INDUCTION OF DORMANCY IN GROUNDNUT - A REVIEW

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1 Agri. Review, 35 (3): , 2014 doli: / AGRICULTURAL RESEARCH COMMUNICATION CENTRE INDUCTION OF DORMANCY IN GROUNDNUT - A REVIEW V.R. Shelar, A.P. Karjule and B. Jayadeva Seed Technology Research Unit Mah. Phule Agricultural University, Rahuri , India Received: Accepted: ABSTRACT The non-dormant character in Spanish and Valencia bunch type is undesirable for groundnut cultivation in summer season where at harvest stage of the crop rains are invariably received and cause heavy losses of produce by way of sprouting of pods in the field. It is more problematic in soil areas where moisture retention capacity is high. A loss of per cent in bunch groundnut pod yield has been reported due to in situ germination. The search for investigation of non-conventional methods of inducing dormancy in bunch types to save the produce and to retain the seed quality against the field sprouting are of greater importance. In the Spanish bunch type, cultivars possessing 3-4 weeks dormancy will be able to save the field losses due to in situ sprouting when the mature crop is caught in untimely rains. Thus the non-dormant nature of bunch groundnuts, besides reducing the yield, also deteriorates seed and oil quality. Seed availability is also reduced because of field sprouting. The research on these aspects of induction of dormancy in bunch groundnut to avoid losses during rainy season has been reviewed in this article. Key words: Ground nuts, Seed dormancy. Groundnut (Arachis hypogaea L.) is an important oil seed crop of India grown during summer season. It ranks first among the oil seed crops of India, which is largest groundnut producing country accounting 33 per cent of world production and 40 per cent of the area. The area under summer irrigated groundnut is increasing, though its yield is very low as compared to USA and China.Several reasons could be ascribed to its low productivity of which nearly 20 per cent loss in the field is by the in situ germination due to lack of dormancy (Anonymous, 1979). There is a need to identify sources of short duration with certain period of dormancy to minimize yield losses due to in situ germination (Ashok Kumar, 1989 and Patil et al., 1991). Dormancy is an important factor in commercial groundnut production. It can be beneficial when dormancy prevents mature seeds from sprouting before harvest. It can be detrimental when dormancy reduces stand or hampers taking a second crop immediately after harvest. Lack of dormancy in bunch types has been described as an inherent property of seed and does not primarily depend on soil conditions The search for investigation of non-conventional methods of inducing dormancy in bunch types to save the produce and to retain the seed quality against the field sprouting are of greater importance. For inducing seed dormancy in groundnut number of methods have been developed. Foliar application of maleic hydrazide at different stages of crop growth has been successfully used to control sprouting. The key idea in the use of growth regulators is to control some aspects of growth, regulate the balance between source and sink, which is the final analysis results in the higher yield of desired product. Factor influencing seed dormancy in groundnut: Seed dormancy in groundnut is controlled by many features. Different causes of seed dormancy in groundnut have been reported by many workers. It is fairly obvious that more than one cause might be responsible for the dormancy of a seed. In a broad view, two types of dormancy can be distinguished i.e. (1) Innate dormancy where the seeds will not germinate even under favourable conditions and (2) Imposed dormancy where seeds will not germinate * Corresponding author s stru.mpkv.rahuri@gmail.com

