No abstract

Phosphorus is one of the essential macronutrient element not only for rice but also for other plants, it is important for plant metabolism and enzymatic activity during the periods of growth and grain filling. Rice growth, yield and its attributes strongly influenced by phosphorus nutrition. This investigation was conducted to study the performance of different rice genotypes i.e. Sakha105 and Sakha106 (japonica), Giza178 (indica/japonica) and Giza182 (indica) under four phosphorus levels namely 0, 18, 36 and 54 P2O5 ha -1 . This study was carried out at Experimental Farm of Rice Research and Training Center during both 2010 and 2011 growing seasons. At harvest, plant height, number of panicles m -2 , panicle weight, panicle length, number of filled grains panicle -1 , number of unfilled grains panicle -1 , 1000 grain weight, grain and straw yield were determined. After harvest, N and P content of rice grain and straw were measured as well as hulling, milling, head rice and amylose percentages were assessed. The obtained results revealed that the rice genotypes were significantly differed in their response to phosphorus application according to genetic background. indica or indica/japonica genotypes responded up to 54 kg P2O5 ha -1 without significant differences with 36 kg P2O5 ha -1 more than japonica type which responded up to 18 kg P2O5 ha -1 . Application of phosphorus fertilizer up to 36 kg P2O5 ha -1 improved rice growth traits i.e. plant height and panicle length as well as grain yield and its attributes. Combination of Giza178 with 36 kg P2O5 ha -1 produced the highest grain yield followed by Giza182 with the same levels of phosphorus. Application of phosphorus fertilizer up to 18 kg P2O5 ha -1 gave the maximum grain yield of Sakh105 and Sakha106. Concerning grain quality traits had positive significant effect with increasing phosphorus levels.

No abstract

Water limit is one of the major a biotic stress limiting plant production in worldwide. The research work of the present study was carried out at the Experimental Farm of the Rice Research and Training Center (RRTC), Sakha, Kafr El-Sheikh, Egypt, during the three successive rice seasons 2010, 2011 and 2012, to study the genetic effects on some of root system related to water limit and yield and its component traits under water limit condition. Six rice genotypes i.e. Giza 177, Sakha 101, GZ 7456-13-6-5-3, Sakha 105 (sensitive to drought stress), IRAT 112 and IRAT 170 (tolerant to drought stress), were chosen for this study. The results of this investigation revealed that both general and specific combining ability variances were found to be highly significant for all studied traits except root thickness, root dry weight and 1000-grain weight, indicating the importance of both additive and non-additive genetic variance in determining the inheritance of these studied traits i.e. root length, root volume, plant height, No. of days to heading, , No. of panicles/plant, No. of filled grains/panicle and grain yield/plant. With the exception of No. of panicles/plant and grain yield/plant, the GCA/SCA variances were found to be greater than unity for all the studied traits except for No. of panicles/plant and grain yield/plant, suggesting greater importance of additive genetic variance in the inheritance of these traits. Therefore, it could be concluded that selection procedures based on the accumulation of additive effect would be successful in improving of these traits. The results showed that IRAT 112 and IRAT 170 were highly significant and positive general combining ability effects for maximum root length, root thickness, root volume, root dry weight and yield and its component traits under water limit condition indicating that these genotypes could be considered as good combiners for the improvement of these traits i.e. Sakha 105 x IRAT 112 for maximum root length, Sakha 101 x IRAT 112 for root thickness, Giza 177 x IRAT 112 for root volume, IRAT 112x IRAT 170 for root dry weight and Sakha 101 x IRAT 170,Sakha 101 x IRAT 112 for grain yield/plant under water limit condition. Frequency distribution of phenotypes for each trait in F2 and their parents, all studied traits approximately fit normal distribution, F2 plants having phenotypic values greater than the higher parent and less than the lower parent (Transgressive Segregates) were observed for all studied traits.

