ICRISAT scientists, working with Indian programme counterparts, developed the world's first cytoplasmic‐nuclear male sterility (CMS)‐based commercial hybrid in a food legume, the pigeonpea [ Cajanus cajan (L.) Millsp.]. The CMS, in combination with natural outcrossing of the crop, was used to develop viable hybrid breeding technology. Hybrid ICPH 2671 recorded 47% superiority for grain yield over the control variety ‘Maruti’ in multilocation on‐station testing for 4 years. In the on‐farm trials conducted in five Indian states, mean yield of this hybrid (1396 kg/ha) was 46.5% greater than that of the popular cv. ‘Maruti’ (953 kg/ha). Hybrid ICPH 2671 also exhibited high levels of resistance to Fusarium wilt and sterility mosaic diseases. The outstanding performance of this hybrid has led to its release for cultivation in India by both a private seed company (as ‘Pushkal’) and a public sector university (as ‘RV ICPH 2671’). Recent developments in hybrid breeding technology and high yield advantages realized in farmers' fields have given hope for a breakthrough in pigeonpea productivity.

The word ‘hybrid’ cultivar excites farmers in the expectations of high yields and greater returns. The hybrid breeding technology has demonstrated quantum yield jumps in various cereal (Alexandratos 2001), vegetable (Rai and Rai 2006) and fruit (Kuznecov 1966) crops. The commercial exploitation of hybrids is known to be directly linked to the ease with which their hybrid seeds could be produced and delivered economically to farmers. The efficiency of mass pollen transfer from male to female parent through air or insects to affect cross‐fertilization plays an important role in commercializing the hybrids in different crops. In most food legumes, the absence of natural cross‐fertilization is the major bottleneck in exploiting hybrid vigour at commercial scale because their flower structure forces high level of self‐pollination (Saxena et al. 1992). Legumes are the major source of protein for the vegetarian population in South Asia. The legume crops are generally grown under low inputs and risk‐prone marginal environments, especially in semi‐arid tropics. At present, the availability of proteins among poor in the developing world is less than one‐third of its normal requirements (Paul et al. 2011), and with growing population (expected to be 9 billion by 2050) and continuing low productivity of legumes, the protein availability to the masses is under threat of further decline. As the food production efforts in past in most developing countries favoured cereals, the issue of protein availability assumes even greater significance from nutrition point of view. Globally, pigeonpea [Cajanus cajan (L.) Millsp.] is cultivated on 4.79 million ha in 22 countries. Besides India, Myanmar and Nepal are important pigeonpea‐growing Asian countries; in the African continent Kenya, Malawi, Uganda, Mozambique and Tanzania produce considerable amounts of pigeonpea (FAO 2010). In India, the pigeonpea area has recorded a significant rise from 2.3 million ha in 1950 to 3.53 million ha in 2010; but the crop productivity has remained stagnant at around 700 kg/ha (FAO 2010). There are a number of factors for low crop productivity, but the lack of high‐yielding cultivars has been identified as one of the major constraints underlying the stagnant productivity (Zaveri and Pathak 1998). The issue of yield plateau in pigeonpea has been a major concern for a long time, and to date, it has remained a challenge. To achieve a breakthrough in pigeonpea productivity, research on breeding a cytoplasmic‐nuclear male sterility (CMS) system was initiated at ICRISAT (Reddy and Faris 1981). In the last decade (2002–2011), significant progress has been made to address various issues related to hybrid breeding and large‐scale hybrid seed production technologies. The hybrid technology in pigeonpea is on the verge of commercialization in India. This study, besides briefly describing the progress in breeding and release of the world's first commercial pigeonpea hybrid, also documents its salient features including productivity in diverse environments.

