Varietal Roles on Morpho-physiological and Yield Attributes of Lentil (Lens culinaris Medik)

Lentil is one of the extensive cultivated pulse crops in Bangladesh. It belongs to the family Leguminosae which grows annually in the cool season (rabi). It is a source of balanced protein supply. On average lentil grain contains around 59% carbohydrate, 24-26% protein, 0.7% fat, 3% vitamin (b-carotene), 4% minerals (potassium, phosphorus, iron, zinc) and 10% moisture (Rasheed et al., 2010). Though the caloric content of lentil is equal to rice, but it provides almost four times the protein and eight times the riboflavin compared to rice (Anonymous, 1966). Lentils are often cooked in the form of dal (a food recipe) and consumed with rice. Combination of rice and dal provides a complete protein package which is well known as the recipe khichuri (Uddin et al., 2008). Thus, it is known as “poor man’s meat” because of its high protein content and quality (Bhatty, 1988). Besides human food source, green lentil plants (Gahoonia et al., 2005) and straws (Erskine et al., 1994) are excellent feed for animals also. In addition to food and feed lentil plays a key role for soil health improvement in the cropping systems (Anonymous, 1984) through addition of nitrogen, carbon, organic matter (Sarker and Kumar, 2011) for ultimate sustainability of crop production systems (Sarker et al., 2004).
 
During 2019-20, globally mean seed yield of lentil was about 1.30 t/ha; whereas in Bangladesh the it was nearly 1.25 t/ha (FAOSTAT, 2022). Although there are a good number of modern lentil varieties developed by research institutes which have high yield potential (about 2.0 t/ha) but due selection of appropriate variety (region specific), lack of desired plant population, poor agronomic management, sowing time (delayed/early), drought, excess moisture, disease and weed infestation etc. factors potential yield is seldomly achieved. Furthermore, low yield demotivates farmers to cultivate lentil instead they are keen to grow other staple foods (rice, maize and wheat) which have higher yield thus pulses have been allotted to marginal or less fertile lands where production is minimized (Aktar, 2013). So far Bangladesh institute of nuclear agriculture (BINA) and Bangladesh agricultural research institute (BARI) together has released eighteen high yielding varieties (nine variety by each institute) of lentil (BINA, 2022; Azad et al., 2020). Among them Binamasur-5, Binamasur-8, Binamasur-9, BARI Masur-5, BARI Masur-6, BARI Masur-8 are quite popular.
               
Desirable yield of a variety primarily dependent on yield contributing characters as well on physiological traits (Mondal et al., 2013). Important physiological attributes viz. leaf area index (LAI), net assimilation rate (NAR), crop growth rate (CGR), relative growth rate (RGR), total dry mass (TDM), absolute growth rate (AGR) are some of the key determinants to find out the limitations and causes of low yield of particular variety (Mondal et al., 2012). Hence to depict the major source sink characters and their relation in contributing yield is essential to evaluate the overall performance a specific lentil variety. Magura district of Bangladesh is very much favorable for pulses specially lentil production due to prevailing weather and soil condition during the rabi season. Our experiment focused on the physiological, morphological and yield characteristics of some BINA and BARI released modern lentil varieties and their relationship with yield.

Location of the experiment
 
Experiment was setup at Bangladesh institute of nuclear agriculture, Sub-station farm, Magura which was under the Agro Ecological Zone 11 (AEZ) the site was characterized by high Ganges river flood plain; with high to medium land type. Soils were calcareous dark grey to brown floodplain. Organic matter content in brown ridge soils is low but higher in dark grey soils. Soils were slightly alkaline with deficit in fertility (FRG, 2012). An overview of the weather parameters during the experimental period is demonstrated in Fig 1.
 

 
Crop establishment and cultural practices
 
Field experimentation was conducted in Rabi (winter) season of 2019. Plot preparation was done according to the procedures described by Chowhan and Nahar (2022). Fertilizers were applied considering low soil analysis interpretation level and applied on soil in accordance with Ahmmed et al., (2018). Unit plot size was 3 m × 1.5 m; where line to line and plot to plot distance was 30 cm and 60 cm respectively. Seeds were line broadcasted at the rate of 40 kg/ha on 21^st November 2019. Before sowing of seeds they were treated with Provax 200 WP (Carboxin 17.5%) + Thiram 17.5%) of Hossain Enterprise C.C. Limited at rate of 3 g/kg of seeds. After sowing no fungicide or insecticide was applied up to harvest. Hand weeding and thinning was done 30 days after sowing (DAS). Crops were harvested when pods along with plants attained brownish color.
 
