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Performance Evaluation of Exotic and Local Landraces of Tomatoes for the Mid-Hill Conditions of Nepal

Received : 09/02/2021 Accepted : 15/07/2021 The productivity of tomato in Nepal is very low due to lack of high yielding, disease and pests resistant varieties. An experiment was carried out to evaluate horticultural traits of 50 genotypes obtained from World Vegetable Centre (WorldVeg), Taiwan and SAARC region, and local collections during March to August 2020 in open field conditions at National Horticulture Research Centre, Khumaltar, Lalitpur. The objectives were to identify promising open-pollinated tomato cultivars for high yield, appropriate fruit size, and disease resistant. The experiment was carried out in a randomized complete block design with three replications. Results showed significant differences in yield and yield attributing characters including virus infection. The highest yield (39.6 mt ha) was produced by HRA43 and it was followed by HRA33 (26.4 mt ha). Among the WorldVeg OP lines, AVTO1429 produced the highest yield (16.21 mt ha) and it was followed by AVTO1717 (12.95 mt ha), AVTO0922 (11.83 mt ha) and AVTO1219 (11.7 mt ha) respectively. Most of the WorldVeg lines performed better than the check variety ‘Pusa Ruby’. Genotype HRA43, Red Local and Sindhupalchock Local were not affected by virus while Yellow Local showed 3.3% infection. Among the WorldVeg lines, AVTO1712 (20%), AVTO1717 (20%) and AVTO1718 (13%) and AVTO1219 (15%) showed less than 20% virus infection in the open field conditions. Cluster analysis using the unweighted paired group method with arithmetic mean showed that cluster-1 was the largest cluster comprised of 40 genotypes followed by cluster-2 and cluster-4. Genotypes from cluster-4 showed the higher fruit yield (25.1 mt ha) and resistant to the virus and the highest number of fruits per plot (1978 in 4.5 m area). The yield was low in cluster1 which could be due to the heavy rainfall during the vegetative and reproductive stages. Genotypes Red Local and Sindhupalchock Local could be used in future tomato breeding program due to their resistant to TYLCV, higher potential yield and highest plant vigour in open field conditions at the mid-hill of Nepal. Considering the overall performance, genotype HRA43, HRA33 and AVTO1429 were promising lines with performance for yield and other horticultural traits.


Introduction
Tomato (Solanum lycopersicum L. 2n=2x=24) is one of the most widely grown vegetables in tropics and subtropics in the world. The total area under tomato cultivation is above 5 million ha with 180 million tonnes of production in the world (FAO, 2019). Tomato is the third largest vegetable crop in Nepal. It covers 22,566 ha with a total production of 406,434 mt (MoALD, 2019). Due to the lack of abiotic and biotic stress tolerant tomato varieties, the productivity is low in Nepal (18.01 mt ha -1 ) (MoALD, 2019) as compared to India (24.33 mt ha -1 ), Asia (43.10 mt ha -1 ) and the world (35.90 mt ha -1 ) (FAO, 2019). The main reasons of low productivity of tomato in Nepal are due to the lack of suitable varieties resistance to diseases and pest, flower drop and poor fruiting, poor quality fruits particularly when the tomato is grown during the rainy season in open field conditions (Paudel et al., 2004). Unavailability of quality hybrid seeds may force the farmers for cultivation of open-pollinated cultivars (Shrestha and Sah, 2014). Imported hybrids are not available in the seed supply system over the years while Nepal cannot produce seeds of these hybrids due to lack of indreds for seed production.
In contrary, it has been observed that many promising local selections of tomato are popular but they are not coming in the national mainstreaming because of unavailability of seed in the national seed system. As hybrids are more vigorous, resistant to insect pests and diseases, high yielding, its use is increasing both commercial and small growers. The continuous inflow of exotic hybrid varieties and risk of getting appropriate variety at the right season and place is a great problem to the growers (Devkota et al., 2018). Hybrid seeds in vegetable crops are importing to Nepal from abroad especially from India, Thailand, Japan, and Korea. It is necessary to develop tomato OP varieties to replace the imported hybrid seeds and availability of sufficient quality seeds in the market.
Research in variety development in tomato has been initiated in Nepal since 1996 (Bhattarai and Subedi, 1996;Budhathoki et al., 2004;Paudel et al., 2004;Regmi et al., 2004). Budhathoki et al. (2004) evaluated 51 tomato genotypes under the open field of Khumaltar conditions, and recommended hybrids 'Swarachha', 'Manisha', 'T 5975' and 'NS 815' for cultivation. Paudel et al. (2004) evaluated 16 genotypes and found that N-162 was the highest yielding, and bacterial wilt resistant in the open field conditions of mid-hills. Devkota et al. (2018) evaluated hybrid cultivars at mid-hill conditions of Nepal (Khumaltar) and found that 'HRA14 x HRD7' produced the highest yield (80.8 mt ha -1 ). Chapagain et al. (2014) evaluated some exotic hybrids and recorded 'Winsari' the highest yielding (105.8 mt ha -1 ) cultivar. However, these exotic varieties may not give stable performance over the season, seeds of these varieties are not available in the market and most of these varieties are not registered in Nepal. Their parental lines are unknown and need to depend to neighboring countries. Therefore, continuous OP varietal evaluation is necessary for providing sufficient varietal options for the farmers. Nepal Agricultural Research Council is keen to promote high yielding, disease resistant OP varieties so that famers can produce seeds. Both local and exotic tomato genotypes are a rich pool of genetic resources and can be used in tomato variety development program. Research is necessary to identify suitable variety at multi-location conditions such as an open field or protected cultivation system; mid-hills or Terai conditions. Therefore, this experiment was carried out to overcome these problems and to develop high yielding and disease-resistant open-pollinated varieties for the mid-hills of Nepal.

