Author: Dr Madhu Patial
Pulses are an integral part of Indian agriculture, being a rich source of protein. Red gram or Pigeonpea [Cajanus cajan (L.) Millsp] occupies an important place in this group and among resource poor farmers because of its multifarious uses as it provides quality food, fuel and fodder besides rejuvenating soil through the release of soil-bound phosphorous, fixation of atmospheric nitrogen, recycling of soil nutrients, addition of organic matter and other nutrients. It is a crop known as poor's man meat and being a hardy crop forms an important ingredient in the food security of the farmers.
Although pigeonpea is globally grown on 5.2 m ha land in about 50 countries, its 77% area is in India (FAO, 2008). To meet the protein needs of the ever growing population it is essential to increase the production substantially. The production could be alleviated either by increasing the area or increasing the productivity of the crop. The opportunity of increase in area is limited, therefore, pigeonpea productivity has to be increased significantly. Among different factor contributing for low productivity (climate, edaphic and crop management), lack of high-yielding cultivars is the most important. So, breeding approaches have to be evolved and implemented for the development of high yielding varieties. Hybrid breeding technology can break the yield plateau of the crop and offers a hope of pulse revolution in India and other developing countries.
Hybrid cultivar development for higher yield:
Pigeonpea is an often cross-pollinated crop and substantial degree of heterosis for grain yield is present which can be exploited for increasing production. Earlier, GMS system was developed in pigeonpea and the first hybrid ICPH8 was developed and released in 1991, which gave 25-30% higher yield than the best check. Latter five more GMS hybrids were developed but they never became popular due to limitation in the seed production. Subsequently, a few more GMS based hybrids were released by national program of ICAR. In 1993, PAU, Ludhiana released a short duration hybrid PPH4. A year later, in 1994 Tamil Naidu Agricultural University, Coimbatore, released another short duration hybrid CoH 2. Subsequently, two more pigeonpea hybrid AKPH 4101 and AKPH 2022 were released by PDKV, Akola in 1997 and 1998, respectively. However, the GMS based hybrids, though high yielding, could not reach farmers' field due to the inherent constraints associated with the maintenance of the male sterile line and hybrid seed production. Every generation about 50% of the plants had to be rouged out, thereby significantly inflating the cost of hybrid seed. So, the constant search for an efficient system led to development of CMS system which offers ample opportunities to bread commercial hybrids in pigeonpea, besides solving the issue of large-scale hybrid seed production.
ICAR has allocated considerable resources to achieve a breakthrough in hybrid breeding technology in pigeonpea which led to the release of ICPH 8 in 1991, in India and became a milestone in the history of legume breeding.
Advantages of pigeonpea hybrids:
• Hybrids in any crop have revolutionized the productivity of crops worldwide. So, to increase pigeonpea productivity, development of hybrids is one of the important steps.
• Hybrid pigeonpea produces greater biomass than the varieties of same duration by efficiently utilizing inputs like sunlight, water and nutrients more efficiently and partitioning of photosynthates leading o the higher grain yield.
• The hybrids have greater plant vigour and produce more number of primary and secondary branches thereby reducing the seed rate and saving the seed cost.
• By virtue of greater root biomass and depth, hybrid pigeonpea have greater ability to draw water from soil from deeper soil depth and so these hybrids have more drought tolerance.
Limitations of exploitation of heterosis:
• Unstable performance of hybrids over the locations and years.
• Low level of heterosis in hybrids.
• Breakdown of sterility in male-sterile lines.
• Fertility restoration is not complete and uniform over the plants of the hybrids.
• Heterogeneity among the F1 plants.
Future strategies for research and development of hybrid pigeonpea:
• Development of region specific hybrids by testing superior cross combinations over location.
• Parents should be diversified to suit target environments.
• Resistance to biotic/abiotic stresses should be incorporated.
• Efficiency of hybrid seed production should be increased.
• Heterotic groups should be identified/developed.
• Parental lines should be pure and tested for gca and sca.
• Molecular characterization of hybrids and their parents should be undertaken.
• Prospects of exploiting heterosis commercially in pigeonpea are bright due to following reasons:
• Substantial standard heterosis have been realized.
• CMS system has been developed.
• Honey bees carry out the pollination process.
• Using A, B and R lines production of hybrid seed is practically feasible.
The hybrid ICPH 8 gave a yield advantage of 41-52%over other varieties. But much remains to be done even after selecting a good heterotic combination. The factor such as stable performance, environment factors, improved seed and pollen parents, resistance to prevalent diseases and pests, seed production research and on farm research have to be given due emphasis in future research.
About Author / Additional Info:
Scientist ICAR-IARI, RS, Shimla (H.P)