Evaluation of Bush Type Common Bean (Phaseolus vulgaris L.) Genotypes for Morphological Characters and Anthracnose under Cold Arid Ladakh Conditions

Ladakh which is wide spread over 80,000 square kilometres being the cold arid, high altitude region of India has a very harsh climate and a short agriculture season. Nearly 89% of people live in rural areas. The villages are remote, unconnected and inaccessible. Agriculture in this region is different from that in other rural areas of India, since farming can be done only for four to five months. Further, the soil suffers from moisture stress. There are socio-economic constraints as well- small land holdings, low productivity, labour shortage, poor post-harvest management and marketing of produce. The region remains landlocked for over six months in a year due to heavy snow fall. Most of the population (>70%) of the region belongs to schedule tribe and are left with a limited period of a year to earn their livelihood. Availability of locally grown fresh vegetables is restricted to summer months and therefore, there are seasonal differences in dietary intake of food. The availability of fresh vegetable decreases significantly during the winter months, so here is great scope of pulses during harsh winter months. In winter when no fresh vegetables are available in Ladakh, Common bean can be used in diet. Wheat and alfalfa are major crops of the Ladakh region and pulses are grown on just 300 hectares with a meagre productivity of 585 kgs/ha (CRIDA, 2012). Common bean is regarded as a nearly perfect food as it contains balanced mixture of different nutrients that promote better health and fight certain diseases. However, due to disappointingly low yield of pulses, they have become less competitive and people mostly prefer wheat and other crops. Therefore, in order to diversify the farming system, it is essential to identify high yielding varieties of common bean that can perform better under Ladakh conditions. This would require characterisation of germplasm for its adaptability and yielding ability in Ladakh.
       
Common bean (Phaseolus vulgaris L.) also known as Rajmash or Rajma (Hindi) or haricot bean or kidney bean or Common bean or snap bean is an important grain legume in human consumption in the whole world. Due to its importance, researchers around the world for many years have been developing new improved varieties from the many useful landraces present (Broughton et al., 2003; Munda, 2009). Common bean have growth habits which vary from determinate dwarf or bush types to indeterminate climbing (Kelly, 2010) and can be grown as a vegetable crop for fresh pods and leaves, or for dry seed. Furthermore, Common bean is important because it plays a role in improving soil fertility through nitrogen fixation. When used in crop rotation or intercropped with cereals it disrupts the life cycle of soil pathogens in an event were soil pathogens are present and supplies nitrogen to the cereal crop (Akibode and Maredia, 2011). Although there has been increase in bean production due to expansion into marginal agricultural lands, productivity has not shown any encouraging improvements. Typical bean yields obtained on farmers fields are only 20% to 30% of the genetic potential of improved varieties (Wortman et al., 1998). One of the reasons for low productivity is lack of effective disease management practices including lack of disease resistant cultivars. The development of cultivars with improved resistance to biotic and abiotic stresses has long been a primary goal for many bean breeding programs (Miklas et al., 2006). Among constraints, bean anthracnose disease caused by Colletotrichum lindemuthianum (Sacc. and Magnus) Briosi and Cavara is one of the most devastating seed-borne diseases of Common bean. Since this pathogen overwinters inside bean seeds hence the losses can be 100% when badly contaminated seed is planted under conditions favourable for disease development (cool and wet weather) (Sharma et al., 1994). Under favourable conditions during the growing season, infected seeds become discoloured, shrivelled and dark acervuli are prominent on the lesions (Gonzalez et al., 1998). Common bean cultivation for green pod has potential to improve the economic conditions of tribal farmers in this Ladakh region. Therefore, the present investigation was done for identification of different resistant genotypes of Common bean.

The present study was carried out during kharif 2018 at the research farm of High Mountain Arid Agriculture Research Institute Leh, SKUAST-K which is situated between 32°N to 36°N latitude and 75°E to 80°E longitude at an altitude of 3319 metres above sea level. 24 bush type genotypes of Common bean belonging to diverse maturity and market classes (comprising local landraces a well as accessions procured from national and international gene banks  including a check variety Arka anup were evaluated in the present study. The experiment was conducted in randomized complete block design (RCBD) with three replications. Each genotype was represented by a plot size of 2 × 2 meter dimensions with 5 lines. Observations were recorded on plant height, days to flowering, days to maturity, pod length, seeds per pod, 100-seed weight, pods per plant and yield per plant. Days to flowering and days to maturity were measured on plot basis whereas above ground biomass and seed yield was measured on five competitive plants from each replication. Data was analysed for ANOVA using OPSTAT-1 (CCS HAU, Hisar).
       
