Displaying 11 - 13 of 13
In the past decade Pgt race Ug99 and its variants have been a challenge to wheat production in Kenya. Towards identifying suitable varieties, 37 lines selected from rust screening nurseries and 3 checks were tested for yield and adult plant reaction to natural stem rust epidemics across 11 diverse Kenyan environments in 2013 and 2014. Trial locations were chosen to mainly represent key wheat growing areas as well as three new sites. Evaluations based on the AMMI linear-bilinear model indicated significant (P≤0.01) genotype (G), environment (E), and GE interactions with the first three principal components (PC) explaining ~70% of the observed variation. With a contribution of over 90% to total sum of squares, environment was the predominant source of variation and the genotypic effect was approximately twofold higher than the GE effect. Based on biplot projections, clusters of lines were most closely associated with specific environments. Biplots also pointed to at least five environments, clearly those in traditional wheat growing areas that were highly correlated and associated with positive PC suggesting a similar ability to discriminate genotypes. Each non-traditional testing environment was associated with negative PC and was uncorrelated in its discriminatory ability. Combined yield and stability results achieved through classifying genotypes based on Shukla’s stability variance and Kang’s stability rating, revealed four genotypes (R1357, R1362, R1372, and R1374) as desirable candidates. The hitherto popular variety Robin, used as the ‘best check’ for yield, posted an at least 10% lower yield relative to the highest yielding genotype (R1357). Moreover, Robin which was released as a high yielding variety with adult plant resistance in 2009, was not stable in performance across environments, perhaps due its current susceptibility to a new Pgt race (TTKTT) within the race Ug99 group, that is virulent to the SrTmp-based resistance.
Turkey is an important producer of bread wheat. Fungal diseases, including the rusts, limit production. Resistant varieties are the main strategy for rust control. In this study 33 doubled haploid lines developed by anther culture and 9 standard cultivars were evaluated for seedling (YR, LR, and SR) and adult plant reactions (YR) to rusts at the Central Research Institute for Field Crops at Yenimahalle and Ikızce in 2014. For adult plant reactions the genotypes were inoculated with local Pst populations (virulent on differentials with Yr2 Yr6, Yr7, Yr8, Yr9, Yr25, Yr27, YrSd, YrSu, and YrA). Stripe rust development on each entry was scored on the modified Cobb scale when the susceptible check Little Club reached 80S disease severity in June 2014. Coefficients of infection below 20 were considered to be resistant. Seedlings were inoculated with local Pgt (avirulent on differentials with Sr24, Sr26, Sr27 and Sr31), Pt (avirulent on differentials with Lr9, Lr19, Lr24 and Lr28) and the Pst population. Seedling reactions were recorded 14 days post inoculation on either 0-4 (SR and LR) or 0-9 (YR) scales. Thirteen (33%), 2 (5%) and 9 (23%) genotypes were resistant to SR, LR and YR, respectively. Fifteen (38%) genotypes were resistant to stripe rust at the adult stage.
Bread wheat is the most important staple crop in Morocco. However, the low national production represents less than 50% of national need. Yellow (stripe) rust (Pst) and Septoria tritici blotch (STB) are the most important foliar diseases limiting bread wheat production in Morocco. The objective of this study was to identify effective sources of resistance to Pst and STB and to select candidate lines displaying high yield and resistance traits. A total of 194 bread wheat accessions provided by ICARDA and CIMMYT were evaluated during 2014 for grain yield and reaction to STB and yellow rust. The field trials were carried out at Douyet station, a key Moroccan rainfed location, and were arranged in a replicated complete block design of 3 replicates. For rust, each entry was scored using the modified Cobb scale when the susceptible check had reached 60S. The Saari Prescott scale was used to score STB reactions. The crop season was characterized by early and late drought associated with high temperatures after flowering. About 50% of accessions (99) showed high yields ranging from 1% to 55% above the highest national check, Arrehane (1.86 t/ha). About 48% (93 accessions) were highly resistant to moderately resistant to yellow rust and about 84% (164 accessions) were resistant to moderately resistant to STB. Overall, about 30% (58 lines) of accessions were high yielding with final disease severities ranging from 0-10% for yellow rust and from resistant to moderately resistant for STB. This group incorporates potentially valuable traits beneficial for our wheat breeding program. QUAIU*2/KINDE was the most promising accession with the highest grain yield (2.9 t/ha) combined with foliar disease resistance. Further multi-environment screening and field evaluations are required before recommending accessions for potential release.