Stability Analysis of Yield and Yield Attributing Traits of Promising Genotypes of Cluster Bean [Cyamopsis Tetragonoloba (L.) Taub.]

Cluster bean [Cyamopsis tetragonoloba (L.) Taub.] with diploid chromosome number 2n=14, is popularly known as guar. It is a self-pollinated crop belongs to the family Fabaceae. Guar originated in India and Pakistan and is characterized as a short day erect or bushy annual plant (Purseglove, 1981). It is a drought tolerant, warm season legume crop with deep and well developed root system, cultivated mainly as rain fed crop in arid and semi-arid regions during rainy season for vegetable, galactomannan gum, forage and green manure. Guar enhances soil productiveness by fixing atmospheric nitrogen for its own necessities and also for the succeeding crop (Bewal et al., 2009). Guar can be successfully grown in soils where no other crops will survive. The guar crop prefers a well drained sandy loam soil. It can tolerate saline and moderately alkaline soils with pH ranging between 7.5 and 8.0 (Venkataratnam, 1973). Germ and hull portion termed as guar meal obtained after the extraction of gum is rich in protein 28.90-46.00 per cent. The endosperm fraction of cluster bean seed is rich in galactomannan (polysaccharide) i.e., 16.80-30.90 per cent (Lee et al., 2004 and Rodge, 2008). The seed also contain 30-35 per cent protein, 26.8-32.2 per cent gum, 6.1-7.7 per cent oil and 2.99-3.75 per cent minerals. Seeds having large endosperm that contains galactomannan gum, which forms gel in water commonly known as guar gum. Guar gum is commonly used as a stabilizer in many food products like ice-cream, fruit beverages, chocolate, milk and milk products, cake toppings etc. These qualities have made it the most favoured crop for marginal farmers in the arid areas. Cluster bean gum has emerged as the most important agro-chemical, which is non-toxic, eco-friendly and Generally Recognized as Safe (GRAS) by Food and Drug Administration (FDA). Assessment of stability will ensure the yielding over seasons and across locations a well (Hemant, 2020). Among the phenotypic stability models, the one given by Eberhart and Russel (1966) is widely used. Keeping the above in view, an investigation was carried out with twenty five genotypes of cluster bean including one check to assess the phenotypic stability over three agro climatic zones of Telangana state.

A set of 24 genotypes comprising of indigenous collections of cluster bean augmented from the ICAR- National Bureau of Plant Genetic Resources, Regional Station, Jodhpur along with one check variety of cluster bean (Pusa Navbahar) from IARI, New Delhi were evaluated in randomized block design with three replications during Kharif, 2019 at three locations representing three agroclimatic Zones of Telangana i.e., PG Research Block, College of Horticulture, Rajendranagar, Hyderabad (Southern Telangana Zone), JVR Horticultural Research Station, Malyal, Mahabubabad (Central Telangana Zone) and progressive  farmers field at Vemulawada, Karimanagar (Northern Telangana Zone). Each germplasm line was grown in a plot of 1.2 m × 0.6 m accommodating spacing of 30 cm × 15 cm.
       
Observations were recorded on five competitive plants in respect yield and yield attributes and quality traits, whereas days to first flowering and days to 50% flowering and days to maturity were recorded on plot basis. Gum, protein and fibre content were estimated by Association of Official Analytical chemists (Anonymous, 1958), Kjeldahl method (Subbaiah and Asija, 1956) and Association of official Analytical chemists (1990), respectively.
       
In the present study, the G × E interaction and stability analysis of different genotypes across the three environments were worked out as per the model given by Eberhart and Russel (1966). A genotype which possess high mean (µ), unit regression coefficient (bi =1) with the deviation from regression line approaching zero (S²di =0) or non significant is considered to be stable one i.e., possessing average stability, whereas a variety with regression coefficient lower than one has above average stability and is specially adapted to unfavourable (poor) environments. They hardly express response to improved environmental conditions. A variety with regression coefficient greater than one (bi >1) has below average stability and is suitable for favourable/rich environments.

