Physiological Maturity and Effect of Seed Priming on Germination Ability of Vegetable Soybean (Glycine max (L.) Merrill) Aye Nwe Win 1 (Master of Science in Horticulture) Kassinee Sitthiwong 1 Surat Nuglor 2 and Pornpan Pooprompan 1 * 1.Faculty of Agricultural Production, Maejo University, Sansai, Chiang Mai, Faculty of Engineering and Agro- Industry, Maejo University, Sansai, Chiang Mai,

Introduction  Good soybean seeds ensure a uniform stand of healthy and vigorous plants, which is essential to get the high yield and good quality needed for profitable vegetable soybean production.  Producing good quality seed depends on many factors, such as, growing season, location, management inputs, diseases and pests, post- harvest handling and storage.

 Physiological maturity is defined as the time when seeds attain maximum dry weight, maximum germination, and maximum vigor. (Mejia, 1985)  Seed priming is a technique in which seeds are partially hydrated until the germination process begins but radicle emergence does not occur. (Bradford,1986)  PEG-6000 increased seed germination and vigor index. (Gongping et al.,2000)

Objectives  To observe the physiological maturity between two varieties of vegetable soybean  To improve the germination rate and uniformity

Materials and Methods Field experiments Physiological Maturity of vegetable soybean  Two environments – Dry and rainy seasons (2010)  Design- RCBD with 2 replications

Field experiments  Variety - Two varieties (AGS 292 and No.75)  Plot size - 8 m x 1 m  Plant spacing - 20 cm x 50 cm  Seed rate - 5 seeds / hill

Tagging of flowers

Moisture content (%) Fresh seed - 5 gmWeigh with Electric balance Oven (103°C 17 hr) Desiccator (20-30minutes) Dry seed wt.

Dry matter (gm) Put 25 pods Weigh with Electric balance Oven (103°C 17 hr) Desiccator (20-30minutes) Dry seed wt.

Germination % SeedGerminatorSeedling Evaluation of germination test (a) Normal seedlings (c) Fresh ungerminated seeds (b) Abnormal seedlings (d) Hard seeds and (e) Dead seeds Number of normal seedlings Germination % = x 100 % Number of seeds

Laboratory experiment Chemical priming method - PEG conc: (Polyethylene glycol) Design- 4 x4 Factorial in CRD

 Factors - concentrations and soaking time  Factor (A) - PEG 6000(conc:) 0, 2.4, 4.7 and 6.5 g/ 100 ml. water  Factor (B) - soaking time 3, 6, 9 and 12 hr  Variety - Two varieties (AGS 292 and No.75)

Chemical- priming method(PEG) 50 seeds / replication PEG conc (A): 0, 2.4, 4.7, 6.5 g / 100 ml. water Soaking Time(B) 3, 6, 9,12hr Washing Drying Germination test (B.P.)

Seed weighing PEG conc.Mixing Seeds and PEG Washing Re-driedWeight (Original weight) Germination test Procedure

 Seeds were soaked in distilled water. After soaking seeds were redried to the original weight with forced air under shade. (Bennett & Waters, 1987 )  The primed seeds were washed with running tap water. (Lee and Kim, 1999)

Germination % SeedGerminatorSeedling Evaluation of germination test (a) Normal seedlings (c) Fresh ungerminated seeds (b) Abnormal seedlings (d) Hard seeds and (e) Dead seeds Number of normal seedlings Germination % = x 100 % Number of seeds

Seedling growth rate (SGR) Normal seedling Oven (80°C 24hr) Weigh with electrical balance Normal seedlings (dry weight) SGR = (mg/seedlings) No. of normal seedling

Electrical conductivity(EC) (µS/cm/seed) Conductivity meter

Results

Pod color of vegetable soybean

Seed color of vegetable soybean

Fig.1. Seed dry matter, moisture content and germination percentage of vegetable soybean variety (AGS 292) during seed development in dry season

Fig.2. Seed dry matter, moisture content and germination percentage of vegetable soybean variety (No.75) during seed development in dry season

Fig.3. Seed dry matter, moisture content and germination percentage of vegetable soybean variety (AGS 292) during seed development in rainy season

Fig.4. Seed dry matter, moisture content and germination percentage of vegetable soybean variety (No.75) during seed development in rainy season

Table 1. Effect of PEG concentration and soaking time on germination percentage of vegetable soybean variety AGS 292 PEG – conc.(A) g/ 100 ml. H 2 0 Germination (%) Soaking time (B) hr Mean b a a a Mean F-test PEG-conc. (A) * Soaking time (B) ns A x B ns

