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Genetic variation is fundamental for plant breeding programmes. Exploiting the genetic variation of wheat for biomass allocation, yield and yield‐related traits enhances breeding for drought tolerance. The aim of this study was to evaluate genetic variation and to select best individuals among 180 M3 mutant families of wheat developed through EMS mutagenesis based on better biomass allocation to root systems, desirable agronomic traits and high yield potential under greenhouse and field environment evaluations with drought‐stressed and non‐stressed conditions. Experiments were conducted using a randomized complete block design with two replications. Days to 50% heading (DTH), days to 90% maturity (DTM), plant height (PH), number of productive tillers (PTN), shoot biomass (SB), root biomass (RB), total biomass (TB), root–shoot ratio (RSR), spike length (SL), spikelet per spike (SPS), one thousand seed weight (TSW) and grain yield (GY) were collected. Mutant families showed significant genotypic (p <.05) variation for yield and biomass traits, whereas genotype × environment × water regime interaction effects were significant (p <.05) for DTM, SB, TB, TSW and GY. Superior families designated as 52, 159, 103, 126 and 145 were selected for improved drought tolerance and high biomass allocation to roots. [ABSTRACT FROM AUTHOR]

The biomass allocation pattern of plants to shoots and roots is a key in the cycle of elements such as carbon, water and nutrients with, for instance, the greatest allocations to roots fostering the transfer of atmospheric carbon to soils through photosynthesis. Several studies have investigated the root to shoot ratio (R:S) biomass of existing crops but variation within a crop species constitutes an important information gap for selecting genotypes aiming for increasing soil carbon stocks for climate change mitigation and food security. The objectives of this study were to evaluate agronomic performance and quantify biomass production and allocation between roots and shoots, in response to different soil water levels to select promising genotypes for breeding. Field and greenhouse experiments were carried out using 100 genotypes including wheat and Triticale under drought‐stressed and non‐stressed conditions. The experiments were set‐up using a 10 × 10 alpha lattice design with two replications under water stress and non‐stress conditions. The following phenotypic traits were collected: number of days to heading (DTH), number of productive tillers per plant (NPT), plant height (PH), days to maturity (DTM), spike length (SL), kernels per spike (KPS), thousand kernel weight (TKW), root biomass (RB), shoot biomass (SB), root to shoot ratio (R:S) and grain yield (GY). There was significant (p < 0.05) variation for grain yield and biomass production because of genotypic variation. The highest grain yield of 247.3 g/m2 was recorded in the genotype LM52 and the least was in genotype Sossognon with 30 g/m2. Shoot biomass ranged from 830 g/m2 (genotype Arenza) to 437 g/m2 (LM57), whilst root biomass ranged between 603 g/m2 for Triticale and 140 g/m2 for LM15 across testing sites and water regimes. Triticale also recorded the highest R:S of 1.2, whilst the least was 0.30 for wheat genotype LM18. Overall, drought stress reduced total biomass production by 35% and R:S by 14%. Genotypic variation existed for all measured traits useful for improving drought tolerance, whilst the calculated R:S values can improve accuracy in estimating C sequestration potential of wheat. Wheat genotypes LM26, LM47, BW140, LM70, LM48, BW152, LM75, BW162, LM71 and BW141 were selected for further development based on their high total biomass production, grain yield potential and genetic diversity under drought stress. [ABSTRACT FROM AUTHOR]

Rice (Oryza species) is a commercial crop worldwide. Across Africa, the potential yield and quality of rice is diminished by a lack of high performance, locally adapted varieties, and the impact of rice yellow mottle virus (RYMV). The objective of this study was to assess the performance of a diverse collection of rice germplasm for RYMV resistance and agronomic traits, and to select promising lines for breeding for Tanzanian conditions. Fifty-four rice genotypes were field evaluated in two important rice production sites (Ifakara and Mkindo) in Tanzania, which are recognized as RYMV hotspots, using a 6 × 9 alpha lattice design with two replications. There was significant (p < 0.05) genotypic variation for agronomic traits and RYMV susceptibility in the tested germplasm. Seven genotypes with moderate to high RYMV resistance were identified, including Salama M-57, SSD1, IRAT 256, Salama M-55, Mwangaza, Lunyuki, and Salama M-19, which were identified as new sources of resistance genes. Positive and significant correlations were detected between grain yield and number of panicles per plant (NPP), panicle length (PL), number of grains per panicle (NGP), percentage-filled grains (PFG), and thousand-grain weight (TGW), which are useful traits for simultaneous selection for rice yield improvement. A principal component analysis allocated five principal components, accounting for 79.88% of the total variation present in the assessed germplasm collection. Traits that contributed most to variability included NPP, number of tillers/plant (NT), PL, grain yield (GY), and days to 50% flowering (DFL). The genotypes Rangimbili, Gigante, and SARO possess complementary agronomic traits and RYMV resistance, and can be recommended for further evaluation, genetic analysis, and breeding. [ABSTRACT FROM AUTHOR]