The present study was conducted to determine the reactions of 88 bread wheat pure lines selected from landraces collected in Central Anatolian Region of Turkey against leaf rust (Puccinia triticina) under field conditions in 7 locations. GGE biplot analysis was used to determine the reactions of landrace genotypes against the disease. The GGE biplot explained 73.89% of total variation. Among the experimental locations, 6 (except for E3) were placed close to each other over the biplot graph, indicating two apparent mega-environments. The GGE biplot visually displayed the resistance and stability of the pure lines to leaf rust. The landrace genotypes L18, L19, L45, and L2 were identified as the most resistant/stable genotypes in all environments and L31 and L56 were the most susceptible/stable genotypes.
Authors:C. Maucieri, C. Caruso, S. Bona, M. Borin, A. C. Barbera, and V. Cavallaro
In many world regions, osmotic and salt stresses are becoming the primary environmental conditions limiting successful establishment of crops. The old durum wheat landraces may provide a source of genes useful to enhance crop resilience to the abiotic stresses of dryland areas or foreseen as a result of climate change. With this in mind, in order to determine the effects of salt and osmotic stresses on durum wheat germination, an old Sicilian durum wheat landrace “Timilia” and a relatively recent cultivar “Mongibello” were investigated at various iso-osmotic solutions of NaCl and mannitol at osmotic potentials of: 0 – control, –0.125, –0.250, –0.500 and –0.750 MPa.
Under stress conditions, different germination and early growth behavior was observed in the two durum wheat genotypes. Timilia presented almost stable germination even at the highest osmotic stresses (96.7% and 88.3% seed germination at 0 and –0.750 MPa, respectively) showing a higher capacity of seed imbibition than Mongibello. The latter thus showed a higher sensitivity than the old landrace to the studied stresses. The variability ascertained in the response to salinity stress indicate that Timilia could be a source of interesting genes for breeding programs.
The multiplication and characterisation of genetic stocks originating under very different ecological conditions is a problem constantly encountered in gene bank research. However, the major components of the original environment, such as temperature, light and humidity, can be reproduced under artificial conditions in the phytotron. The gradient, or inhomogeneous, chamber available in the phytotron of the Agricultural Research Institute of the Hungarian Academy of Sciences, Martonvásár, makes it possible to elaborate plant growth programmes optimised for the various developmental phases of each population in a single step. In this chamber gradients of two extremely important environmental factors, temperature and illumination, can be simultaneously programmed, thus allowing the optimum light × heat combinations to be identified. However, the use of complete inhomogeneity (light × heat) makes it extremely difficult to evaluate the experimental results, since biometric methods based on traditional statistics are unable to handle this situation. It is thus essential to find a method suitable for the comparative analysis of continual variables (Okada et al., 2000). The present paper reports on the first phase in the development of a plant growth programme for emmer, based on investigations made on two gene bank accessions of winter Triticum turgidum ssp. dicoccon (Schrank) Thell. (MvGB 301 and MvGB 304). In the gradient chamber study the accumulation of dry biomass in three-week-old plants was investigated as a function of temperature and light intensity. The results suggest that a temperature of 10-12°C combined with low or moderate light intensity is optimum for the germination and initial development (0-4 weeks) of emmer. These conditions also induced good tillering, which is extremely important, especially for gene bank accessions where the possibility of seed multiplication and field cultivation is limited.
Authors:S. Farooq, S. Gilani, R. Arshad, M. Afzaal, M. Akram, N. Iqbal, and F. Azam
Rice germplasm comprising wild species, low land and upland genotypes and 7 progenies of their inter-specific hybrids were tested under water levels of field capacity (100% moisture) and 75, 50 and 25% of field capacity. The objectives were to identify i) most water stress tolerant genotype, ii) characters associated with that genotype and iii) its ability to contribute water deficiency tolerance to lowland rice varieties. Experiment was conducted in potted soil with Randomized Complete Block two-factor factorial design and three replications. Different growth parameters were studied at tillering stage. Within an entry, reduction due to water level was significant in all the parameters. The interaction between various water levels and rice entries was also highly significant. We observed six parameters (shoot length, root length, shoot and root dry weight, number of tillers and leaf area) that were comparatively less affected in some of the progenies such as WAB-56-50 (shoot dry weight and root length), WAB-56-104 (root dry weight and tillers), WAB-272-H3 (leaf area) and WAB-272-H2 (shoot length) when tested under water level which is only 25% of the field capacity. This indicated that using these progenies as donor; water deficiency tolerance in lowland rice cultivars can be improved.
Authors:O. A. Ariyo, A. G. O. Dixon, and G. I. Atiri
Twenty-five cassava genotypes were exposed to natural infection by African cassava mosaic disease (ACMD) in plots at the International Institute of Tropical Agriculture (IITA), Ibadan (forest-savanna transition zone), Nigeria. The effect of removing the shoot tips (detopping) of cassava plants on disease incidence and symptom severity was assessed fortnightly for 14 weeks, starting 8 weeks after planting (WAP). There were highly significant differences (P < 0.01) in disease incidence (DI) and symptom severity (ISS) among clones throughout the period of observation, indicating different levels of resistance to infection. Detopping produced a significant effect on disease incidence in clones 91/02322, 91/02324, 91/02327 and 92/0427. It also had a significant effect on symptom severity of clones 92/0342, M94/0177 and TMS 4(2) 1425. The interaction between the treatment (TRT) and clone was highly significant (P < 0.01) for DI and ISS throughout the period of observation, an indication that there are differential responses of the clones to detopping. Cassava genotypes M94/0121 and Isu were observed to be highly resistant and highly susceptible respectively to the disease, while plants of genotypes 82/00058 and 91/02322 showed moderate susceptibility. None of the genotypes was immune to the disease. There was also a highly significant and positive correlation between DI and ISS in both detopped and undetopped plants. A conclusion from this study is that removal of shoot tips from moderately resistant cassava clones for consumption should be discouraged as it increases the severity of ACMD infection in the regenerating shoots of these clones.
Authors:H. Kang, H. Zhang, Y. Wang, Y. Jiang, H. Yuan, and Y. Zhou
Fu, T.H., Ren, Z.L., Lin, W.J. 1992. Study on
genes in natural population of Sichuan common wheat landraces. In: Ren, Z.L., Peng, J.H. (eds), Exploration of Crop Breeding. Sichuan Science and Technology Press, Chengdu, pp. 177
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