Table 2. Effect of PEG concentration and soaking time on seedling growth rate (SGR) of vegetable soybean variety AGS 292 PEG – conc.(A) g/ 100 ml. H 2 0 SGR (mg/seedling) Soaking time (B) hr Mean Mean F-test PEG-conc. (A) ns Soaking time (B) ns A x B ns

Table 3. Effect of PEG concentration and soaking time on electrical conductivity (EC) of vegetable soybean variety AGS 292 PEG – conc.(A) g/ 100 ml.H 2 0 EC(µS/cm/seed) Soaking time Mean hi 19.8 de 27.8 b 33.7 a 23.5 w hi 15.8 efgh19.9 de 26.2 bc 18.2 x i 14.0 fghi 19.1 def 21.9 cd 16.1 y i 13.3 ghi 15.9 efgh 18.7 defg 14.2 z Mean 10.4 D 15.7 C 20.6 B 25.1 A F-test PEG-conc. (A) ** Soaking time (B) ** A x B *

Seed germination of vegetable soybean seeds from AGS 292 PEG 0PEG 2.4 gPEG 4.7 gPEG 6.5 g

Table 4. Effect of PEG concentration and soaking time on germination percentage of vegetable soybean variety No.75 PEG – conc.(A) g/ 100 ml. H 2 0 Germination (%) Soaking time (B) hr Mean Mean F-test PEG-conc. (A) ns Soaking time (B) ns A x B ns

Table 5. Effect of PEG concentration and soaking time on seedling growth rate (SGR) of vegetable soybean variety No.75 PEG – conc.(A) g/ 100ml.H 2 0 SGR (mg/seedling) Soaking time (B) hr Mean Mean F-test PEG-conc. (A) ns Soaking time (B) ns A x B ns

Table 6. Effect of PEG concentration and soaking time on electrical conductivity (EC) of vegetable soybean variety No.75 PEG – conc.(A) g/ 100 ml.H 2 0 EC(µS/cm/seed) Soaking time (B) hr Mean gh 17.0 cdef 24.0 ab 29.1 a 20.1 w gh 14.0 efgh20.4 bcd 27.6 a 17.9 x h 12.6 fgh 16.1 cdef 21.2 bc 14.6 y h 11.4 fgh 15.2 defg 19.0 bcde 13.7 z Mean 9.4 D 13.8 C 18.9 B 24.2 A F-test PEG-conc. (A) ** Soaking time (B) ** A x B *

Seed germination of vegetable soybean seeds from No.75 PEG 0PEG 2.4 gPEG 4.7 gPEG 6.5 g

Table 7. Effect of PEG conc: and soaking time duration treated with two vegetable soybean varieties (AGS 292 and No.75) for germination percentage, seedling growth rate (SGR) and electrical conductivity (EC) VarietyGer %SGR (mg/seedling) EC (µS/cm/seed) AGS b No a LSD (0.05)2.2ns ns= not significantly different (p> 0.05) *= significantly different (p< 0.05) **= highly significantly different (p< 0.01)

Table 8. Effect of different PEG concentration treated with two vegetable soybean varieties (AGS 292 and No.75) for germination percentage, seedling growth rate (SGR) and electrical conductivity (EC) PEG conc: (g/ 100 ml.H 2 O) Ger %SGR (mg/seedling) EC (µS/cm/seed) b a a b a c a d LSD (0.05)3.1ns1.0 ns = not significantly different (p> 0.05) * = significantly different (p< 0.05) **= highly significantly different (p< 0.01)

Fig.5. Effect of PEG concentration and soaking time on electrical conductivity value of vegetable soybean (AGS 292 and No.75)

Discussion  The change in seed color and in pod color could be dependable indicators in vegetable soybean. Visual indicators of PM had also been suggested for soybean (Crookston and Hill, 1978; Tekrony et al.,1979 and Gibkpi and Crookston,1981).  Odell et al., (1992) reported improvement in the germination of PEG treated tomato seeds than non treated tomato seeds.

Murray (1990) observed in germination due to PEG. This may be due to fact that response to the PEG treatment is dependent on cultivars. Murray (1989) concluded that over priming may cause oxygen deficiency. Priming seeds might have plasma membrane structure by slow hydration than non treated seeds. ( Jett et al., 1996) Discussion

Conclusion AGS 292 and No.75 vegetable soybean varieties should be harvested within two weeks after physiological maturity to obtain maximum yield without any loss in quality. PEG concentration improved the germination percentage than non treated PEG. Seed treated with PEG decreased electrical conductivity value.

Acknowledgements Thailand International Co-operation Agency (TICA)

Fig.1. Temperature and rainfall in dry season

Fig. 2.Temperature and rainfall in rainy season