Performance of some promising germplasm of Fenugreek (Trigonella foenum-graecum L) towards growth and yield and their response to accumulated heat towards rate of flowering and pod development

Fenugreek (Trigonella foenum-graecum L.) is an annual legume plant of family Fabaceae and primarily used as a spice in many parts of the world. It is a native to the Mediterranean region and is grown extensively in Rajasthan, Gujarat, Madhya Pradesh, Uttar Pradesh and few other states of India. The area and production of fenugreek in India during 2015-16 is estimated as 1,24,710 hectares and 1,34,100 tonnes, respectively (Spice Board, 2016). It is a cold season crop and is fairly tolerant to frost as well as very low temperature. Being a valuable medicinal plant with potential for multipurpose uses, fenugreek is extensively used in the pharmaceutical industry. The leaf and shoot is quite rich in protein, minerals as well as vitamins A and C. The seeds contain cellulose, hemicellulose, major nutrients such as calcium, iron, sodium and amino acid like leucine, valine, lycine and phenylamine. Seeds are bitter in taste due to the presence of an alkaloid trigonelline. In recent times the importance of fenugreek has further increased due to the presence of a steroid called diosgenin which is essential in the synthesis of sex hormones and oral contraceptives. Fuller and Stephens (2015) opined that the diosgenin, 4-hydroxyisoleucine and the fiber component of the plant are the most valuable bioactive constituents present in fenugreek. The seeds are used in colic flatulence, dysentery, diarrhoea, dyspepsia, chronic cough and enlargement of liver and spleen, rickets, gout and diabetes. In spite of all these qualities the crop has not gained due importance primarily because of paucity of information regarding good planting materials and their attributing parameters towards growth and yield. Some aspects of fenugreek including the varietal performances, sowing time, water relation to growth dynamics are there (Sharangi et al., 2005; Bhutia and Sharangi, 2016, 2018), but location specific information as well as their relationship with agro-meteorological indices (Sharangi et al., 2011) is always crucial for any location to screen the right planting material.  Available variability is a prerequisite for planning any breeding programme with a view to improvement. The evaluation also helps to assess the relative merits of different genotypes having varied traits towards selection of appropriate parents for hybridization (Narolia et al., 2017). There are defined phases in the life cycle of an annual crop like fenugreek namely vegetative (between seedling emergence and floral initiation), reproductive (between floral initiation and flowering) and grain filling (between anthesis and physiological maturity). The genotypes-environment interaction study was conducted by Meena et al., (2015) showing the significantly non linear response of genotypes to environments. Simple correlations between seed yield and other traits indicated that pods per plant and the test weight are the two important component traits. In another legume (pigeon pea), five lines, three testers and their fifteen crosses were evaluated by Rama Devi et al., (2012) to study the genetic relationship among yield components through association and path analysis. The association studies indicated significant positive correlation of seed yield with pods per plant in parents and plant height, pods per plant and harvest index in crosses.Ionescu and Roman (2013) studied on the biology, ecology and productivity of Trigonella foenum-graecum L. species with observations and measurements, concerning: morphological and biological peculiarities of species, productivity elements and seed yield, chemical composition and quality. They found that fenugreek cultivated in South Romania reached harvesting maturity in the third decade of July, after 95 days of vegetation and the accumulation of 922.24 GDD (St>10°C). A thorough study is still required to correlate the rate of development of vital phenophases for determining their ultimate expression in terms of yield and quality. The present research was, therefore, designed to evaluate some promising germplasms of fenugreek, to find out the most important parameters contributing the seed yield and also to relate their two crucial phasic development with agrometeorological indices.

