Pangirayi Tongoona

Sorghum production systems and constraints, and coping strategies under drought-prone agro-ecologies of Ethiopia

Sorghum is one of the most important cereal crops worldwide after wheat, rice, maize and barley. Examining the present socio-economic conditions of sorghum-producing farmers in different agro-ecologies in Ethiopia is of importance for the design of improvement strategies. The objectives of this study were to evaluate the sorghum production system and patterns, major production constraints and related coping strategies in north-eastern Ethiopia. Twelve sorghum-growing villages in the North Welo, South Welo and Waghemra districts were surveyed. Descriptive statistics and a generalised additive model were used for data analysis. Constraints affecting the productivity of sorghum include moisture stress, insect pests, striga, farmland shortage, poor soil fertility, diseases, and low-yielding local cultivars. Among the constraints, drought at the grain-filling stage was identified as the most important production problem in the target region. The productivity of sorghum was also hindered by the use of local drought-tolerant but low-yielding landraces, because farmers had been forced to abandon high-yielding and late-maturing landrace cultivars because of the frequent occurrence of drought. To enhance sorghum productivity, farmers’ knowledge and practices, and production constraints need to be integrated from the initial stages of breeding and technology development.

Estimates of Combining Ability and Heterosis for Yield and Its Related Traits in Pearl Millet Inbred Lines under Downy Mildew Prevalent Areas of Senegal

Pearl millet is an important cereal crop for smallholder farmers’ food security in West and Central Africa. However, its production has stagnated due to several factors such as the continuous use of local populations. A set of 17 inbred lines was crossed with Sosat C 88 and Souna 3 following a line × tester mating design. The hybrids, their parents, and a check were evaluated in Bambey and Nioro research stations during the rainy season of 2017. Data on downy mildew incidence, plant height, flowering time, panicle length and diameter, productive tillers, thousand-grain weight, panicle, and grain yield were recorded. GCA and SCA mean squares were significant for most of the traits indicating that both additive and nonadditive gene effects were involved in the control of the inheritance of these traits. However, the contribution of GCA to total mean squares was higher than that of SCA for all the traits, providing that additive gene action was more important in their inheritance. The top-cross hybrid IBL155-2-1 × Sosat C 88 exhibited negative and significant SCA effects for downy mildew incidence, flowering time, and plant height. Lines IBL003-B-1, IBL091-1-1, IBL095-4-1, IBL110-B-1, and IBL 206-1-1 had positive GCA effects for grain yield and negative GCA effects for downy mildew, flowering time, and plant height. These lines can be used as parents to create synthetic varieties or hybrids.

Development, evaluation and genetic analysis of sulfosulfuron herbicide resistance in sorghum

Herbicide tolerant varieties in combination with herbicide seed treatments can be used to manage Striga. However, there are no herbicide resistant sorghum varieties in Kenya. The objectives of this study, therefore, were to develop sulfosulfuron resistance in sorghum, to determine the level of resistance in resultant herbicide tolerant mutants, and to determine the genetic inheritance of herbicide tolerance in sorghum. Five ethyl methane sulphonate (EMS)-derived sulfosulfuron tolerant mutants (designated hb6, hb8, hb12, hb56, and hb462) were identified and selfed to M4 generation. Varying rates of sulfosulfuron, either as a spray or seed coat, were applied to determine the level of tolerance of the mutant lines. Mutant lines were also crossed with the wild-type Seredo and among themselves to determine mode of inheritance. Results showed that the susceptible wild-type Seredo was killed at the lowest herbicide rates of 0.5 g ha-1 and 1 g ha-1 sulfosulfuron. Dry matter from the spraying and seed coating experiments showed mutants to be up to 170 times more resistant to sulfosulfuron than the wild-type. The LD50 values indicated a general trend of hb46 > hb12 > hb462 ~ hb56 > hb8 for level of tolerance under both spraying and seed coating experiments. The F2 progeny of mutant X wild-type crosses segregated in a 1:2:1 fashion for resistant, intermediate, and susceptible, indicating semi-dominant inheritance. Intercrosses between mutant lines did not segregate for resistance in the F2 generation indicating the same mutation could be responsible for the tolerance in all five mutants.

Genetic analysis of resistance to spot blotch disease in wheat (Triticum aestivum L.) in Zambia

ABSTRACT Understanding the genetics of resistance to spot blotch disease, caused by Bipolaris sorokiniana (Sacc.) Shoem, is important to design an appropriate breeding strategy to improve the trait. The objective of this study was to determine the gene action and mode of inheritance of resistance to spot blotch in wheat. Eight genotypes with varying resistance to the disease were crossed in a full diallel mating design. Parents and their progenies were evaluated for spot blotch resistance. Data were analyzed using Hayman’s diallel analysis. The results suggested the importance of additive gene effects in controlling the resistance to spot blotch in the materials under study. No epistasis, maternal, or reciprocal effects were detected. Resistance to spot blotch exhibited partial dominance. Therefore, exercising selection for resistance in the early segregating generation should be an effective approach because of the predominance of additive gene effects. The Wr/Vr graph showed that the parents 30SAWSN5 (P3) and Coucal (P4) possessed more dominant genes, which makes them particularly suitable for inclusion in breeding for resistance to spot blotch.