Pigeonpea Variants: The Ultimate Source for Pigeonpea Improvement
Authors: D.R. Sapkal, V.R. Sapkal and M.Y. Ladole
Many crop improvement programmes have been initiated to enhance yield potential of pigeonpea including hybridization and selection of superior genotypes. Improving crop yield is now based on developing better variety and hybrid of plants.
The use of molecular markers in crop cultivars gives an additional advantage in characterizing, selection and maintaining the genetic purity. The hybrid seeds are beneficial to farmers only if their genetic purity is maintained and sufficient quantity and quality seeds are available for cultivation. For this purpose morphological markers (mainly leaf traits) are available to ensure the genetic purity of hybrids and their parents.
The best way to ensure the genetic purity of seed ( to really classify it as a "Hybrid seed") is to conduct the "Grow Out Test" (GOT) or field test. GOT results are based on the stable morphological characters. Several morphological markers for shape, colour, size and pigmentation are used in different crops. Among them, leaf shape is useful morphological markers in pigeonpea because it shows polymorphism on seedling which is one month in age, even with a naked eye. The genetics involved in the shape of a leaf and many other traits are not well understood as the information available so far is very limited.
The development of fertilizer for short statured plants like wheat and rice revolutionized the production of these crops and received international acclaim in 1960s. From 1960s, until now dwarfism has been emphasized in most crops even though the purpose for shortening the plant height varies from crop to crop. Management practices play a vital role too. In wheat and rice the dwarfism is used to prevent lodging under high input conditions while in sorghum dwarfism is necessary for convenience in mechanical harvesting. In plantation crops such as citrus and coffee, dwarfism facilitates spraying and harvesting (Githirs Mwangi, 1988)
Traditional pigeon pea cultivars grow two to three meter in height and are susceptible to insect damage. Due to the lacking genetic resistance to insects, the use of chemicals to control insect for achieving high yields is necessary. The height of pigeon pea plants is a major problem in achieving effective spraying.
Agronomic dwarfing, which can be induced by sowing pigeon pea under reducing day-lengths (Spence and Williams, 1972) is one way to restrict plant height, but such plantings fail to produce the biomass that is essential for realizing high yields. In addition, pigeonpea is cultivated as rain-fed crop. Sowing it in the shorter photo-periods of the post-rainy season invariably result in poor root and canopy establishment. Such crops suffer from both intermittent and terminal droughts. Under the circumstances of not having insect resistance, the introduction of dwarfing genes into productive genetic backgrounds is the best approach to enable control of insect damage through spraying (Saxena and Sharma 1995).
Pigeonpea has the genetic potential for very high seed yields under favorable management, but lower yields of pigeonpea relative to wheat are obtained because of their poor harvest index. Except for a few improved types, pigeonpea cultivars are very tall (over two meters) and utilize a lot of photosynthates in the development of large woody stems at an expense of grain production. Now a days, mechanical harvesting is necessary in India where farmers are facing labour problems. Mechanization and effective spraying become easy when dwarf cultivars are developed.
1.Githris Mwangi 1988. Inheritance of dwarfism in pigeon pea (Cajanas cajan L. Millsp), Thesis (Unpub.) University of Nairobi.
2. Saxena, K. B., D. Sharma.1995. Sources of dwarfism in pigeonpea. Ind J Pulse Res. 8:1-6.
3. Spence J.A. and S.J.A. Williams, 1972. Use of photo-period response to change plant design. Crop Sci. 12:121-122.
About Author / Additional Info:
Dr. Deepak R Sapkal, Assistant Professor (Genetics and Plant Breeding), Lovely Professional University, Jalandhar, State : Punjab (INDIA)