Highly significant differences were observed among the genotypes for all characters (Table 1) under study. This indicated enough genetic variability among the genotypes. Significant variation among the environments was observed for almost all the characters studied except for number of branches.  While, E + (G × E) interaction was also highly significant for all characters except for number of branches per plant, pod length and number of seeds per pod. The environments linear were highly significant for all the traits. This revealed that the environments were affecting the performance of all the genotypes with respect to cluster bean yield attributing traits. Wankhade et al., (2016) observed significant E + (G × E) interaction for plant height (cm), number of pods per plant, gum content (%) and protein content (%) in cluster bean genotypes. Genotype × environment interactions and linear component of G × E interaction were highly significant for most of important traits viz., plant height (cm), days to maturity, pod weight (g), number of pods per plant,  pod yield per plant(g) and pod yield per hectare (q/ha), protein content (%), gum content (%) and fibre content (%). Similar results of significant G × E interactions were also been observed by Pereira et al., (2009) in 16 varieties of french bean; for plant height (cm), pod yield per plant(g) and pod yield per hectare (q/ha), gum content (%) and protein content (%) in cluster bean by Wankhade et al., (2016); for plant height (cm) and number of pods per cluster and days to maturity in cluster bean by Pawan et al., (2016). Whereas, it was non-significant for number of branches per plant, days to first flower, days to 50% flowering, number of clusters per plant, pod length (cm) and number of seeds per pod. This is in conformity with finding of Altaf et al., (2020) in French bean.
 

       
The mean sum of square due to G × E interaction was partitioned into linear and non-linear components. The environment (linear) component of variance was significant for all the characters studied indicating that macro-environmental differences were present in all the three locations studied and was still predictable. The mean sum of squares due to pooled deviation (non-linear) was also significant for all the characters viz., indicating role of unpredictable causes that affect stability. Similar response was also obtained by Chaudhary et al., (2005a) and Chaudhary et al., (2005b) and Pawan et al., (2016) in cluster bean; Fayaz et al., (2017) in common bean, Sanjeev et al., (2018) in cow pea and Altaf et al., (2020) in french bean.
 
Stability of plant characters
 
On the basis of mean performance over environments, the plant height ranged from 43.9 cm (IC-28283) to 119.744 cm (IC-103295). Genotype IC-140777 showed regression coefficient near to unity with non significant deviation from the regression line indicating average stability. While the genotypes IC-9233-P3, IC-10333, IC-10520, IC-103295, IC-140774, IC-200679, IC-200680 and Pusa Navbahar had high mean value with regression coefficient less than one and small non significant deviation from regression line indicating above average stability suitable in unfavourable or poor environments (Table 2). Four genotypes IC-9077-P1, IC-10323, IC-28287 and IC-200696 had higher mean performance with regression values more than unity and non significant deviation from regression line indicating their suitability for favourable environments with below average stability. Similar interactions for this trait are reported earlier in cluster bean (Jain et al., 2012, Wankhade et al., 2016 and Satish et al., 2017).
 

       
For plant spread (cm) in E-W direction, among 25 genotypes fourteen genotypes viz., IC-9052, IC-9233-P3, IC-10323, IC-10333, IC-10520, IC-13348, IC-28287, IC-34344, IC-39989, IC-103295, IC-140774, IC-140791, IC-200679 and IC-200680 are significantly higher than the general mean (26.607 cm). Genotype IC-10323 (26.153 cm) recorded highest plant spread, while Pusa Navbahar (14.644 cm) recorded lowest plant spread (Table 2). The regression (bi) value ranged from -0.98 (IC-90523) to 4.50 (IC-9229-P3). The genotypes viz., IC-9233-P3, IC-10323, IC-10333, IC-10520, IC-13348, IC-28287, IC-34344, IC-140774, IC-140791, IC-200679 and IC-200680 are adapted to poor environments as they had bi less than unity and high mean with small non significant deviation from regression line. While, the genotype IC-103295 adapted to favourable environment as it had bi above unity higher mean with non significant deviation from regression line.
       
