Morphological study of elite lathyrus (Lathyrus sativus L) germplasm under Vidarbha Region

Introduction

Lathyrus (Lathyrus sativus L.) is an important protein rich crop (28%) next to soybean (43%) belonging to family luguminaceae, subfamily papilionaceae and chromosome number 2n= 14 (FAO 1997) [10] . It is originated in Indian subcontinent. The crop is sturdy and grown on residual moisture hence considered as a model crop for sustainable agriculture. Lathyrus serves as better alternative to the traditional pulse crop like chickpea and pigeonpea especially in the area under dryland condition (Thakur and Rai 1985 [29] , Lal et al. 1986) [20] . Not only it is rich source of protein to poor people but also it provides good quality fodder for animals. The cultivation of lathyrus is prominent in India, Bangladesh, Nepal and Ethiopia. In India lathyrus is cultivated in an area of 0.85 million ha in Uttar Pradesh, Bihar, West Bengal, Madhya Pradesh, Chattisgarh and Maharashtra state. In Maharashtra, it is cultivated in Bhandara, Chandrapur, Gadchiroli, Gondia and Nagpur district accounting 24,800 ha area (Anonymous, 2008) [1] . Lathyrus is consumed in various forms like chapattis, wadas, curies and also fed to cattles as a green fodder. The most common farming system is relay or utera under which its cultivation is mainly prevalent in India. Its ability to restore soil fertility makes it useful in crop rotation system. Being a legume it fixes atmospheric nitrogen through root nodules, part of which is made available to succeeding crop. It is relatively resistant to disease and pest (Arya, 1991) [2] . Flower colour in grass pea varies form blue to pink, red and white. Grass pea types with blue flowers and speckled (coloured) seed coat are common in the Indian subcontinent whereas white flowers with white seed coat are common in the Mediterranean region (Jackson and Yunus, 1984) [19] . Inspite of presence of the toxic compound i.e. ODAP (-N-oxalyl-L--diamino propionic acid). Lathyrus seed contain 28% protein, 58% carbohydrates, 0.6% fat, 3% mineral and vitamins  1 , 2 and niacin. In Maharashtra and some other states, sale and cultivation of grasspea is banned since 1961. The reasons for ban being ODAP i.e. -N-oxalyl-L--diamino propionic acid, the neurotoxin present in the seed. Which is reported to be responsible for human neurolathyrism a crippling disorder of lower limbs if consumed in large quantity over prolonged period (Dwivedi and Prasad, 1964) [8] . The consumption of 15 to 150 mg kg -1 body weight per day for prolonged period is enough to develop disease symptom (Cohn and Streifler, 1981) [7] . This work is helpful for further improvement of genetic material for crop breeding in lathyrus genus.

Materials and Methods

The present investigation entitled "Morphological study of elite Lathyrus (Lathyrus sativus L.) germplasm was carried out during rabi season of 2009-2010 at experimental field of Department of Agricultural Botany, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola located at 304.415 meter altitude, 20 0 31 ' N latitude and 72 0 02' longitude.

Treatment details

Biometric Observations

Five plants per treatment were randomly selected for recording all the periodical biometric observations at an interval of 20 days during the growth and development of lathyrus crop as affected by the given treatments. The various parameters of observations are indicated below.

Height of each plant was measured in cm at 20 days intervals. Five plants were randomly selected from each plot and replications and tagged for recording observations periodically from base level to the terminal stem at 30, 50, 70, 90, DAS (Days after sowing) and recorded. The mean of treatments and replication wise were worked out.

Leaf area /plant (dm 2 )

Leaf area was measured in cm. five plants were randomly selected in each plot. The plant leaves were grouped under the three groups i.e. large, medium and small and measured the leaf area. The leaf area (dm 2 ) was calculated treatments and replication wise and mean of three groups (large, medium and small) was recorded. The leaf area was measured on automatic leaf area meter at 30, 50, 70 and 90 DAS.