Evolution of Hybrid Breeding Technology in Pigeonpea Shull (1908) for the first time demonstrated hybrid advantage in maize (Zea mays) and foresaw the potential of this phenomenon in enhancing crop yields. Subsequently, the breeders of cross‐pollinated crops designed suitable mating and selection schemes to enhance yields by exploiting hybrid vigour. As dominant genes generally contribute towards hybrid vigour, it was considered useful for only cross‐pollinated crops; but later its utility was also established in self‐pollinating crops (Sharma and Dwivedi 1995). They reviewed the phenomenon of heterosis in food legumes and concluded that dominance, overdominance, additive and various interallelic interactions play a significant role in the expression of hybrid vigour. They further postulated that the likelihood of obtaining heterotic crosses in pigeonpea is high because this crop also has a fairly good inherent capacity to carry a considerable genetic load of recessive genes due to partial natural outcrossing in the crop. In a subsequent review, Saxena (2008) showed that in pigeonpea important economic traits such as seed yield, pods/plant, plant height, seed size and seeds/pod are predominantly controlled by both additive as well as non‐additive genetic variances. The level of realized heterosis for seed yield in pigeonpea is comparable to other crops where commercial hybrids have already made a mark in global agriculture (Saxena 2009). A search for male sterility in pigeonpea germplasm led to the selection of a genetic male‐sterility (GMS) system that was controlled by a single recessive gene (Reddy et al. 1978). A breeding programme was launched to generate valuable data on the extent of hybrid vigour and various other issues related to large‐scale hybrid seed production in pigeonpea. The GMS hybrids showed 25–30% heterosis for seed yield in farmers' fields with wide adaptation, but various seed production difficulties and seed quality concerns did not permit commercialization of these hybrids (Saxena et al. 1992). The hybrid breeding programme at ICRISAT was then shifted towards developing a more efficient cytoplasmic‐nuclear male‐sterility (CMS) system.

Development of A 4 CMS System Cytoplasmic‐nuclear male sterility system is ideal for commercial hybrid seed production of field crops. The expression of CMS, in part, is controlled by genetic factors that are carried through both the male and female parents and retained over the generations. The male‐sterile (A) line with ‘sterile’ cytoplasm and homozygous recessive (frfr) nuclear genes is maintained by its counterpart male‐fertile maintainer (B) line that carries a normal (fertile) cytoplasm, and the same homozygous recessive (frfr) nuclear genes. To produce male‐fertile hybrids, the A‐line is crossed with a male‐fertile restorer (R) line, which carries normal cytoplasm and dominant nuclear alleles (FrFr) for fertility restoration. To sum up, the CMS‐based hybrid system consists of an A‐line, its corresponding B‐line, and R‐line. As no CMS system was available in pigeonpea germplasm, efforts were made to breed for this trait by placing pigeonpea genome into the cytoplasm of its related wild species. The CMS system in pigeonpea was developed by crossing Cajanus cajanifolius as female parent with a pigeonpea cv. ‘ICP 28’ as a male parent. Cajanus cajanifolius (Haines) Maesen (Fig. 1) is a wild relative of pigeonpea belonging to secondary gene pool. Based on various considerations, van der Maesen (1990) and De (1974) concluded that C. cajanifolius is the most closely related wild species to the cultivated pigeonpea and is a putative progenitor of the cultivated type. They also mentioned that these two species differ by a single gene. Cajanus cajanifolius has a chromosome complement (2n = 22) similar to that of cultivated pigeonpea. According to Ohri and Singh (2002) the karyotype of C. cajanifolius is almost similar to that of pigeonpea in morphology and number of satellite chromosomes. The close relationship between C. cajan and C. cajanifolius was also established through various studies on plant morphology (van der Maesen 1990), isozyme analysis (Krishna and Reddy 1982), seed protein profiles (Ladinzinsky and Hamel 1980), trypsin and chymo‐trypsin inhibitors (Kollipara et al. 1994), RAPD (Nadimpalli et al. 1993) and RFLP markers (Ratnarpakhe et al. 1995). Such a close relationship of the donor species generally reduces the problems of negative linkage drag, commonly observed in interspecific crosses. The CMS system derived from C. cajanifolius (accession ICPW 29) was designated as A 4 (Saxena et al. 2005); and it is an excellent male‐sterility system because of its high stability across environments (Sawargaonkar 2011). In addition, this system has a number of good maintainers and fertility restorers in the cultivated Cajanus germplasm. The F 1 hybrid plants derived from this CMS produce excellent pollen load and pod set. At present, the A 4 CMS system is being used by pigeonpea breeders in India, Myanmar and China (Saxena 2009) for genetic diversification of A‐lines and to produce commercial hybrids. Figure 1 Open in figure viewer PowerPoint A snapshot of Cajanus cajanifolious – a wild relative of pigeonpea that has been used to develop cytoplasmic‐nuclear male‐sterility system (A 4 )

Development of Seed Production Technology The benefits of hybrid technology cannot be realized unless sufficient quantities of genetically pure hybrid seed is commercially produced and sold at affordable prices. The experiments conducted at different locations have shown that extent of partial natural outcrossing (20–70%) in pigeonpea varies considerably (Saxena et al. 1990). The hybrid seed set on the male‐sterile plants is chiefly determined by the availability of bee population in the vicinity. The known prime pollinating vectors in pigeonpea are Megachile lanata, Apis florea and Apis mellifera (Pathak 1970, Brar et al. 1992). Onim (1981) reported that each insect visit lasts for 15–55 s when they trip the unopen floral buds, thereby introducing foreign pollen on the stigmatic surface to affect the cross‐fertilization. Williams (1977) counted 5500–107 333 pollen grains on the body of a single pollinating insect, of which pigeonpea pollen accounted for 98–100%. As pigeonpea flowers are prone to natural cross‐pollination by insects, a safe isolation distance (about 500 m) is essential to produce pure seed of hybrids and their parents. The commercial seed production of pigeonpea hybrids involves large‐scale seed production of A‐, B‐, R‐lines, and the hybrid combination (A × R). For seed production of A‐line, breeder seed of both A‐ and B‐lines are planted using a female : male row ratio of 4 : 1. In the production areas where greater bee activity is observed, a higher row ratio can be used for getting high yields. For hybrid seed production (A × R) also, the same ratio can be used. In general, roguing of off‐type plants is carried out both at seedling as well as reproductive stages. For effective hybrid seed production, it is important that flowering of the male and female parents synchronizes well to affect cross‐pollination. The other issues related to productivity of seed parents have to be looked into by considering the interaction of genotype with biophysical factors such as spacing and irrigation. Mula et al. (2011) reported that growth and yield of female parent ICPA 2043 were significantly affected by row ratio, plant spacing and soil moisture availability. In Alfisols, the spacing of 75 cm × 30 cm with 3 : 1 row ratio and irrigation at every 14 days produced A‐line seed yield of 1872 kg/ha. In vertisols, the seed yield of 2357 kg/ha was recorded at Patancheru at the spacing of 75 cm × 30 cm with 3 : 1 row ratio and irrigation at every 21 days. To harvest good hybrid seed yield, it is imperative to select suitable seed production sites with good insect pollinator activity. To achieve this, a few small pilot seed production plots were sown at a number of locations in diverse environments, and the sites with abundance of bees (as indicated by pod set on male‐sterile plants) were selected for hybrid seed production. Large‐scale hybrid seed production in central India was successful with hybrid yields ranging between 1333 and 3040 kg/ha (Table 1). Similarly, a few high‐yielding seed production sites were also identified in the Indian states of Andhra Pradesh, Maharashtra and Gujarat. Table 1. Hybrid pigeonpea seed production in some selected areas in India, 2011 Location Area (ha) Production (kg) Yield (kg/ha) Madhya Pradesh Tikamgarh 5.0 15 200 3040 Seoni 1.0 2500 2500 Indore 0.15 340 2267 Rewa 1.0 1740 1740 Katni 3.0 4350 1450 