2 when conditions are unfavorable. Several forms of innate dormancy have been recognized. Seeds may fail to germinate because of impermeable seed coat to water (Matthews, 1975). Presence of inhibitors and ratio between growth promoters to inhibitor: In recent years the presence of naturally occurring growth inhibitors have received increased attention which is supposed to play an important role in induction and termination of dormancy. Amen (1968) has developed a general model for seed dormancy based on the assumption that the state of dormancy is determined by the balance between growth inhibitors and growth promoters. Nagarjun and Gopalkrishnan (1958) reported that non-dormant seeds of TMV-2 groundnut contained a water soluble growth promoting hormone and the seed extract induced root initiation in the dormant seeds of TMV-3 groundnut. The physiological studies done by Sreeramulu and Rao (1971) revealed that the water soluble hormone was indole acetic acid which has root inducing activity. This auxin was noticed at high levels in the embryonic axis and seed coat of non-dormant seed. Genetic aspects of dormancy: Dormancy, the physiological phases in seed, is initially determined by the genetic make up of the seed and varies largely among species and even within a species. The variation may be expressed in the strain which is used for the improvement of varieties. Hull (1937) reported that dormancy in groundnut is an inherited character and the rest period extended even upto two years in some varieties. John et al. (1950) pointed out that dormancy is an inherent property of Virginia groundnut. The trait dormancy was found to be partially dominant over the trait nondormancy. Genetic differences in seed dormancy between strains with different botanical groups have been demonstrated for several investigators (Ramachandran et al., 1967 and Lin and Lin, 1971). Yaw et al., (2008) reported that the seed dormancy is controlled by monogenic inheritance with dominant over non-dormant Mechanical restriction of the seed coat: Hardness or impermeability of seed coat is said to be one of the many causes for dormancy. This causes physical restriction to the exchange of gas and water which are essential for the initiation of germination process. Vol. 35, No. 3, The inheritance of hard seed coat varies among and within the species. This dormancy is also mediated by environment prevailing during seed ripening period. Significant morphological differences in the testa among the different cultivars of groundnut were reported. The seeds of starr variety showed relatively thin compact testa while that of Virginia type is thicker (Gulek et al., 1977). Presence of ethylene: Ethylene was involved in the normal regulation of seed dormancy (Toole et al., 1964). Ketring and Morgan (1969) reported that the embryonic axis of non-dormant seeds of peanut actively produced ethylene during germination, where as ethylene production was low in dormant seeds. Chemicals for inducing dormancy: Barrie et al. (1967) reported a large number of coumarin derivatives and a few isocoumarines have capacity to induce light sensitive dormancy in seeds of Lactuca sativa L. Jangaard et al. (1971) reported the high concentrations of salicylic acid and eugenol inhibited the sprouting of nut sedge tubers. Shibakusha (1972) reported synthetic salicylic 500 ppm inhibit the growth of Avena sativa and salicylic acid present in abies sachal inesis mainly responsible for seed dormancy. Sreeramula (1974) studied seed of dormant groundnut cv. TMV-3 during storage at 0, 10, 20, 30 and 40 days after harvest. Dormancy ended at 30 days after storage. In both cotyledons and emrgyonic axis, inhibitory phenolic aci d decreased and the synergistic one increased.oblidalova(1975) studied theexcised embryos of barely. He reported that state of dormancy was stimulated by addition of solution containing 1.0 mg coumarin, 0.1 mg chlorogenic acid, 10 mg chloromequat, 1.0 mg ABA and 10 mg cinnamic acid. Thakur (1976) isolated the phenolic growth inhibiting substances from dormant buds of sugarmaple by paper chromatography of their aqueous methanolic extract. An inhibition was attributed by four major phenolics identified as fearulic, vanillic, coumarin and cinnamic acid. Khan (1982) found abscisic acid involved in the inhibition of the embryo growth rather than in the initiation of germination. Naqvi and Hanson (1982) studied bioassays of aqueocy extracts of guayule, lettuce and tomato seed. He reported that phenolic acid responsible for dormancy in guayule. Williams and Hougland (1982) revealed exogenous application