It was observed that days to maturity ranged from 84.172 (IC-10323) to 94.06 (IC-39989) across the environments. The genotype IC-10323 had significantly lower mean than general mean, regression coefficient equivalent to unity and S²di equivalent to zero, exhibiting average stability and adaptability, hence, most suitable and desirable. The genotypes viz., genotype IC-13365, IC-200680, IC-140777 and IC-200715 had mean significantly lower than general mean, regression coefficient less than unity and S²di equivalent to zero, exhibiting low responsiveness and more stable hence, this genotype was suited for poor environmental condition (Table 3). Genotypes namely, IC-9233-P3, IC-140774, IC-200679 and IC-200696 had mean significantly lower than general mean, regression coefficient more than unity and S2di equivalent to zero, exhibiting below average stability hence, this genotype was suited for better environmental condition. Satish et al., (2017) and Altaf et al., (2020) reported similar findings.
 

       
The mean performance of genotypes for number of pods per plant ranged from 37.03 (IC-13348) to 103.15 (IC-103295) with overall mean of 64.25 (Table 2). Among the 13 genotypes that were recorded high mean, seven genotypes viz., IC-9052, IC-10323, IC-103295, IC-200680, IC-177844, IC-200715 and IC-200679, which also showed bi around unity (bi=1) with non significant S2di and stable ones across environments. The genotype IC-140777 recorded more number of pod per plant and bi value less than one with non significant S²di, explaining its suitability in poor environments (unfavourable) as they showed above average stability. The genotypes IC-9229-P3 and IC-140774 recorded more number of pods per plant and bi value more than one with non significant S²di, explaining their suitability in favourable environments (below stability). Variable performance of cluster bean genotypes under different environmental regimes for number of pods per plant are also reported by Satish et al., (2017), Fayaz et al., (2017) and Altaf et al., (2020).
 
Stability of yield attributes
 
Considering pooled mean performance of pod length (cm), it was found that three genotypes viz., IC-28283 (8.85 cm), IC-39989 (13.67 cm) and IC-103295 (8.84 cm) had significantly higher pod length than check variety Pusa Navbahar (8.71 cm) (Table 3). Pooled analysis showed that linear component of G × E interaction was not significant for this trait. Hence, it indicates that there was no environmental effect on this trait. Out of 25 genotypes, three genotypes viz., IC-39989, IC-103295 and IC-200696 possessed significantly higher mean than general mean, regression coefficient equivalent to unity and S²di equivalent to zero, exhibiting average stability and adaptability, hence, most suitable and desirable. The genotypes viz., IC-28283, IC-28287 and IC-177844 had mean significantly higher than general mean, regression coefficient more than unity and S²di equivalent to zero, exhibiting below average stability. Hence, this genotype was suited for better environmental condition. Pawan et al., (2016) in cluster bean, Satish et al., (2017) in french bean and Sanjeev et al., (2018) in cowpea also reported similar findings.
       
The mean performance of pod girth (mm) of genotypes ranged from 5.73 mm (IC-10520, IC-13348) to 10.16 cm (IC-39989). Eight genotypes viz., IC-9052, IC-10323, IC-28269, IC-34344, IC-39989, IC-103295, IC-140774 and IC-200680 had higher pod girth than check variety Pusa Navbahar (8.50 mm). The deviation from regression was significantly greater than zero in one genotype (IC-13365) and it was near to zero in twenty four genotypes. Genotypes IC-39989, IC-103295 and IC-140774 showed significantly higher mean, with regression coefficient unity and non significant deviation from regression coefficient indicating average stability suitable for all environmental conditions. Other six genotypes viz., IC-9052, IC-9233-P3, IC-10323, IC-28269, IC-34344 and IC-200680 regression coefficient less than unity were adapted to unfavourable environment (Table 3). Results are in accordance with reports of Tamene et al., (2015) in faba bean and Satish et al., (2017) in french bean.
       