Jabalpur 1.5 2000 1333 Andhra Pradesh Nizamabad 0.4 700 1750 Patancheru 0.4 500 1250 Medchal 1.4 1700 1214 Warangal 1.2 1275 1063 Nalgonda 2.0 2000 1000 Maharashtra Risod 0.6 600 1000 Gujarat Ahmedabad 0.8 850 1063 Mean – 2597 1590 In most field crops, it may not be possible to produce large quantities of crossed seed with such a moderate level of outcrossing, but in the male‐sterile populations of pigeonpea, good amounts of seed set are often recorded. In the present context, good hybrid yield is obtained even with 25–30% outcrossing. This is primarily attributed to prolonged flowering in pigeonpea as an evolutionary consequence. The pollinating insects may visit the male‐sterile plants several times, and in each visit, a certain proportion of the flowers are pollinated to set the pods while the un‐pollinated flowers should drop. This is followed by the emergence of new flowers on the same plant, and again a proportion of them set pods through open pollination. This cycle continues, and at the end of the season, plenty of crossed pods are observed (Fig. 2) on each male‐sterile plant (Saxena et al. 2005). This phenomenon delays pod maturity on female parent by 3–4 weeks. Figure 2 Open in figure viewer PowerPoint A snapshot showing the pod set on hybrid seed production plot

Economics of Hybrid Seed Production The cost–benefit estimates are vital for every business enterprise. The hybrid seed cost should be such that the hybrid could be made available to small‐holder farmers at affordable prices. Also, this endeavour should yield sufficient profits to the seed companies. According to Saxena et al. (2011), the cost of producing hybrid seed in one hectare was Rs. 26 395 (US$ 523). One kilogram of seed was sold at Rs. 60 (US$ 1.2)/kg and generated a total revenue of Rs. 86 400 (US$ 1728)/ha. Further, it was also estimated that the hybrid pigeonpea seed production can yield profits as high as Rs. 60 000 (US$ 1205)/ha as compared to Rs. 34 996 (US$ 693)/ha for pure line variety. In this study, the cost of producing 1 kg hybrid seed was estimated at Rs. 18.32 (US$ 0.37)/kg.

Development of Marker‐Based Hybridity Test For sustaining the productivity of hybrids, it is important to produce and supply genetically pure hybrid seed to farmers. In general, the purity of hybrid seed is assessed through standard ‘grow‐out test’ using simply inherited morphological traits (Saxena 2006). In pigeonpea, such tests take more time due to the long duration of the crop and feasibility to raise a single crop in a year, particularly in medium and long duration of pigeonpea hybrids. Therefore, a simple, rapid and cost‐effective hybrid seed quality testing approach in pigeonpea based on molecular markers assay is very much needed. Saxena et al. (2010) identified a set of simple sequence repeat (SSR) markers for testing the hybridity of ICPH 2671. They used 148 SSR markers for polymorphism survey on 159 parental lines of hybrids. Of these, a total of 41 markers were found polymorphic. Bohra et al. (2011) used a set of 18 149 SSR markers that could be used in multiplexes for assessing the hybridity of ICPH 2671. From this study a set of 42 SSR diagnostic markers were identified for hybrid ICPH 2671. This assay (Fig. 3) can now be used by both the public and private seed companies for reliable detection of seed purity within the commercial seed lots of hybrids ICPH 2671 to ensure the supply of high‐quality seeds. For assessing the genetic purity of a large number of farmers' samples, alternative genomics technologies were explored and found that the single‐nucleotide polymorphisms (SNPs)‐based marker purity assay was the best. In this approach, 16 SNPs (R. K. Varshney, unpublished data) could be used for testing the genetic purity of the parents (ICPA 2043 and ICPR 2671) and the hybrid ICPH 2671. This is an easy, rapid and relatively cheap approach with a single data point costing 0.5 US$. Figure 3 Open in figure viewer PowerPoint 2011 A snapshot showing the hybrid purity assessment of hybrid ICPH 2671 with the CcM 0021 marker. The parental lines ICPA 2043 (A‐line) and ICPR 2671 (R‐line) show 298‐ and 301‐bp alleles, respectively, on screening with a diagnostic simple sequence repeat (SSR) marker (CcM 0021), while ICPH 2671 seed showing the presence of both alleles (298 and 301 bp) represents true hybrid (Bohra et al.

