In order to identify appropriate container for high throughput phenotyping of root characteristics, nine genotypes belonging to different Capsicum sp. IHR 3226, IHR 3455, IHR 3575, IHR 4517, IHR 3476 (C. annuum) IHR 3240, IHR 3241, IHR 4491(C. baccatum) and IHR 3529 (C. chinense) were selected. The genotypes were evaluated in three types of containers having different dimensions and soil media holding capacity. The containers used were: (i) bucket type container (Empty paint container, 30 cm diameter, 32 cm height having capacity to hold 23 kg soil), (ii) PVC pipe container (20 cm diameter, 64 cm height having capacity to hold 26 kg soil) and (iii) pot type container (18 cm diameter, 27 cm height having capacity to hold12 kg soil). The containers were filled with soil, Farm Yard Manure (FYM) and sand (2:1:1 v/v). The experiment was laid out in a factorial completely randomized block design with five replications.

Eighteen genotypes belonging to different Capsicum sp. were evaluated for root characteristics in the bucket type container (30 cm diameter, 32 cm height having capacity to hold 23 kg soil). The experiment was laid out in a completely randomized block design with five replications.

1. Seedling raising and crop care: The seeds of genotypes used in both the experiments were sown in pro trays filled with coco peat as a growing medium. The seedlings were maintained in the shade net nursery for 45 days and recommended cultural practices were adopted to maintain plant health status and population. Forty-five-day old seedlings were transplanted into the containers. The plants were provided with recommended dose of fertilizer and crop protection measures. The plants were irrigated regularly to maintain 100 per cent field capacity.

2. Growth parameters: The observations in both the experiments were recorded at peak flowering stage (50 DAT). Plant height was measured using graduated scale and expressed in centimeters. The number of primary branches were counted manually at the point of initiation. The plant shoot parts were excised and the leaf and stem portions were separated. The entire root portion was carefully extracted from the soil medium using water jet to clean the soil. Soon after extracting the roots, observations on root parameters like root length (using graduated scale), root volume (water displacement method), number of primary roots and fresh and dry weights were recorded. Fresh weights of the root and shoot samples were measured immediately after extraction by using a Sartorius BSAZZAS-CW balance. The root, stem and leaf parts were dried in oven separately at 80ºC for 72 h to achieve stable weight. The dry weight was recorded as total biomass accumulated and expressed as gram per plant.

   To quantify the leaf area, representative sample of 20 leaves from each plant was taken and the leaf area was determined using leaf area meter (Biovis, PSM-L2000, India). Then the leaves were kept in oven at 70ºC for five days and leaf dry weight was measured using Sartorius BSAZZAS-CW balance. The ratio of leaf area to the leaf dry weight was computed as specific leaf area (SLA). The leaf dry weight of each plant was multiplied with SLA to arrive at the total plant leaf area (TLA).

3. Root: shoot ratio: It was arrived by dividing root dry matter with shoot dry matter.

ANOVA: The data obtained in different experiments was analyzed in factorial completely randomized block design and completely randomized block design for first and second experiment, respectively using two factors statistical package OPSTAT developed by CCSHAU (Sheoran et al.,1998).

The container size plays a major role in plant root and shoots growth. The root length was not significantly influenced by the container type. However, among the three containers, higher root length was observed in PVC pipe container compared to bucket type and pot type containers. The root volume in bucket type container was 35.8% and 72.4% higher compared to pot type and PVC pipe containers, respectively (Figure 1). The studies conducted in bell pepper have shown that the container size has influence on the root volume and plant growth (Weston, 1988; Nesmith et al.,1992). In this experiment, among the three types of containers, the plants grown in bucket type container produced significantly a greater number of primary roots (44.8) compared to pot type (33.1) and PVC pipe (25.4) containers (Figure 1). Studies conducted by Cantliffe, (1993) and Kharkina et al., (1999) have shown that there is a strong positive correlation between container size and root biomass. In the present study, significantly higher root fresh weight and dry weights were observed in bucket type container compared to other two types of containers (Figure 1). The genotypes IHR 4491, IHR 3241, IHR 4517 and IHR 3529 produced significantly higher root fresh weight as compared to remaining genotypes (Figure 1). Plants grown in bucket type container recorded 73.14 % (4.32 g) and 40.86% (5.31 g) higher root dry weight compared to PVC pipe and pot type containers (Table 1).

Figure 1
Influence of containers on root length (A), root volume (B), primary root number (C) and root fresh weight (D) of Capsicum sp.

Healthy root system growth promotes better above ground canopy growth. Hence, providing appropriate space for adequate root growth is essential. It is observed that the shoot growth is greatly impacted by varying container size and root restriction (Poorter, 2012). The plant height was significantly higher in bucket type container compared to remaining types of containers. Genotypes, IHR 3241 (68.1 cm) and IHR 3226 (57.2 cm) recorded significantly higher plant height compared to rest of the genotypes (Table 2). Tomato plants when grown in containers with low volume showed reduction in shoot height and biomass (Peterson et al., 1991). Hence, providing better rooting space helps the plants to produce higher above ground biomass with increased shoot height. Among the three types of containers, plants grown in bucket type produced significantly a greater number of branches compared to remaining two types of containers (Table 2). In bell pepper (Capsicum annum L.), root restriction caused reduction in number of branches (Nesmith et al.,1992). In container grown bell pepper plant, reduction in leaf area was observed mainly due to smaller and fewer leaves per plant (Weston, 1988; Nesmith et al., 1992). With the increase in container size, the leaf area and shoot biomass has increased (Cantliffe, 1993). In this experiment, the leaf area was significantly higher in plants grown in bucket type container (5690 cm2) as compared to pot (3797 cm2 ) and PVC pipe (2690cm2 ) containers (Table 2).

