Kidney bean (Phaseolus vulgaris L.) is one of the most globally important grain legume crops and a major component of human food and nutrition. It is an important and economical source of supplementary protein for the global nutritional security due to its high protein content (20-25%) and a good source of vitamins, minerals, polyunsaturated fatty acids and an appreciable amount of folate and fiber (Punia  et al., 2020). This crop is especially grown for its dry seeds, but sometimes its green pods and young seeds are used as a fresh vegetable. It is a good source of income and has cultural value due to its common use as a vegetable in different cultural and celebratory functions. It is popularly known as kidney bean due to its visual resemblance to the kidney shape and is known as ‘Rajma’ in Nepal and its’ neighboring country India.
       
The kidney beans are cultivated on about 33,701 thousand hectares worldwide, with an average productivity of 898 kg per hectare, of which South Asia contributes about 36% with a productivity of 696 kg per hectare and in South Asia, India alone contributes about 97% (FAOSTAT, 2026). Although reliable national data on the area and production of Kidney beans are limited in Nepal, the kidney beans are cultivated on approximately 22 thousand hectares of land in the country, with a total production of about 19 thousand tons and an average productivity of 855 kg per hectare (FAOSTAT, 2026).
       
The crop is commonly cultivated as a winter crop in the Terai and hilly regions of Nepal. Owing to its high market demand and economic value, its cultivation is also becoming increasingly popular in the high-hill areas, where it is grown during the summer season. The country imports approximately 4,080 tons of dry beans per year, with an import value of around 480 million Nepalese rupees (Pokhrel and Poudel, 2025a).
       
Several factors contributed to the low production and productivity of kidney bean, among them, the inappropriate selection and unavailability of high-yielding diversified varieties are the most important aspects that influence crop production (Singh et al., 2025; Pokhrel and Dangi, 2022; Jan  et al., 2021). In Nepal, the Grain Legumes Research Program (GLRP) under Nepal Agricultural Research Council (NARC), whose major task is to develop the grain legume varieties suited to different agro-ecological regions of the country has until now registered and recommended only one variety of kidney bean, PDR 14, suitable from Terai to Mid-hills. The GLRP is expected to develop more varieties to be released for commercial cultivation so that its production and productivity can be significantly increased (Pokhrel and Poudel, 2025b).
       
Therefore, this research was designed and conducted by the GLRP to evaluate the performance of different kidney bean varieties to identify high-yielding and well-adapted varieties across different environmental conditions of Nepal as the country has diverse agro-ecological regions. One of the major roles of the GLRP is to develop the grain legume varieties suited to different agro-ecological regions of the country. Hence, it is important to assess the performance of different kidney bean varieties under the Coordinated Varietal Trials (CVTs) and Coordinated Farmers’ Field Trials (CFFTs) to select the suitable, high-yielding and farmer-preferred varieties to release for commercial cultivation in the country as until now only one kidney bean variety has been released.

Evaluation of varieties
 
Seven varieties of kidney bean were selected from the previous years’ observation of nursery, which comprised of 24 varieties. In this study, PDR 14 was used as check variety to further evaluate Amber, Utkarsh, Arun-2, BL-63, Pant-1, Chitra and NL-1 in CVT at GLRP, Banke and Directorate of Agricultural Research (DoAR), Bara, Madhesh Province and Directorate of Agricultural Research (DoAR), Surkhet, Karnali Province and Jute Research Program (JRP), Sunsari, Nepal in four consecutive years from 2015/16 to 2018/19. The origin of all these varieties used in the study is India, except Arun-2 and NL-1 which are of the Nepalese origin. Moreover, a set of four selected superior varieties from the CVT and a standard check, was verified in the CFFT in the farmers’ fields of eight districts, i.e., Dang, Banke, Bardiya, Surkhet, Bara, Morang, Sunsari and Jhapa, from the year 2016/17 to 2024/25.

Location, climate and soil conditions of the study area
 
The research site, the GLRP, located at an altitude of 181 masl in the geographical coordinates of 28.11014, 81.59489; the DoAR, Surkhet, at 580 masl with coordinates of 28.49017, 81.75719; the DoAR, Bara, at 115 masl with coordinates of 27.07817, 84.93370; and the JRP, Sunsari, at 175 masl with coordinates of 26.65746, 87.28037 fall under the subtropical climatic zone. The maximum temperature reaches up to 41°C in June/July. The average annual rainfall is 1378 mm at GLRP, 1100 mm at DoAR, Surkhet, 1521 mm at DoAR, Bara and 1874 mm at JRP, Sunsari, where more than 80% of the annual rainfall occurs in the months between June and September. The soils of all the multi-location experimental stations were sandy loam.
 