No abstract

Egypt has the world's highest rice productivity from unit area, yet yield was constrained by biotic stresses being targeted by breeders. This work was carried out at the experimental Farm of Rice Research and Training Center, Sakha Kafer El-Sheik, Egypt, during 2011 and 2012 rice growing seasons. Five parents and their 10 hybrids were used to study gene action, combining ability and heterosis for certain agronomic traits and biotic stresses. Giza177 and M101 rice varieties were resistant to rice blast, while GZ6214 and M202 were resistant to stem borer, and both M201 and M202 to white tip nematode. General combining ability (GCA) and specific combining ability (SCA) were highly significant for all studied traits. M202 gave highly significant and negative estimates of GCA effects desired for plant height, vegetative stage, reproductive stage and days to heading. Significant and highly significant negative estimates of SCA effects were found for plant height, vegetative stage and days to heading. The best crosses for yield and its components were Giza177 x GZ6214, Giza177 x M201, Giza177 x M202, GZ6214 x M201 and GZ6214 x M202. Regarding stem borer infestation, the crosses M101 x M201, M101 x M202 and Giza177 x GZ6214 gave highly significant and desirable negative estimates of SCA. For blast reaction, stem borer infestation and white tip nematode two hybrid combinations, Giza177 x GZ6214 and GZ6214 x M201 recorded highly significant negative desirable heterosis and showed highly significant negative SCA effects. M202 was a good resource for resistance to white tip nematode, with all crosses with this cultivar having low levels of infection. Principal component analysis as one of Multivariate analysis components was used to study the genetic dissimilarity and relative importance of agronomic and biotic traits as a source of variation among the five parents and their hybrids. The first three principal components were significant and accounted about 80.4 % of the total variance of all characters. The 15 rice genotypes were grouped into three major clusters based on relative dissimilarity among them with significant differences among these groups for most characters, the progeny produced from crossing between Egyptian and US parents which are distantly related showed divergent distance and gave values surpassed their parents in most characters. The results of all multivariate analysis showed that US parent M202 is the most divergent parent. Grain yield plant -1 , filled grains panicle -1 and blast reaction were the most important source of variation among all genotypes with largest coefficients on the first PC axis. However, the second axis PC2 deals with the most earliness characters; vegetative stage and days to heading. On the other side, PC3 was dominated by white tip nematode. Finally, crossing among more genetic divergent Egyptian rice varieties Giza 177, GZ6214 and US parents created new suitable combinations in breeding program. Rice breeder can maximize genetic diversity among new cultivars, meanwhile at the s...

Genetic diversity underlies the improvement of crops by plant breeding. In Egypt, pedigree analyses indicate that the rice varieties currently under cultivation are closely related in there genetic background. Effective breeding programs, based on the information about of the genetic diversity of cultivars, are needed to broaden the genetic bases of local rice germplasm in the country. The present study has been conducted to evaluate the pattern, type and extent of genetic variability and relatedness among some rice varieties and new promising lines of Egypt based on important agronomic traits and some biotic stresses of some common diseases using simple-sequence-repeat (SSR) markers. In this study, we used a set of twelve SSR markers to assess the genetic diversity of 22 Egyptian rice cultivars and new promising lines, which released by the National Rice Breeding Program between years of 1975 and 2010. The 12 microsatellite markers used in this study produced a total of 73 alleles. The number of alleles per marker ranged from 3 (RM282) to 9 (RM488), with an average of 6.08. The polymorphism information content (PIC) values were high for all microsatellites with average of 0.588 and ranged from a low of 0.345 for RM249 to a high of 0.716 for RM488 and RM144. UPGMA-cluster-analysis based on genetic distance coefficients clearly separated all the genotypes, and showed that the Egyptian rice varieties are closely related. Although the genetic diversity was low, SSRs proved to be an efficient tool in assessing the genetic diversity of rice genotypes. Implications of the low genetic diversity detected and relative relationship among Egyptian varieties are discussed. Varieties like Giza177, Sakha 102 and Sakha 103 are still resistant for most of the biotic stresses and become good sources for biotic stress resistance relating to different disease blast in the national breeding program.

The experiment was carried out in strip plot design with three replications to evaluate 14rice genotypes under normal and water deficit in the field and biotechnology lab of Rice research and Training Center at Sakha Agricultural Research Station, Sakha, Kafr EL-Sheikh Egypt, during2021 and 2022summer seasons. Results revealed a wide variation among rice genotypes and their parents for agronomical characteristics and SSR markers. Data showed that days to maturity, plant height, Flag leaf area, number of panicle-1 , Panicle length, number of filled and unfilled grains panicles-1 as well as grain yield t ha-1 were significantly affected by irrigation treatments. Grain yield was affected significantly according to the genotypes and irrigation treatments. The combination between Egyptian Yasmin with normal irrigation produced the highest values of grain yield with the lowest percentage(14.58%) of yield reduction compared to its production under water deficit conditions. While, the lowest values of grain yield were obtained with Nerica7 (V2) under water shortage conditions with the highest percentage(33.63%) of yield reduction compared to its production under normal irrigation. Fifty SSR markers were used for estimating the genetic variation among the 14rice genotypes. Rice genotypes were divided into two main groups based on the polymorphism revealed by the SSR markers. The first group has the aromatic genotype, Egyptian yasmine and the promising newly developed genotype No.2. While, the second main group has the other tested rice genotypes, NERICA7 and the other genotypes. The data indicated that phenotypic variance was generally superior than genotypic variance for all studied traits.