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Zaidi, P.

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Zaidi
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Zaidi, P.

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Now showing 1 - 8 of 8
  • Morpho-physiological traits associated with cold stress 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.; Yadav, M.; Maniselvan, P.; Khan, R.; Shadakshari, T.V.; Singh, R.P.; Pal, D.
    Winter season maize (Zea mays L.) has emerged a new crop in many parts of South and Southeast Asia, where the crop has to face low temperature regimes (<5°C) for few weeks during vegetative growth stage. The objective of this study was to identify the morphological and physiological traits associated with cold stress tolerance during vegetative growth period, when maximum dry matter is accumulated and floral primodia are formed. A total of 80 cultivars, including hybrids and open pollinated varieties (OPVs) from International Maize and Wheat Improvement Center (CIMMYT) and Indian maize program were evaluated in replicated trials at Indian Agricultural Research Institute (IARI), New Delhi and at Regional Research Station, Haryana Agriculture University, Karnal, India during the winter season, where critical period of vegetative growth and floral primodia developmental stage was exposed to <10°C temperature. Data on various growth and developmental traits and key physiological traits were recorded during the low temperature regime. Except ears per plant and physiological maturity, the cold stress significantly affected all the growth and developmental traits and also physiological traits studied. However, significant genotypic variability was observed for most of the traits studied. Genotypes with relatively high leaf appearance and extension rate, less cold injury symptoms and cell membrane damage showed good level of cold tolerance in terms of reproductive behavior and eventually grain yield under cold stress. These secondary traits could be used in selection index along with days to anthesis, anthesis-silking interval (ASI) and grain yield for selection and improvement of tropical maize for low temperature adaptation.
    Publication
  • 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.
    Publication
  • 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.
    Publication
  • Stability in performance of quality protein maize under abiotic stress
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2008) Zaidi, P.; Vasal, S.K.; Maniselvan, P.; Jha, G.C.; Mehrajjudin; Singh, R.P.
    Quality protein maize (QPM) has emerged an affordable and viable option to alleviate protein malnutrition and reduce animal feed costs, given that its grain protein contains more than double the lysine and tryptophan concentrations of normal endosperm maize. For commercial success, QPM cultivars must be competitive with normal maize in productivity and should show stable performance across environments, especially with respect to yield and protein quality traits. In the tropics, drought and low-nitrogen (N) fertility are major constraints to maize productivity. In this study, we analyze the stability of performance of CIMMYT tropical and subtropical elite QPM hybrids across stressed (drought and low N) and unstressed environments. In general, stress significantly affected all agronomic traits except male flowering. The effect was comparatively large under drought stress. Among the quality traits, grain protein, tryptophan, and lysine contents showed significant variation across environments. There was an increase in grain protein (12.7%) and in lysine (10.3%) and tryptophan contents (8.1%) under drought stress, while levels of these grain quality traits were reduced under low N by 17.0, 12.5, and 15.6%, respectively. However, the effect of stressed environments was comparatively small on protein quality traits, including tryptophan and lysine content in protein. The variation in protein quality across environments was statistically significant but largely due to genotypic variability. Variation due to environment and genotype by environment (G x E) interaction was statistically non-significant for protein quality traits, except in the case of lysine content in protein, where G x E was significant. Our results suggest that grain yield and grain protein content are the most unstable traits, whereas tryptophan followed by lysine content are the most stable, across stressed and unstressed environments.
    Publication
  • Relationship between drought and excess moisture tolerance in maize (Zea mays L.)
    (Southern Cross Publishing Group, 2008) Zaidi, P.; Yadav, M.; Singh, D.; Singh, R.P.
    Maize crops grown during summer-rainy season in Asian tropics are prone to face both drought and excess moisture stress due uneven distribution patterns of monsoon rains in the region. We attempted to identify the relationship between drought and excess moisture tolerance through evaluation of a set of elite maize inbred lines, including lines with known performance under drought, excess moisture and normal inbred lines with unknown performance under either of the stresses. Under normal moisture, performance of normal lines was slightly better than drought and excess moisture lines. However, under stress condition performance of normal lines was very poor with average yield 9.1% under drought and 18.7% under excess moisture stress in comparison to normal moisture. On the other hand, drought lines yielded up to 61.8% under drought and 52.1% under excess moisture in comparison to their yields under normal moisture. Performance of excess moisture lines was also good across stress environments with average yield 68.2% under excess moisture and 35.6% under drought. Relationship between yields under drought and excess moisture stress was strong and significant with drought lines (R2 = 0.587**), but it was relatively weak with excess moisture lines (R2 = 0.288*), while the relationship highly weak with normal lines (R2 = 0.043ns). Our results suggest that improved performance of drought tolerant lines across environments might be related to constitutive changes in stress-adaptive secondary traits such as - anthesis-silking interval <5.0 days, reduced barrenness, delayed senescence and minimum loss of leaf chlorophyll under stress conditions. These constitutive changes with selection and improvement for flowering stage drought tolerance might resulted in improved performance of genotypes under both drought and excess moisture stress, without any yield penalty under normal moisture.