Features of the First Commercial Pigeonpea Hybrid ICPH 2671 Parentage and morphological traits Hybrid ICPH 2671 (Fig. 4) was produced by crossing CMS line (ICPA 2043) with pedigree reading as (ICPA 2039 × ICPL 20176) × ICPL 20176 × ICPL 20176 × ICPL 20176 × ICPL 20176 × ICPL 20176 × ICPL 20176 with a restorer line (ICPR 2671) with pedigree of ICPX 78143 (C 11 × ICP 1‐6)‐WB‐WB‐WB‐WB‐W27–B. The plants of ICPH 2671 are semi‐spreading and non‐determinate in growth habit with profuse secondary and tertiary branches achieving a height of 210–226 cm at Patancheru (17°N). Inherently, the canopy of ICPH 2671 is sensitive to photoperiod and plastic in nature and responds to both spacing and planting time. The sowings around the longest day produce large canopy, and it reduces gradually as the sowings approach shorter days. Similarly, the size of canopy is big at wide spacing and small at close spacing. The deep roots of ICPH 2671 impart ability to tolerate drought and produce reasonably good yields under stress conditions (Saxena 2008). On average, ICPH 2671 flowers in 114–120 days and its 75% pod maturity is achieved in 164–184 days at Patancheru, India. The flowers of ICPH 2671 are yellow with dense red streaks on their petals. The pods of this hybrid are dark purple in colour and on average contain 3.7–4.0 seeds. The genetics of seed colour in this hybrid is interesting. The seed colour of both the parents and the F 1 hybrid (A × R) is brown, but the commercial seed produced on the F 1 plants are purple (colour code 183C of the Standard Identification Numbers of Royal Horticulture Society). However, the colour of cotyledon is yellow. Saxena et al. (2012a) reported that the seed colour in this hybrid is controlled by three dominant genes; the female parent carries two such genes while the third gene is present in the male parent. The purple colour in the seed is produced when one or both the genes present in the female parent interact with the gene present in the male parent. The 100 seeds of ICPH 2671 weigh between 10.5 and 11.2 g. The fertility restoration in this hybrid is high (95–100% pollen fertility), stable across environments and controlled by two dominant genes (Dalvi et al. 2008, Sawargaonkar et al. 2012). Figure 4 Open in figure viewer PowerPoint The world's first commercial pigeonpea hybrid ICPH 2671 released in India has shown in the picture at pod maturity stage The plants of hybrid ICPH 2671 are more vigorous than pure line varieties, and it helps in quick establishment and competitiveness (Saxena et al. 1992). They also reported that 1‐month‐old seedlings of the hybrids produced 43.9% higher shoot and 42.8% higher root mass than that of traditional cultivars. Higher crop growth rate of the hybrid results in more biomass production, which helps in significant (50%) reduction in the seeding rate of the hybrid crop. Resistance of ICPH 2671 to biotic stresses Fusarium wilt and sterility mosaic are major pigeonpea diseases, and together, they cause significant yield losses every year (Reddy et al. 1990). ICPH 2671 has demonstrated high levels of resistance to both the diseases over years in farmers' fields as well as at research stations. In general, the hybrids are known to express better environmental buffering compared with pure line cultivars (Saxena 2009). Therefore, the yield fluctuations brought about by various stresses could be reduced by cultivating pigeonpea hybrids based on genetically diverse parentage. Resistance to abiotic stresses As pigeonpea is grown as a rainfed rainy season crop, it is subjected to both drought (intermittent and terminal) and