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Sterility mosaic disease (SMD) caused by Pigeonpea sterility mosaic virus and vectored by the eriophyid mite is a serious disease of pigeonpea in almost all pigeonpea-growing areas. Managing the disease with chemicals such as acaricides is very difficult, non-eco-friendly and costly; hence, host plant resistance is the best strategy implemented to manage this disease. In this context, 28 pigeonpea genotypes identified as resistant from preliminary screening of 976 pigeonpea accessions were evaluated in field at eight different agro-ecological locations in India for the stability of their resistance against SMD during 2007/2008 and 2008/2009. Genotype plus genotype × environment (GGE) analysis partitioned main effects into genotype, environments and G × E interactions and showed significant effects (P < 0.001) for SMD percentage incidence. Environment variance had the greatest effect (76.68 %), indicating the maximum variation in the disease due to the environment. At Bangalore, Dholi and Rahuri locations, all genotypes were susceptible to SMD with mean disease incidence of 71.1, 50.4 and 32.6 % respectively. However, most of the genotypes were resistant at four locations, Akola, Badnapur, Patancheru, and Vamban, and moderately resistant at Coimbatore. The GGE biplot analysis explained about 67.26 % of total variation and identified four genotypes (ICPLs 20094, 20106, 20098, 20115) as the most stable and resistant to SMD. Three genotypes (ICPLs 20096, 20107, 20110) showed moderately stable performance against SMD. These genotypes should be included in pigeonpea breeding programs as additional sources of resistance to SMD.

Botrytis grey mould (BGM), caused by Botrytis cinerea Pers. Ex. Fr., is a destructive foliar disease of chickpea (Cicer arietinum L.) worldwide. Disease management through host-plant resistance is the most effective and economic option to manage this disease. The objective of this study was to identify new sources of resistance to BGM, validate their stability across environments and determine the magnitude of G × E interaction. One hundred and nine chickpea genotypes with moderate levels of resistance (BGM severity ≤5.0 on a 1–9 scale) were selected from the preliminary evaluation of 412 genotypes including germplasm and breeding lines under controlled environmental conditions in 2004–2005 at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, India. In order to validate resistance stability, an ‘International Botrytis Grey Mould Nursery’ (IBGMN) was constituted with 25 genotypes and tested in multi-environments for BGM resistance at two locations (Gurdaspur and Pantnagar) in India for 4 years and two locations (Tarahara and Rampur) in Nepal for 3 years. Additive main effects and multiplicative interaction (AMMI) analysis showed significant genotype (G), environment (E) and G × E interaction (p < 0.0001) with largest contribution by environment (47.36%). The first two principal component axes were significant, and contributed 48.21% to the total G × E interaction. The AMMI biplot analysis allowed the selection of five genotypes ICCV 96859, ICCV 96853, ICCV 05604, ICCV 96852 and ICCV 05605 with low BGM severity (between 3.7 and 4.7 on 1–9 scale) and moderate stability. Genotype ICCV 96859 having least disease severity and moderate stability could be highlighted and exploited in chickpea resistance breeding programmes

A survey was conducted in 2010-2011 rabi cropping season to obtain information on the distribution and incidence of chickpea diseases in respect to soil type, cultivar used, seed treatment in central and southern parts of India. Local cultivars predominated in most farmers’ fields (25% - 48%). 63% of the farmers were practices seed treatment with fungicide. Dry root rot and collar rot diseases were found at all of the sites and incidence ranged from 8.9% - 10.3% and 7.1% - 10.5% respectively irrespective of cultivar type and locations. Incidence of wilt and black root rot disease ranged from 9.7% - 13.8% and 6.6% - 7.4% respectively. Black root rot disease was found in Andhra Pradesh and Karnataka states only. The result indicated that dry root rot and collar rot is currently highly distributed in all surveyed chickpea growing areas of central and southern parts of India. Therefore, possible management options are vital to alleviate the problem.

Fusarium wilt (Fusarium udum Butler) is an important biotic constraint to pigeonpea (Cajanus cajan L.) production worldwide. Breeding for fusarium wilt resistance continues to be an integral part of genetic improvement of pigeonpea. Therefore, the study was aimed at identifying and validating resistant genotypes to fusarium wilt and determining the magnitude of genotype × environment (G × E) interactions through multi-environment and multi-year screening. A total of 976 genotypes including germplasm and breeding lines were screened against wilt using wilt sick plot at Patancheru, India. Ninety two genotypes resistant to wilt were tested for a further two years using wilt sick plot at Patancheru. A Pigeonpea Wilt Nursery (PWN) comprising of 29 genotypes was then established. PWN was evaluated at nine locations representing different agro-climatic zones of India for wilt resistance during two crop seasons 2007/08 and 2008/09. Genotypes (G), environment (E), and G × E interactions were examined by biplot which partitioned the main effect into G, E, and G × E interactions with significant levels (p ≤ 0.001) being obtained for wilt incidence. The genotype contributed 36.51% of resistance variation followed by the environment (29.32%). A GGE biplot integrated with a boxplot and multiple comparison tests enabled us to identify seven stable genotypes (ICPL 20109, ICPL 20096, ICPL 20115, ICPL 20116, ICPL 20102, ICPL 20106, and ICPL 20094) based on their performance across diverse environments. These genotypes have broad based resistance and can be exploited in pigeonpea breeding programs.

Background Phytophthora blight caused by Phytophthora cajani is an emerging disease of pigeonpea (Cajanus cajan L.) affecting the crop irrespective of cropping system, cultivar grown and soil types. Current detection and identification methods for Phytophthora species rely primarily on cultural and morphological characteristics, the assessment of which is time-consuming and not always suitable. Sensitive and reliable methods for isolation, identification, zoospore production and estimating infection severity are therefore desirable in case of Phytophthora blight of pigeonpea. Results In this study, protocols for isolation and identification of Phytophthora blight of pigeonpea were standardized. Also the method for zoospore production and in planta infection of P. cajani was developed. Quantification of fungal colonization by P. cajani using real-time PCR was further standardized. Phytophthora species infecting pigeonpea was identified based on mycological characters such as growth pattern, mycelium structure and sporangial morphology of the isolates and confirmed through molecular characterization (sequence deposited in GenBank). For Phytophthora disease development, zoospore suspension of 1 × 105 zoospores per ml was found optimum. Phytophthora specific real-time PCR assay was developed using specific primers based on internal transcribed spacer (ITS) 1 and 2. Use of real-time PCR allowed the quantitative estimation of fungal biomass in plant tissues. Detection sensitivities were within the range of 0.001 pg fungal DNA. A study to see the effect of elevated CO2 on Phytophthora blight incidence was also conducted which indicated no significant difference in disease incidence, but incubation period delayed under elevated CO2 as compared to ambient level. Conclusion The zoospore infection method for Phytophthora blight of pigeonpea will facilitate the small and large scale inoculation experiments and thus devise a platform for rapid and reliable screening against Phytophthora blight disease of pigeonpea. qPCR allowed a reliable detection and quantification of P. cajani in samples with low pathogen densities. This can be useful in early warning systems prior to potential devastating outbreak of the disease.