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Yadav, P.

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Yadav
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Yadav, P.

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    Genetic analysis of water-logging tolerance in tropical maize (Zea Mays L.)
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2010) Zaidi, P.; Maniselvan, P.; Srivastava, Ashish; Yadav, P.; Singh, R.P.
    Approximately 80% of maize (Zea mays L.) in South and Southeast Asia is grown as a rain-fed crop, where temporary excessive soil moisture or water-logging during the summer-rainy season is one of the major production constraints in large areas of this region. The present genetic study analyzed the tolerance of tropical maize to water-logging stress. Elite maize inbred lines with known stable performance in terms of improved grain yield under water-logging stress were crossed using half-diallel (7 x 7) and line × tester (8 × 3) mating designs, in which four lines were common in both the mating designs. F1 progenies (excluding reciprocals) and their parents were evaluated under managed water-logging stress at knee high stage (V7-8 growth stage) at the maize research farm, Indian Agricultural Research Institute, New Delhi, India (28.4°N, 77.1°E, 228.1 masl). In addition, the same set of entries was simultaneously evaluated under a normal moisture regime. Analysis showed that both general combining ability (GCA) and specific combining ability (SCA) effects were statistically significant. However, the GCA effect was comparatively higher (P<0.01) than the SCA effect (P<0.05). This result suggests that both additive and non-additive factors affect the expression of tolerance to water-logging stress in tropical maize. Analysis of the diallel and L × T dataset showed that water-logging tolerance in maize followed an additive-dominance genetic model, with additive gene effects dominating. Our findings suggest that reciprocal recurrent selection would be an effective approach for improving water-logging tolerance in tropical maize. Evaluating S1 progeny per se and their test-crosses under managed water-logging stress, discarding susceptible fraction and combining the selected best lines in terms of per se and test-cross performance could result in improved water-logging tolerant population. The new lines derived from the improved population could be used in developing water-logging tolerant synthetic varieties to exploit the additive gene effects and hybrids to exploit the non-additive gene action.
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    Stress-adaptive changes in tropical maize (Zea mays L.) under excessive soil moisture stress
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2007) Zaidi, P.; Maniselvan, P.; Yadav, P.; Singh, A.K.; Sultana, R.; Dureja, P.; R.P. Singh; Srinivasan, G.
    Response of maize plants to excessive soil moisture (EM) has been studied extensively. However, systematic information on the stress-adaptive changes and cascade of events conferring the EM-tolerance is yet to be established. We attempted to assess the stress-adaptive physiological changes associated with EM-induced anoxia stress, and to establish mechanism of EM-tolerance in tropical maize. Tropical/sub-tropical elite maize inbred lines with known reaction to EM-stress were used in this study. Germplasm were exposed to EM-stress at knee-high stage (V7-8 growth stage) by flooding the plots continuously for seven days. EM-induced changes in root geotropism (surface rooting) and increased brace roots development were identified as stress-responsive traits; however, the later one was found to be a stress-adaptive trait resulting in improved stress tolerance. Anatomical studies showed drastic changes in cortical region of root tissues in tolerant genotypes in terms of development of large aerenchymatous spaces. In terms of stress-induced metabolic adjustments, increased NAD+-alcohol dehydrogenase (ADH) activity was prevalent in all the genotypes under EM-conditions.Though, the enzyme activity was slightly higher in tolerant entries but not high enough to justify the significant genotypic variability. However, the product of ADH-activity (ethanol) was relatively much higher in root and leaf tissues of susceptible genotypes. Analysis of ethanol concentration in shoot, root and inundated water showed that the level of ethanol was relatively much higher in the water present in rhizosphere of relatively tolerant genotypes. The finding suggested that EM-tolerant maize genotypes were able to extrude out the toxic level of ethanol from root tissues to rhizosphere. Our results suggest that mechanism of EM-tolerance in maize germplasm involves morphological and anatomical adaptation through development of brace roots and aerenchyma formation, and metabolic adjustment through regulatory induction of alcohol dehydrogenase (ADH) and extrusion of ethanol out of root tissues.
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