    Publication
  • Morpho-physiological traits associated with variable field performance of different types maize germplasm across multiple environments
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2003) Zaidi, P.; Srinivasan, G.; Sanchez, C.
    Field performance of maize varies substantially among various types of germplasm, such as- hybrids, inbred lines, and often with open pollinated varieties (OPVs). Variations in per se performance is better realized under optimal growing conditions, and further widened with increase in level of stresses. We examined sub-tropical/mid-altitude germplasm, including promising hybrids, OPVs and inbred lines under different growing conditions, including optimal conditions, mild-stress (double population density) and severe drought stress. At vegetative growth stage, dry mater partitioning between vegetative and reproductive plant parts, proportion of dry matter allocated to leaf growth in relation to stem, and within reproductive parts the amount of dry matter available for ear development varied significantly among the types of germplasm, across the growing conditions. The best performing genotypes, both within a germplasm type and across the germplasm, showed relatively more biomass allocation to leaf at the cost of stem dry weight, and more dry matter accumulation for ear development at the cost of both tassel and stem biomass. Apart from relatively more leaf area, the longevity of active leaf area duration was one of the important characteristics of superior germplasm, across the types of germplasm and growing conditions. Comparatively more cob weight at anthesis was positively correlated with grain yield under drought stress. However, under unstressed or mild stress conditions the relationship was significant only with inbred lines. Across the environments, striking difference was observed for percent kernel abortion during early stage of grain filling (lag phase), both among the germplasm, and also between the best and worst entries within a germplasm type. Rate of kernel growth clay -1 and length of grain filling period were comparatively higher with hybrids than with inbred lines and OPVs. Our findings indicate that these variations in constitutive traits might be the factors responsible for distinct differences in field performance of different types of germplasm. Emphasis on these constitutive traits during selection and improvement of germplasm may prove to be beneficial in improving the performance of genotypes across the unstressed and less-favorable environments.
    Publication
  • Relationship between line per se and cross performance under low nitrogen fertility in tropical maize (Zea mays L.)
    (Consiglio per la Ricerca e la sperimentazione in Agricoltura, Unità di Ricerca per la Maiscoltura, 2003) Zaidi, P.; Srinivasan, G.; Sanchez, C.
    Improved maize yields under low nitrogen (N) fertility is desired for both low- input production systems and also for judicious application of fertilizer nitrogen for a sustainable and environment friendly production systems. A key question in breeding for tolerance to low-N fertility is to what extent the performance of maize hybrids can be predicted on the basis of performance of their inbred lines under low-N supply. Past studies showed varied degree of correlations between line and hybrid performance under low-N fertility, ranging from weak to fairly strong relationship. We attempted to examine the impact of low-N supply on relationship between morpho-physiological traits and grain yield measured on inbred parents, all advance generation lines, and their single cross progenies. Reactions of various morpho-physiological traits, except days to anthesis (male flowering), differ significantly at low- and optimal level of N-fertility. Superiority of hybrid progenies over parental lines declined under low-N stress, which indicates that hybrids were comparatively more affected than lines due to low-N supply. Data on individual contributions of heterosis and performance of mid-parent showed that per se performance of lines was relatively more important factor in determining the hybrid performance under both the levels of N-supply. Correlations between various secondary traits and grain yield under both low and optimal-N fertility were moderate to strong in case of both parental lines and hybrids. However, it was comparatively stronger in case of hybrid progenies under low-N stress. Correlations between morpho-physiological traits of lines and hybrids, except for ear rots, were fairly strong and significant under both the level of N supply. The relationship between grain yield of mid-parent and hybrids was comparatively stronger under low-N fertility. Our findings suggest that performance of hybrid progenies under low-N fertility can be predicted to some extent on the basis of advance generation elite inbred parents with proven performance across N-supply.
    Publication
  • Improving maize productivity under abiotic stress; ICAR & CIMMYT Hyderabad, India; 2-12 February 2004
    (CIMMYT, 2004) Zaidi, P.; Harrington, K.; De Meyer, J.; Singh, N.N.
    Publication