Materials and Methods
A total of 50 germplasms were collected both from national and international sources particularly from World Vegetable Center, Taiwan including SAARC region. Five local landraces were collected from farmer's field and included in the evaluation (Table 1).
The seeds of collected tomato germplasms were sown in poly-pot on February 26, 2020. The experiment was carried out in a randomized complete block design with three replications. Individual plant size was 4.5 m 2 with two rows having 10 plants in each plot. Manure and fertilizers were applied at the rate of 25 mt ha -1 FYM and 200:150:120 kg N: P2O5:K2O per hectare. i.e., 1.08 kg farmyard manure (FYM), 10.15 g urea (46% nitrogen), 14.08 g di-ammonium phosphate (DAP; 18% nitrogen and 46% phosphorus) and 4.8 g muriate of potash (MoP) per plot. All FYM, P2O5:K2O and half of N were applied before one week of transplanting of seedlings. About 28 days old seedlings were transplanted in the open field in March 2020. Planting was done at a spacing of 75 cm x 60 cm distance. The remaining half dose of nitrogen was equally top-dressed at 30 and 60 days after transplanting. The source of the fertilizer was urea which was applied at the rate of 5 g per plant. The plant extract, Vircon H was sprayed at the rate of 2 mL L -1 water as a protective spray against viruses. For control of late blight, systematic fungicide Dimethomorph 50% WP (Acrobat) was sprayed at the rate of 1.5 g L -1 water. The protective fungicides Krinoxyl Gold Mz 72% (metalaxyl 8% + mancozeb 64%) was sprayed 3 times at the rate of 2 g L -1 water at 10 days intervals to manage late blight and other fungal diseases. A micronutrient, Multiplex at the rate of 2 mL L -1 water was foliar sprayed along with the first spay of Krinoxyl Gold. Other intercultural operations as staking, earthing-up and weeding were carried out as per recommendation. Removal of suckers and removing of dead leaves was done first time on May 2020 and regularly at 7 days intervals.

Plant Vigour
Vigour was recorded at about 50% flowering stage using a 1 to 5 rating scales methods described by Gotame et al. (2019Gotame et al. ( , 2021

Days to 50% Flowering
The number of days after transplanting (DAT) to 50% anthesis (50% of plants in a plot have open flowers) was recorded. Each plot was checked three times a week and recorded the data.

Growth Habit
Growth habit was evaluated based on three types of growth habits as methods described by Hanson et al. (2013) and Gotame et al. (2019).
Determinate (D): Short and bushy, producing two leaves between flower clusters and about five clusters per branch were recorded as the determinant. They produced most of the fruits on terminal end and stopped to further growth and flowering. In this type, the number of leaves or internodes between inflorescences was varied from one to three.
Semi-determinate (SD): It lies in between determinate and indeterminate. They were capable of producing fruits longer period. Plants were more compact but less tall than indeterminate type. Indeterminate (ID): Tall, producing three leaves between flower clusters and more than six clusters per branch were recorded as indeterminate. The terminal axes did not stop to grow and flowering occurred from auxiliary buds.

