Identification of groundnut genotypes resistant to iron deficiency chlorosis

Groundnut (Arachis hypogaea L.) is the second most important oilseed in India, which is mainly grown in states like Gujarat, Andhra Pradesh, Karnataka, Tamil Nadu and Maharashtra. More than one-third of the soils in India are calcareous and spread mostly in the low rainfall areas of the western and central parts of the country where groundnut is a major crop. As calcareous soils are deficient in available iron (Fe2+), iron deficiency chlorosis (IDC) is more prevalent in Saurashtra region of Gujarat, Marathwada region of Maharashtra, and parts of Rajasthan, Tamil Nadu and Karnataka causing significant reduction in yield (Singh et al., 2004). Iron deficiency leads to interveinal chlorosis of younger leaves, while under severe deficiency they turn into white and papery and further as brown and necrotic. Genetic variability for resistance to IDC has been reported earlier in groundnut (Samdur et al., 2000; Li and Yan-Xi, 2007). Cultivation of IDC resistant cultivars in calcareous soils is economically feasible and sustainable approach compared to application of iron containing fertilizers through soil or foliar spray

Genetic divergence analysis in groundnut (Arachis Hypogaea l.) Under calcareous soil of northen Karnataka

Groundnut (Arachis hypogaea L.) is an important annual oilseed legume crop, valued as a rich source of proteins, minerals and vitamins. It is an unpredictable crop due to its underground pods development. For improvement of yield in groundnut direct selection is often misleading. The knowledge of existing variability is essential for developing high yielding genotypes in groundnut. An experiment was conducted with 43 gronudnut genotypes at college of agriculture, Vijayapura, UAS Dharwad, during kharif, 2013-14 to study the genetic diversity for IDC resistance related traits, yield and its component characters. The estimates of GCV and PCV were high for net plot yield (22.722 and 47.915) and low heritability with moderate GA as % mean was observed for net plot yield (22.5 and 22.197). The genotypes were highly diverse for IDC resistance and classified into 18 clusters. The diversity among the genotypes measured by intra-cluster & inter cluster distance in the present investigation was adequate for improvement of groundnut genotypes for IDC resistance by hybridization and selection. Seventeen clusters found to be solitary these can be used as promising parents for hybridization programme for obtaining high heterotic response for IDC resistance and thus better sergeants in groundnut

Biochemical basis of iron deficiency chlorosis resistance in groundnut (Arachis hypogaea L.)

A pot experiment with factorial design involving normal and calcareous soil and five genotypes with differential response to iron deficiency chlorosis (IDC) viz., ICGV 86031 and A30b (Resistant), TG 26 (moderately Resistant), TAG 24 and TMV 2 (susceptibe) were tested for various traits like VCR and SCMR, chlorophyll a, b and total chlorophyll, active iron content, specific activity of peroxidase at five different stages and also know the effect of IDC on yield and yield components. Iron deficiency chlorosis resistant genotypes recorded significantly lower VCR, higher SCMR, higher active iron content, chlorophyll a, b and total chlorophyll and peroxidase activity in leaf across all stages compared to susceptible genotypes. A strong and positive correlation was observed between peroxidase activity and leaf iron content. Yield and yield components were significantly reduced in susceptible genotypes compared to resistant genotypes

Genetic analysis of recombinant inbred lines for iron deficiency chlorosis and productivity traits in groundnut

Iron deficiency is an important abiotic constraint reducing the growth and yield of groundnut especially under calcareous soils. Foliar application of Fe-chelates can overcome iron deficiency but it is not economical. Evaluation of 318 recombinant inbred lines (RILs) along with parents for iron deficiency chlorosis (IDC) and productivity traits under iron deficient soils over three years indicated significant genotypic and genotypic x environment interaction (GE) component for both IDC and productivity traits. Among the RILs, range of variation was higher than that of the parents for visual chlorotic rating (VCR), SPAD chlorophyll meter reading (SCMR) and productivity parameters across three years indicated the presence of transgressive segregants. VCR had higher phenotypic and genotypic, variances, heritability and genetic advance as per cent of mean (GAM) in all the three years as compared to SCMR. Among productivity traits, pod yield (g plant–1) had higher PCV and GCV compared to shelling per cent and 100 seed weight. Significant negative correlation between VCR and pod yield per plant indicated effect of IDC on productivity in RILs. Nine lines were superior for both IDC tolerance and productivity traits. This extensive phenotyping of RIL population for IDC tolerance under iron deficient conditions can be used for identification of genomic regions associated with IDC tolerance by genotyping of this RIL population

