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Pigeonpea—Phytophthora cajani isolates characterization and assessment of resistance in elite pigeonpea germplasm and breeding lines
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DOI：10.3389/fmicb.2026.1910854.png)
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Abstract
En 中文
Phytophthora blight (PB); caused by Phytophthora cajani; is a key constraint limiting pigeonpea productivity across the tropics and subtropics. Frequent PB outbreaks under erratic rainfall and warm temperatures intensifies the need for a holistic understanding of pathogen variability and stable host resistance. This study evaluated the morpho-cultural; physiological; and molecular diversity of P. cajani and investigated pigeonpea genotypes for resistance against representative isolates. Twenty-two isolates collected from diverse agro-ecological zones of India were purified; and six representative isolates (Pc-04; Pc-06; Pc-07; Pc-08; Pc-16 and Pc-20) were selected for detailed characterization. Significant morpho-cultural variability was observed across nine solid media; with TEA; V8J and OMA supporting maximum mycelial growth. Colony morphology; sporangial papillation; size and abundance varied among isolates. Physiologically; isolates differed markedly in pH and temperature responses; with optimum growth recorded between pH 5.5–8.0 and at 25–30 °C. Growth declined sharply below pH 4.5 and above pH 9.0; and no growth occurred at extreme temperatures (5–10 °C and 40 °C); although viability was retained upon shifting from cooler to permissive conditions. ITS-based phylogenetic analysis confirmed all isolates as P. cajani with high sequence similarity and discernible phylogenetic clustering with other Phytophthora spp. were also established. Fourteen pigeonpea genotypes found promising in previous studies; were screened against the six isolates under greenhouse conditions. Distinct differential reactions were recorded; with ICPL 99008 and ICPL 99009 showing consistent broad-spectrum resistance to all the isolates of P. cajani. Isolates Pc-04 and Pc-07 exhibited high aggressiveness; whereas Pc-16 and Pc-20 were comparatively less aggressive. This integrated analysis elucidates substantial diversity within P. cajani populations and identifies promising pigeonpea genotypes with stable resistance.
Keywords:
variability
pigeonpea
oomycetes
Phytophthora blight
stable resistance
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