Relative Growth rate (RGR)

Relative growth rate is the increase in plant material per unit of time. It was calculated as per formula given by Fisher (1921) [11] and expressed in g\g\day.

Where, W 1 and W 2 are dry weight of crop at t 1 and t 2 time intervals. Log e =Napier logarithm (logarithm to the base of 2.303)

Net Assimilation Rate (NAR)

According to Verman and Allison (1963) [30] NAR is a useful measure of the photosynthetic efficiency of plant. Gregory (1926) [14] defined it as increase in dry weight of plant per unit leaf area. Williams (1946) [32] provided equation for estimating mean NAR as...

Where, W 1 and W 2 were total dry weight of whole plant at time intervals t 1 and t 2 . LA 1 and LA 2 are leaf area per plant (dm 2 ) measured from consecutive samples collected at time t 1 and t 2 in days, respectively.

Crop Growth Rate (CGR)

It was calculated by the equation worked out by Blackman (1919) [5] and Watson (1958) [31] Where,

• W 1 = Dry weight of plant at time t

Relative Water Content (RWC)

Dry weight of leaves was recorded after keeping it in hot air oven at 70 0 C (Barrs and Weatherly, 1962) [4] .

Relative water content was calculated by using following formula.

Biochemical Observations

Estimation of total Chlorophyll content in leaves (mg/g) Total chlorophyll content in leaf was estimated with DMSO (Dimethyl sulphoxide) method by adopting the procedure given by Hiscox and Israelstan (1979) [18] .

The total chlorophyll content of leaves was calculated as per Arnons (1949) [3] equations and was expressed in (mg/g).

Where,

• V = Final volume of DMSO (10 ml)

• W = Weight of fresh leaves (0.1 gm)

Statistical analysis

The statistical analysis of the data was done by statistical method as suggested by Panse and Sukhatme (1985) [24] and Gomez and Gomez (1983) [12] `F' test of significance was used to know whether observed treatment effects were significant or not. The standard error (SE) and critical difference (CD) at 5% level of probability were calculated. The value of CD was used to interpret the results

Results

In view of above studies, sixteen genotypes of lathyrus including, Ratan as a check were analyzed to ascertain their physiological, biochemical and yield contributing characters.

The results and discussion of above investigation are given below.

Studies on plant height were undertaken at four stages i.e. Plant height is one of the important morphological characters of lathyrus. The results clearly suggested the increasing trend for plant height. Which is statistically significant at all the growth stages of crop. It might be due to indeterminate behavior of species (Goyal 2003) [13] .

The genotype EC-540902 was found tallest with respect to other genotypes. Its tallness is due to erect type and longer internodes, as a resultant of the favorable cell elongation at endogenous level taken place. The present findings are supported with the results obtained by Falco et al. (1991) [9] where they concluded that the selected lines were generally taller (73 cm) than local ones (67cm). The genotypic differences for plant height in lathyrus (54 cm to 74 cm) were also noted by Zode et al. (1999) [34] and Pandey et al. (2001) [23] and Goyal (2003) [13] .

Tallness is due to the activity of ribulose phosphate carboxylase and sucrose phosphate synthatase of flag leaves, which leads to photosynthetic activities of the plant and helped in enhancement of cell elongation and increased plant height (Goyal 2003) [13] .

Leaf area per plant (dm -2 )

The total leaf area per plant was recorded at 4 stages i.e. at 30, 50, 70 and 90 DAS. The data are presented in Table 2.

Genotype EC-539032 recorded numerically higher leaf area per plant at all the growth stages. At 30 DAS, leaf area was found to be significant. The none of the genotypes recorded significantly higher leaf area than check Ratan (0.72). However the genotype EC-539032 (0.74) and IC-120497 (0.70) were found to be at par with check Ratan (0.72).