3 218 AGRICULTURAL REVIEWS of phenols (10-3 M) to crop and weed seeds substantially delays germination. Khan and Ungar (1986) reported presence of endogenous inhibitors like salicylic acid, syringic and chlorogenic acid in small seeds, could account for germination inhibition in these seeds. He reported that inhibition of germination can be done by exogenous applications of all highly active phenols at 10-2 M concentration. Farooqi et al. (1987) reported P coumaric acid, cinnamic acid and small amount of salicylic acid were responsible for rhizome dormancy in Coctus speciosus. Mohanti and Sahoo (1992) reported coumarin ( ppm) gradually decreased the seed germination in rice, ragi, bajara, sesame and B. juncea. Mallik et al. (1994) reported the presence of growth inhibitor substances in lettuce seed. They evidenced the aqueous extract inhibited the germination and growth of radish and wheat seeds, attributing the activity to the presence of phenols. Cutillo et al. (2003) reported the cinnamic acid amides isolated from chenopodium album delayed the germination of Lactuca sativa L., Lycopersion esculentum L. and Allium cepa L. seeds. 50 per cent inhibition was observed at 10 mg/ml concentration. Williams and Robert (2002) observed coumarin is a compound that inhibits seed germination and seedling growth of radish. The greatest inhibitory effect was observed at 10-3 M concentration. Jaykumar and Manikandan (2005) reported the aqueous leaf extract of Acacia leucopholea showed inhibitory effects on seed germination, shoot length, root length and leaf area and yield of Arachis hypogaea (groundnut) and sorghum due to presence of different phenolic acids viz., hydoguinone, salicylic acid, trans cinnamic acid etc. Rajjou et al. (2006) studied the influence of salicylic acid on elicitation of defense mechanism in arbidopsis (Arbidopsis thaliana). They also reported that the salicylic acid inhibits the germination of arbidopsis seed and increase the water stress resistance. Abenavoli et al. (2008) reported at concentration above 200 mm, coumarin inhi bited seed germination in a concentration dependent manner in duram wheat. Inhibition occurred early during seed imbibition (Phase-I) was rapid and irreversible. During phase-i coumarin inhibited water uptake, electrolyte retention capacity and O 2 consumption. Maleic hydrazide for inducing dormancy: Maleic hydrazide (diethanolamine salt of 1,2-dihydroxy-3,6 pyridazine-dione), a growth inhibitor has been successfully used to induce dormancy and thus to reduce sprouting losses in potato, sugarbeat, onion, carrot and rice. Schoene and Hoffmann (1949) reported the growth inhibiting and herbicidal properties of maleic hydrazide. The effectiveness of Maleic hydrazide in preventing sprouting of potato tuber was first reported by Zukel (1950). Naylor and Davis (1950) found that MH was uniformly effective as a growth inhibitor both for dicotyledonous and monocotyledonous plants. Vaithialingam and Rao (1973b) reported that induction of dormancy in TMV-2 bunch groundnut by the foliar application of Maleic hydrazide -30, in a field trial conducted at Coimbatore. Nagarjun and Radder (1983) reported that foliar application of Maleic hydrazide could induce dormancy in bunch type of groundnut variety in the field trials. Gupta et al. (1985) reported that induction of dormancy in bunch type of groundnut variety T-64 by the foliar spray of Maleic hydrazide in the field trials conducted at Allahabad. Appalanavidu and Murthy (1961) reported that the maleic hydrazide (MH) was found to be successful in inducing dormancy in tubers, bulbs and seeds. Maleic hydrazide concentrations for induction of seed dormancy: The concentration of Maleic hydrazide is important in obtaining the higher degree of dormancy. Krishnamurthy (1969) conducted the pot culture experiment and revealed that foliar spray of 500 ppm Maleic hydrazide at 15 and 25 days prior to harvest induced dormancy in two varieties of bunch groundnut (Spanish improved and TMV- 2). The number of sprouts reduced from 13.3 to 1.8 in Spanish improved and 17.5 to 5.8 in TMV-2. In a field trial he observed the induction of dormancy in Spanish improved with 200, 400 and 600 ppm concentrations of Maleic hydrazide sprayed at 75, 81 and 106 days after sowing. Sprouting was 10.3, 12.7 and 10.5 per cent due to 200, 400 and 600 ppm concentrations respectively as compared to that of unsprayed control (25.6 %). Vaithialingam and Rao (1973a) reported that the Maleic hydrazide 5000 ppm at 70 DAS, ppm at 80 DAS and 10,000 ppm at 90 DAS induced dormancy ranging from 30 to 40 per cent. Vaithialingam and Rao (1973b) reported that the Maleic hydrazide -30 application as foliar spray was done at 0, 5000,

