Heterosis studies in brinjal (Solanum melongena L.) using Line X Tester mating design

Introduction

Brinjal (Solanum melongena L.), commonly known as eggplant or aubergine, is one of the most important solanaceous vegetable crops cultivated worldwide. It holds great significance in India, which is considered a center of diversity for this crop (Zeven and Zhukovsky, 1975) [24] . India is having a vast variety of eggplant genetic resources, including a wide variety of plant kinds, fruit colours, forms, sizes, yields, and other quality characteristics (Meyer et al., 2012) [10] . Globally, brinjal occupies about 1.8-2.0 million hectares with an annual production exceeding 57 million tonnes, of which China and India together contribute nearly 90% (FAOSTAT, 2022) [6] . India is the second largest producer with around 0.73 million hectares under cultivation and a production of 12-13 million tonnes, giving an average productivity of about 18-19 tonnes per hectare, which is lower than the realized potential under hybrid cultivation. Within India, brinjal holds immense economic and nutritional importance, especially in states like West Bengal, Odisha, Bihar, and Maharashtra. In Maharashtra, brinjal is cultivated on approximately 0.02 million hectares, producing nearly 0.34 million tonnes, with average productivity ranging between 16-17 tonnes per hectare (NHB, First Advance estimates 2021 -22). Despite being a key brinjal-producing state, productivity is often constrained by pest and disease incidence, varietal limitations, and climatic variability. To enhance yield and quality, the exploitation of heterosis (hybrid vigor) has become a crucial breeding strategy. In brinjal large number of seeds are produced in single act of pollination, crop hardiness, comparatively large size of flowers etc. features promotes breeders for exploitation of hybrid. In brinjal the cost of hybrid seed production is low as compare to other vegetable crops hence exploiting hybrid vigour has become an effective method for brinjal development (Pal and Singh 1949, Mishra 1961, Samandam 1962, Dhankar et al. 1980, Chadha and Sidhu, 1982) [15,12,20,5,3] .

Rabi 2023-24. The experimental materials comprised of eight parents out of which Bandhtiware (BDHE), Kali Ravai (KR), Kasral (KL) were used as lines whereas Konkan Prabha (KP), Swarn Pratibha (SP), Singnath (S), Lanja Local (LL), BB 64 (BB64) were used as testers. Konkan Prabha (KP) used as resistant check to bacterial wilt and Kali Ravai (KR) used as susceptible check to Bacterial wilt. 15 F1's made were made among 8 parents by using LXT mating design. All 8 parents, 2 checks along with 15 F1 were raised in a Randomized Block Design with three replications. All the recommended package of practices were adopted for raising a healthy crop. Five randomly selected plants, from each plot of all the three replications were tagged and used for recording the observations on 9 traits namely Days to first flowering, Plant height (cm), Number of primary branches per plant, Number of fruits per plant, Fruit length (cm), Fruit diameter (cm), Fruit weight (g), Fruit yield per plant (kg), Terminal Bacterial Wilt Incidence (%) and average values were computed across replications. The magnitude of heterosis was estimated in relation to mid parent, better parent and standard check values. They were thus, calculated as percentage increase or decrease of F1s over the Mid-parent (MP), Better parent (BP) and Standard check (SC).

Results and Discussion

Analysis of variance (ANOVA) The analysis of variance for various characters has been represented in Table .1. It is showed that mean sum squares due to genotypes were highly significant for all the characters studies. This stated that there was significant genetic variation across genotypes for every trait under investigation. Further dividing of genotypic variance into components viz., parents, crosses and parents vs. crosses were highly significant for all traits studied except for plant height and terminal bacterial wilt incidence due to parent vs. crosses. This suggested that there were significant variations between the parents and crosses