Thirteen genotypes recorded significantly lower leaf area than check Ratan. Significantly Lowest was found in genotype IC-420784 (0.38). At 50 DAS, leaf area was found to be significant. The none of the genotypes recorded significantly higher leaf area than check Ratan (1.72). However twelve genotypes were found to be at par with check Ratan. Three genotypes recorded significantly lower leaf area than check Ratan. The significantly lowest leaf area was found in genotype IC-420784 (1.09), and by IC-420785 (1.09). At 70 DAS, leaf area was found to be significant. The genotype EC-539032 (4.24) recorded significantly highest leaf area than check Ratan (4.08). None of the genotypes was found to be at par with check Ratan. Rests of the fourteen genotypes were recorded significantly lower leaf area than check Ratan.

The significantly lowest leaf area was found in genotype IC-420784 (2.35). At 90 DAS, leaf area was found to be significant. The none of the genotypes recorded significantly higher leaf area than check Ratan (9.02), however the genotype EC-539032 (9.13) was found to be at par with check Ratan (9.02). Fourteen genotypes recorded significantly lower leaf area than check Ratan. The significantly lowest leaf area was found in genotype IC-420784 (4.05).

Leaf area had increased gradually from vegetative to flowering stage and rapid at pod development stage (i.e. 70-90 DAS). Genotype EC-539032 showed maximum leaf area at all the growth stages. The maximum number of leaves plant -1 contributed towards maximum leaf area while it was least in IC-420784, which could be probably due to increased assimilatory surface at all subsequent growth stages. Similar findings of leaf area ranges from 3 dm 2 to 9 dm 2 in lathyrus were also reported by Zode et al. (1999) [34] and Goyal (2003) [13] . It was also reported by Naidu et al. (2001) [22] that, high yielding genotypes exhibited maximum leaf area. It is a function of cell expansion which again depends upon turgidity of cell. More leaf area is due to more elongation and enlargement of cell coupled with higher photosynthetic rate.

The data regarding dry matter accumulation of lathyrus plant was recorded at 30 to 90 days after sowing with an interval of 20 days. Data are presented in Table 3.

All the genotypes responded significantly at all the growth stages of crop. At 30 DAS, total dry matter per plant was found to be significant. Eight genotypes recorded significantly higher total dry matter per plant than check Ratan (0.54 g). The genotype EC-389370 accumulated maximum total dry matter plant-1 (g) in comparison with other genotypes, which might be due to its higher capacity to accumulate photoassimilate as a result of increased activity of RuBPcarboxylase and moderate leaf area per plant. It might be due its physiological superiority and capability of genotypes for efficient accumulation of reserve material as well as the faster translocation of assimilates from source to sink. The genotypic differences with respect to total dry weight was also reported by Pawar and Bhatiya (1986) [25] in mung, Hemchandra et al. (1997) [16] in chickpea, similar results was reported by Zode et al. (1999) [34] was found that, total dry matter accumulation ranges from 8.3 to 13.80 g in lathyrus as well as similar type of results were also quoted by Goyal (2003) [13] in lathyrus.

Growth analysis

Growth analysis is one of the measures for assessing seed yield of a plant. Recently an importance to physiological aspects is given in breeding for potentially higher yield, particularly to the significance of photosynthesis. The physiological basis of yield difference can be examined through an evaluation of differences in growth parameters and their impact on yield. The genotypic variation in the productivity of crop may be related the parameters such as RGR, NAR, CGR and partitioning of total photosynthesis into economic and non-economic sink. This was reported by Prasad et al. (1978) [26] . (1999) [34] in lathyrus and Harshvardhan (2004) [17] in lathyrus.

Crop Growth

Increase in drymatter of a plant is a process of continuous compound interest where in the increment in any interval adds to the " Capital for subsequent growth." This rate of increment in growth is called as relative growth rate.