Means of pod weight (g) varied from 1.07 g in IC-10520 to 2.474 g in IC-39989. Seven genotypes, IC-9052, IC-10333, IC-13365, IC-39989, IC-103295, IC-177844 and IC-200696 recorded higher pod weight than check variety Pusa Navbahar (1.68 g) out of 25 genotypes, three genotypes viz., IC-10323, IC-13365 and IC-28287 showed significant regression coefficient (bi) values and remaining 22 genotypes had non-significant regression coefficient (bi) values. Most of the genotypes had S²di values non-significant and not different from zero (S²di=0) except three genotypes IC-10333, IC-140777 and IC-200715 indicating stable performance across the environments.  Among ten genotypes, which showed high mean, three genotypes namely, IC-9052, IC-13365 and IC-39989 were exhibited were also not different from unity and zero, respectively, hence showing stability for this trait. While, genotypes IC-103295, IC-177844 and IC-200696 had high mean value with regression coefficient less than one and small nonsignificant deviation from regression line indicating above average stability suitable to grow unfavourable/poor environments (Table 3). Many workers i.e., Pawan et al., (2016) in cluster bean, Satish et al., (2017) in french bean and Yirga et al., (2019) in field pea were found similar findings.
 
Stability of pod yield per plant
 
It was found that mean pod yield per plant ranged from 47.9 g in IC-28283 to 187 g in IC-103295. Ten genotypes viz., IC-9052, IC-10323, IC-10333, IC-34344, IC-39989, IC-103295, IC-140774, IC-140777, IC-177844 and IC-200680 recorded higher pod yield per plant (Table 4) than the check variety Pusa Navbahar (106.8 g). Considering all stability parameters i.e., high mean, bi near to one and S²di close to zero, five genotypes viz., IC-9052, IC-10323, IC-103295, IC-200680 and IC-10333 were found superior and stable across environments. Genotypes viz., IC-140774 and IC-177844 had mean significantly higher than check variety, regression coefficient more than unity and non significant deviation from regression coefficient, exhibiting below average stability, hence, this genotype was suited for better environmental condition. Genotype IC-140777 recorded more pod yield per plant and bi value less than one with non significant S²di, explaining its suitability in poor environments (unfavourable) showed above average stability. The results are concomitant with the results reported by Pawan et al., (2016) in cluster bean and Satish et al., (2017) in french bean.
 

       
The highest pod yield per hectare was 196.7 q/ha in IC-103295 and lowest was 50.03 q/ha in IC-28283 with population general mean of 103.78 q/ha. Eight genotypes viz., IC-9052, IC-10323, IC-10333, IC-34344, IC-200680, IC-177844, IC-103295 and IC-39989 recorded higher pod yield per hectare (Table 4) than check variety Pusa Navbahar (112.19 q/ha). Two genotypes viz., IC-140774 and IC-200679 showed significant bi values. Twenty one genotypes had deviation from regression (S²di) values, non-significant from zero indicating stable performance across the environments. However, based on Eberhart and Russell’s stability criteria high mean, bi=1 and S²di=0, five genotypes IC-9052, IC-10323, IC-10333, IC-103295 and IC-200680 were considered as desirable and stable. While, genotype IC-177844 recorded high mean, bi values significantly >1 and S2di with non significant deviation, Hence, these were considered specifically adapted to favourable environments. Similar findings are also obtained by Tamene et al., (2015) in faba bean.
 