Genetic Differences for Iron Absorption Efficiency Related Traits in Groundnut

Iron deficiency chlorosis (IDC) is of common occurrence in groundnut growing areas with calcareous, alkaline and black SOils which accounts to one-third of the Indian soils. Groundnut is sensitive to iron deficiency, but shows genotypic differences for iron absorption efficiency (IAE) response. A pot experiment was conducted using five genotypes with varying degree of IAE [ICGV 86031 , A30b (efficient), TG 26 (moderately effiCient), TAG 24, TMV 2 (inefficient)] in normal and deficit Fe soil types to determine underlying mechanisms. They were assessed for IAE related traits like visual chlorotic rating (VCR), SPAD chlorophyll meter reading (SCMR), chlorophyll (a, b and total) content, active iron (Fe2+) content. and peroxidase activity in initial expanded leaves across five crop growth stages (20, 40, 60, 60, 100 days) and also for productivity traits. Iron absorption efficient groundnut genotypes recorded significantly lower VCR, higher SCMR, higher active iron, chlorophyll (a, b and total) and peroxidase activity across all five crop growth stages compared to inefficient genotypes. Severity of chlorosis was highest at 60 days during which significant negative correlation was observed between VCR and IAE related traits like SCMR, chlorophyll (a, band total) content, active iron content, and peroxidase activity indicating their utility as surrogate traits In screening for IAE in groundnut. IAE related traits showed significant positive association with productivity traits like pod yield, 100 seed weight, number of pods and primary branches. Pod yield reduction due to iron chlorosis in efficlent genotypes was very less compared to inefficient genotypes

Morpho-Physiological Parameters Associated with Iron Deficiency Chlorosis Resistance and Their Effect on Yield and Its Related Traits in Groundnut

Iron deficiency chlorosis (IDC) causes a significant reduction in yield of groundnut grown in calcareous and alkaline soils in India. The main aim of the study was to assess genotypic differences for morpho-physiological parameters associated with IDC resistance across different stages and their effect on yield and its related traits. The factorial pot experiment was comprised of two major factors, i) soil-Fe status [normal-Fe, deficit-Fe], and ii) genotypes [five] with differential IDC response, constituting 10 treatments. They were assessed for five morpho-physiological parameters associated with IDC resistance across five crop growth stages and also yield and its related traits. Associations between these traits were also estimated. Under deficit-Fe conditions, IDC resistant genotypes recorded significantly lower visual chlorosis rating (VCR), higher SPAD values, active Fe, chlorophyll content, peroxidase activity, and high yield compared to susceptible ones. Between normal- to deficit-Fe soils, resistant compared to susceptible genotypes showed no change in VCR scores; a lower reduction in SPAD, chlorophyll, active Fe, peroxidase activity, and pod yield. Under deficit-Fe conditions, high yield among resistant genotypes could be attributed to higher seed weight, number of pods and haulm yield, while contrasting reduction in main stem height and number of primaries. The results indicate that for initial large-scale screening of groundnut genotypes for IDC resistance, SPAD values are most ideal while active Fe could be utilized for confirmation of identified lines

Identification of quantitative trait loci associated with iron deficiency chlorosis resistance in groundnut ( Arachis hypogaea )

Iron deficiency chlorosis is an important abiotic stress affecting groundnut production worldwide in calcareous and alkaline soils with a pH of 7.5–8.5. To identify genomic regions controlling iron deficiency chlorosis resistance in groundnut, the recombinant inbred line population from the cross TAG 24 × ICGV 86031 was evaluated for associated traits like visual chlorosis rating and SPAD chlorophyll meter reading across three crop growth stages for two consecutive years. Thirty-two QTLs were identified for visual chlorosis rating (3.9%–31.8% phenotypic variance explained [PVE]) and SPAD chlorophyll meter reading [3.8%–11% PVE] across three stages over 2 years. This is the first report of identification of QTLs for iron deficiency chlorosis resistance- associated traits in groundnut. Three major QTLs (>10% PVE) were identified at severe stage, while majority of other QTLs were having small effects. Interestingly, two major QTLs for visual chlorosis rating at 60 days (2013) and 90 days (2014) were located at same position on LG AhXIII. The identified QTLs/markers after validation across diverse genetic material could be used in genomics-assisted breeding