Allelochemicals Biologica... - Name

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ANA LUISA ANAYA
characteristics and herbicide and insect resistance. Additional commercial applications
of genomics in weed science will be identification of genes involved in crop ability.
Genes controlling early crop root emergence, rapid early-season leaf and root
development for fast canopy closure, production of allelochemicals for natural weed
control, identification of novel herbicide target sites, resistance mechanisms, and genes
for protecting crops against specific herbicides can and will be identified. Successful
crop improvement in these areas using the tools of genomics will dramatically affect
weed-crop interactions and improve crop yields while reducing weed problems. In
relation to improved basic knowledge of weeds and the resulting ability to improve
our weed management techniques, genomics will offer the weed science community
many new and exciting research opportunities. Scientists will be able to determine
the genetic composition of weed populations and how it changes over time in relation
to agricultural practices, Identification of genes contributing to weediness, perennial
growth habit, herbicide resistance, seed and vegetative structure dormancy, plant
architecture and morphology, plant reproductive characters (outcrossing and
hybridization, introgression), and allelopathy will be identified and utilized with highthroughput
DNA sequencing and other genomics-based technologies. Using genomics
to improve our understanding of weed biology by determining which genes function
to affect the fitness, competitiveness, and adaptation of weeds in agricultural
environments will allow the development of improved management strategies.
Information is provided concerning the current state of molecular research in various
areas of weed science and specific genomic research currently being conducted at
Purdue University using transfer DNA (TDNA) activation tagging to generate large
populations of mutated plants that can be screened for genes of importance to weed
science (Weller et al., 2001).
6. SUPPRESSIVE SOILS
When soils are characterized by a very low level of disease development even though
a virulent pathogen and susceptible host are present, they are known as suppressive
soils. Biotic and abiotic elements of the soil environment contribute to suppressiveness,
however most defined systems have identified biological elements as primary factors
in disease suppression. Many soils possess similarities with regard to microorganisms
involved in disease suppression, while other attributes are unique to specific pathogensuppressive
soil systems. The organisms’ operative in pathogen suppression does so
via diverse mechanisms including competition for nutrients, antibiosis and induction
of host resistance (Mazzola, 2002). Non-pathogenic Fusarium spp. and fluorescent
Pseudomonas spp. play a critical role in naturally occurring soils that are suppressive
to Fusarium wilt. Suppression of take-all of wheat, caused by Gaeumannomyces
graminis var. tritici, is induced in soil after continuous wheat monoculture and is
attributed, in part, to selection of fluorescent pseudomonads with capacity to produce
the antibiotic 2,4-diacetylphloroglucinol. Cultivation of orchard soils with specific
wheat varieties induces suppressiveness to Rhizoctonia root rot of apple caused by
Rhizoctonia solani AG 5. Wheat cultivars that stimulate disease suppression enhance