Heterosis Days to first flowering

Negative heterosis for this trait indicates earliness. The ranges of average heterosis, heterobeltiosis, heterosis over check Konkan Prabha and heterosis over check Kali Ravai were-6.96 (Bandhtiware X Konkan Prabha) to 23.31 (Bandhtiware X Singnath),-7.97 (Bandhtiware X Konkan Prabha) to 18.84 (Bandhtiware X Singnath),-9.29 (Bandhtiware X Konkan Prabha) to 22.14 (Kali Ravai X BB 64) and-16.99 (Bandhtiware X Konkan Prabha) to 11.76 (Kali Ravai X BB 64) respectively. One cross (Bandhtiware X Konkan Prabha) manifested significantly negative heterosis over susceptible check Kali Ravai. None of the cross shown significantly negative heterosis over resistant check Konkan Prabha. This result is in accordance with the results of Rani et al. (2018) [18] and Samatha et al. (2021) [21] Plant Height (cm) Negative heterosis for this trait is desirable. Maximum and significant negative heterosis (-21.41%) over mid parent and (-23.87%) over better parent was found in cross Bandhtiware X Swarn Pratibha. Significantly negative heterosis was displayed by one cross over mid parent, four crosses over better parent. None of the cross showed significantly negative heterosis over resistant check Konkan Prabha and susceptible check Kali Ravai. Similar results were depicted by Kalaiyarasi et al. (2018) [7] and Susmitha et al., (2023) [23] Number of primary branches per plant Significantly posistive as well as negative heterosis over mid parent, better parent, resistant check Konkan Prabha and susceptible check Kali Ravai was observed for this character. [22] , Samantha et al. (2021) [21] Number [2] , Khapte et al. (2017) [8] .

For this character out of 15 [4] , Susmitha et al., (2023) [23] Fruit Diameter (cm) Thirteen crosses recorded significantly positive heterosis over check Konkan Prabha. None of the cross displayed significantly positive heterosis over mid parent and over better parent and susceptible check Kali Ravai. Maxmum significant positive heterosis (52.40%) over resistant check Konkan Prabha was shown by Karal X BB64. Ramani et al.

(2015) [16] , Balwani et al (2017) [2] found similar results for fruit diameter.

Maxmum significant positive heterosis (75.56%) over resistant check Konkan Prabha and 75.68% over susceptible check was shown by Karal X BB64. Three crosses displayed significantly positive heterosis over mid parent, none of the cross manifested significantly positive heterosis over better parent, twelve crosses recorded significantly positive heterosis over check Konkan Prabha and Kali Ravai. These findings were supported by Ramireddy et al. (2011) [17] , Reddy and Patel (2014) [19] .

Significantly posistive as well as negative heterosis over mid parent, better parent, resistant check Konkan Prabha and susceptible check Kali Ravai was observed for this character. Maxium significant and positive heterosis over mid parent (45.23%), better parent (32.08%), resistant check (36.99%) and susceptible check (82.77%) observed in the cross Bandhtiware X Konkan Prabha This result was similar to results obtained by Nikhila et al. (2022) [14] and Mishra et al (2023) [11] .

Negative heterosis for this trait is desirable. Bandhtiware X Konkan Prabha and Kasral X Konkan Prabha both shown significant and negative heterosis (-100%) over mid parent, better parent, resistant check and susceptible check. Out of 15 crosses eight crosses displayed significantly negative heterosis over mid parent, thirteen crosses manifested significantly negative heterosis over better parent, two crosses and fourteen crosses recorded significantly negative heterosis over check Konkan Prabha and Kali Ravai respectively. This is supported by Ajjappalavara et al.

(2013) [1] , Kurhade et al. (2017) [9] and Mishra et al (2023) [11] .

In present investigation Bandhtiware X Konkan Prabha recorded maximum significant positive heterosis for the character fruit length, fruit yield per plant and significant negative heterosis for terminal bacterial wilt incidence. Out of 15 cross combinations Bandhtiware X Konkan Prabha, Kasral X Konkan Prabha, Bandhtiware X Singnath, were found promising for fruit yield per plant with heterosis component showing significant desired heterosis. Hybrids in brinjal not only provide higher yields but also ensure improved fruit quality, resistance to diseases, thereby strengthening the productivity and profitability of this crop

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