Seed treatment for improving quality of hybrid seeds of rice

Seeds of 15 hybrid rice varieties viz. Durber, Agomoni, Meghna, Hybrid super, Moyna, Tia, Gold, Aloron, Jagoron, Suborno, Safollo, Hira-1, Hira-2, Hira-4 and Hira-6 were collected from five different seed producing companies of Bangladesh. BAU-Biofungicide (3%), extracts of Garlic (1:1), Allamanda leaf (1:1) Bavistin (0.3%), Thiovit ( 0.3%) and Provax (0.3%) were used for treating seeds to improve quality of hybrid seeds of rice. The moisture content of seed samples ranged 12.20% to 14.37%, where highest moisture content was found in variety Meghna and lowest in variety Moyna. 1000-seed weight of seed samples ranged from 20.00 to 26.00g, where highest weight was recorded in Hira-4 and lowest was recorded both in Aloron and Hira-1. Seed health test revealed 11 different seed borne fungi viz. Bipolaris oryzae (0.0 to 25.5%), Fusarium moniliforme (0.00 to 3.0%), Fusarium oxysporum (0.0 to 18.0%), Aspergillus flavus (0.00 to 11.0%), Aspergillus niger (0.00 to 5.0%), Aspergillus candidus (0.00 to 15.0%), Penicillium spp. (0.0 to 7.0%) , Alternaria padwickii (0.0 to 1%), Alternaria tenuis (0.0 to 11.0%), Curvularia lunata (0.0 to 40.0%) and Nigrospora oryzae (0.0 to 4.0%) . Germination test resulted normal seedlings from 26.00 to 97.00%, where highest was recorded in variety Jagoron that treated with BAU-Biofungicide resulting highest increase in number of normal seedlings by 239.28% over untreated control. BAU-Biofungicide significantly decreased (upto 90.00%) formation of abnormal seedlings over untreated control. Moreover, BAU-Biofungicide increased up to 713.78% Vigor index over untreated control.


Introduction
Rice (Oryza sativa L.) is the most important cereal crop and one of the major sources of calories for a large percentage of the world population, particularly in Asia (Datta, 1981).It alone provides 76% of the total calories and 66% of the protein in a typical Bangladeshi diet of the people (Bhuiyan et al, 2002).It (Oryza sativa) is the staple food of Bangladeshi people and it constituted about 90% of the total food grain production.It covers about 75% of the total cultivable land in Bangladesh (Ahmed et al. 2013).Rice covers about 11533.60 ha land in Bangladesh and the production of rice is 33890 tons where 644.94 ha land is covered by hybrid rice and the production of hybrid rice is 3022 tons (BBS, 2012).The average world yield of rice is 3.84 tons/ha (Ahmed et al. 2013).But the average yield of rice in Bangladesh is only 2.98 tons/ha.So the average per hectare production of rice in Bangladesh is extremely low as compared to other rice growing countries of the world.Rice covers about 11533.60 ha total cropped area in Bangladesh where 1138.46 ha by Aus, 5582.60 ha by Aman and 4812.15ha by Boro season (BBS, 2012).The production of rice in Aus, Aman and Boro season is 2332, 12798 and 18759 tons, respectively (BBS, 2012).Seed is one of the most important technologies for crop production.For successful crop production there is no other alternative but to use good seed.This is true for all crops including rice.It has been shown experimentally that only by using good quality healthy seed, rice yield could be increased by 10-15% (Mia et al., 2004).In the Philippines, yield increase due to use of good quality seed was 7-25% (Diaz et al., 2001).The yield of conventional rice varieties is comparatively low and it seems impossible to change this yield with reachable resources under the prevailing situation.At this situation hybrid rice varieties may be a break through which could help to achieve the goal of self-sufficiency of food.Therefore, cultivation of hybrid varieties of rice is the utmost priority for increasing yield.In Bangladesh, more than 78 hybrid rice varieties are grown in the field and about 75% of seed demand is met from import mostly from China (Ora et al. 2011).Major constraints in hybrid rice adoption were identified; these were high cost of seed, requirement of more crop care and management time, high pest and disease attack, low profits and lack of suitability for home consumption.Seed borne diseases are very important from the following points of view; (i) introduction of new pathogens (ii) quantitative and qualitative crop losses and (iii) permanent contamination of soil (Ora et al. 2011).Among reasons of low yield of rice, diseases pose a major threat to its production (Ou, 1985;Groth et al. 1991;Webster, 1992).Most of the diseases of rice are seed borne.In Bangladesh, approximately 2.5 million tons of rice worth more than Tk.12000 Millions lost annually due to diseases caused by seed borne pathogens (Fakir et al. 2003).A total of 153 seed borne pathogens were detected from rice of which 18% are of quarantine importance, 65% are native and 17% are storage pathogens (IRRI, 1987).Evidently, there is a need to increase the yield of the crop by controlling seed-borne fungal pathogens.Among the control practices used, seed treatment is one of the effective technique to eliminate seed borne inocula which prove the 'arsenal' of Plant Pathology is now equipped with most sophisticated ammunitions to wage war on the unscrupulous pathogens, which are many and deceitful.Treatments of seed should be done as a routine practice as it is a cheap insurance against possible disasters at a later stage (Bilgrami and Dube 1976).The disease can be controlled by the application of fungicides.Thrimurty (1986) and Karmakar (1992) have reported the efficacy of carbendazim (Bavistin) in reducing disease severity.Existing practice of chemical control is too costly, particularly for poor farmers in the country.Botanicals in controlling pathogens against certain fungal pathogens have been reported by Hossain et al., (1997), Suratuzzaman et al., (1994), Fakir andKhan (1992), Miah, (1990) and Assdi and Behroozin (1987).BAU-Biofungicide resulted significant higher germination and plant stand, less disease incidence and higher yield of different crops (Hossain, 2011), Chowdhuryet al. (2013), Hossain and Hossain (2012).The present study was conducted to assess quality of hybrid seeds of rice and their improvement by seed treatment.

