Elucidation of Heterosis for Seed Yield and its Attributes in Pigeonpea [Cajanus cajan (L.) Millsp.]

Pulses play a crucial role in the vegetarian Indian diet, serving as essential components that contribute significantly to protein and calorie intake. Pulses are regarded as “poor man’s meat” because they are high in protein, high dietary fiber and low in fat. Pigeonpea is famous with different names as tur, red gram and arhar. Barbados gave the name “pigeonpea” to the plant because its seeds are used to make pigeon feed (Gowda et al., 2011). Pigeonpea belongs to the family ‘Fabaceae’ and sub-family ‘Faboideae’. Pigeonpea crop is diploid (2n = 2´), with a genomic size of 1C = 858 Mbp and a chromosomal number of 22. It is an often-cross-pollinated crop in which 25 to 70 per cent natural out-crossing observed (Saxena et al., 1990). It is the handiest food legume with widespread uses as food, feed, fodder and fuel. The protein content of commonly grown pigeonpea cultivars ranges from 17.9 to 24.3 per cent for whole grain and split-grain. Moreover, pigeonpea seeds contain 0.6 to 3.8 per cent lipids, 1.2 to 8.1 per cent crude fibre and 57.3 to 58.7 per cent carbohydrates (Sinha, 1977). Critical amino acids such as lysine, tyrosine, cysteine and arginine are abundant in pigeonpea seeds. Additionally, pigeonpea are a good provider of iodine and iron. One of the factors attributed to the low productivity levels is the inherent low yield potential of the currently accessible cultivars. The crop’s low yield potential is mainly caused by cultivation on marginal ground, a lack of robust and high-yielding cultivars. Therefore, must need arise to develop high-yielding and stable cultivars through efficient breeding programme to eliminate this factor. Heterosis has been shown to be a useful tool for increasing yields in a variety of crops by breaking the existing yield barrier. Gaining an under standing of heterosis is essential to identifying particular cross combinations that can be used to strategically exploit hybrid vigour or accumulate fixable genes through selective breeding. The pre sent investigation was undertaken to find out the extent of various types of heterosis (Economic heterosis, Heterobeltiosis and Standard heterosis) for seed yield and its component traits.

The five females (Banas, GT 102, GT 103, GT 100 and GT 1) used as lines and four males (SKNP 1408, SKNP 1406, Vaishali and BDN 2004-01) used as testers  were crossed in Line x tester mating design during kharif  2019 to produce 20 F1’s under insect proof net house. Thus, the 31 genotypes including 9 parents, 20F1’s and two checks were grown during kharif  2020 at Pulses Research Station, Sardarkrushinagar Dantiwada Agricultural University, Sardarkrushinagar using randomized block design with three replications. Each male and female lines were grown in a single row of 3.0 m length keeping an inter-row and intra-row distance of 60 cm and 20 cm respectively. The observations were recorded from five randomly chosen plants for each genotype in each replication for thirteen characters viz., days to flowering, days to maturity, plant height (cm), number of branches per plant, number of pods per plant, pod length (cm), number of seeds per pod, test weight (g), seed yield per plant (g), biological yield per plant (g), harvest index (%), total protein content (%) and leaf area per plant (cm²). The data were compiled for analysis of the variance of different traits using the method suggested by Panse and Sukhatme (1978). Heterosis was estimated as per cent increase or decrease in the mean value of F1 hybrid over the mid parent i.e., relative heterosis (Briggle, 1963), over the better parent, i.e., heterobeltiosis (Fonseca and Patterson, 1968) and standard check, i.e., standard heterosis (Meredith and Bridge, 1972) for each other.

 

The variations observed among both parental lines and hybrids across the 13 attributes assessed. Notably, the results unveiled significant mean squares attributed to genotypes across all traits, underscoring the ample genetic variability inherent in the studied materials. The values of relative heterosis, heterobeltiosis and standard heterosis of all crosses for various characters are presented in Table 1 to 5. Sixteen out of twenty hybrids exhibited significant positive relative heterosis for seed yield per plant. In which, Banas x BDN 2004-01, Banas x Vaishali and Banas x SKNP 1406 showed the most significant and positive heterosis over mid-parent. Heterobeltiosis revealed that nine hybrids had significant positive heterosis. Upon scrutinizing the results, it became evident that all hybrids displayed noteworthy and positive standard heterosis when compared to both reference checks GTH 1 and GT 101. Crosses, GT 1 x Vaishali, GT 1 x BDN 2004-01 and GT 102 x SKNP 1408 displayed maximum standard heterosis over both checks (Table 1). The results are in accordance with similar findings of Kumar et al., (2009), Gedam et al., (2013), Chethana et al., (2015), Soni et al., (2017) and Patel et al., (2020).