Evaluation of Genotypes Against Tomato Yellow Leaf Curl Virus (TYLCV)
The individual plot was visited, monitored the appearance of the individual plant at least weekly early in the morning, to observe virus diseased plants, and counted the numbers of infected plants per plot in each observation under natural field conditions. Data were recorded on the data sheet as methods described by Hanson et al. (2013) and Gotame et al. (2019).
Tomato yellow leaf curl virus infection (TYLCV) % was computed as virus incidence percent as:

Yield and Yield Attributing Parameters
Total number of fruits per plot, total yield per plot (kg), and fruit size (g) were recorded at each harvesting time. There were 7 harvestings of the fruits.

Number of Fruits Per Plant
Number of fruits per plant was recorded in each harvest lot separately and cumulative number of fruits was obtained by adding after the complete harvest.
Fruit Weight (g) Average fruit weight (g) was measured from randomly selected 20 marketable fruits per plot. The weight was recorded in two times, first at third and second at fifth harvest lot.
Fruit Length and Diameter (mm) Fruit length and diameter were measured by using a vernier caliper in randomly selected 20 marketable fruits harvested at third and fifth lot.
The total soluble solids of the selected samples were determined with a hand refractometer, Model ATAGO, Tokyo, Japan (0-32°Brix range). The refractometer was washed with distilled water each time after use and dried with blotting paper to avoid contamination.

Weather Data
The weather data during the crop period (March to August 2020) were obtained from the National Agronomy Research Centre, Khumaltar, Lalitpur. The rainfall ranges from 24.1 to 132.3 mm from 15 March to 15 August. But there was heavy rainfall during the flowering and fruiting period (i.e., June-July, 2020) ranging from 82.6 mm in June to 273 mm in July. The continuous heavy rainfall during mid-April (89.8 mm) to end of May (82.6 mm) was very unusual in Nepal (Table 2).

Data Analysis
The experimental data were processed by using MS Excel 2016 and analysed by using Genstat var. 18.0 (GenStat). Two-way ANOVA for F-test for RCBD design was used to analyse the differences between the means observed parameters on growth, yield and yield attributing characters, and virus. Normality was checked using histogram before analysis. Clustering observations unweighted paired group method with arithmetic mean (UPGMA) clustering divided 50 lines of tomato into five clusters by using Minitab version 17. Pearson's correlation analysis between 9 quantitative traits was carried out by using Minitab version 17.

Morphological Traits
Highly significant differences were observed in days to 50% flowering, plant vigour, yield and yield attributing parameters and virus incidence (Table 3a, 3b and Table 4). Most of the lines received from WorldVeg performed better than the check variety Pusa Ruby. Pusa Ruby is an established and released variety of tomato in Nepal.
Plant vigour is a significant factor of tomato that affects yield attributing parameters and helps towards the final yield. In our study, plant vigour was highly significantly different between genotypes which could be due to genotypic variations existed in the tomatoes (Gurung et al., 2020;Gotame et al., 2021). Genotypes Red Local and Sindhupalchok Local were found to be highly vigorous (4.5 out of 1-5 scale). Genotypes HRA43, HRD109 and HRD1455 were also found to be vigorous with a vigour score of 4.33 out of 1-5 scale. Days to 50% flowering was also highly significantly different between genotypes. Sarlahi Purbely Chiuri, Sindhupalchok Local and HRA34 were the earliest genotype which showed 50% flowering at 26 days after transplanting while AVTO1420 was the late (44 days after transplanting) genotype.
Genotypes HRA43, Red Local and Sindhupalchock Local were not affected by tomato yellow leaf curl virus (TYLCV) while Yellow Local showed 3.3% infection with the virus. Among the WorldVeg lines, AVTO1718, AVTO1219, AVTO0922, and national collections HRD1455, HRDTOM035 and Yellow Local showed less than 14% TYLCV infection in the open field conditions. These genotypes could be promising genotypes for the future tomato breeding program in the country.
In tomato, the most easily visible traits are fruit size and shape. The highest fruit length and diameter was found in AVTO1409 (50.02 and 52.78 mm respectively). Sindhupalchock Local has the lowest fruit length (12.9 mm). The smallest diameter was found in Red Local (17.39 mm). Fruit shape is considered by the ratio of length and diameter and describes the overall shape. Based on the descriptor developed by IPGRI (1996), fruit shapes were varied from high-rounded, rounded, rounded slightly, flattened (oblate), slightly flattened, heart-shaped, ellipsoid (plum shaped) in our genotypes. This variation is genotypic variations. In our study, it varied from heart-shaped, rounded, flattened and ellipsoid. Many factors are controlling these traits probably depending on the genotypic background (Panthee and Gotame, 2020).