Experimental design
 
Randomized complete block design (RCBD) with 3 replicates was followed for experimentation. Distance between replications were 1m. Variety was the only treatment. The 7 lentil varieties were-  
Data collection and analysis
 
For ontogenetic growth characteristics, five plants were randomly sampled for growth parameters from 30 days after sowing (DAS) and continued at an interval of 15 days up to harvest. Plants were separated into roots, stems, leaves and pods and the corresponding dry weights were recorded after oven drying at 80±2°C for 72 hours.
 
Morpho-physiological and yield features
 
Plant height (cm), number of branches (primary) per plant, number of secondary branches per plant was recorded 15 days interval up to harvest. Data on plant population, number of pods per plant, number of seeds per pod, thousand grain weight (TGW) (g), crop duration (days to maturity) was recorded during final crop cutting. The following physiological attributes were noted according to Hunt et al., (2002).
   
Where,
 
D₁= Fresh weight of the plant (g).          
W₁= Total plant dry matter at initial time t1 (g).
D₂= Oven dry weight of the plant (g).     
W₂= Total plant dry matter at final time t2 (g).
t₂= Final time (day).   t₂> t₁                                                       
t₁= Initial time (day).
A = Ground area (m²).                           
ln= Natural logarithm.
 
Yield
 
All yield related data like- seed yield (calculated by adjusting 10% moisture), stover yield and harvest index were collected after harvesting the whole crop.
 
Statistical analysis
 
Data obtained from the parameters were analyzed statistically with ANOVA (analysis of variance) technique by Statistix 10 and the mean differences were adjudged by LSD (least significant difference) test (Russel, 1986) at 5% or 10% level of probability.

Morpho-physiological and yield properties
 
Plant height increase of all the varieties followed a similar trend up to 75 DAS (Fig  2). But a variation was seen between 90 DAS to harvest. Though at harvest the plant height remained statistically similar among the varieties but at 90 DAS, longest height was observed with BARI Masur-8 (V₇) and the shortest was noted in BARI Masur-5 (V₅). Deviation in plant height might be due to genetic attributes and soil fertility status. Khatun et al., (2016) reported variations in plant height in different BINA and BARI lentil varieties.
 

       
In case number of branches (primary) per plant, all the seven varieties exhibited a rising trend up to 75 DAS except BARI Masur-8 (V₇) (Fig 3). After 75 DAS the number of branches gradually declined. Whereas, except for BARI Masur-5 (V₅) and BARI Masur-6 (V₆) rest five varieties showed an upward tendency in secondary number of branches per plant up to harvest (Fig 4). In order to build vegetative structure, plants developed branches but when it commenced reproductive growth cessation in some parts occurred and the primary branches might have been converted in secondary branches thus a reduction was noticed; which gave rise number of secondary branches with elapse to time. Zahan et al., (2009) observed varietal differences in branch number in BARI varieties.
 

 

       
Initially up to 75 DAS TDM demonstrated a slow increase (Fig 5). From 75 DAS to 90 DAS the rise was very slow. But from 90 DAS to harvest TDM boosted rapidly. Though significant differences were noted among the varieties in dry mass accumulation up to 75 DAS but at harvest it was non-significant. Shrestha et al., (2005) reported an increase in the amount of dry matter accumulation with elapse of time (with increasing DAS) on lentil genotypes.
 

       
AGR followed a divergent trend in the lentil varieties (Fig 6). Varieties Binamasur-8 (V₂) and Binamasur-10 (V₄) showed downward trend in AGR at 45 DAS to 60 DAS but other five varieties showed upward trend. Though at 60 DAS to 75 DAS a rise in AGR of all the varieties were noticed but it again declined at 75 DAS to 90 DAS. During final harvest all varieties showed increased and similar AGR. Dissimilarities in AGR among the varieties might be ascribed to varied physiological factors among the varieties. Greater growth rates during the vegetative and blooming stages are preferred for improved grain production in lentil. Yield properties are reflected by the crop’s capacity to capture solar energy early on and then use it for biomass production later on (Hanlan et al., 2006). Similar findings were also narrated by Mondal et al., (2013).
 

       
RGR ensued a zigzag pattern in the lentil varieties excluding Binamasur-9 (V₃) (Fig 7); which appeared a straight decline up to 75 DAS to 90 DAS. During harvest highest RGR was obtained from Binamasur-8 (V₂) and the lowest was found with BARI Masur-5 (V₅). Khanam et al., (2018) spotted similar patterns in RGR among four lentil genotypes in Magura district at rabi season.