Table 1
Influence of containers on root dry weight and shoot dry weight in Capsicum sp

Table 2
Influence of containers on plant height leaf area and number of branches in Capsicum sp

Table 3
Variability in root and shoot growth characteristics among 18 Capsicumsp genotypes

RL Root length, RV: Root volume, PRN: Primary root number, RFW: Root fresh weight, RDW: Root dry weight, SDW: Shoot dry weight, PH: Plant height, BN: Branch number and LA: Leaf area Phenotyping of Capsicum genotypes for desirable root characteristics

Shoot growth is greatly impacted by varying container size and root restriction in tomato (Kemble et al., 1994) and soybean (Krizek et al.,1985). In this study, among the three types of containers, plants grown in bucket type container produced significantly higher amount of shoot biomass compared to remaining two types of containers. Plants in bucket type container produced 57.1% (15.9 g) and 114.2% (23.3 g) higher shoot biomass than plant grown in pot type and PVC pipe containers, respectively (Table 1). Therefore, the bucket type container with higher soil volume and area enabled the Capsicum spp. genotypes to express their genetic potential with higher shoot and root growth.

Roots, stems and leaves are functionally interdependent and these three systems maintain a dynamic balance in biomass production and distribution. It is clearly evident from the study that the bucket type container provided enough rooting space for Capsicum spp. genotypes to express their genetic potential in terms of shoot and root biomass production. Hence, the bucket type container was chosen for further studies on phenotyping Capsicum spp. genotypes for desirable root characteristics.

The importance of plant phenotyping based on specific root characteristics like root length, number of primary roots and root volume are of practical value for crop improvement (Garcia, 2015). Genetic potential of a genotype for root characteristics plays a critical role during growth and metabolic aspects of the plants. In this study, to know the genetic potential and behavior of each genotype under optimal moisture condition Capsicum sp. genotypes were evaluated for desirable root characteristics and shoot growth. The results clearly indicated that genotypes, IHR 4501, IHR 4491, IHR 3241, IHR 4550, IHR4517, IHR 3529 exhibited

desirable root characteristics such as root length, root volume, primary root number, root fresh and dry weight. The genotypes, IHR 3982 and IHR 3447 showed poor root characteristics (Table 3). Studies have indicated that root length, root volume and root dry weight have strong positive correlation with total dry matter production (Lakshmamma et al., 2014). The genotypes which showed higher root length and volume also produced higher biomass because of adequate water and nutrients uptake from deeper layers of the soil and maintained the tissue water potential (Khan et al., 2008).

Under ample supply of water and nutrient, the plant height, leaf area, branch number and shoot biomass production are dependent on the size of the root system (Zakaria et al., 2020). Our results clearly demonstrated that genotypes, IHR 3241, IHR 4501, IHR 4491, IHR4517 and Guntur Local exhibited better shoot growth in terms of plant height, number of branches, leaf area and shoot biomass. The genotypes, Chikkaballapur Local, IHR 3447 and IHR 3982 showed poor shoot growth (Table 3). In fact; leaf area determines the light interception capacity of a crop and is often used as a surrogate for plant growth and above ground biomass. From the results it is clear that the genotypes having higher leaf area showed better shoot biomass. Concurrently, our results suggested that number of branches in a plant is independent with plant height. The branching pattern in a plant depends on the genetic makeup of each genotype and it is not linked with plant height and other characteristics. Similar observations were made in chilli (Bijalwan et al., 2018) and tomato (Malaker et al., 2016).

At optimal moisture condition, shoot and root dry weights are interred linked (Brdar-Jokanovic et al., 2014). Root to shoot ratio is an important index and it reflects the plant health status. In this regard our results confirms that genotypes, IHR 4550, IHR 4501, IHR 3529 and IHR 4491 recorded significantly higher root to shoot ratio compared to other genotypes. The genotypes, IHR 4108, IHR 3455 and IHR 3226 showed significantly lower root shoot ratio (Table 3).

Though enough rooting space was available in the bucket type container only few genotypes had higher shoot and root growth. This could be due to the genetic potential of the genotypes exhibiting higher root and shoot biomass (Chowdary et al., 2015). Based on the growth pattern with respect to root and shoot characteristics, six genotypes, IHR 4517 (C. annuum), IHR 3241 (C. baccatum), IHR 4491 (C. baccatum), IHR 4550 (C. chinense), IHR 3529 (C. chinense), IHR 4501 (C. chinense) were identified having desirable root characteristics and IHR 3447 (C. annuum) and IHR 3982 (C. chacoense) were identified having poor root characteristics.