The data on relative growth rate was recorded at different growth intervals are presented in Table 5. At 30-50 DAS, the RGR was found to be non-significant. The genotype EC-539032 (0.0433 g/g/day) showed numerically maximum RGR followed by genotype Ratan (0.0369 g/g/day) over rest of the genotypes. Similarly numerically lowest RGR was recorded in genotype IC-208430 (0.0266 g/g/day). At 50-70 DAS, the RGR was found to be non-significant. The genotype EC-539032(0.0807 g/g/day) showed numerically maximum RGR followed by genotype IC-420785 (0.0802 g/g/day) over rest of the genotypes. Similarly numerically lowest RGR was recorded in genotype EC-389370 (0.0602 g/g/day). At 70-90 DAS, the RGR was found to be non-significant. The genotype EC-539032 (0.0369 g/g/day) showed numerically maximum RGR, followed by genotype IC-345413 (0.0368 g/g/day) over rest of the genotypes. Similarly numerically lowest RGR was recorded in genotype EC-540902 (0.0330 g/g/day).

The RGR is the measures of dry matter production on per day basis. RGR increased upto 50-70 DAS and thereafter it declined. Similar results were also reported by Goyal (2003) [13] in lathyrus Net Assimilation Rate (g/dm 2 /day) Net assimilation rate is closely associated with photosynthetic efficiency of plant but it is not a absolute measure of photosynthesis. The apparent photosynthesis depends upon the excess of dry matter gain over loss of respiration. The NAR is the increase in plant dry weight per unit leaf area of assimilatory tissue per unit time.

The data on net assimilation rate are presented in Table 6.

NAR differed significantly at different growth intervals of crop. At 30-50 DAS, the NAR was found to be significant. None of the genotypes recorded significantly higher NAR than check Ratan (0.0361 g/dm 2 /day). However eleven genotypes were found to be at par with check Ratan (0.0361 g/dm [35] and Goyal (2003) [13] . The genotypic differences with respect to NAR were also reported by Shrivastava et al. (1982) [27] in soybean and Zode et al. (1999) [34] in lathyrus and Mundada (2000) [21] in lathyrus.

The data on relative water content are presented in Table7. 2004) [17] . At subsequent stages genotypic difference in relation to relative water content were observed. The present investigations are in supported with the results of Gupta et al. (2004) [15] and Reddy et al. (2003) [28] .

The data are presented in Table 8. Total chlorophyll content in leaves of different lathyrus genotypes was estimated at four different consecutive growth stages i.e. at 30, 50, 70, and 90 DAS.

It is revealed from the Table 4.5 that, total chlorophyll content in leaves has increased upto 50 DAS and thereafter decreased at 70 DAS and 90 DAS respectively. At 30 DAS, significant differences in respect of the total chlorophyll content in different lathyrus genotypes were observed. The genotypes viz., EC-539032 (1.34 mg/g) and IC-120463 (1.33 mg/g) recorded significantly higher chlorophyll content in leaves than check Ratan (1.23 mg/g). However the genotypes viz., IC-120442 (1.24 mg/g), IC-345413 (1.24 mg/g) and EC-540902 (1.22 mg/g) were found to be at par with check Ratan (1.23 mg/g). Ten genotypes recorded significantly lower total chlorophyll content in leaves than check Ratan. The significantly lowest total chlorophyll content was found in genotypes IC-120536 (1.12 mg/g). At 50 DAS, significant differences in respect of total chlorophyll content in different lathyrus genotypes were observed. Five genotypes viz., IC-120463 (1.74 mg/g), EC-539032 (1.74 mg/g), IC-345413 (1.67 mg/g), IC-120442 (1.65 mg/g), and EC-540902 (1.64 mg/g) were recorded significantly higher total chlorophyll content than check Ratan (1.60 mg/g). Grand mean total chlorophyll content of 1.54 mg/g fresh leaves was observed at 50DAS which was highest value as compared to 30,70 and 90 DAS. Similar findings were observed by Harshvardhan (2004) [17] . The genotype IC-120463 (1.74 mg/g) and EC-539032(1.74 mg/g) recorded highest chlorophyll content. Ten genotypes recorded significantly lower total chlorophyll content than check Ratan. The significantly lowest total chlorophyll content was found in genotype IC-120536 (1.33 mg/g). At 70 DAS, significant differences in respect of the total chlorophyll content in different lathyrus genotypes were observed. None of the genotypes was found significantly superior to check Ratan (1.29 mg/g). However seven genotypes viz., the genotype IC-420494 (1.31 mg/g), IC-208430 (1.27 mg/g), IC-120463 (1.25 mg/g), IC-420784 (1.25 mg/g), EC-540902 (1.25 mg/g), EC-389370 (1.24 mg/g) and IC-120536 (1.22 mg/g) were found to be at par with the check Ratan. Eight genotypes recorded significantly lower total chlorophyll content than check Ratan. The significantly lowest total chlorophyll content was found in genotype IC-345448 (0.86 mg/g). At 90 DAS, significant differences in respect of the total chlorophyll content in different lathyrus genotypes were observed. Only one genotype IC-420494(0.86mg/g) recorded significantly higher total chlorophyll content than check Ratan(0.82mg/g). However none of the genotypes was found to be at par with the check Ratan Fourteen genotypes recorded significantly lower total chlorophyll content than check Ratan at this important stage. The significantly lowest total chlorophyll content was found in genotypes EC-405302 (0.47 mg/g) Similar findings were observed by Zode (1998) [35] they reported that chlorophyll content in leaf ranges from 1.13 to 1.18 mg/g at flowering stage in lathyrus and Harshvardhan (2004) [17] observed that chlorophyll content in leaves ranges from 0.96 to 1.26 mg/g at 30 DAS while 0.96 to 1.17 mg/g at 70 DAS in lathyrus. ------------------ a) Field study 1. The maximum plant height was recorded in genotype EC-540902 at all stages of plant under study.

