Abiotic and biotic stresses in Plantation Crops: Adaptation and Management
ABSTRACT Plantation crops include perennials grown over large areas in monoculture, excepting fruit trees grown in orchards. These crops face both abiotic and biotic stresses, incited by factors those coexist in plantations. Although Plantation crops are well adapted and are grown mostly in the tropics, where innumerable stress factors operate. Historical significance of few stress havocs in plantation species is remarkable. A wide range of anatomical, physiological and biochemical features contribute to various stress adaptation in plantation crops. Notwithstanding, improvement of stress resistance in plantation species has been mandated to combat unfriendly factors that jeopardize intensive and extensive cultivation. Conventional breeding is cumbersome in plantation crops, where in the process has to involve many generations running for decades, and expensive in terms of time, space and large volume of individuals handled. Recent developments in molecular genetics and biotechnology are aiding acceleration of breeding process in plantation species. Integration of proper crop management strategies with improved cultivars is essential to meet the goals of stress management. This review presents a comprehensive coverage of various adaptive mechanisms and mitigation strategies for several biotic and abiotic stresses affecting major plantation crops like cardamom, cashew, cocoa, coconut, coffee, date, eucalyptus, oil palm, rubber and tea.
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ABSTRACT: Two C-repeat binding factor genes (EguCBF1a/b), isolated from E. gunnii and differentially cold-regulated, were constitutively overexpressed in a cold-sensitive Eucalyptus hybrid. In addition to the expected improvement on freezing tolerance, some resulting transgenic lines (EguCBF1a-OE and EguCBF1b-OE) exhibited a decrease in stomata density and an over-accumulation of anthocyanins also observed to a lesser extent in a cold-acclimated control plant. Given that the induction of five putative CBF target genes was observed in CBF-overexpressing lines as well as in the cold-acclimated control line, these phenotypes might be related to cold acclimation. In comparison with the control plant, the most altered transgenic line (EguCBF1a-OE A1 line), exhibited reduced growth and better water retention capacity. This modified phenotype includes reduced leaf area and thickness associated with a decrease in cell size, as well as a higher oil gland density and a wax deposition on the cuticle. Surprisingly, the EguCBF1b-OE B9 line, with a level of transgene expression equivalent to the A1 line, showed a less marked phenotype, suggesting a difference in transactivation efficiency between EguCBF1A and B factors. The features of these transgenic lines provide the first signs of adaptive mechanisms controlled by CBF transcription factors in an evergreen broad-leaved tree. These data also open new prospects towards genetic improvement on Eucalyptus for freezing tolerance.Plant Biotechnology Journal 01/2011; 9(1):50-63. · 6.28 Impact Factor
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ABSTRACT: The rhinoceros beetle, Oryctes rhinoceros L., is an economically important pest of the coconut palm. Management of this pest has been accomplished using microbial agents viz., Oryctes virus (OrV) and an entomofungal pathogen Metarhizium anisopliae. Recently an opportunistic bacterial pathogen Pseudomonas alcaligenes has also been noticed to cause septicaemia in the grubs when under stress. To unravel the influence of abiotic weather factors and the interactions amongst these microbial pathogens, a 3 year study was conducted from September 1996 to August 1999 in three of the southern districts of Kerala, India. Of the 6627 grubs and 307 adults collected from various breeding sites of the pest, 5% of the grubs and 22% of the adults had natural virus infection, 3% larvae died of M. anisopliae mycosis and 20% larvae succumbed to bacterial septicaemia. Oryctes virus infection in grubs and adults was negatively correlated to minimum temperature (correlation co-efficient, r = –0.4, and –0.6 respectively, sample size, n = 0). Increase in relative humidity increased the fungal activity (r = 0.8) whereas, maximum temperature had a negative impact (r = –0.7). Occurrence of virus infection in grubs and adults was positively correlated (r = 0.6), supporting the contention of active transmission of the virus pathogen between these two stages. The bacterial septicaemia in the grubs was marginally correlated with virus infection and P. alcaligenes undermined the efficiency of the virus pathogen.World Journal of Microbiology and Biotechnology 06/2002; 18(5):417-421. · 1.26 Impact Factor