Abstract: In this study, we investigated the natural nodulation of legume forage crops were widely grown in the natural pastures in Şanliurfa, Turkey. This legume forage crops are Vicia sativa L. subsp. sativa L., Vicia narbonensis L. var. narbonensis L., Vicia palaestina Boiss., Vicia hybrida L., Vicia lutea L. var. lutea Boiss. ET Ball., Pisum sativum L. subsp. sativum L. var. sativum L, Cicer echinospermum P.H. Davis, Trifolium tomentosum L., Trifolium retusum L., Trifolium campestre SCHREB., Medicago truncatula GAERTN. var. truncatula Schultz Bip., Trigonella mesopotamica Hub.-Mor., Lens culinaris Medik., Onobrychis crista-galli, Lathyrus cassius Boiss., Melilotus officinalis (L.) DESR., Coronilla scorpioides (L.) W.D.J. Koch. Nodulation, nodule colors and shapes were examined at the blooming period of forage legumes. In this study, the colour of the interior of nodules are pink-red colour and may be related to high rates of nitrogen fixation in legume crops.
INTRODUCTION
The pastures are an important part of farming systems (Albayrak and Sevimay, 2005). Forage legumes are commonly grown to provide a seed and hay crop in many different farming systems in Turkey (Avcýoðlu et al., 2009). Forage legumes have a symbiosis life with specific bacteria called Rhizobium (Hansen, 1994).
Rhizobium bacteria are genetically diverse and physiologically heterogeneous group of symbiotic nitrogen fixing bacteria that the bacteria which fix atmospheric nitrogen within nodules in the roots (Alexander, 1984). Root nodulating isolate of Rhizobium bacteria provide a significant amount of nitrogen. For instance; in pastures, about 80% of the total nitrogen with legume plants is provided (Hansen, 1994).
Sanliurfa’s natural pastures are approximately 234.537 ha. Vicia, Trifolium species are the primary legumes used in pasture in Şanliurfa, Turkey (Sayar et al., 2010). Environmental conditions negative effects root nodulation and nitrogen fixation of legumes. Drought and low temperature is detrimental to nitrogen fixation (Hungria and Vargas, 2000). Present research aimed to study the shape of nodule, color of nodule and morphology of nodules of forage crops were investigated in semiarid region in Turkey.
MATERIALS AND METHODS
Region of study: Şanliurfa which states in Turkey’s Southeast Anatolia region lies between 37°49‘12"- 40°10'00" east of the meridian 36°41 ‘28"-37°57'50" north latitude. The altitude of Şanliurfa is about 500 m and surrounded by places 600-800 m in elevation. The city Şanliurfa (Fig. 1) is situated in semi-arid region of Mediterranean climate. In this region, the days are hot and arid in summer, mild and rainy in winter.
The climate of the region was evaluated according to the records of Şanliurfa Meteorology Station (Table 1). As shown according to the records, the climate is dry for a long period from June to October (Anonymous, 2001). Legume forage crops from Şanliurfa’s natural pastures were collected Atatürk forest, Kýrbadi, Ýkizce, Bozova, Birecik, Kulaflý, Osmanbey Campus, Osmanbey village, AKB status, Hilvan, Airport vicinity, Karaköprü (Table 2). The fodders were collected and dried. Plant identifications were made according to Davis (1988), Donner (1990).
| Table 1: | Climate and rainfall of the research field |
| P: The average annual rainfall (mm), M: The average maximum temperature of the warmest month (°C), m: The average minimum temperature of the coldest month (°C), PE: Summer rainfall (mm), S: Drought index S: PE/M, Q: Rainfall-temperature precedent Q: 2000xP/(M+m+546.6) (M-m) | |
| Fig. 1: | Location map of study area |
| Table 2: | Locations of forage legumes and some soil properties |
| OM: Organic matter | |
These plants are kept in Herbarium of Biology Department, Harran University. Leguminous fodder crops are identified in Table 2.
Nodulation in plants, shape, size, color were investigated. Soil samples of plant samples were taken and some soil physical and chemical properties (pH, EC, Lime, P2O5, K2O, OM) of soil samples were made. Some characteristics of the soil samples used in this study were determined in samples taken from 0-15 cm depth. After soil samples were air dried and passed through a sieve with 2 mm size, some soil properties were determined as follows; soil reaction pH 1:1 (w/v) soil water suspension by pH meter (Rowell, 1996). Electrical conductivity (EC) in the soil samples suspension by EC meter (Rowell, 1996). CaCO3 contents were determined by volumetric method (Martin and Reeve, 1955). Organic matter contents were determined by the wet oxidation method with K2Cr2O7 (Walkley and Black, 1934). P content was determined according to Olsen et al. (1954). Some soil chemical properties are given in Table 2.
RESULTS AND DISCUSSION
In the studied soils, pH changes between 7.18-7.79, amounts of organic matter (%) are between 1.3-4.7%. The Electrical Conductivity (EC) is between 1.18-1.62 (Table 2).