temporary waterlogging. It has been observed that in comparison with pure line cultivars, the hybrid ICPH 2671, by virtue of its greater root mass and depth, possesses greater ability to draw water from deep soil profiles (Sultana et al., 2012). Its fast root growth also helps plants to tide over early season drought conditions. Lopez et al. (1996) demonstrated that early maturing hybrids maintained relatively high water content under adverse conditions, which contributed to its capacity to enhanced drought tolerance. Evaluation of pigeonpea hybrids and pure line varieties under 8 days of continuous waterlogging revealed that hybrid ICPH 2671 had survival rate (88%) as compared to a pure line variety (58%), irrespective of their stage of testing (seed, early seedling and late seedling stages). The high survival rate in the hybrid was attributed to its ability to utilize the stored assimilates through anaerobic metabolism during germination and early seedling growth (Choudhary et al. 2011). In another set of experiment, it was also observed that the genotypes with dark seed coat exhibited greater (64.5%) survival in comparison with the light‐coloured (54.4%) genotypes. As seed coat colour of ICPH 2671 is dark, the presence of various phenolic and tannins reduced the rate of water uptake in the seeds. Khare et al. (2002) reported that the dark‐seeded pigeonpea genotypes encountered waterlogged situations much better than those with light‐coloured seeds. The greater waterlogging tolerance in the hybrid may also be related to relatively high initial vigour of the hybrid plants, which experienced less oxygen deprivation during submergence as compared to pure line cultivars. Quality parameters and consumer preference It is essential that any new food product matches well with those in common use with respect to various quality, organoleptic and market preferred traits. It is more important in the present case because one of the parents of the hybrid is derived from a wild species. Hence, the hybrid was compared to the local cultivar ‘BSMR 736’ for important food quality parameters (Table 2). The data showed that the hybrid ICPH 2671 compared well with respect to milling recovery, an important trait for traders and for dal mill industry. The protein content of hybrid (20.73%) was more or less similar to that of local cultivar (19.86%). The hybrid ICPH 2671 took about 5 min less to cook, a trait that is preferred by most consumers (Sawargaonkar 2011). In addition, we also conducted 357 organoleptic tests of dal (decorticated split peas) in Maharashtra, Andhra Pradesh and New Delhi. The survey reported that 79.2% consumers preferred hybrid dal over the market samples for its taste and flavour; 18.6% found it as good as the market sample, and 2.2% rated the hybrid dal inferior to market sample (unpublished data). Table 2. Important quality parameters of hybrid ICPH 2671 and control cultivar ‘BSMR 736’ Quality parameters ICPH 2671 ‘BSMR 736’ Dal recovery (%) 77.42 76.49 Processing losses (%) 6.83 5.96 Protein (%) 20.73 19.86 Cooking time (min) 32.44 38.25 Water absorption (g/g) 1.74 2.14 Taste Excellent Excellent Flavour Very good Good General acceptability Excellent Very good As the seed colour of commercial grains of hybrid ICPH 2671 is dark due to specific complementary gene action (Saxena et al. 2012a), its marketing posed some problems in the states of Karnataka, Andhra Pradesh and Maharashtra where brown seeded pigeonpea is preferred. However, in the states of Madhya Pradesh and Jharkhand, the seed colour was not an issue, and hence, this hybrid was released in Madhya Pradesh.