Statistical analysis
 
The data of plant growth, development, yield and yield-attributing parameters of kidney bean varieties were statistically analyzed at a probability level of <0.05 using RStudio.

Coordinated varietal trial
 
The analyzed data of CVTs, showed significant variation among the tested varieties for all the traits studied, which included growth, development, yield and yield-attributing parameters, i.e., days to flowering, days to maturity, plant height, pods per plant, seeds per pod, pod length, hundred seed weight and grain yield at all the experimental sites, DoAR, Bara and GLRP, Banke, DoAR, Surkhet and JRP, Sunsari (Table 1, 2 and 3).






       
A summary result across the DoAR, Bara and GLRP, Banke, indicated that Utkarsh needs a longer duration for flowering (59 days) and maturity (118 days), in contrast, BL-63, Chitra and NL-1 matured early within 109-110 days. Similarly, Utkarsh was noted as the tallest (59.6 cm) and the highest yielder at both the DoAR, Bara (1079 kg ha^-1) and GLRP, Banke (2053 kg ha^-1), followed by PDR-14, which produced 2032 kg ha^-1 grain yield at GLRP, Banke and also maintained a good yield at DoAR, Bara (1014 kg ha^-1). The next high-yielding genotype at both locations, DoAR, Bara (956 kg ha^-1) and GLRP, Banke (1577 kg ha^-1), Arun-2 had the longest pod length (14.0 cm) and the highest hundred-seed weight (38.2 g). The Pant-1 was found to be the lowest yielder at both the research stations, with 635 and 1102 kg ha^-1 (Table 1). 
       
The combined analysis across DoAR, Surkhet and JRP, Sunsari, also revealed that BL-3, Chitra and NL-1 were earlier maturing varieties, taking only 109-110 days to mature, while the Utkarsh, Amber and PDR-14 took longer, i.e., 116-119 days to mature. Arun-2 and Utkarsh had the highest plant height (64.1-66.7 cm) among the tested varieties. The number of pods per plant and seeds per pod were found to be significantly higher in Amber (28.3) and Utkarsh (4.5), respectively, but the hundred-seed weight (38.2 g) and grain yield (1442 kg ha^-1) were found to be the highest in Arun-2. Pant-1 (842 kg ha^-1) and BL-63 (907 kg ha^-1) produced the lowest average grain yield across locations, while Chitra (551 kg ha^-1) and NL-1 (520 kg ha^-1) were poor yielders in JRP, Sunsari, among the varieties (Table 2).
       
The combined analysis of CVT across four research stations showed that most of the varieties had flowering and maturity duration of 49 to 58 days and 109 to 118 days, respectively. BL-63, Chitra and NL-1 were medium-duration types (Table 3). Conversely, Utkarsh took more days to flower (58 days) and mature (118 days) and also had the tallest plant height (61.5 cm) (Table 3).
       
The highest number of pods per plant (25.9) was observed in Amber, which is statistically similar to NL-1 (23.7), Utkarsh (22.4), PDR-14 (21.0) and Arun-2 (20.0), while Utkarsh, Pant-1 and Chitra had the highest number of seeds per pod (4.4). In contrast, Arun-2 had the highest hundred-seed weight (38.1 g), closely followed by PDR-14 (37.1 g), Pant-1 (36.7 g), Chitra (35.9 g) and NL-1 (35.6 g). PDR-14 and Utkarsh recorded the highest grain yield (1465 and 1458 kg ha^-1, respectively), followed by Arun-2 (1341 kg ha^-1). Pant-1 was observed to be the lowest yielder (857 kg ha^-1) among the tested varieties (Table 3).
 
Coordinated farmers’ field trial
 
A set of CFFTs was conducted with the help of the multi-location research stations under the coordination of GLRP from the year 2016/17 to 2024/25. The data obtained were analyzed with a statistical analysis performed by considering a farmer as a replication in a year. The data analysis showed significant variation for all the traits examined, including growth, development, yield and yield-assigning parameters, except the number of pods per plant, among the candidate varieties (Table 4).


       
Arun-2 and Utkarsh recorded the tallest plants (76.3 and 69.5 cm, respectively), the highest number of pods per plant (21.6 and 22.6, respectively) and the highest number of seeds per pod (4.1 and 5.2, respectively). Likewise, Arun-2 had the highest seed weight (42.8 g), which was statistically similar to all other varieties except NL-1, which recorded the lightest weight of hundred seeds (36.5 g). The longest and shortest pod lengths were documented for Arun-2 (14.2 cm) and Amber (7.5 cm), respectively. NL-1 was observed to be an early maturing genotype, which took only 48 days to flower and 101 days to mature, while Amber and Utkarsh were the late maturing varieties, taking 111 to 112 days to mature (Table 4).
       