        
Among the twenty hybrids evaluated, six displayed significant relative heterosis in the desired (negative) direction, in which Banas x Vaishali displayed maximum value among them. None of the hybrids exhibited negative significant heterobeltiosis in the desired direction. While, four hybrids exhibited negative and significant standard heterosis in desired direction. Out of which, GT 102 x SKNP 1406, GT 102 x BDN 2004-01 and GT 102 x SKNP 1408 are the best one  (Table 1). For days to maturity, none of the hybrids exhibited negative significant heterobeltiosis in the desired direction. Whereas, one out of twenty hybrids (GT 102 x BDN 2004-01) showed early maturity in terms of relative heterosis. GT 102 x BDN 2004-01, GT 102 x SKNP 1406 and GT 102 x SKNP 1408 were the top three superior hybrids over standard check for days to maturity (Table 1).                              

Only one cross, GT 100 x Vaishali exerted negative significant relative heterosis and heterobeltiosis for plant height. While, crosses, GT 100 x Vaishali, GT 100 x BDN 2004-01 and GT 103 x BDN 2004-01 were the best performing hybrids with significant negative standard heterosis over standard check. (Table 2) Above results are in accordance with the findings of Mhasal et al., (2015), Soni et al., (2017) and Patel et al., (2020) for traits like, days to flowering, days to maturity and plant height. Plants with a greater number of primary branches per plant are closely associated with higher seed yields. Out of 20 hybrids assessed, nine hybrids recorded significant and positive heterosis over mid-parent in the desirable direction. Crosses, Banas x SKNP 1406, GT 1 x Vaishali and GT 100 x SKNP 1406 illustrated positive significant heterosis in desirable direction over mid-parent and also for heterobeltiosis (Table 2). For number of pods per plant, thirteen out of twenty hybrids were found significant positive heterosis over mid-parents and eight hybrids demonstrated significant and positive heterosis over the better parents. In both the parameters, GT 1 x BDN 2004-01, GT 1 x Vaishali and GT 102 x BDN 2004-01 were the superior crosses among them. For standard heterosis, GT 102 x Vaishali, GT 102 x BDN 2004-01 and GT 1 x Vaishali most promising hybrids showed significant positive heterosis for this trait (Table 2). Similar findings were recorded by Soni et al., (2017) and Patel et al., (2020) for number of branches per plant and number of pods per plant. Twelve hybrids exhibited significant and positive relative heterosis, while eight hybrids showed significant and positive heterobeltiosis for pod length. While, GT 1 x Vaishali, GT 1 x  SKNP 1408 and GT 1 x BDN 2004-01 were the top three hybrids exerted significant and positive standard heterosis over the checks (Table 3). The results are in accordance with findings of Ajay et al., (2015) and Soni et al., (2017) for pod length.


       
For number of seeds per pod, Banas x Vaishali, Banas x BDN 2004-01 and Banas x SKNP 1408 were top three best crosses exhibited superior performance for relative heterosis. While, eighteen out of twenty hybrids exhibited significant and positive standard heterosis over both the standard checks for this trait (Table 3). Mhasal et al., (2015) and Soni et al., (2017) observed similar results for number of seeds per pod. For biological yield per plant, GT 103 x Vaishali was the best cross exhibits positive and significant relative heterosis, heterobeltiosis and standard heterosis (Table 4). Similar results obtained by Soni et al., (2017) and Patel et al., (2020) for this trait. Banas × SKNP 1406 and GT 102 x SKNP 1408 were the superior crosses exerted significant and positive relative heterosis and hetero beltiosis for harvest index. While, GT 1 x Vaishali and GT 1 x BDN 2004-01 displayed standard heterosis in desired direction (Table 4). For the trait like total protein content, Banas x  Vaishali was the common and superior performing cross with significant and positive heterosis for all three types i.e., relative heterosis, heterobeltiosis and standard heterosis (Table 4). For leaf area per plant, crosses, GT 1 x Vaishali, GT 1 x BDN 2004-01 and GT 102 x Vaishali exhibited significant and positive heterosis in desired direction for relative heterosis, heterobeltiosis and standard heterosis parameters (Table 5). The results were found similar with Saritha et al., (2012), Soni et al., (2017) and Patel et al., (2020) for leaf area per plant.

       
Table 6 illustrates that the hybrid GT 1 x Vaishali displayed the highest standard heterosis (193.41%) over GTH 1 for seed yield per plant. This finding aligns with previous studies conducted by Shoba and Balan (2010), Gupta et al., (2011), Chethana et al., (2015), Soni et al., (2017) and others, which also reported higher standard heterosis for this trait. Notably, eight out of ten hybrids exhibited positive heterobeltiosis for seed yield per plant, indicating promising hybrid viguor. The results are in accordance with Chandra et al., (2024).  Furthermore, these hybrids demon-strated significant heterosis for various component traits such as the number of branches per plant, number of pods per plant, number of seeds per pod, test weight,biological yield per plant, harvest index, total protein content and leaf area per plant.

Hybrids which displayed significant heterotic effects over their better parents and over the checks may use to produce synthetic populations to utilize heterosis in this crop. From the resultant crosses, GT 102 ´ SKNP 1408 and GT 103 ´ BDN 2004-01 were produced good amounts of heterosis, heterobeltiosis and standard heterosis for various characters. While, hybrid GT 102 ´ SKNP 1408 was found to be the most promising based on its per se performance and standard heterosis, which may be exploited in further breeding programmes for pigeonpea.

All authors declare that they have no nconflict of interest.