Productivity of ICPH 2671 Performance in on‐station multilocation trials During 2005–2008, the hybrid ICPH 2671 was tested in 21 multilocation trials (Table 3) and its mean performance in different years ranged from 2117 to 3183 kg/ha. On average, the hybrid produced 2736 kg/ha yield, demonstrating 47% superiority over the control ‘Maruti’ (1862 kg/ha). The highest yield of 5375 kg/ha was recorded at Aurangabad. Further, to generate the performance data of the hybrid in central and south zone, it was tested in the All India Co‐ordinated Research Project (AICRP) on pigeonpea under the aegis of Indian Council of Agricultural Research (ICAR) at six locations in 2007. In Warangal, it recorded the highest yield of 3583 kg/ha as against 2134 kg/ha for control ‘Asha’ and 1549 kg/ha for control ‘Maruti’. Over all the six locations, the hybrid ICPH 2671 produced 2490 kg/ha yield, and it was, respectively, 35% and 29% superior to control cultivar ‘Maruti’ and ‘Asha’. Table 3. Yield of hybrid ICPH 2671 and control cultivar ‘Maruti’ in multilocation trials conducted in India Year Location Hybrid yield (kg/ha) Control yield (kg/ha) Standard heterosis (%) SEM± CV (%) 2005 Patancheru 2671 1677 59 207.7 13.7 Medchal 2996 1041 188 331.1 21.1 Bangalore 2571 1476 74 540.7 32.2 Jalna 3416 2541 34 152.1 7.3 Coimbatore 4262 2538 68 252.7 17.3 Mean 3183 1855 72 – – 2006 Patancheru 2660 1919 39 140.7 7.8 Coimbatore 1823 1100 66 324.7 28 Jalna 1948 1092 78 91.8 10.2 Phaltan 3208 2243 43 270.1 19.1 Mean 2410 1589 52 – – 2007 Patancheru 2373 1931 23 191.8 12.1 Aurangabad 5375 3893 38 267.8 7.6 Jalna 2038 1713 19 206.8 17.8 Medchal 2936 2350 25 604.0 26.4 Pargi 2253 1328 70 493.5 28.2 Akola 2489 1557 60 288.8 21.1 Phaltan 3439 2694 28 281.1 12.1 Mean 2986 2209 35 – – 2008 Patancheru 2534 1790 42 194.8 15.4 Jalna 2670 2083 28 43.7 3.1 Parbhani 2006 1863 8 334.8 23.3 Medchal 707 391 81 58.9 14.0 Aurangabad 3085 1889 63 145.0 9.0 Mean 2117 1603 45 – – Grand mean 2736 1862 47.0 – – Performance in farmers' fields During 2009 and 2010, ICPH 2671 was evaluated in 2013 on‐farm locations of five Indian states (Table 4). Each trial involving hybrid and local check was grown on one‐acre land, and the farmers were allowed to use their own package of practices. A total of 782 trials were conducted in seven districts of Maharashtra, and on average, ICPH 2671 (969 kg/ha) produced 35% more yield over the control variety ‘Maruti’ (717 kg/ha). In Andhra Pradesh (399 trials), the hybrid exhibited 56% superiority over the control. Similarly in Karnataka (184 trials) and Madhya Pradesh (360 trials), the hybrid outyielded the control cultivar by the margin of 26% and 56%, respectively. In Jharkhand, ICPH 2671 was evaluated in 288 on‐farm trials, and the hybrid ICPH 2671 demonstrated 69% superiority over the control cultivar ‘Bahar’. Considering the overall performance in the five states, the hybrid ICPH 2671 produced 1396 kg/ha yield, and it was 46.5% more than the local check (953 kg/ha). The yield advantages recorded by ICPH 2671 are very encouraging, and it is expected that a large‐scale adoption of the hybrid could enhance productivity of pigeonpea in India. In 2009, the hybrid ICPH 2671 was evaluated in 36 on‐farm trials conducted in six provinces of Myanmar (Table 5), and, on average, the hybrid (1057 kg/ha) was 20% superior (Kyu et al. 2011) to local control (881 kg/ha). Table 4. Mean yield of hybrid ICPH 2671 and control ‘Maruti’ in on‐farm trials conducted in five states of India during 2009 and 2010 State Districts Number of farmers Hybrid yield (kg/ha) Control yield (kg/ha) Standard heterosis (%) Maharashtra 7 782 969 717 35 Jharkhand 9 288 1460 864 69 Andhra Pradesh 8 399 1411 907 55 Karnataka 4 184 1201 951 26 Madhya Pradesh 10 360 1940 1326 46 Mean/total 38 2013 1396.2 953.0 46.5 Table 5. Performance of pigeonpea hybrid ICPH 2671 in farmers' fields in Myanmar, 2009 