INTRODUCTION
The development of high yielding varieties/hybrids is the most cost-effective strategy for increasing the production and productivity of vegetables in Nepal. Hybrids have the major advantage of high productivity, earliness and uniformity, better transport quality, and abiotic and biotic stress resistance. As hybrids have preferable characteristics according to the demand of farmers and consumers, its use is increasing not only in commercial farmers but also in small farmers. Use of hybrid varieties of major vegetable crops like cabbage, tomato, cauliflower, most of the cucurbits, onion, carrot etc. is increasing every year even in a small pocket areas of Nepal. About 73% of the area of vegetable production is estimated to be covered by hybrid varieties in Nepal. A huge volume of hybrid seeds in vegetable crops are importing from abroad especially from India, China, Thailand, Japan, Korea, and Netherland.
On the other hand, there are many hybrid varieties already registered through private seed business companies but they are not consistent in their performance across the agro-ecological regions and over the seasons. It is necessary to develop suitable vegetable varieties in Nepal to replace the imported hybrid seeds and make available in the market all-round the years.
Considering the urgent need and technology demand of the Nepalese farmers, the National Horticulture Research Centre (NHRC), Khumaltar, Lalitpur has started hybrid breeding in tomatoes since 2002/03 (HRD, 2008). The Centre is collecting popular genotypes from local and exotic sources for hybrid variety development. Hybrid cv. ‘Srijana’ was registered in 2010 (HRD, 2010). This variety is gaining popularity among tomato growers across the country and is estimated to cover about 35% of the total tomatocultivated area. The hybrid breeding process has been started in hot pepper and brinjal in the fiscal year 2019/20. NHRC has released 2 hybrid tomato varieties in 2021. However, at foothill and mid-hills, the appropriate variety having multiple stresses tolerance (disease, insects, drought, and heat) was still lacking.
Extensive researches have been conducted on tomato using following cross combinations: HRA13 × HRD7, HRA14 × HRD7, HRA17 × HRD1, HRA20 × HRD6, and HRA20 × HRD2 in tomatoes have shown superior performance (HRD, 2016). Similarly, crossings such as HRDTOM005 × HRDTOM010, cv. ‘Makis’ and cv. ‘Srijana’ were selected and recommended for cultivation in central Tarai region. In 2021, two tomato hybrids namely ‘Khumal Hybrid Tomato-2’ and ‘Khumal Hybrid Tomato- 3’ were released in the National Seed Board (NSB).
MATERIALS AND METHODS
Most of the hybrid breeding in vegetable was carried out in National Horticulture Research Centre, (NHRC, former Horticulture Research Division; HRD) Khumaltar, Lalitpur and multi-location evaluation was done at different stations under NARC. Hybrid breeding in tomatoes was started in 2003/04 while hybrid breeding in cucumber was started in 2007/08. Evaluation of hybrid tomatoes was carried out at five NARC’s Regional Agricultural Research Stations (RARS) (RARS, Khajura; RARS, Parwanipur; RARS, Tarahara; RARS, Lumle) ARS, Doti and HRD,Khumaltar during the FY 2019/20. The experiments were carried out in randomized complete block design (RCBD) with three replications. The seeding was done in March and 25 days old seedlings were transplanted in 75 × 60 cm. The plot size was 4.5 square meters with two rows having 10 plants in each plot. The evaluation was done in open field conditions in all stations except at RARS, Lumle where the evaluation was done under plastic house conditions. The standard recommended dose of fertilizers (200:150:100 NPK kg/ha + 15 MT/ha farmyard manure) was applied and fungicide (copper oxychloride) was sprayed only two times in the crop season.
However, hybrid breeding in cucumber has been started since 2007/08, extensive breeding works have been carried out from 2016/17. Evaluation of newly developed crosses (hybrids) including Indian hybrid cucumbers was tested both in an open and plastic tunnel at Horticulture Research Division (present NHRC) in 2016, 2017, 2018 and 2019 in rod row plot adjusted 4 plants at a spacing of 1 meter plant to plant and row to row. The seed was shown in February in a polythene bag and 25 days old seedlings were transplanted in March in both open and plastic house conditions. The seedlings were transplanted in a square plot adjusted with 4 plants at a spacing of 1 meter. Three shoots were maintained in a single plant by removing other shoots by secateurs. The plants were trained with the help of bamboo, GI wire and plastic rope. For the plastic house environment, the seeding and transplanting times were the same as open field conditions.
Yield per plot was recorded in each harvest date and cumulative yield per plot was used to calculate yield MT/ ha. Tomatoes were harvested 4-6 times in weekly intervals and cucumbers were harvested 6-8 times in a season. The yield attributing characteristics was recorded from 10 fruits harvested in 3rd and 5th lot in tomatoes while it was recorded in 5 fruits harvested at 3rd and 5th lot in the season.
The experimental data were processed by using MS Excel 2016 and analyzed by using GenStat var. 18.0 (Gen- Stat). Two-way ANOVA for F-test for RCBD design was used to analyze the differences between the means observed parameters (Gomez and Gomez, 1984).
RESULTS AND DISCUSSION
Hybrid breeding of tomato
National Horticulture Research Centre (NHRC, former HRD), Khumaltar, Lalitpur has started hybrid breeding in vegetables using the conventional approach in 2003. Cultivar ‘Srijana’, the first hybrid tomato developed by NHRC has become very popular in Nepal in a short period of time because of its productivity, fruit size and field tolerance on bacterial wilt and late blight diseases. The major objectives of hybrid tomato breeding at NHRC were the development of bacterial wilt and late blight resistance, high yielding, appropriate fruit size (consumer-preferred size), and plants with indeterminant growth habit and suitable table purpose (medium, fleshy cum juicy) varieties.
