The purposes of this study were to assess the effectiveness of drought tolerance indices for selection of drought tolerance in orange fl eshed sweet potato genotypes. In order to assess effi ciency of drought tolerance indices, 10 Orange Fleshed Sweet Potato genotypes (OFSP) were evaluated under Normal or full irrigation and extreme water stress environments. A total of 9 drought tolerance indices including Stress tolerance index (STI), Tolerance (TOL), Mean Productivity (MP), Geometric Mean Productivity (GMP), Stress Susceptibility Index (SSI) Yield Index (YI), Yield Stability Index (YSI), Harmonic Mean (HM), and Stress Intensity Index (SII) were calculated based on yield obtained from the two moisture regimes. Rank mean, standard deviation of ranks and rank sum were calculated to identify well-performed varieties according to all indices. These STI, GMP, YI, SII and TOL showed high and signifi cant correlation under both (Yp) and (Ys) condition. In consideration of all indices a variety MUSG014065-21-13, MUSG014065-21-14, and MUSG014019-7-50 exhibited the best mean of ranks and almost low standard deviation of rank. Among 10 genotypes, the combination of nine drought indices and deviation identifi ed MUSG014065-21-13, MUSG014065-21-14, and MUSG014019-7-50 as a three promising and drought tolerant genotypes.
This research mainly focuses on the morphological characterization of genotypes of sweet potatoes present in Ethiopia for the selection of those with optimum dual-purpose (as food and feed characteristics). From August to December 2019, alpha lattice design using two replication was performed under fi eld condition for this experiment. At 90 days and 180 Days After Planting (DAP), morphological characterization of the 40 sweet potato varieties based on 16 vine, leaf characters and storage root descriptors was performed. In order to exclude those that clearly did not meet the minimum appropriate value of the descriptors provided for selecting dual-purpose cultivars, fi eld observational yield trials were conducted using CIP descriptors. The data generated in this study, using RSTUDIO software, Agricole kit, Partially Balanced Incomplete Block (PBIB), test function, were subject to Variance Analysis (ANOVA). The substantially different mean values were compared using the Tukey test at the p< 0.05 stage. Cluster and main component analyses were both conducted using SPSS software (version 20.0). There were major differences among the 40 varieties in almost all of the leaf, vine and root characters examined except Central Leaf Lobe (CLL), Petiole Length (PL) and Storage Root Cortex Thickness (SRCT). Calculations based on root to vine ratio formulas were used to classify dual-purpose use varieties. When the 40 sweet potato genotypes were also tested for dual-purpose use, the analysis found signifi cant phenotypic diversity using the data from the calculation and analyzed data from morphological descriptors. Varieties with R/V values in the 0.2-0.3 range are recommended as dual-purpose high forage varieties, whereas those with R/V values in the 0.3-0.55 range are graded as dual-purpose high root varieties. As a result, 30 varieties can be recommended as dual-purpose based on the root/vine ratio.
Rice (Oryza sativa L.) is an annual grass with the third-highest world production after sugarcane and maize. However, due to losses in vigor caused by poor seed storage, global consumption has surpassed production. Preservation of germ plasma both in-situ and ex-situ is the key to the conservation of rich biodiversity. Seed vigor is a key element of seed quality and high vigor seeds give uniform plants stand and higher yields per area. Accelerated ageing tests enable testing the vigor of stored seeds by subjecting the seeds to a particular temperature and relative humidity over time and then performing standard germination tests. Viability of most seeds normally reduces with the storage period, storage temperature and relative humidity. There is limited information on the duration of storage for rice seeds. Accelerated ageing is considered an excellent option as a vigor test when compared to seedling emergence and index of emergence speed because of the shortest time of acquisition and efficient results. Accelerated ageing tests at 0, 24, 48 and 72 hours (45ºC and 98% RH) were carried out JKUAT post-harvest laboratory using eight rice varieties’ in four replications of 100 seeds each. Data were analyzed using GENSTAT statistical package. ANOVA and T-tests at 5% significant level. Results showed that there was significant variation in both coleorhiza and coleoptile formation among rice varieties (p<0.001), treatments (p<0.001) and interaction between rice varieties and treatment (p<0.001). The difference between all treatments was significant with 72 hours’ treatment having the highest number of days to coleorhiza and coleoptile formation. The present study has shown that prolonged duration of higher temperatures results in a reduction of seed viability. The earliest coleorhiza formation was observed on day 2 and the latest on day 6. Results from this study will guide farmers and seed processors on considerations regarding storage period and storage temperature to ensure high-quality seeds.
Purpose: The primary objective of any breeding program is to increase yields, thus superior lines based on yields are used as parents. After parents’ selection, hybrids may not perform as expected because the performance is influenced by the interactions of genotypes used, which the breeder must be well conversant with for accurate prediction of the ultimate hybrids. Methodology: This study aimed at characterizing tropical maize germplasm on plant density tolerance and comparing combining abilities for grain yield on 120 hybrids obtained by crossing 24 males with 30 female lines using North Carolina design 2 (sets option). This was done under low (53,333), medium (66,666), and high density (88,888) plants per ha in three different zones; Kiboko (marginal zone), Embu (transitional medium), and Kakamega (upper medium). General combining ability (GCA) of 54 maize inbred lines was estimated and specific combining ability (SCA) established for 120 hybrids in 6 sets of 20 each based on family decent. They were evaluated under optimal conditions in the 3 sites named above. Evaluation was done at low, medium and high plant densities under study. The hybrids were planted in a 31*8 alpha lattice design, four local commercial varieties incorporated as checks, and the experiment replicated twice. Data collected included various agronomical traits associated with tolerance to high plant density. Field book software (CIMMYT) was used to organize data and perform preliminary analysis while SAS program (Frederick, 1999) was used to compute analysis of variance (ANOVA) for North Carolina design 2 (NC2). Findings: Observation revealed increase in plant height, grain yield, ear height, anthesis silking interval, days to 50% silking but lead to reduction in leaf angle with increase in plant density from 53,333 to 66,666 and then to 88,888. Six hybrids were significantly earlier than the check hybrids CKH10717, H517, WH505 and PHB30G19 under the 3 densities. In contrast, 6 varieties were later than all the above checks for the 3 densities. Line CKL15276 had the highest GCA effects for anthesis and days to silking at the three plant densities and highest grain yield at 66,666 plant density. In contrast female line CKL15303 had the highest negative GCA effects for anthesis and days to silking at the three plant densities revealing earliness traits. Likewise, lines CML444, CML 436 and CKL151431 had highly significant GCA effects for field and grain weights. The hybrid CKH 156598 had the highest significant SCA effects for grain yield at 66,666 plant density and for field weight at the three plant densities. Unique Contribution to Theory, Practice and Policy: The study was informed by Diallel Crossing Theory and conducting systematic field trials, researchers can gain insights into the genetic effects of combining different maize inbred lines and identify potential candidates for developing maize varieties with improved high plant density tolerance in the specified region. This reveals presence of superior alleles and desirable SCA effects and thus can be utilized as parents in hybrid formation and further breeding work. The study also recommends that support should be garnered from relevant government agencies and policymakers to allocate resources for the collaborative network's activities. Advocate for policies that promote research and development in maize breeding for high plant density tolerance.
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