Yield and Yield Attributing Traits
Fruit weight plays an important role in yield. Within conditions, there was a significant difference in fruit weight (Table 4). In the present study, maximum fruit weight (76.9 g) was produced by AVTO1464 and it was followed by AVTO1409 (71.2 g) and AVTO1713 (70.6 g) while minimum fruit weight was recorded in Red Local (3.7 g), Sindhupalchock Local (4.0 g) and Yellow Local (6.2 g). The variations in fruit weight may be attributed to inheritability of the genotypes.
Taste of tomato is determined by the ratio of total soluble solid (TSS) (°Brix) and titratable acidity. In our study, TSS varied from 2.26 °Brix (AVTO1720) to 5.23 °Brix (AVTO1422). The highest yield (39.63 mt ha -1 ) was produced by the genotype HRA43 and it was followed by HRA33 (26.40 mt ha -1 ). Among the WorldVeg lines, AVTO1429 produced the highest yield (16.21 mt ha -1 ), followed by AVTO1717 (12.95 mt ha -1 ), AVTO0922 (11.83 mt ha -1 ) and AVTO1219 (11.68 mt ha -1 ). The yield was found to be low in most of the WorldVeg lines which could be due to the heavy rainfall during the vegetative growth and fruiting period ( Table 2). The check variety 'Pusa Ruby' produced fruit yield 2.98 mt ha -1 while most of the AVTO lines produced yield ranged from 1.48 to 16.19 mt ha -1 . Yield, a complex character, is governed by many factors such as genotype, environment and management. Yield in each genotype is a result of the cumulative effect of different yield attributing characters. The poor yield of tomato in open field conditions was due to adverse weather which was un-predicted heavy rainfall during the flowering and fruiting period (April-May) ( Table  2). The adverse weather condition was mostly associated with disease development. Even in such adverse open field conditions, three lines received from WorldVeg (AVTO1429, AVTO1717 and AVTO1219) were found to be promising in the mid-hill condition of Nepal due to higher yield and medium disease resistant (Table 2).

Cluster Analysis
Clustering observations Un-weighted paired group method with arithmetic mean (UPGMA) clustering divided 50 lines of tomato into five clusters in more than 80% similarity level (Figure 1).
Cluster-1 was the largest cluster comprised of 40 genotypes followed by cluster-2 and cluster 3 comprised of 3 genotypes. Cluster 4 and cluster 5 comprised of 2 lines (Table 5). Cluster 4 comprised of 2 genotypes showed the highest fruit yield (25.10 mt ha -1 ) and the highest number of fruits per plot (1978 per 4.5 m 2 area) ( Table 5). Genotypes from this cluster could further be evaluated and used for future tomato breeding program. According to dendrogram Cluster 3 consisted of 3 genotypes (HRA33, Sidhupalchock Local and HRA34) and cluster 4 consisted up 2 genotypes (HRD109 and Yellow Local) could be useful genotypes due to their resistant to the virus, higher potential yield and highest plant vigour to develop high yielding genotypes for mid-hill conditions of Nepal.

