No abstract

Background: Peanut (Arachis hypogaea L.) is an important crop economically and nutritionally, and is one of the most susceptible host crops to colonization of Aspergillus parasiticus and subsequent aflatoxin contamination. Knowledge from molecular genetic studies could help to devise strategies in alleviating this problem; however, few peanut DNA sequences are available in the public database. In order to understand the molecular basis of host resistance to aflatoxin contamination, a large-scale project was conducted to generate expressed sequence tags (ESTs) from developing seeds to identify resistance-related genes involved in defense response against Aspergillus infection and subsequent aflatoxin contamination.

A technique for screening peanut for. Seed from 293 peanut plant introducresistance to Meloidogyne arenaria. Plant Disease 67:957-958. tions (PIs) were provided by the USDA Southern Regional Plant Introduction Two hundred ninety-three peanut accessions were screened for resistance to the peanut root-knot Station, Experiment, GA or the Departnematode using visual galling and egg-mass ratings. Staining with phloxine B greatly expedited the ment of Agronomy, University of egg mass screening process. No high level of resistance was observed in any of the accessions Florida, Gainesville. M. arenaria inoculum evaluated, for greenhouse screening was obtained from a culture established and maintained on Rutgers tomato, (Lycopersicon Development of a peanut cultivar 93 cultivars in 15 major crops resistant to esculentum Mill.) by D. W. Dickson resistant to the peanut root-knot M. arenaria (3); however, there is no (Department of Entomology and nematode, Meloidogyne arenaria (Neal) known source of resistance to this Nematology, University of Florida, Chitwood, would reduce losses in peanut-nematode that can be used in breeding Gainesville). The culture came from an producing regions throughout the cultivated peanuts. Minton and Hammons infested peanutfield in Levy County, FL. southeastern United States. In Florida (8) screened 512 peanut entries on the Inoculum was extracted using a alone, R. A. Dunn (unpublished) basis of galling severity and reported that modification of the sodium hypochlorite estimated a loss in 1981 of more than $2.2 all entries were susceptible to M. (NaOCI) method developed by Hussey million in peanut production caused by arenaria. and Barker (7). Tomato roots with egg M. arenaria. Resistance to plant-parasitic nematodes masses were washed clean of soil and Selection and development has yielded is commonly defined as a reduction or agitated in a 20% solution of commercial inhibition of nematode reproduction bleach for 30 sec. After the tomato roots (3,9,10). Fassuliotis (3) noted that were removed and placed in a beaker of Portion of first author's M.S. thesis. U.SC. 1 34 oley o i dictethi fat.peanut germ plasm for resistance to the Ten m illiliters of inoculum of 5,000,

The genetic base of peanut (Arachis hypogaea L.) in the U

No abstract

No abstract

D rought is the major abiotic constraint aff ecting peanut (Arachis hypogaea L.) productivity and quality worldwide. Twothirds of the global production occurs in rain-fed regions of the semi-arid tropics where rainfall is generally erratic and insuffi cient, causing unpredictable drought stress, the most important constraint for peanut production (Wright and Nageswara Rao, 1994; Reddy et al., 2003). Even peanut grown under irrigation may experience drought because of limited water supply or because irrigation water is applied in amounts at frequencies less than optimal for plant growth. Improving water access and management are practically diffi cult since water is a scarce resource. Therefore, breeding for drought resistance is an important strategy in alleviating the problem and off ers the best long-term solution. Selection of segregating populations under stress conditions has been a standard approach for developing cultivars with improved stress tolerance. While direct selection for yield under stressed conditions can be eff ective, the limitations of this approach are high resource investment and poor repeatability of the results due to the large genotype ×

The relationship between biomass production and N2 fixation under drought‐stress conditions in peanut genotypes with different levels of drought resistance is not well understood. The objective of this study was to determine the effect of drought on biomass production and N2 fixation by evaluating the relative values of these two traits under well watered and water‐stress conditions. Twelve peanut genotypes were tested under field conditions in the dry seasons of 2003/2004 and 2004/2005 in north‐east Thailand. A split‐plot design with four replications was used. Main‐plot treatments were three water regimes [field capacity (FC), 2/3 available soil water (AW) and 1/3 AW], and sub‐plot treatments were 12 peanut lines. Data were recorded on biomass production and N2 fixation under well watered and water‐stress conditions. Genotypic variations in biomass production and N2 fixation were found at all water regimes. Biomass production and N2 fixation decreased with increasing levels of drought stress. Genotypes did not significantly differ in reductions for biomass production, but did differ for reductions in N2 fixation. High biomass production under both mild and severe drought‐stress conditions was due largely to high potential biomass production under well‐watered conditions and, to a lesser extent, the ability to maintain high biomass production under drought‐stress conditions. High N2 fixation under drought stress also was due largely to high N2 fixation under well‐watered conditions with significant but lower contributions from the ability to maintain high nitrogen fixation under drought stress. N2 fixation at FC was not correlated with the reduction in N2 fixation at 2/3 AW and 1/3 AW. Positive relationships between N2 fixed and biomass production of the tested peanut genotypes were found at both levels of drought stress, and the relationship was stronger the more severe the drought stress. These results suggested that the ability to maintain high N2 fixation under drought stress could aid peanut genotypes in maintaining high yield under water‐limited conditions.