4 10000, 15000, 20000, and ppm at 70, 80 and 90 DAS. Revealed that irrespective of stages of application, all the treatments reduced the germination of the non-dormant seeds severely and increased the total free amino acid content while inducing dormancy. Nagarjun et al. (1980) conducted a field trial with bunch groundnut to study the optimum stage and concentrations of Maleic hydrazide for foliar spray on the seed quantity and subsequent growth of seedlings. They reported that there was a reduction in seed moisture content due to foliar spray of 250 ppm Maleic hydrazide in the early stage of crop growth (60 days). However, the MH application did not show any effect on seed purity, seed viability and seed protein content and seedling growth, while Maleic hydrazide at concentrations greater than 500 ppm increased oil content significantly. Nagarjun and Radder (1983) observed that foliar spray of maleic hydrazide (MH) after 60 days of sowing was found to be superior in inducing seed dormancy compared to later stages of Maleic hydrazide application (75 and 90 days of crop growth). The concentrations ranging from 250 to 1000 ppm remarkably enhanced the seed dormancy to the extent of per cent. However, application of Maleic hydrazide in lower concentrations (250 ppm) at an early stage of crop growth (60 days) was found to be as good as that of higher concentrations in inducing seed dormancy. Reduction in moisture content and the rate of catalase enzyme activity were in association with increase in the degree of induced seed dormancy. Gupta et al. (1985) have reported that a foliar spray of 15 x 10 3 or 20 x 10 3 ppm applied to groundnut variety (T-64) at 90 days after sowing induced the seed dormancy. Bhapkar et al. (1986) revealed that a foliar application of Maleic hydrazide -30 at different concentrations viz., 5000 ppm at 70 DAS, ppm at 90 DAS induced seed dormancy ranging from 30 to 40 per cent. Abrar and Jadhav (1991) reported that the seed dormancy period was increased from 5 to 25 days in cv. PI and PI by 200 ppm MH applied as foliar spray one month before harvesting. Jagatap (2000) studied the induction of seed dormancy in bunchy groundnut genotypes viz., RHRG-12, TAG-24, RHRG-16 and SB-XI. He revealed that seed dormancy could be induced upto Vol. 35, No. 3, , 10, 30 and 20 days, respectively by foliar application of Maleic 250 ppm than other concentrations of Maleic hydrazide applied viz., 500 and 750 ppm. The seed viability remains unaffected due to Maleic hydrazide 250, 500, 750 ppm in all the genotypes. Nautiyal (2004) reported that foliar spray of malic 1000 ppm at 60 days after crop emergence was found to be superior in inducing dormancy in Spanish groundnut cultivars. Seed dormancy period in bunch groundnut varieties: Kramer and Kozlowski (1960) reported that the dormant nature of seed appears to vary according to the geographic spread of species or genera. Gavrielith (1962) reported that the dormancy period of a variety changes from year to year. Varisai and Dorairaj (1968) screened 206 groundnut varieties under irrigated condition for dormancy. Only 6 bunch varieties had a dormancy period of about days. None of the bunch varieties studied was completely dormant. Bailey et al. (1972) reported that the Spanish and Virginia genotypes showed as much as 70 per cent seed dormancy and one Virginia genotype as little as 3 per cent. Narasimha Reddy and Swamy (1979) studied gibberellins and germination inhibitors in viable and non-viable seeds of peanut and reported that the more acidic and basic germination inhibitors were present in viable seeds. Loss of viability is associated with presence of inhibitors and absence of gibberellin like substances. Reddy et al. (1985) studied 17 groundnut varieties belonging to Spanish and Valencia botanical groups reported that the derivative of the cross, J-11 x Robout-33-1 was found to possess seed dormancy for a period of about 35 days. Pandya and Patel (1986) studied seeds of 4 Virginia and 73 Spanish bunch varieties and 5 Spanish x Virginia hybrids for percentage germination after 3-50 days of storage at room temperature. Virginia types and their crosses, particularly G-201, ICGS-6, Robout and (TMV 10 x Robout-33-1)-2, were more dormant than most of the Spanish types tested. Among the Spanish varieties, RSHY-6, ICGS-21, ICGS-30, ICGS-57, TG-9 and TG-17 were identified as sources of dormancy for breeding. Kamala et al. (1987) reported that the germination percentage (pre-harvest sprouting) was scored 105-

