and 2016 seasons to detect the effect of water regime and weed control treatments on weeds, growth and yields of hybrid rice (Sk2034H). Water regime (4-days on and 6-days off, saturation and continuous flooding) were allocated in main plots while weed control treatments were Thiobencarb 50% EC at three rates; 1.8 , 2.4 and 3.6 kg ai ha-1 in addition to weedy check were distributed in sub-plots. Weed species and hybrid rice yields were greatly influenced by water regime and weed control treatments. Echinochloa crus-galli and total weeds dry weights were significantly reduced under flooded or saturated plots than under shortage of water (4-days on + 6-days off). In different response, Cyperus difformis considerably reduced under the water shortage than saturated or flooded plots. The highest values of panicles per hill and grain yield of hybrid rice were recorded under flooding conditions followed by saturated soil. The application of Thiobencarb 50% EC at the high rate (3.6 kg ai h-1) resulted in the best weed control and highest grain yield followed by the application of 2.4 kg ai ha-1 from the same compound, while weedy check plots recorded the highest in weed presence and the lowest in rice yields. For the interaction, the lowest dry weights of Echinochloa crus-galli, Cyperus difformis and total weeds, also the largest weed control efficiency (%), number of panicles per hill and the highest rice grain yields were obtained under flooded plots treated with Thiobencarb at both rates of 2.4 and 3.6 kg ai ha-1. This trend was true under all treatments even the weedy check plots except for Cyperus difformis which increased significantly by soil saturation or flooding in untreated plots.

Two field experiments were carried out at the experimental farm of Sakha Research Station, Kafrelsheikh, Egypt during 2016 and 2017 summer seasons to select the best weed control treatments for two Egyptian hybrid rice varieties under broadcasting method. Two rice hybrids {Hybrid-1 (Sk2034H) and Hybrid-2 (Sk2151H)}. Six chemical weed control treatments included; Penoxsulam 2.5% at two rates (0.018 and 0.024 kg ai ha -1 ) + Azimsulfuron 50% at rate of 0.014 kg ai ha -1 , Bispyribacsodium 2% at two rates (0.029 and 0.038 kg ai ha -1 ) + Azimsulfuron 50% at rate of 0.014 kg ai ha -1 , and Fenoxaprop-ethyl 7.5% at two rates (0.045 and 0.063 kg ai ha -1 ) + Azimsulfuron 50% at rate of 0.014 kg ai ha -1 , were applied as compared to weedy check plots (control). A split plot design with four replications was used where, rice hybrids were allocated in the main plots while weed control treatments were applied in sub-plots. The results showed that, H 1 rice variety (Sk2034H) recorded the lowest dry weight of grassy weeds, C. difformis and total weeds, and scored the highest rice dry weight, number of panicles per square meter, filled grains per panicle and rice grain yield, while H 2 was the best in 1000-grain weight and panicle weight during the two seasons. Bispyribac-sodium 2% at recommended dose (0.038 kg ai ha -1 ) or Fenoxaprop-ethyl 7.5% at reduced rate mixed with Azimsulfuron 50% at rate of 0.014 kg ai ha -1 gave the lowest weed biomass and the best rice growth values in addition to yield and yield components in 2016 and 2017 seasons. The obtained results revealed that the best weed control, rice dry matter, yield and yield components were achieved by applying Bispyribac-sodium 2% at recommended dose (0.038 kg ai ha -1 ) or Fenoxapropethyl 7.5% at reduced rate mixed with Azimsulfuron 50% at recommended dose (0.014 kg ai ha -1 ) with cultivation of Egyptian hybrid-1 (Sk2034H) except for panicle weight and 1000-grain weight of rice which obtained by H 2 rice hybrid treated with the same mixtures of herbicides during the two seasons of study.