Stability of quality traits
 
With respect to crude protein content (%), the mean values varied from 15.3% in IC-9077-P1 to 23.86% in IC-28287 with general mean of 19.83%. Fifteen genotypes i.e., IC-9052, IC-9229-P3, IC-9233-P3, IC-10323, IC-10333, IC-10520, IC-13348, IC-13365, IC-28286, IC-28287, IC-34344, IC-103295, IC-140777, IC-200696 and IC-200715 registered higher crude protein content (%) than check variety Pusa Navbahar (18.69%) and general mean (19.83%) (Table 4). Out of 25 genotypes, twenty three genotypes had S²di close to zero indicating that these genotypes were stable across the environments. Considering mean above average, bi near to unity and S2di close to zero, the genotypes, IC-10333, IC-28286, IC-103295 and IC-200715 were stable. However, the genotypes IC-9233-P3, C-10323, IC-13365 and IC-140777 had high mean, bi significantly >1 and S²di=0, hence were considered as specifically adapted to favourable environments. Genotypes IC-9052, IC-10520, IC-13348, IC-28287 and IC-34344 recorded above average stability due to more protein percentage in seed and bi value less than one with non significant S2di, explaining their suitability in poor environments. Present results confirm the findings of Razvi et al., (2011) in common bean and Wankhade et al., (2016) in cluster bean.
       
With regard to gum content (%), it was found that gum content (%) varied from 17.07% in IC-13348 to 33.02% in IC-103295 (Table 5). Seven genotypes namely, IC-9077-P1, IC-10323, IC-34344, IC-103295, IC-140774, IC-140791 and IC-200715 were recorded higher gum content (%) than check variety Pusa Navbahar (28.1%). All genotypes except IC-10520 had deviation from regression (S²di) values close to zero indicating that these were stable across the environments. Two genotypes namely, IC-103295 and IC-140791were exhibited higher gum content (%) and their bi and S2di were also not significantly differed from unity and zero, respectively. Hence, these were considered as superior genotypes for gum content (%) and also stable. However, genotype IC-200715 were considered specifically adapted to rich environments as bi is significantly >1. While, the genotypes IC-34344 and IC-140774 recorded above average stability due to bi value less than one and non significant deviation from regression line. The results obtained are in agreement with the findings of earlier workers in cluster bean (Dalmeida and Tikka, 2003 and Wankhade et al., 2016).
 

       
The mean values for crude fibre content (%) varied from 4.36% in IC-9077-P1 to 8.7% in IC-34344 with general mean of 6.40 %. Twenty one  genotypes namely, IC-9052, IC-9233-P3, IC-9229-P3,  IC-10323, IC-10333, IC-10520, IC-13348, IC-13365, IC-28269, IC-28283, IC-28287, IC-28286, IC-34344, IC-39989, IC-177844, IC-140774, IC-140777, IC-200679, IC-103295, IC-200696 and IC-140791 had significantly higher means for fibre content (%) than the check variety Pusa Navbahar (4.95%). Based on Eberhart and Russell’s stability criteria, high mean, but for this character low means could be desirable, bi=1 and S²di=0, the genotype IC- 9077-P1 were considered as desirable and stable over the environments. However, genotype IC-200680 recorded low mean, bi values significant >1 and S²di not different from zero, indicated specifically adapted to favourable environments. Genotype IC-140774 has lower than general mean, bi values significant less than one and S2di not different from zero, indicated specifically adopted to poor environments.

Based on the stability analysis over three environments, four genotypes viz., IC-103295, IC-9052, IC-200680 and IC-10323 were identified as promising for yield per plant and stable genotypes when compared to check variety Pusa Navbahar. Three cluster bean genotypes viz., IC-103295, IC-10323 and IC-9077P1 for higher gum content, Genotypes i.e., IC-10333, IC-28286, IC-103295 and IC-200715 for protein content and genotype IC- 9077-P1 for fibre content were considered as desirable and stable over the environments. These genotypes can be utilized in pedigree crop improvement and can be released for commercial cultivation. The selected germplasm can be used as parental source for the development of superior, stable cluster bean varieties for commercial cultivation.