Pigeonpea Improvement at ICRISAT______________________________

Evolution and origin
As an orphan crop, the evolution of pigeonpea had received only limited study until the 1970s (van der Maesen 1990). Even the origin of the crop was in question – did it evolve in Asia, or Africa? In 1977, ICRISAT staff found Atylosia cajanifolia, a wild relative, in the jungles of the Bailadilla Hills in India. By studying the species closely, including its crossability with cultivated species, it became clear that it was very closely related to cultivated pigeonpea, being mainly separated by a single visible trait: a prominent strophiole, or raised ridge on the "eye" of the seed. This evidence, combined with available floristic, linguistic, and cytological data, argued strongly for an Asian origin for the cultivated species (van der Maesen 1980).

Another important germplasm achievement was an in-depth morphological, cytological, and chemo-taxonomical characterization which resulted in the revision the subtribe Cajaninae. Cajanus now includes 32 species, and detailed botanical descriptions of each were jointly published by ICRISAT and the Agricultural University of Wageningen (van der Maesen 1985). These studies demonstrated close affinity between the genera Atylosia and Cajanus, and the former was consequently merged into the latter.

Collect, conserve, characterize
Strengthening this fundamental asset, ICRISAT has expanded initial holdings of about 4,000 lines to a current total of 13,015. These include accessions from 72 countries and 47 species belonging

to 6 genera of Cajaninae. These collection and and conservation activities could not have been as extensive without the steadfast support of the Asian Development Bank.

The collection has been exhaustively characterized for agronomic, morphological, and disease/pest resistance traits. A number of important traits have been found, and many of them have been utilized in the breeding program. These include resistances to the diseases fusarium wilt, alternaria leaf spot, cercospora leaf spot, phytophthora stem blight, sterility mosaic, and powdery mildew; and to the podfly insect, Helicoverpa and Maruca pod borers, and the Clavigralla pod-sucking bug.

To access traits residing in wild species, ICRISAT has developed procedures for rescuing embryos in wide crosses (Mallikarjuna et al. 1995). Wide crosses are also being successfully applied in the search for cytoplasmic male sterility for hybrid seed production (see page 15). Resistances to such important abiotic stresses as salinity, water-logging, and drought have also been identified.

In a pioneering study supported by the Government of Japan and with direct involvement of seconded scientists from the Japan International Research Center for Agricultural Sciences (JIRCAS), it was found that pigeonpea could extract 2–7 times more iron-bound phosphorous (P) from typical Alfisol soils than could maize, millet, sorghum, or groundnut   (Ae et al. 1990).