The present investigation was carried out at the Horticultural Research Station, Mandouri, BCKV, West Bengal (23.5°N, 89°E, 9.75 m MSL, soil entisol with sandy clay loam, pH 6.9) for initial characterization study during the years 2014-15 and 2015-16. The experiment was laid out in randomized block design with three replications of fourteen germplasms namely V1=Agf-1, V2=Agf-2, V3=Agf-3, V4=Rmt-303, V5=Rmt-305, V6=Rmt-1, V7=Rmt-143, V8=Rmt-351, V9=Co-1, V10=Raj Kanti, V11= Hissar Suvarna, V12=Gm2, V13=Pant Ragini, V14=Local collected from NRC, Seed Spices, Ajmer, Rajasthan except the local. Seed sowing was done on 2^nd November of 2014 and 2015. The row to row and plant to plant distance was kept at 30 cm and 10 cm, respectively. FYM @ 25t/ha as well as NPK @ 25:25:50 kg/ha were applied and all other recommended cultivation practices were followed to raise a good crop. Five plants were randomly selected and tagged before flowering from each line to record the data on selected attributes. Observations on different morphological, phenological, yield and yield attributing characters viz., pod length, branch number, pod per plant, pod length, seed per pod, test weight, seed weight per plot and yield were recorded from five randomly selected plant of each plot. All data were analyzed using analysis of variance (ANOVA) to determine the significance of the main effects and their interaction. Least significance difference (LSD) tests were performed to determine the significant differences between individual means following procedures suggested by Gomez and Gomez (1984). All statistical analyses were performed using the SPSS Version 16.0 statistical software.
        
The two major agro-meteorological indices such as helio-thermal unit (HTU) and growing degree days (GDD) were taken into account to relate the vegetative and reproductive phenophases. The heliothermal unit (HTU) was considered to relate with the floral and pod development rate of fenugreek.
        
Growing degree days is the total amount of heat required between the lower and upper thresholds. The growing degree days were worked out by considering the base temperature of 10°C. The total growing degree days  for different phenophases were calculated by using the following equation:     

                              
 

 
where, GDD = Growing degree day, Tmax = Daily maximum temperature (°C), Tmin = Daily minimum temperature (°C), Tb = Base temperature (10°C).
        
The HTU is the accumulated product of GDD and bright sunshine hours between the developmental thresholds for each day. Simply, HTU is the product of GDD and the mean daily hours of bright sunshine. The sum of HTU for each phenophase was worked out by using the following equation:                                                 

 

 
 where, HTU = Helio-thermal units, T = Mean daily tempe rature (°C), Tb = Base temperature (10°C), ds = Date of start, dh = Date of end, BSS= Bright sunshine hours.
        
The relationship of HTU and rate of development can be linearized by plotting the inverse of duration 1/D against HTU (Fig 1). 1/D is defined as the mean rate of development, with units of day^-1 and is equivalent to the proportion of development per day.
 

Morphological and yield attributing characters
 
Morphological as well as yield attributing characters differed significantly among the germplasms (Table 1). Of the 14 germplasms evaluated, maximum plant height was recorded in Agf-1 (97.33cm) followed by Rmt-303 and Gm-2 (91.00cm), Hissar Suvarna (87.67cm) etc. Minimum plant height was recorded in Agf-2 (78.33cm) and Pant Ragini (78.66cm). The maximum number of branches was recorded in Rmt-143, Rmt-303, Co-1, Raj. Kranti, Hissar Suvarna and Local (8.33cm) followed by Agf-1 (8.00cm) which is followed by Gm-2, Rmt-305, Rmt-1 and Rmt-351 etc. and minimum number of branches was recorded in Agf-2 (6.33cm). In pod per plant maximum number was recorded in Rmt-1 (98), followed by Rmt-305 (75), Local (65) and Agf-1 (56) etc and minimum pod per plant was found in Co-1 (18). The maximum pod length was recorded in local (13.33cm)  followed by Agf-2 and Agf-3 (13.00cm), Agf-1 (12.33cm), Rmt-303 (11.33cm) etc. and minimum pod length was recorded in Pant Ragini (8.66cm). Pod per seed was recorded highest in Rmt-305 and Rmt-303 (18) followed by Rmt-351, Agf-1 and Pant Ragini (17) and lowest pod per seed was recorded in Raj. Kranti (15). Maximum test weight was recorded in Local (14.46g) followed by Rmt-305 (14.3g), Rmt-303 (14.06g and Agf-3 (13.70gm) etc. and minimum test weight was recorded in Co-1 (9.30g). Seed weight per plot was found highest in Local (455.0g) followed by Agf-1 (420.0g), Agf-1 (405.0g) and Agf-2 (390.0gm) etc and lowest test weight was found in Co-1 (181.6g). Seed yield per hectare was recorded maximum in Local (15 qha^-1) followed by Agf-1 (14 qha^-1), Agf-2 (13 qha^-1), Agf-3 (12.56 qha^-1) etc. minimum yield was recorded in (6.0 qha^-1). Higher seed yield in fenugreek was always associated with the higher number of branches, pods, seeds (Datta and Chatterjee, 2014).
 