A field study was carried out at the Experimental Farm of Rice Research Dept., Sakha Agricultural Research Station, ARC, Egypt through 2016 and 2017 seasons to study allelopathic activity of selected rice genotypes to integrate with herbicides use under field conditions and to assess genetic diversity using SSR markers linked to allelopathic activity. Six rice entries were used in field study included MBG-41, HHZ-12-SAL8-Y1-Y2, FFZ-1, Weed tolerant-1, Sakha 106 and non-allelopathic check Sakha 101. Pre-mixed herbicide Top Shot 6% OD (penoxsulam 1% + cyhalofop-butyl 5%) was applied at recommended and half doses as compared with untreated (weedy check) plots. Sakha 106 and Weed tolerant-1 performed the best in weed control, yield and yield attributes in both seasons, while Sakha 101 recorded the highest dry weights of studied weeds and lowest values of rice dry weight as well as grain yield and its attributes during both seasons. The recommended dose of Top Shot 6% OD was the best as compared to either half dose or untreated plots. Sakha 106 as allelopathic rice cultivar had same behavior under both recommended and half doses of herbicide in controlling grasses, sedges, broad leaves and total weeds, and produced the highest rice dry weight, grain yield and its attributes in both seasons. For molecular study, Rikuto Norin22 was used as identified allelopathic genotype. Four previously identified SSR markers linked to allelopathic activity in rice were used to study genetic diversity among studied rice genotypes. A total number of 13 alleles were generated and number of alleles per locus varied from 2 to 5. Heterozygosity (H e) values ranged from 0.490 to 0.735 with an average of 0.607. Polymorphic Information content (PIC) values ranged from 0.37 to 0.685. Genotypes were clustered based on genetic background and allelopathic activity. The results demonstrated the power of SSR markers in detecting molecular diversity as they separated indica from japonica genotypes. SSR 227 was able to detect Weed tolerant-1 and Rikuto Norin22 and Sakha106. This marker could be a potential candidate for MAS-based allelopathic selection.

A field study was conducted during 2015 and 2016 seasons in Sakha experimental farm, Kafrelsheikh, Egypt to study the effect of sowing dates and weed control on growth and yield of broadcasted-seeded rice (Giza 179 cv). Three sowing dates viz., May 20 th , May 30 th and June 10 th in individual experiments. Seven weed control treatments i.e., weedy check, Penoxsulam (2.5% OD) at 24 g.ai ha -1 , Bispyribac-sodium (2% SL) at 38 g.ai ha -1 , Fenoxaprop-p-ethyl (7.5% EW) at 63 g.ai ha -1 , Penoxsulam (2.5% OD) plus Azimsulfuron (50% WG) at 14 g.ai ha -1 , Bispyribac-sodium plus Azimsulfuron (50% WG) and Fenoxaprop-pethyl (7.5% EW) plus Azimsulfuron (50% WG), companied analysis was done for the three sowing dates. The results showed that rice sowing on May 20 th reduced the highest number of tillers m -2 and total weeds dry weight while increased dry weight for rice, number of panicles m -2 , panicle weight, number of filled grains panicle -1 and rice grain yield as compared to rice sowing on May 30 th and June 10 th . The application of Penoxsulam (2.5% OD) or Bispyribac-sodium (2% SL) mixed with Azimsulfuron (50 %WG) at recommended doses recorded the lowest number of weed tillers m -2 , total weeds dry weight and highest rice yields as compared to weedy check. The interaction between sowing date and weed control treatment was significant for number of tillers m -2 , total weeds dry weight, rice yield and its components. Sowing date May 20 th with The mixture of Penoxsulam (2.5% OD) or Bispyribac-sodium (2% SL) mixed with Azimsulfuron (50% WG) recorded the lowest total weed characters, highest dry weight, number of panicles m -2 panicle weight, number of filled grain panicle -1 and yield of broadcasted-seeded rice under this study conditions. ai= active ingredient ha. = Hectar

Two field experiments were carried out at the farm of Sakha Agric., Res., Station, Kafrelsheikh, Egypt, through 2018& 2019 seasons to study the role of allelopathy and transplanting space in reducing herbicide use under transplanted rice (Sakha 106 cv). Rice seedlings were manually transplanted under three spaces included 15x20cm, 20x20cm and 25x20cm. Four weed control treatments included pre-mixed herbicide Pindar 13.6% OD (triclopyr-butotyl 12 % + penoxsulam 1.6%) was used at recommended and ½ recommended dose compared with hand weeding and weedy check. Narrow transplanting space recorded the best in controlling E. crus-galli, C. difformis, Eclipta sp., as well as total weeds. Besides, achieved the highest dry weight of rice; panicles m -2 ; panicle weight and grain yield during both seasons. The highest dry weights of tested weeds and lowest values of rice characteristics were recorded under wider transplanting space throughout the tested seasons. Recommended rate of herbicide exceeded other weed control treatments in weeds control and produced highest dry matter and yield of Sakha 106 cv through both seasons. Recommended or half herbicide rate were the best in controlling weeds; dry weight of rice; grain yield and its attributes under 15 x 20 cm space without significant differences in the two seasons. It could be concluded that allelopathic rice cultivar Sakha 106 can be helpful in reducing herbicide use up to half dose when rice plants were transplanted on 15 x 20 cm.