Screening of 25 Common bean genotypes including popular local land races and released variety was done against anthracnose. The sowing was done on 5^th of May in randomized complete block design (RCBD) with three replications. Recommended agronomic practices were followed to raise a good crop. No disease protection measures were adopted. From each representative collection, 10 plants were selected randomly, kept unsprayed throughout the season and were tagged for the assessment of the disease. All the pods of the ten plants were counted and then grouped as healthy and diseased. The disease incidence and intensity was assessed in the month of September. Per cent disease incidence was worked out as per the following formula given by (James, 1974):
                                                    
The severity of the disease was recorded on the basis of 1 to 9 scales (CIAT 1987). The description of the scale is given below in Table 1.
       

 
Per cent disease index (PDI) was calculated on the basis of rating scale using the following formula:
                                                    
On the basis of PDI, genotypes were classified into different categories (Table 2).
 

The general descriptive features of 25 genotypes used in the study are presented in Table 3. The growth habit of all the genotypes was bush type. Out of 25 genotypes 12 were exotic (procured from NBPGR, CIAT Columbia and IPK Germany) and 12 were local land races and arka anup was used as check. Seed colour revealed that out of 25 genotypes ten were red in colour, five were brown in colour and four genotypes were white, two purple and one each was black, pink, yellow and chocolate in colour.  For seed shape, 16 genotypes were Kidney shaped, 3 each were cylindrical, cuboidal and oval. Seed coat pattern revealed that 19 genotypes were having plain seed coat pattern and 6 had mottling of variable colours and intensities. Seed size revealed that out of 25 genotypes, six were large, 17 were medium and two were small. For pod colour 14 genotypes were having green colour pods, ten were yellow and one light green in colour. The pod curvature revealed that 15 genotypes were having medium pod curvature, 7 were curved and 3 genotypes were having straight pod curvature.  The results indicated diversity of market classes in the material evaluated in terms of seed size, shape and colour and pod colour and curvature.
 

       
Mean performance of genotypes for morphological and yield traits revealed that WB-185 was earliest to flower (65.333) followed by WB-252 (65.667), WB-1435 (66.333), WB-195 (66.667) and WB-811 (67.333) whereas WB-1690 (85.333) took the highest number of days to flower (Table 4). For days to maturity, results showed that WB-956 (106.667) matured earlier which was followed by WB-252 (109.333), WB-811 (109.333), WB-195 (110.000) and WB-185 (110.000) whereas WB-1690 (132.667) was late maturing. Highest pod length was recorded in case of WB-185 (11.667 cm) followed by WB-216 (10.933cm), WB-1492 (10.867 cm), WB-1129 (10.833 cm) and Arka anup (10.700 cm) whereas lowest pod length was recorded in case of WB- 6 (8.833 cm) and local Ladakh (8.833 cm). Seeds per pod was recorded highest in genotype WB-185 (5.700) followed by WB-1129 (5.500), WB-6 (5.333), WB-1492 (5.300), WB- 1690 (5.067) and WB-1643 (5.000) whereas lowest seeds per pod was recorded in WB-956 (3.200). Plant height was recorded highest in genotype WB-1690 (42.033cm) which was followed by WB-216 (38.333 cm) and Arka anup (37.800 cm). The lowest plant height was recorded in genotype WB-662 (23.967 cm).
 

       
The highest value for 100-seed weight was recorded in genotype WB-966 (50.100 g), followed by WB-216 (43.767 g) and WB-22 (43.333 g) and lowest value was recorded for WB-6 (22.400 g). Seed yield measured on per plant basis was recorded highest in case of WB-185 (12.733 g) followed by SKUAWB-5001 (9.033 g) and lowest in case of WB-1129 (5.100 g). For pods per plant maximum number of pods per plant were recorded in WB-185 (9.667) followed by WB-1643 (9.633), WB-216 (9.367), WB-719 (9.333) and WB-22 (9.333). The lowest pods per plant were recorded in WB-662 (4.367). Based on CD values, it could be safely concluded that the lines were significantly different from each other for various traits studied. Sofi et al., (2014), Razvi et al., (2018) and Iram Saba et al., (2017) have also reported significant variability for morphological and yield traits in Common bean germplasm tested under Kashmir valley condition. The results were also in agreement with Singh et al., (2009). Analysis of variance (Table 5) for the traits studied revealed that mean squares due to genotypes were significant for all the traits studied indicating presence of substantial variability in the lines evaluated that can be used to develop high yielding common bean genotypes for Ladakh region.
 

