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A study was conducted during 2008–2010, to estimate heterosis for yield component traits and protein content in bread wheat under normal and heat-stress environment by utilizing a set of 45 half diallel cross combinations, involving 10 diverse parents. Analysis of variance revealed significant differences for the two environements, whereas differences over the years were non-significant for all the traits. The pooled data over the years, exhibited highly significant differences for all the traits under both normal and heat-stress environments. The number of tillers/plant exhibited maximum degree of standard heterosis under normal and heat-stress environment (with value of 12.62% and 53.75%), respectively. In general, spike length (16.02%) and number of grains/spike (52.10%), showed higher magnitude of standard heterosis under normal environment than heat-stress environment, whereas number of tillers/plant (53.75%) and gain filling duration (43.68%) showed higher standard heterosis in heat-stress environment than the normal one. For grain yield/plant, 1000-grain weight and protein content, the number of cross combination showing standard heterosis were almost same in both the environments. The ten crosses, out of forty-five crosses, namely HD 2733/WH 542; PBW 343/UP 2425; HD 2687/PBW 343; PBW 343/UP 2382; PBW 343/HD 2285; WH 542/UP 2425; PBW 343/PBW 226; UP 2382/HUW 468; PBW 343/WH 542 and PBW 226/HD 2285 can be used to select transgressive segregants for normal as well warmer wheat growing areas. These ten combinations can be used by involving, the trait grain filling duration, tillers per plant, spike length, grains per spike, 1000-grain weight to improve grain yield for warmer areas. In all 45 cross combinations, six cross combinations were identified for better per se performance for grain yield as well as protein content under heat-stress environment. These combinations may thus be used for developing superior genotypes through fixation of heterosis are also supported by high SCA. Besides, results of present study also revealed ample scope for developing transgressive segregants involving some of these parents to develop high yielding genotypes in wheat suitable for heat stress environments.

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Abstract  

Precursor powders for yttrium aluminum garnet (YAG) were synthesized by solution combustion reactions (nitrate–glycine reaction with stoichiometric and sub-stoichiometric amount of fuel) and simple decomposition of nitrate solution. The TG-DTA, FTIR and XRD analyses of the precursors and the typical heat-treated samples were carried out to understand the processes occurring at various stages during heating to obtain phase pure YAG. Precursors from all the reactions exhibited dehydration of adsorbed moisture in the temperature range of 30 to 300°C. The precursor from nitrate–glycine reaction with stoichiometric amount of fuel (precursor- A) contained entrapped oxides of carbon (CO and CO2) and a carbonaceous contaminant. It exhibited burning away of the carbonaceous contaminant and crystallization to pure YAG accompanied by loss of oxides of carbon in the temperature ranges of 400 to 600 and 880 to 1050°C. The precursor from simple decomposition of nitrates (precursor-B) exhibited denitration cum dehydroxylation and crystallization in the temperature ranges of 300 to 600 and 850 to 1050°C. The precursor from nitrate–glycine reaction with sub-stoichiometric amount of fuel (precursor-C) contained entrapped carbon dioxide and exhibited its release during crystallization in the temperature range of 850 to 1050°C. This study established that, in case of metal nitrate–glycine combustion reactions, crystalline YAG formation occurs from an amorphous compound with entrapped oxides of carbon. In case of simple decomposition of metal nitrates, formation of crystalline YAG occurs from an amorphous oxide intermediate.

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Correlations between juvenile wheat root traits, and grain yield and yield component traits under optimal field conditions have previously been reported in some conditions. The aim of this study was to test the hypothesis that juvenile wheat root traits correlate with yield, yield components and grain mineral composition traits under a range of soil environments in India. A diverse panel of 36 Indian wheat genotypes were grown for ten days in ‘pouch and wick’ high-throughput phenotyping (HTP) system (20 replicates). Correlations between juvenile root architecture traits, including primary and lateral root length, and grain yield, yield components and grain mineral composition traits were determined, using field data from previously published experiments at six sites in India. Only a limited number of juvenile root traits correlated with grain yield (GYD), yield components, and grain mineral composition traits. A narrow root angle, potentially representing a ‘steep’ phenotype, was associated with increased GYD and harvest index (HI) averaged across sites and years. Length related root traits were not correlated with GYD or HI at most sites, however, the total length of lateral roots and lateral root number correlated with GYD at a sodic site of pH 9.5. The total length of lateral roots (TLLR) correlated with grain zinc (Zn) concentration at one site. A wider root angle, representing a shallow root system, correlated with grain iron (Fe) concentration at most sites. The total length of all roots (TLAR) and total length of primary roots (TLPR) correlated with grain S concentration at most sites. Narrow root angle in juvenile plants could be a useful proxy trait for screening germplasm for improved grain yield. Lateral root and shallow root traits could potentially be used to improve grain mineral concentrations. The use of juvenile root traits should be explored further in wheat breeding for diverse environments.

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Cereal Research Communications
Authors: S. Sareen, N. Bhusal, G. Singh, B.S. Tyagi, V. Tiwari, G.P. Singh, and A.K. Sarial

Heat stress is a matter of a great concern for the wheat crop. Heat stress usually either hastens crop development or shortens the grain filling duration, which severely reduces grain yield. Being a complex trait, understanding the genetics and gene interactions of stress tolerance are the two primary requirements for improving yield levels. Genetic analysis through generation mean analysis helps to find out the nature of gene actions involved in a concerned trait by providing an estimate of main gene effects (additive and dominance) along with their digenic interactions (additive × additive, additive × dominance, and dominance × dominance). In the present investigation, we elucidated the inheritance pattern of different yield contributing traits under heat stress using different cross combinations which could be helpful for selecting a suitable breeding strategy. Thus six generations of five crosses were sown normal (non-stress, TS) and late (heat stress, LS) in a randomized block design with three replications during two crop seasons. The model was not adequate for late sown conditions indicating the expression of epistatic genes under stress conditions. The traits i.e. Days to heading (DH), Days to anthesis (DA), Days to maturity (DM), Grain filling duration (GFD), Grain yield (GY), Thousand grain weight (TGW), Grain weight per spike (GWS) and Heat susceptibility index (HSI) under heat stress conditions were found under the control of additive gene action with dominance × dominance interaction, additive gene action with additive × dominance epistatic effect, dominance gene action with additive × additive interaction effect, additive and dominance gene action with dominance × dominance interaction effect, additive gene action with additive × dominance epistatic effect, additive gene action with additive × additive interaction effect and dominance gene action with additive × additive interaction effect, respectively.

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