Late blight (LB) and bacterial wilt (BW) were the major diseases of tomatoes in Nepal (HRD, 2019). NHRC has been involved in the hybrid breeding of tomatoes with a special focus on developing resistance to bacterial wilt and late blight. Further breeding program was initiated to develop additional tomato hybrids with late blight resistance and better fruit quality attributes. Among the promising hybrids developed in 2019, two superior tomato hybrids ‘Khumal Hybrid Tomato-2’and ‘Khumal Hybrid Tomato-3’ has been released by National Seed Board (NHRC, 2020). Characterization of inbred lines of tomatoes used to develop two superior hybrids was done and their heterosis was estimated. It was found that the heterosis for yield was 87% in ‘Khumal Hybrid Tomato-2’ (HRA14 × HRD7) and 95% in ‘Khumal Hybrid Tomato-3’. (HRA20 × HRD2) (Table 1). The detailed characteristics of the recently released two hybrids are presented in Table 1.
A comparative study of 7 tomato hybrids including two check varieties at different research stations of NARC has been done and found that F1 (HRA13 × HRD7) could be a potential hybrid for the western region. It produced 116.8 MT/ha at RARS, Lumle under plastic house conditions (Table 2).
Tomato hybrids F1 from cross combination HRA13 ×HRD7 and HRA20 × HRD1 have shown superior performance at RARS, Lumle and RARS, Khajura conditions.
Newly developed tomato hybrids have shown promising for late blight tolerance in field conditions. To continue the selection process, seeds of tested hybrids were produced by using six female and five male inbreds. About 2-3 gram seed of each of the 14 hybrids was produced in the fiscal year 2019/20.
Hybrid breeding of cucumber
Hybrid breeding in cucumber has been started from 2007/08 at NHRC, Khumaltar. Major objectives of cucumber hybrid breeding at NHRC, Khumaltar are to develop hybrid varieties with high yielding, better taste, early maturity, uniform size, disease-resistant, and producing higher female to male ratio flower and consumer-preferred colour. Male and gynoecious inbred lines of cucumber used for hybrid breeding in cucumber at NHRC, Khumaltar has been characterized and is presented in Table 3.
A total of 12 crosses in cucumber have been done after collecting gynoecious lines. Performance study of these hybrids has also been completed and is presented in Table 5. Among several crosses F1 (HRDCUC004 × HRDCUC001) which is ‘GYC’(female) × ‘Bhaktapur Local’(male) found to be a promising cucumber hybrid for commercial cultivation.
Similarly, the performance study of promising 4 hybrid cucumbers was studied at NARC stations. It was found that in the eastern region, F1 (HRDCUC009 × HRDCUC003) performed better and was mostly preferred by the consumer (Table 5).
The yield potential of the F1 (HRDCUC004 ×HRDCUC001) was 100-110 MT/ha and male to female ratio was1:21 compared to 11:1 in ‘Bhaktapur Local’. Since F1 (HRDCUC004 × HRDCUC001) was found to be early matured than local cultivars (‘Bhaktapur Local’ and ‘Kusle’) and average fruit size was 350-400 g and found better taste than exotic hybrids, it can fulfil the temporal production gap associated with existing open-pollinated varieties.
Hybrid breeding of brinjal
Local germplasm collection, characterization, evaluation, and purification started from the fiscal year 2019/20. Seed production of those collected lines has been started. It is necessary to import pure lines from WorldVeg, India and Bangladesh.
Hybrid breeding of hot pepper
Eight germplasms were received from Gene Bank (NARC) and characterization, evaluation and purification have been started from the fiscal year 2020/21. Seed production of those collected lines have been started. It is also necessary to import CMS lines and pure lines from World- Veg, India, and Bangladesh.
Hybrid breeding of bitter gourd
Local germplasm collection, characterization and evaluation have been started from the fiscal year 2019/20. There were 4 local lines collected from national sources and 2 lines were collected from World Vegetable Research Centre. It is necessary to import gynoecious lines from CG Centres, WorldVeg, India, and Bangladesh.
FUTURE PLANS
Considering the importance and constraints of vegetable breeding and variety development, NHRC has developed five-year strategic plan to increase the production and productivity of vegetables. It has been set a target of development of 6 hybrid vegetable cultivars within the five years period from 2018 (HRD, 2018). Target numbers of hybrid varieties including was one in each of tomato, cucumber, brinjal, bitter gourd, and hot pepper for registration/ release by 2023.
For hybrid vegetable breeding, dedicated and trained manpower is necessary in the organization but there is a lack of trained manpower in NHRC under NARC. Also, a well-equipped laboratory is necessary for molecular breeding. Advance infrastructures such as climate-controlled chambers, climate automated greenhouse is still lacking in NARC. Moreover, there is a problem of maintenance of inbred lines, lack of sufficient inbreds, e.g. cytoplasmic male sterile lines, gynoecious and pure lines. To solve the existing problems and strengthen the hybrid vegetable breeding in NHRC under NARC should follow and adopt strategies as soon as possible. For example, collection and utilization of genetic resources from local and exotic sources, expand collaboration with international organizations (CG Centers, WorldVeg etc) for germplasm exchange, collaboration with private seed companies/cooperatives and agro-vets, hiring external exports in hybrid breeding, improvement of technical capacity of researchers, training to technician and farmers in hybrid seed production in collaboration with NHRC, import of cytoplasmic male sterile (CMS) lines of crucifers, gynoecious lines for cucurbits and CMS lines, the establishment of the molecular laboratory, infrastructure and breeding facility at a central level and hiring experts for training to staffs are very necessary.