5 220 AGRICULTURAL REVIEWS 140 days after sowing in 15 bunch varieties of 105 days duration. TG-9, TG-17 and TG-15 showed the lowest germination percentage (8-10 % after 140 days), followed by CGS-1-19 and Dh-8. Reddy et al. (1987) observed that CGC-7, also known as CGS-1-19 possesses a seed dormancy period of 5 weeks. The F 8 of CGC-7 shows differential germination, indicating variation for dormancy period. Kumar et al. (1991) reported that the cultivars of subsp fastigiata generally lacked dormancy while those of subsp hypogea were characterized by long dormancy periods. Varman and Raveendran (1991) observed that varieties of bunch groundnut Arachis hypogaea subsp. Fastigiata, show little seed dormancy, with a result that per cent of pods germinate in situ due to rains at the pod maturity stage. With a view of identifying seed dormancy, some 55 high yielding genotypes of subsp. Fastigiata were grown in the field during kharif. Pods were collected at maturity and evaluated for seed dormancy. ICGV possessed seed dormancy, with pods sprouting 18 days after harvest compared with 2-4 days for the other genotypes. Seed dormancy was also observed in pods of ICGV subjected to water stress at pod maturity. Nautiyal et al. (1993) reported that the degree of maturity, position of kernel in the pod and the storage period all had a confounding influence on the seed dormancy. Venu et al. (1995) studied the relationship of seed moisture content with dormancy and seedling vigour in Spanish and Virginia genotypes of groundnut. It was observed that the whole seed dormancy was higher in both Spanish and Virginia types as compared to embryo dormancy. The genotype Dh-3-30 indicated dormancy period of days with whole seeds but did not show embryo dormancy, indicating the presence of dormancy factors in seed coat. On the contrary, the removal of seed coat in ICGS-30, EDR, Bidar local and Mardur local improved the germination but failed to release the dormancy completely, thereby indicating that the factors responsible for dormancy might be residing both in seed coat and embryo. The embryo of Dh-3-30 which had no dormancy exhibited higher seedling vigour index values than the whole seeds of the same genotype as well as whole seeds and embryo s of the other dormant genotypes. Nautiyal et al. (1996) screened about 200 Spanish germplasm lines for fresh seed dormancy during rabi/summer. They revealed that genotypes showed variation in germination percentage. During rabi/summer, the crop was harvested at 110 DAS and most of the genotypes showed more than 60 per cent fresh seed dormancy, finally they concluded that the dormancy period of most of the genotypes was laid between days. Anonymous (1999) reported that three mutants of cv. Girnar-1 (nondormant) namely PBS-30021, and were found to possess fresh seed dormancy about 1-4 weeks. Joshi and Nautiyal (1999) conducted an experiment at NRC, Junagarh (Gujarat) on groundnut to screen about 180 Spanish type germplasm accessions alongwith the cultivars having fresh seed dormancy viz., ICGS-11 and ICGS-44 as checks, both under field and laboratory conditions. They reported that the genotypes NRCG-7197, NRCG-7186 and NRCG-835 had 23, 24 and 28 per cent pods were sprouted, respectively in the field. They concluded that these genotypes had 8, 1 and 5 per cent fresh seed dormancy. Upadhyay and Nigam (1999) conducted an experiment to determine the fresh seed dormancy index (FSDI) percentage in 200 groundnut germplasm accessions and 21 cultivars belonging to the Spanish group and revealed that, large variation in pod loss due to in situ sprouting of seed. The fresh seed dormancy was found among the accessions and cultivars. Fresh seed dormancy index varied from 2 per cent in chico to 88 per cent in ICGS-44 (check). They concluded that cultivars with an FSDI value of less than 10 per cent, showed more pod loss in situ than the cultivars with high FSDI. Thus, pod loss due to in situ sprouting increased with a decrease in FSDI. Cultivar SB-XI did not show any in situ sprouting or pod loss. Mathur et al. (2000) stated that two cultivars of groundnut viz., PBS and PBS were found to be higher yielder and PBS possessed fresh seed dormancy of days, while PBS possessed fresh seed dormancy of about days and suggested to use these two genotypes as donar parents for incorporation of fresh seed dormancy in breeding programme. Swain et al. (2001) studied 17 erect, 8 semi-spreading and 5 spreading varieties to analyze the nature of variation