Correlation Analysis
The Pearson's correlation analysis between 10 quantitative traits showed that there was a positive correlation between growth habit and number of fruits per plot and yield per ha (r =0.58 and r = 0.53 respectively). A highly significant positive correlation was observed between fruit weight (g) with fruit length, fruit diameter (r = 0.94) but there was a negative correlation with fruit weight and the number of fruits per plot (r =-0.76) ( Table 6).
Tomato genotypes behaved differently in morphological and physiological parameters (Rawal et al., 2017;Panthee and Gotame, 2020). The results of this study indicated significant differences among genotypic response towards growth and days to 50% flowering, virus infection, yield and yield attributing parameters which is in agreement with the findings of previous research reported by Shrestha and Sah (2014), and Gotame et al. (2021). Moreover, heavy rains and humid conditions result in poor flower development and low fruit set in tomato (Sato et al., 2000), which could be the reason for the low yield in our study. Wide variation has been observed in tomato yield among genotypes (Devkota et al., 2018). They found that yield variation from 54.39 to 80.83 mt ha -1 among 13 hybrids evaluated in the same field conditions at an altitude of 1350 m (mid-hills) of Nepal. Chapagain et al. (2014) reported tomato yield ranging from 71.4 to 105.8 mt ha -1 among six genotypes at an altitude of 1640 m (mid-hills) under plastic house conditions. In our open field study, the highest yield was produced by HRA43 (39.63 mt ha -1 ) which was higher than the national average of the country (18.01 mt ha -1 ) and comparable with world productivity (35.90 mt ha -1 ). Generally, tomato yield increases two times under plastic house as compared to open field condition in mid-hills of Nepal. This suggests that yield is not only a genetic factor, it is also governed by the environment (Bhurtyal et al., 2007;Devkota et al., 2018). Chapagain et al. (2020a) studied in tomatoes for fruit yield and yield contributing traits and were grouped into one cluster having taller plants with higher marketable fruits per plant, fruit set percentage, flowers per inflorescence, marketable fruits and fruit yield per plant. Tomato genotypes with semi-determinate to indeterminate growth habit with medium sized fruits performed better in yield and quality attributes (Chapagain et al., 2020b). It has been reported that the highest marketable fruit yield of 34.0 and 32.0 mt ha -1 was recorded in genotype AVTO9802 in 2018 and 2019, respectively with the mean yield of 32.9 mt ha -1 . In contrary to their report, the yield of AVTO lines in our study was low which was due to heavy rainfall and disease problem. Chapagain et al. (2020a) found that the highest positive effect of marketable fruit per plant (r=0.99) on fruit yield per plant. Correlation analysis revealed that plant height, fruit weight and diameter were positively associated with fruit yield (Reddy et al., 2013;Chapagain et al., 2020a). Chapagain et al. (2020a) reported that fruit diameter showed positive and significant correlation with average fruit weight (0.983). It was also found that there was strong positive correlation between fruit number per inflorescence and marketable fruit per plant. Bojarian et al. (2019) carried out path analysis and found that number of fruits per line and single fruit weight had the highest positive direct effect on yield.
A positive correlation of growth habit and plant vigour with the number of fruits per plot and fruit yield were observed in our study indicates the growth attributes are interlinked to maintain a higher and sustainable yield. Genotypes with indeterminate growth habit may have the ability to take up nutrients and water in amounts sufficient for the plant's growth and development, resulting in better vigour and yield as compared to determinant and semideterminate tomato. Similarly, fruit weight was highly and strongly correlated with fruit length and diameter. Balcha et al. (2015) found that fruit yield per hectare and fruit weight per plant was significantly and positively correlated. Fruit weight per plant was highly significantly and positively correlated with fruit yield per hectare. Reddy et al. (2013) also found that fruit yield per plant was positively and significantly correlated with number of fruits per plant and fruit width.

Conclusion
Among the 50 evaluated genotypes, high yielding lines HRA43 (39.63 mt ha -1 ) and HRA33 (26.43 mt ha -1 ) could be the most potential varieties for an open field of the midhill of Nepal. As this study was carried out in open field in OP lines, yield is above average level as compared to other OP cultivars. Three lines received from WorldVeg were also found to be promising. These lines produced higher yield and showed disease resistant as compared to check variety Pusa Ruby in open field conditions. These lines were AVTO1429, AVTO1717 and AVTO1219. Genotypes HRA43, Red Local and Sindhupalchock Local could be used in future tomato breeding program due to their resistant to TYLCV. These landraces could be selected for further evaluation in the farmers' field and considered as important genetic resources to develop tomato varieties resistant to the virus at the mid-hill's region of the country. This study showed high agromorphological diversity among exotic and local landraces. We provide varietal options to farmers to produce tomato in mid-hill conditions of Nepal.

Authors Contribution
T.P. Gotame designed the experiment, wrote the draft and finalized the manuscript, I.P. Gautam designed, executed the experiment and finalized the initial draft, D. Ghimire involved in the field layout, genotype evaluation, data collection and analysis, and S.L. Shrestha executed the experiment and finalized the initial draft of the manuscript.