The variety PDR-14 (1857 kg ha^-1) logged the highest average yield, while Utkarsh (1769 kg ha^-1) and Arun-2 (1761 kg ha^-1) were at par with its grain yield (Table 4). PDR-14 was mainly superior in Dang (1939 kg ha^-1), Bardiya (1710 kg ha^-1) and Sunsari (1941 kg ha^-1), while Arun-2 performed best in Banke (2338 kg ha^-1), Bara (1152 kg ha^-1), Morang (2396 kg ha^-1) and Jhapa (1678 kg ha^-1). Moreover, Utkarsh was particularly superior in Surkhet (3118 kg ha^-1), among the varieties (Table 5).

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The results of the CVT indicated that yield differences were more influenced by seed size, seed number and adaptation to the environment than by pod number alone. PDR-14 produced the highest grain yield at Banke and also maintained good performance at Bara, indicating its yield stability and wide adaptability across environments. The superior performance of PDR-14 at Sunsari also suggests strong environmental adaptation. The grain yield of the tested varieties at Surkhet was somewhat closer to each other, indicating that environmental conditions at Surkhet may have reduced genotypic differentiation.
       
The variety, Arun-2 had the highest pod length and heavier seeds, indicating a strong source-sink relationship and superior yield attributes, which contributed to its good yield performance. Arun-2 has strong yield components but may not consistently translate these into maximum grain yield. Utkarsh also performed well with higher plant height, more seeds per pod and pods per plant. This result is further supported by the findings of the researchers (Das et al., 2026; Dawood et al., 2026; Jan et al., 2021), as they reported that the number of pods per plant, seeds per pod and seed weight were important parameters for obtaining higher yield. Early maturing varieties such as BL-63, Chitra and NL-1 may be advantageous in areas with shorter growing seasons or terminal drought and can be beneficial for crop intensification.
       
However, neither of these traits, number of pods per plant, seeds per pod, nor seed weight alone ensured higher grain yield. These early varieties generally produced lower grain yield compared to other varieties, indicating that earliness alone may not ensure higher productivity. This suggests that grain yield in kidney bean is governed by the combined effect of several yield attributing components rather than a single trait (Parkina et al., 2025; Reinprecht et al., 2021).
       
Overall, two varieties, i.e., Arun-2 and Utkarsh showed superiority in growth and yield-contributing traits. Moreover, Utkarsh signified the highest mean grain yield and good stability potential across locations, while PDR-14 showed relatively good yield potential but had a low stability compared to Arun-2. In a similar study, researchers Pokhrel and Poudel (2025a) had also reported higher grain yields of Utkarsh and Arun-2 compared to other kidney bean varieties.
       
The large standard deviation for grain yield and plant height suggests substantial variability among varieties, which is useful for breeding and selection as it provides wider variation (Punia et al., 2020). The wide range between minimum and maximum values of growth, development, yield and yield-attributing parameters further demonstrates the presence of diverse genetic materials that can be utilized in future varietal improvement programs (Jan et al., 2021). The significant year effects for all traits indicated that climatic conditions, rainfall distribution and soil fertility varied considerably across years. The G´E interaction is the most important factor in kidney bean production and hence the varieties should be selected according to the targeted environmental conditions (Parkina et al., 2025).

Kidney bean holds substantial importance in Nepal, acting as an integral part of a balanced diet to supply protein to the rice-based meal system. It is imported in large quantities annually, reflecting its high demand within the country; therefore, increasing its production is crucial. Having only one registered and recommended variety so far has limited its widespread cultivation. Consequently, identifying high-yielding varieties and having them released and registered will promote their commercial cultivation, which can help to substitute imports and reduce the agricultural trade deficit of the country to some extent, as well as contribute to food and nutrition security. This study has identified two varieties, Arun-2 and Utkarsh as potential high-yielding varieties of kidney bean which can be cultivated across different parts of the country. Examining more varieties, both indigenous as well as those developed by neighboring countries, will help to identify appropriate varieties for specific agro-climatic areas, which can significantly improve its yield sustainably.

The authors thank the Grain Legumes Research Program (GLRP) under the Nepal Agricultural Research Council (NARC) for providing research funds for the study.
 
Disclaimers
 
The views and conclusions expressed in this article are those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy of the information presented.
 
Informed consent
 
This article does not contain any studies with human and animal subjects.

The authors declare no conflict of interest. Researchers are welcome to contact the corresponding authors for any additional information or clarification regarding the study.