Division Township Number of trials Yield (kg/ha) Standard heterosis (%) Hybrid Local check Sagaing Monywa 6 1830 1414 29.4 Sagaing Depeyin 6 1051 1051 0.0 Sagaing Myinmu 6 619 542 14.2 Mandalay Myingyan 6 1300 1162 11.9 Mandalay Nhahtoegyi 6 842 550 53.1 Mandalay Taungtha 6 700 567 23.5 Mean 36 1057 881 20.0 Hybrid to resolve the pigeonpea yield plateau: general view Even after centuries of cultivation and natural selection, pigeonpea still retains unique characteristics such as perennial and indeterminate growth habit, low harvest index, and photo – and thermosensitivity. Its ability to survive and produce high protein food even under stress conditions helps in providing food and nutrition security to subsistence farmers, and therefore, it may be considered as the ideal rainfed legume crop of small‐holder farmers. As the demand for food legumes like pigeonpea is ever increasing and the scope for area expansion is limited, the attention is now focusing on increasing and stabilizing its economic yield. In order to enhance the productivity, more than 100 pure line varieties were released in India, but these could not bring any significant improvement in the crop productivity, and the yields have remained consistently low for the past six decades. In this context, ICRISAT and partners took an initiative to explore the possibility of enhancing yield by breeding high‐yielding hybrids. The successful developments of a stable CMS system and the existing natural cross‐pollination have opened up an avenue for enhancing the yield potential of pigeonpea through hybrids. The yield superiority recorded in pigeonpea hybrids in different years and different locations has conclusively established the high yield potential of hybrids. The magnitude of realized standard heterosis for yield over check varieties in pigeonpea is high, and under well‐managed and high‐input conditions, the productivity of the crop can approach about 4000 kg/ha or more (Table 6). We believe that the CMS‐based hybrid pigeonpea technology is now ready for take‐off with all its major components in place, and our major responsibility is to take this new product to both small‐ as well as large‐scale farmers. To achieve this, it will be necessary to keep the hybrid seed costs within the reach of resource‐poor farmers. In India, both public and private seed sectors are strong, and these are being harnessed to improve the accessibility of hybrid seed to farmers. As a grower‐friendly hybrid seed production technology is now available, it can be concluded that hybrid vigour can be exploited commercially to increase the pigeonpea production and productivity. The scientific community firmly believes that in pigeonpea, the breakthrough in yield will come through the hybrids. In this endeavour, an excellent beginning has been made, and it is expected that the farmers of the tropics and subtropics will benefit from this technological breakthrough. Table 6. High yields from pigeonpea hybrids recorded under irrigated conditions as a sole crop, in 2009 in Maharashtra (India) Locations Area (m2) Hybrid yield (kg/ha) Control yield (kg/ha) Standard heterosis (%) Salod 450 3956 2044 94 Nimgaon 1012 3951 2469 60 Kothoda 450 4667 3556 31 Tamoli 450 3889 2278 71 Mean 4115.8 2586.8 59.1

Acknowledgements The authors express their sincere thanks to various research partners of Marathwada Krishi Vidhyapeeth, Parbhani; Panjabrao Deshmukh Krishi Vidhyapeeth, Akola; Agricultural Research Station, Gulbarga; and various seed companies that collaborated with us in evolving and testing the hybrid pigeonpea technology. The financial support received from Bill and Melinda Gates Foundation (TL II project), Hybrid Pigeonpea Parents Research Consortium, ICRISAT, Patancheru, India, and National Food Security Mission, Department of Agriculture and Cooperation, Government of India, New Delhi, India, is acknowledged.