 
Correlation analysis
 
The knowledge of correlations between seed yield and its attributing characters is important for simultaneous consideration of several characters in selection for a breeding programme. Correlation coefficient were worked out for all possible combinations of eleven yield and its attributing characters. The result of correlation analysis of the seed yield with its component traits is indicated in Table 2. Seed yield per hectare showed highly significant (p<0.01) positive correlation with plant height (r=0.947**), number of branches(r=0.694**), pod length (r=0.753**), seed weight per pod (r=0.983**), seed weight per plot(r=0.999). Seed yield showed positive correlation with number of leaf (r=0.212), pod per plant(r=0.266), seed per pod (r=0.263), 50% flowering (r=0.086), maturity (r=0.146). Soori and Mohammadi-Nejad (2012) also reported positive and highly significant correlations of seed yield per plant with seeds per plant, plant height and number of pods per plant. They also reported significant positive correlation of seed yield with branch per plant.  Plant height showed highly significant (p<0.01) positive correlation with number of branches (r=0.673), pod length (r=0.707**), seed weight per pod (r=0.938**), seed weight per plot (r=948**), seed yield per hectare (r=0.947**) and plant height show positive correlation with number of leaf (r=0.189), pod per plant (r=0.354), seed per pod (r=0.209), 50% flowering (r=0.085), maturity (r=0.049). Number of leaves showed significant (p<0.05) negative correlation with seed per pod (r=-0.379*) while it had a negative correlation with pod per plant (r= -0.102). It had a positive correlation with number of branches (r=0.220), pod length (r=0.074), 50% flowering (r=0.089), maturity (r=0.056), seed weight per pod (r=0.226), seed weight per pod(r=0.214) and seed yield per hectare (r=0.213). Number of branches showed highly significant (p<0.01) positive correlation with pod per plant(r= 0.654**), pod length (r=0.639**), seed weight per pod (r=0.681**), seed weight per plot(r=0.697**) and seed yield per hectare (r=0.694**) while it had a positive correlation with seed per pod (r=0.334), 50% flowering (r=0.245) and maturity (r=0.176). Pod per plant showed positive correlation with seed per pod, pod length, 50% flowering, maturity, seed weight per pod, seed weight per plot and seed yield per hectare. Seed per pod had a highly significant (p<0.01) positive correlation with pod length (r=0.544**) while it had negative correlation with 50% flowering (r= -0.281) and maturity (r= -0.234). It showed positive correlation with seed weight per pod (r=0.252), seed weight per plot (r=0.261) and seed yield per hectare (r=0.264). Pod length showed highly (p<0.01) positive correlation with seed weight per pod (r=0.758**), seed weight per plot (r=0.754**) and seed yield per hectare(r=0.754**) while it had a negative correlation with 50% flowering (r= -0.010) and maturity (r= -0.030).  50% flowering had a highly significant (p<0.01) positive correlation with maturity (r=0.650**). It had a positive correlation with seed weight per pod (r=0.133), seed weight per plot (r=0.088) and seed yield per hectare (r=0.086). Maturity had a positive correlation with seed weight per pod, seed weight per plot and seed yield per hectare. In an evaluation trial for twenty two quantitative traits of 74 french bean genotypes, seed weight per pod showed highly significant (p<0.01) positive correlation with seed weight per plot (r=0.983**) and seed yield per hectare (r=0.984**) (Panchbhaiya et al., 2016). Seed weight per plot had a highly significant (p<0.01) positive correlation with seed yield per hectare (r=1.000**). Moreover, pods per plant showed positive and low correlation with biomass and seed yield per plant. Seeds per pod showed positive and negative correlation with seed and biomass yield per plant respectively. Found the pod yield to be highly significant and positively correlated with days to 50% flowering, seed yield per plant, plant height, number of pods per plant, number of  clusters per plant, number of pods per cluster, number of seeds per pod, pod length and weight of single pod. Significant positive correlation of seeds per pod and seed yield per plant was also reported (Kole and Saha, 2013).
 

