Tolerance to reniform nematode (Rotylenchulus reniformis) race A in pigeonpea (Cajanus cajan) genotypes

The reniform nematode (Rotylenchulus reniformis) is an important pathogen o f pigeonpea (Cajanus cajan). Forty-six medium maturity (mature in 151-200 d ays at Patancheru, India) pigeonpea genotypes were evaluated for resistance and tolerance to the reniform nematode in greenhouse and field tests, over the period 1990-97. Each genotype was screened for number of nematode egg masses on a 1 (no egg mass = highly resistant) to 9 (> 50 egg masses = high ly susceptible) scale. Plant biomass production in carbofuran-treated plots was compared with that in non-treated plots in a field naturally infested with R. reniformis. Pigeonpea genotypes C 11, ICPL 87119 and ICPL 270 were used as nematode susceptible checks. Genotypes with good plant growth, both in nematode-free and nematode-infested plots, were identified as tolerant and evaluated for plant growth and yield for at least three years. All the tested genotypes were susceptible (7 and 9 egg mass score). Single-plant-se lections, based on plant vigour and yield, were made from genotypes showing tolerance to nematode infection. The level of tolerance was enhanced by pl ant-to-progeny row selection for plant vigour and seed yield in a nematode- sick field for at least three years. The most promising nematode tolerant g enotypes produced significantly greater yield and biomass than the locally grown pigeonpea cultivars in fields naturally infested with R. reniformis a t two locations. Pigeonpea landraces are considered to be the most likely s ources of tolerance to the nematode. These reniform nematode tolerant lines represent new germplasm and they are available in the genebank of pigeonpe a at ICRISAT bearing accession numbers ICP 16329, ICP 16330, ICP 16331, ICP 16332, and ICP 16333.