       
Preliminary rise in CGR was extremely slow up to 60 DAS to 75 DAS; but after that RGR dropped remarkably at 75 DAS to 90 DAS (Fig 8). Afterward all the seven varieties displayed a mounting at 90 DAS to harvest. At this time utmost CGR was shown by Binamasur-9 (V₃) and the least with BARI Masur-8 (V7). Maximum utilization of environmental resources aided lentil varieties to peak CGR at the reproductive phase. During harvest CGR was supposed to decline but the varieties might still be accumulating dry mass thus CGR did not drop. Singh et al., (2016) noticed a downward trend of CGR in lentil treated with phosphorus and biofertilizers. Khan et al., (2015) reported similar results in soyabean genotypes.
 

       
Amongst the varieties abundant plant population in the unit plots (4.5 m²) was noticed with BARI Masur-6 (V6); whereas Binamasur-5 (V₁) had the scarce number of plants. Reason of heterogenous number of plants was due to insect pest and disease infestation (Table 1). Tolerant varieties showed satisfactory plant population over susceptible varieties. Adhikari et al., (2018) narrated deviations in plant population among the lentil genotypes.
 

       
Number of pods per plant and seeds per pod was most in Binamasur-5 (V₁) and Binamasur-10 (V₄) (Table 1). Contrary the least pods and seed per plant was recorded with BARI Masur-6 (V₆). Dissimilarities in number of pods and seeds per plant might be due to genetic variability among the varieties. Ouji et al., (2021) found the existence of significant genetic variability among the lentil lines.
       
Heaviest TGW was noticed in Binamasur-9 (V₃) conversely, lightest was noted with BARI Masur-6 (V6) (Table 1). Disparities in TGW was may be due to seed size, shape and boldness. Varied TGW due to genotypes were previously annotated by Yadav et al., (2016).
       
In terms of maturity, BARI Masur-5 (V₅) matured most late while earliest days to maturity was marked in Binamasur-8 (V₂) (Fig 9). Duration of a variety is mostly genetic character but it may also be influenced by environmental factors. Sarkar et al., (2021) stated that, cultivation in medium low land may delay lentil maturity.
 

 
Yield
 
Highest seed yield and HI was obtained from Binamasur-10 (V₄) (Table 1, Fig  9). However, the lowest seed yield was gained with BARI Masur-6 (V₆) but least HI was produced by BARI Masur-5 (V₅). Stover yield was maximum in BARI Masur-5 (V₅) and minimum at BARI Masur-5 (V₅). Seed yield was relied on better assimilate partitioning to economic yield, genetic potentiality, insect disease tolerance, better utilization of natural resources, inputs etc. factors. Varieties which build up more vegetative growth yielded less seed, HI and vice versa. Roy et al., (2019) found maximum yield of Binamasur-10 (LG-208 line) among numerous lentil accessions in Magura grown in winter. Singh and Sharma (2021) indicated that nutrient uptake significantly improved grain and biomass yield of lentil. Current outcomes are in conformity with the previous findings.
 
Correlation study among different attributes
 
Number of pods per plant is the main seed yielding indicator that has a positive relationship with plant height. The pod number showed significant positive correlations with secondary branch number (r = 0.71*), TDM (r = 0.78*), seed yield (r = 0.79*) and HI (r = 0.755*). TGW showed significant positive correlations with plant height (r = 0.88**), primary branch number (r = 0.81*), TDM (r = 0.93**), seed yield (r = 0.90**) and HI (r = 0.75*). The seed yield was also significantly correlated with plant height (r = 0.78*), primary branch number (r = 0.76*), secondary branch number (r = 0.75*), TDM (r = 0.87**) and HI (r = 0.85**). Hence seed yield was strongly correlated with all the yield contributing parameters (Table 2). This suggests that increasing sink (pod number) production would increase seed yield and pod production depending on morpho-physiological characters. These findings are in good agreement with Kumar et al., (2017).
 

Besides satisfactory yield component characters a variety should also bear the ability to develop a higher growth rate during it’s vegetative stage and utilize effective partitioning of dry matter for delivering better economic yield. It should also possess some tolerance to biotic and abiotic stresses. Here, Binamasur-10 performed better over the other varieties in terms of seed and stover yield following moderate life duration. Thus, for Magura district cultivation of Binamasur-10 as a new and promising variety may give higher yield over the existing variety or cultivars.