In Şanliurfa and the surrounding natural pasture, legume forage were collected. In this study, Vicia sativa L. subsp. sativa L., Vicia narbonensis L. narbonensis L., Vicia palaestina Boiss., Vicia hybrida L., Vicia lutea L. lutea Boiss. Meat Ball., Pisum sativum L. subsp. Sativum L. Sativum L., Cicer echinospermum P.H. Davis, Trifolium tomentosum L., Trifolium retusum L., Trifolium campestre Schreb., Medicago truncatula Gaertn. Schultz Bip truncatula, Trigonella mesopotamica Hub.-Mor., Lens culinaris Medik., Onobrychis crista-galli, Lathyrus cassius Boiss., Melilotus officinalis (L.), Coronilla scorpioides (L.) wdj Koch have grown extensively determined (Table 2, 3). Legume forage crops distribution was studied in relation to the level of disturbance. During flowering of plants were taken root samples and the nodule shape, nodule color, formation of nodulation were obtained (Table 4). The colors of nodule exterior varied from white to white-brown (Table 4). Ott et al. (2005) reported that the color of nodule exterior isn’t related to nitrogen fixation. The nodule interior color is related to leghemoglobin (Ott et al., 2005). In our results, the pink-red color in the nodules related to the presence of leghemoglobin. Its presence in the nodule seems to be essential to the nitrogenase activity (Ott et al., 2009). The efficiency of the assimilation of the fixed nitrogen by the plant could play an important role productivity and effective isolate. In the simplest, activity of nodule isolates is determined by the number of nodules formed by plants (Freiberg et al., 1997; Hungria and Stacey, 1997; Krishnan and Bennett, 2006). Effective of Rhizobium strains specific in the various legume crops were formed dark red nodules (Atallah et al., 2008; Rejili et al., 2009). Fourteen species were presented with cylindrical nodules determined. The remaining species had multi-branched structure, long-thin structure and long elipse nodules (Table 4). The nodules shape depends upon the plant host (Zahran, 1998).
The number of nodule were differentiated according to plant species. This difference may be associated with the soil adaptation of Rhizobium bacteria and the plant species. Lowest nodulation examined the roots of Vicia narbonensis L. var. Narbonensis L. Plant species are differentiated according to the number of nodule. This difference may be associated with the adaptation of bacteria and the plant species.
Zahran (1998, 1999) determined that Trifolium resupinatum, Melilotus indica, Medicago intertexta, Trigonella hamosa, Alhagi murarum grows naturally in Egypt, and the number of nodules and nodule weight of the studied plants were obtained. Researcher has determined nodule number and shape, former vary according to plant species. In our study, we determined different shapes and sizes in forage legume nodule Similar results were obtained with Zahran (1998)’s findings.
Zahran (1999) reported that a successful symbiotic relationship with leguminous crops-Rhizobium bacteria are sensitive high soil temperature in semiarid and arid regions. For most Rhizobium bacteria, the optimum temperature range for growth in culture is 28-31°C (Hungria and Vargas, 2000).
| Table 3: | Legume forage characteristics |
| Table 4: | Some morphological features of leguminous fodder crops nodules |
Present study must be more depended to improve the output of nitrogen fixation in the semi-arid region.
In our study, the number of rhizobial nodulation in leguminous forage crops detected to be different, such as result from differences in isolates that infect plant species and microorganisms in the soil density may be the competitiveness between. V .narbonensis in the territory of the region V .narbonesis lack of nodule formation in the lack of nodule isolates thought to be forming. The climate data of the study area, especially soil temperature is also believed to affect some of the negative development of rhizobial isolates. Grover et al. (2011) and Zahran et al. (1999) have been reported that especially in free-living and symbiotic bacteria living in conditions of precipitation is less than the majority negatively affected by high soil temperature. The optimum temperature development of Rhizobium bacteria is between 28-31°C in broth culture (Graham, 1992). Hungria and Stacey (1997) reported that cellular polysaccharides secreted by Rhizobium bacteria play an important role in the nodulation formation.
The most important function of leghemoglobin in the cells of the nodule is that the diffusion of oxygen (Appleby, 1984; Gordon et al., 1999; Ott et al., 2009). Present study also the root nodules of the plant species identify to be red colors, indicate the presence in Şanliurfa pasture soil of natural and effective Rhizobium bacteria. Atallah et al. (2008) was studied the formation of nodulation wild grown Astragalus, Bituminara, Calicotome, Cicer, Hippocrepis, Hymenocarpos, Lathyrus, Lotus, Lupinus, Medicago, Melilotus, Onobrychis, Ononis, Physanthyllis, Scorpiurus, Securigera, Spartium, Trifolium and Vicia species. Nodulation of Medicago coronata was reported for the first time in France (Atallah et al., 2008). Host specificity and certain symbiotic genes of nodule formation was examined (Hungria and Stacey, 1997).
CONCLUSIONS
Nitrogen fixing ability of legume forage crops lies environmental conditions such as temperature. In this study, we investigated natural nodulation of forage crops in semiarid region, Şanliurfa, Turkey. Pastures in Şanliurfa (semi-arid region of Turkey), Rhizobium bacteria show a host specificity for the species of forage crops that they infect. Therefore, isolation of bacteria from nodules and the amount of fixed nitrogen has not determined. Thus, selected Rhizobium bacteria, increasing the rate protein of legume forage crops would be expected to. The bacteria will be isolated from fodder crops, effectively isolate and/or isolates will be selected and effectiveness rhizobial isolates were identified by comparison of greenhouse and field trials.