        
The present result was in close agreement with the work of Jian et al., (2013) who found significant and positive correlation of seed yield with plant height, number of pods on main axis and total number of pods per plant. They also reported non-significant but positive correlation of seed yield per plant with secondary branches per plant and number of seeds per pod. Generally, this study revealed the importance of focusing on plant height, number of branch, pod length, pods per plant, seeds weight per pod and seeds weight per plot while selecting for seed yield. Dhama et al., (2009) also opined in case of pea that selection of parents can also be made on the basis of divergence, across the environments and can be considered as the reliable estimates of genetic divergence.
 
Relationship of floral and pod development rates with accumulated heat unit
 
The rate of floral and pod development of fenugreek varieties were related with accumulated heat units from flower initiation (Fig 1 and 2). In the present study, accumulated heat unit had a linear effect on the rate of development (here defined as the proportion of progress to flowering or pod development per day) from flower initiation to 50% emergence (R² = 0.662) and from 50% emergence to pod maturity (R² = 0.813). Rate of development was negatively related with accumulated heat units. However, in a separate study, a positive correlation was observed between the rate of floral development with degree days (Lovatt et al., 1984). In many crop species, the simultaneous progress of vegetative and reproductive development is rapid with the rise in temperature up to a species-specific optimum, after which growth and development slows and eventually stops (Hatfield et al., 2011).
 

 
Agro-meteorological indices
 
Different direct and derived agro meteorological parameters such as helio-thermal unit (HTU), growing degree days (GDD) and bright sunshine hours (BSS) both at vegetative and reproductive phases were significantly varied with varieties (Fig 3). It is difficult to predict plant growth based on the calendar because temperatures can vary greatly from time to time. So far as the growing degree days is concerned, the varieties Hisar Suvarna (502.65°C), Raj Kanti, Agf-1 and the Local required more than 500°C during vegetative phase. Rest of the varieties required below that mark ranging from 456.60 to 497.25. However during reproductive phase the variation between the varieties is less and the value of GDD ranged from 657.45°C (V₁₄=Local) to 749.75°C (Pant Ragini). During vegetative stage the requirement of HTU was found maximum (3730.73°C) in Hisar Suvarna, Raj Kanti, Agf-1, the minimum HTU (3435.21°C) being in Pant Ragini. The range of variation of HTU during reproductive phase was very meagre (5307.45°C to 5629.06°C). It might be due to the genetic makeup of the respective varieties. Some varieties show decreased duration of phenology as compared to others due to fluctuated unfavorable high temperature during the growing period (Ram et al., 2012). The above results are in agreement with those obtained by Radojka and Jevdjovic (2007) who reported that plants require a specific amount of heat to develop from one point in their lifecycle to another. Abou-Shleel (2014) projected that increase of air temperature under futuristic climate change could have some impact on the growth, yield and chemical composition of fenugreek seeds as a result to accumulation of heat units (GDD).
 

On the basis of certain vegetative as well as yield and yield attributing parameters, varieties like Agf-1, Agf-2, Agf-3 and the local existing varieties may be suggested for cultivation in this agro climatic zone. For selection purpose towards contributing seed yield, some attributing parameters like plant height, number of branches, pod length and seed weight per pod may be taken into consideration. Agro-meteorological indices like helio-thermal unit (HTU), growing degree days (GDD) and bright sunshine hours (BSS) both at vegetative and reproductive phases influenced the rate of flowering and pod development of fenugreek.