6 of seed dormancy in different varietal forms of groundnut and revealed that dormancy period of the varieties ranged from 33 to 107 days. Most erect varieties showed short to moderate dormancy period and most semi-spreading and spreading varieties possessed longer dormancy period coupled with strong intensity of dormancy. The seeds of kharif showed the highest degree of dormancy followed by rabi and summer. Finally they stated that, TG-26 had the longest dormancy period of 107 days. Swain and Sahoo (2001) studied the duration of seed dormancy in different bunch type groundnut cultivars and reported wide variation in their duration ranging from 5.4 days to days. Manon Mani (2002) studied both dormant and nondormant cultivars of groundnut and reported that dormant cultivars maintained higher seed germinability in storage for a longer period than the non-dormant cultivar of groundnut varieties. Singh et al. (2002) screened 5 different cultivars of groundnut for detection of dormancy periods. They revealed that all the cultivars possess dormancy period ranging from 4 to 5 months. Minimum dormancy of 4 months was observed in non-dormant bunch type groundnut cultivars viz., Chitra, Prakash and Kaushal whereas in spreading type groundnut cultivars viz., Chandra and Amber possessed 5 months dormancy period. The results indicated that bunch type varieties had less dormancy in comparison to spreading type of cultivars. Yaw et al. (2008) conducted an experiment at Ghana (Africa) to determine the heritability of fresh seed dormancy in groundnut and to transfer this trait from dormant exotic lines (ICGV and ICGV-87388) into non-dormant groundnut varieties Vol. 35, No. 3, (Shitaochi and Aprewa). They reported that seed dormancy is controlled by monogenic inheritance with dormancy dominant over non-dormant. They also reported showed that more than 90 per cent of the freshly harvested seeds of the non-dormant parents germinated before 14 days, whereas less than 10 per cent of the seeds of the dormant parents germinated during the same period. Jaydeva (2008) tried to i nduce the dormancy in summer groundnut varieties viz., TG- 26, SB-XI & TAG- 24 by spraying Maleic hydrazide at different concentrations. The concentrations used were 250, 500, 750, 1000 & 1250 ppm. Foliar spray of MH at 60 and ppm concentration was found to be superior in inducing seed dormancy up to 40 days, irrespective of genotypes as compared to MH 250, 500, 750 & 1250ppm concentrations. Among the varieties the genotype TG- 26 and SB- XI responded well in getting induce the dormancy up to 30 days, where as in the genotype TAG-24 the dormancy induced was only for 5 days. CONCLUSION Application of maleic hydrazide at different stages of crop growth has the capability of altering the seed dormancy. The foliar application of Maleic hydrazide a growth inhibitor can be successfully used as a source of short duration of dormancy to minimize yield losses due to in situ germination by application of proper concentrations of maleic hydrazide and its time of application on the locally available groundnut.similarly the review also made available various dormant and non dormant genotypes to use in breeding programme. This review will help to conduct further studies in dormancy of groundnut. REFERENCES Abenavoli, M. R., Cacco, G., Sorgona, A., Marabottni, R., Paolacci, A.R., Ciaffi, M. and Badiani, M. (2008). The inhibitory effect of coumarin on the germination of durum wheat seed. J. Chemical Ecology., 34(2): Abrar, A. K. and Jadhav, B. B. (1991). Effect of growth regulators, chemicals and temperature on dormancy in peanut. Ann. Pl. Physiol., 5(1): Amen, R. D. (1968). A model of seed dormancy. Bot. Rev., 34: Anonymous. (1999). Screening for seed dormancy. Annual Report National Research Centre for Groundnut, Junagarh, , Gujarat, India. pp. 35. Appalanaida, B. and Murthy, K. S. (1961). Effect of maleic hydrazide on ragi. The Andhra Agric. J., 8: Ashok Kumar, T. S. (1989). M.Sc. (Agri.) thesis, Univ. Agric. Sci., Dharwad. Bailey, W. K. and John, E. Bear. (1972). Seed dormancy of different botanical types of peanut (Arachis hypogaea L.). J. American peanut Res. and Edu. Assoc., 5(1):

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