The excessive application of synthetic fertilizers can result in severe environmental risks, while composting green and fresh feedstocks can provide slow-release nutrients. Therefore, the aim of the current investigation was to study the effects of eight individual and combination treatments of azolla compost and NPK synthetic fertilizers (control = no fertilizer and compost; 100% NPK = full recommended dose of synthetic fertilizers as follows: 165 kg N/ha−1, 37 kg P2O5/ha−1 and 50 kg K2O/ha−1; 70% NPK; 40% NPK; 100% azolla compost (5 t DM ha−1); 50% NPK + 50% azolla compost; 70% NPK + 30% azolla compost and 40% NPK + 60% azolla compost) on rice growth, productivity and nutrient uptake in semi-arid agro-ecosystems. The results indicated that the combination of 40% NPK + 60% azolla compost or 50% NPK + 50% azolla compost resulted in the most optimal growth and the highest yield components. In addition, the application of 40% NPK + 60% azolla compost exhibited similar rice grain yields (10.76 t ha−1) as well as N, P, and K content and uptake compared with the full recommended dose of NPK fertilizer (100% NPK). This study declared that the utilization of azolla compost as an individual or combination application can reduce usage of synthetic fertilizers by up to 60% without significant reduction in the growth and grain productivity of rice.
Plant hybridization is an important breeding technique essential for producing a genotype (hybrid) with favorable traits (e.g., stress tolerance, pest resistance, high yield potential etc.) to increase agronomic, economic and commercial values. Studying of genetic dominance among the population helps to determine gene action, heritability and candidate gene selection for plant breeding program. Therefore, this investigation was aimed to evaluate gene action, heritability, genetic advance and heterosis of rice root, agronomic, and yield component traits under water deficit conditions. In this study, crossing was performed among the four different water-deficit tolerant rice genotypes to produce better hybrid (F1), segregating (F2) and back-cross (BC1 and BC2) populations. The Giza 178, WAB56-204, and Sakha104 × WAB56-104 populations showed the better physiological and agronomical performances, which provided better adaptability of the populations to water deficit condition. Additionally, the estimation of heterosis and heterobeltiosis of some quantitative traits in rice populations were also studied. The inheritance of all studied traits was influenced by additive gene actions. Dominance gene actions played a major role in controlling the genetic variance among studied traits in both crossed populations under well-watered and drought conditions. The additive × additive type of gene interactions was essential for the inheritance of root length, root/shoot ratio, 1,000-grain weight, and sterility % of two crossed populations under both conditions. On the contrary, the additive × dominance type of gene interactions was effective in the inheritance of all studied traits, except duration in Giza178 × Sakha106, and plant height in Sakha104 × WAB56-104 under water deficit condition. In both crosses, the dominance × dominance type of gene interactions was effective in the inheritance of root volume, root/shoot ratio, number of panicles/plant and 1,000-grain weight under both conditions. Moreover, dominance × dominance type of gene interaction played a major role in the inheritance of root length, number of roots/plant, plant height, panicle length, number of filled grain/panicle and grain yield/plant in Giza178 × Sakha106 under both conditions. The studied traits in both crossed populations indicated better genetic advance as they showed advanced qualitative and quantitative characters in rice populations under water deficit condition. Overall, our findings open a new avenue of future phenotypic and genotypic association studies in rice. These insights might be useful to the plant breeders and farmers for developing water deficit tolerant rice cultivars.
The present investigation aimed to study the genetic diversity among some genotypes of rice in two rice successive seasons 2014 and 2015 at the experimental farm of Sakha research station. Thus, genotypic coefficient of variance (GCV), phenotypic coefficient of variance (PCV), heritability in broad sense (h 2 ) and genetic advance (GA) were determined for all the studied traits. In addition, the nature and magnitude of genetic divergence estimated in 24 rice genotypes using Mahalanobis D 2 -statistics by considering 17 quantitative traits. High estimates of GCV and PCV were recorded for panicle excretion%, gelatinization temperature, grain elongation% and amylose content%. Heritability in broad sense was high for all characters under study. High heritability coupled with high genetic advance were recorded for number of filled grains/panicle and plant height traits. Based on genetic distance, the 24 studied genotypes were grouped into 11 clusters. Cluster III was the largest and consisted of five genotypes, followed by cluster X with four genotypes, while clusters VI and XI contained two genotypes for each one. However, clusters I, V, VII, VIII and IX included one genotypes for each one. The highest inter clusters distance (102.605) was between cluster V and XI while, the lowest one was found between cluster II and X (22.017). Principal component analysis revealed that seven quantitative traits (grain length, grain shape, plant height, amylose content%, 1000-grain weight, number of panicles/plant and panicle length) were significantly influenced the variation in these genotypes. Therefore, the present investigation determined the genetic variability in some genotypes that could be used to improve the rice breeding programme with respect studied traits.
This study was carried out to evaluate some rice varieties for their ability to immature embryo culture under salt stress condition. Therefore, three varieties were used as the donor plants for immature embryo culture in order to assessment their abilities for response under salinity stress. The recorded data on the embryo response percentage, shoot bud percentage and plantlet percentage were subjected for statistical analyses. The test of significance of the mean squares of genotypes at the three levels of NaCl except for embryo response percentage at control level, indicated the presence of significant differences among these genotypes for all in vitro traits. This finding indicated that these genotypes were varied in their response to immature embryo culture. Furthermore, levels and genotype × levels interaction mean squares were highly significant in plantlet percentage trait. This result indicated that these genotypes gave different response for different NaCl levels. At level 2000 ppm, although the greatest mean values for shoot bud percentage was recorded in Giza 177 with the mean of 69.98% which was not significantly differed than Giza 182 (64.00%). Also, the greatest mean values for plantlet percentage was recorded in Giza 182 with the mean of 58.79%. On the other hand, the lowest shoot bud percentage was observed in Giza 178 with the mean of 44.80% as well as, Giza 177 which recorded the lowest values for plantlet percentage with the mean of 34.58%. Regarding the third level of NaCl 4000 ppm, the best variety with the highest mean values for shoot bud and plantlet percentages was Giza182. This finding indicated that Giza 182 was highly tolerant to NaCl concentration at in vitro levels and may produce somaclones with NaCl tolerance genes.
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