Study area
The experiment pertaining to the present investigation was carried out in the Seed Pathology Centre (SPC), Bangladesh Agricultural University (BAU), Mymensingh; Eco-friendly Plant Disease Management Laboratory and MS Laboratory of the Department of Plant Pathology, BAU, Mymensingh, Bangladesh.

Determination of moisture content and 1000-seed weight
Moisture content of the collected seed samples were determined with the help of electronic moisture meter before preserving the seed in seed storage at Eco-friendly Plant Disease Management Laboratory, Department of Plant Pathology, BAU, Mymensingh and the moisture content of seed was expressed in percentage.For each seed sample 1000 seed-weight was taken with the help of electronic balance.The seed weight was taken after counting 1000-seed at Eco-friendly Plant Disease Management Laboratory and expressed in percentage.

Detection of seed borne fungi by blotter method
To detect the seed borne pathogens associated with the seeds in seed samples the Blotter method was used by following ISTA rules for seed testing (ISTA, 1996).In this method, three layers of blotting paper (Whatman filter no. 1) were soaked in sterilized water and placed at the bottom of 9 cm dia plastic petridish and thereafter 25 seeds were plated.Eight replicates (petridishes) were used for each sample where 200 seeds were needed.The seeds in the petridishes were incubated in the incubation chamber at 20 ± 2 °C under alternating cycles of 12 hours near ultraviolet (NUV) light and darkness for 7 days.Time to time watering was done to keep the blotting paper moist.

Seed treatment and vigor test
Seed treatment for improving quality of seeds studied by treating seeds with BAU-Biofungicide (3%), a Trichoderma based preparation along with extracts of two botanicals viz Garlic (Allium sativum) (1:1) and Allamanda leaf (Allamanda cathartica) (1:1) and three selected chemicals namely Bavistin (0.3%), Thiovit (0.3%) and Provax (0.3%) (Hossain, 2011).The seeds were treated by soaking in solutions for 1 hr of each treatment separately, except in control.In case of control, seeds were soaked in normal water.After 1 hour the fungicidal solutions were drained out and the moistened seeds were kept in the blotter paper to remove excess moisture from the seed surface.Then the seeds were ready for sowing on blotter (blotter method) and tray experiment.Seeds were set for each treatment according to ISTA rules for testing germination of seeds (ISTA 2001).Germination was recorded twice at 7 and 14 days after sowing.Normal seedlings, abnormal seedlings, non-germinated seed and diseased seedlings were counted and expressed in percentage.Vigor test was done following (ISTA, 2001).After 14 days shoot and root length were measured by using measuring scale.15 seedlings (30 seedlings of each treatment) were randomly selected for measurement of shoot or root length.The seedling vigor was determined following the formula of Baki and Anderson (1972): Vigor index= (mean of root length+ mean of shoot length) X % of seed germination.