MABC from by crossing ICC 4958 and Ejere, these ILs were tested in multi-location field trial under full-water (FW) and under water-stress (WS) conditions to select ILs tolerant to moisture stress with good agronomic traits. Data were collected on number of days to flowering (DTF), maturity (DTM and grain filling (DTGF), number of pods per plant (PPP) and seeds per pod (SPP), plant height (PHT), hundred seed weight (HSW), biomass (BMY) and grain yields (GYLD) and harvest index (HI), and subjected to statistical analyses. The result of the ANOVA indicated that there were significant differences among the ILs for the traits at each location and combined over locations under both FW and WS conditions. Significant difference was also observed beteen the locations and genotype by location interaction for almost all the traits. There relative reduction (RR) in traits‘ means due to WS for almost all the traits except DTF and SPP ranged from 0.2% for DTF to 41% for GYLD. The RR of GYLD for different genotypes ranged from 19.0 to 41% with average of 37.5%. The highest RR in GYLD was recorded for the recurrent parent (41%) followed by the ILs without markers (26.1%), while the least (19%) was for best ILs with markers for drought tolerance.

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