9 research outputs found
Genotypic variability among peanut (Arachis hypogea L.) in sensitivity of nitrogen fixation to soil drying
Peanuts (Arachis hypogea L.) are often grown on sandy soils and drought stress can be a major limitation on yield. In particular, loss in nitrogen fixation activity associated with soil drying might be limiting due to the need for high nitrogen amounts in both vegetative tissues and seeds of peanut. This study examined the response of nitrogen fixation of intact plants of seventeen peanut genotypes when subjected to soil drying in pots over approximately a 2-wk period. A large range in the sensitivity of nitrogen fixation to soil drying was observed among the seventeen genotypes. Genotype ICGV86015, in particular, was found to have nitrogen fixation that was especially tolerant of soil drying. Significant positive (P<0.0001) correlation was found between the soil water content at which nitrogen fixation began decreasing and the amino acid concentration in the leaves of severely stressed plants
Genotypic variation in peanut for transpiration response to vapor pressure deficit
Conservation of soil water resulting from
decreases in stomata conductance under atmospheric
high vapor pressure defi cit (VPD) conditions
is a possible approach for enhanced
tolerance of water defi cit by crops. Water defi cit
is usually a concern in peanut (Arachis hypogea
L.) since it is frequently grown on sandy soils
with low water-holding capacity. Seventeen peanut
genotypes were studied to determine the
response of their transpiration rates (TR) to VPD.
The results of this study demonstrated variation
among peanut genotypes with nine genotypes
exhibiting a breakpoint in their VPD response
at about 2.2 kPa, above which there was little
or no further increase in TR. Therefore, these
genotypes with a breakpoint have the possibility
of soil water conservation when VPD exceeded
2.2 kPa. The remaining eight genotypes had a linear
response in TR over the whole range of tested
VPD. Also, the 17 genotypes could be separated
into groups with differing rates of increasing TR
at low VPD. The change in TR with increasing
VPD may be important in determining the rate at
which soil water is used under fi eld conditions
Variation in Transpiration Efficiency and Related Traits in a Groundnut Mapping Population.
Transpiration efficiency (TE) was evaluated in groundnut genotypes JUG 26, ICGS 76, CSMG 84-1, ICGS 44, ICGV 86031, TAG 24 and ICG 2773 using the dry-down method. Pot-grown plants were irrigated to 90% field capacity then subjected to drought stress (i.e. irrigating plants with 70% of the water lost the day before the onset of drought stress) at 28 days after sowing (DAS). Significant variation among the genotypes for TE was evident, with TAG 24 and ICGV 86031 showing the lowest and highest values of TE, respectively. The soil water content where transpiration began to decline relative to the control varied among the genotypes, and these threshold values were negatively correlated to TE. In another dry-down experiment, 318 F8 recombinant inbred lines (RILs) obtained from a cross between ICGV 86031 and TAG 24 were also characterized, along with their parents, for TE. Substantial variation was observed among the RILs for transpiration, TE and specific leaf area (SLA) before and after the imposition of drought stress, and for SPAD chlorophyll meter readings (SCMR) before, during and at the end of drought stress. ICGV 86031 recorded greater TE and SCMA, and lower SLA than TAG 24. The analysis of TE values for the RILs revealed that the trait segregated transgressively and was governed by polygenes. The heritability value was highest for SLA, followed by SCMR. The heritability values were low for TE and transpiration. SLA and SCMR can be useful as alternative indices when the direct biomass-based evaluation of TE is not possible