 
Screening of genotypes
 
The evaluation study of 25 Common bean accessions conducted during the year 2018 under natural epiphytotic conditions against anthracnose indicated that disease occurred in variable proportion on all the tested cultivars during both years (Table 6). However, analysis of data showed a differential response among the accessions with regard to incidence as well as intensity.
 


Disease incidence
 
The disease incidence among the genotypes ranged between 10.53 to 68.63 per cent. Maximum disease incidence (68.63%) was recorded in genotype WB-1690, which was statistically at par with WB-257 and WB-1643 with average disease incidence of 64.50% and 64.36% respectively. The minimum disease incidence was recorded in genotype WB-719 (10.53%) which was statistically at par with genotype WB-22 (11.66%). Rest of the accessions observed have significant differential response to the maximum and minimum disease incidence.
 
Disease intensity
 
The disease intensity among the genotypes ranged between 5.83 to 36.00 percent. Maximum disease incidence (36.00%) was recorded in genotype WB-1690, which was statistically at par with WB-257 and WB-1643 with average disease intensity of 33.50% and 33.30% respectively. The minimum disease intensity was recorded in genotype WB-719 (5.83%) which was statistically at par with genotype WB-22 (6.36%) and WB-1435 (6.96%). Among 25 Common bean accessions screened nine of the accessions viz., WB-1435, WB-719, WB-22, WB-811, WB-4564, WB-662, WB-6, Local Ladakh and SKUAWB-5002 exhibited highly resistant reaction to the disease (rating between 0.01-12.21% PDI), fourteen accessions viz., WB-966,WB-335, WB-1129, WB-216, WB-1643,  WB-1247, WB-185, WB-956,WB-252, WB-1492, WB-195, Arka Anup, SKUAWB-5000 and SKUAWB-5001 were moderately resistant (rating between 12.22-33.33% PDI). Rest of the two accessions viz., WB-1690 and WB-257 were moderately susceptible. The development of anthracnose resistance genotypes can be expected to increase profitability by reducing the amount of fungicides used to produce a crop. Plant species have a defense mechanism to avoid and resist pathogens and pests (Parlevlite, 2002). Similar findings were reported by Maibam Nirmala et al., (2015).
       
Screening is one of the important processes involved in breeding programmes and it ensures that cultivars chosen exhibits increased resistance to a wide range of diseases and insects, better tolerance to environmental stress, better seed quality and improved efficiency in the utilization of limited soil nutrients. Many workers have conducted screening and reported varying degree of resistance to anthracnose in local land races and exotic Common bean genotypes (Pathania et al., 2006; Kour et al., 2012). More than 10 different anthracnose resistance genes have been identified in a number of bean varieties (Kelly and Vallejo 2004). According to Mahuku and Riascos (2004), the best strategy to manage this disease is planting resistant cultivars, which is most effective, least expensive and easiest for farmers to adopt.
       
Hence the moderately resistant and moderately susceptible accessions identified during the present investigation (Table 7) can be screened at different stages over locations and years to confirm their reaction to anthracnose so that promising accessions/resistant donors can be identified and used in future breeding programs for the development of anthracnose resistant varieties.
 

Out of 25 genotypes screened, nine genotypes viz., WB-1435, WB-719, WB-22, WB-811, WB-4564, WB-662, WB-6, Local Ladakh and SKUAWB-5002 were found highly resistant, fourteen genotypes viz., WB-966,WB-335, WB-1129, WB-216, WB-1643,  WB-1247, WB-185, WB-956, WB-252, WB-1492, WB-195, Arka Anup, SKUAWB-5000 and SKUAWB-5001 were moderately resistant, whereas other two genotypes were categorized as moderately susceptible. None of the genotypes was found highly susceptible to anthracnose disease.