2. None of the genotypes exhibited significantly higher in total leaf area per plant than check Ratan at 30, 50 and 90 DAS while the genotype EC-539032 recorded significantly superior in total leaf area per plant at 70 DAS. 3. The genotype EC-389370 exhibited significantly superior in total dry matter production. 4. Regarding the physiological parameters, crop growth rate was found non significant at 30-50 DAS. Significant differences were found at 50-70 and 70-90 DAS in genotype EC-539032 was found superior. 5. Relative growth rate was found to be non significant at all the growth stages. The genotype EC-539032 was found numerically superior to check Ratan. 6. None of the genotypes exhibited significantly higher net assimilation rate than check Ratan at 30-50 DAS. But the genotype EC-539032 was found significantly superior at both the stages (i.e. 50-70 and 70-90 DAS).

b) Laboratory study 7. The relative water content (RWC) (%) was found to be non significant at 30 DAS. The genotype EC-539032 was found to be significantly superior at remaining stages (i.e. 50, 70 and 90 DAS. Grand mean relative water content in leaves was increased at 70 DAS as compared to 50 DAS due to rainfall. 8. The total chlorophyll content (mg/g) was found significantly superior in genotype EC-539032 at 30 and 50 DAS while genotype IC-420494 was found significantly more at 70 and 90 DAS.

Conclusion

1. In the light of the results obtained, it can be concluded that, the genotypic variability existed regarding the physio-morphological, biochemical and other attributes at various growth stages of the crop. 2. In present investigation, among all the genotypes studied EC-539032 exhibited superior performance in leaf area, CGR, NAR, relative water content as well as total chlorophyll content the average content than safe value for consumption. 3. The genotype EC-539032 and EC-389370 could be used in breeding programme for developing genotypes of highest dry matter production.

Acknowledgement

AcknowledgmentsThe present investigation entitled "Morphological studies of elite lathyrus (Lathyrus sativus L) germplasm was undertaken at experimental field of Department of Agricultural Botany, Dr. P.D.K.V., Akola (M.S.) during rabi season of 2009-2010 in RBD with three replications consisted of sixteen treatments with the net plot size of 1.20m x 1.90m. thanks to Head Department of Agricultural Botany, Dr. P.D.K.V., Akola (M.S.) for provided to all facility for given experiment and my all staff members of agriculture research station under Dr. PDKV Akola and my friends to help to taken observation and analysis of data and also laboratory work.

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