Analysis of a mutant population in groundnut

Fifty three mutants derived from Dharwad Early Runner (DER), a true breeding variant from a cross between two Valencia varieties of groundnut were evaluated for taxonomic, productivity and quality traits for assessing its suitability to ascertain marker-trait association. Mutants were confirmed for subspecific changes. Sixteen independent mutants shared common taxonomic shift from DER type to that of ssp. hypogaea var. hypogaea. Seventeen and nine mutants showed taxonomic shift to ssp. fastigiata var. fastigiata and ssp. fastigiata var. vulgaris, respectively. Four mutants had a shift from var. fastigiata to var. vulgaris. Significant shifts both in positive and negative direction were observed for most of the productivity and quality traits along with resistance to late leaf spot and rust. Since these mutants are derived from a common source (Dharwad Early Runner), those contrasting for any trait are expected to differ for a small genomic region. Role of transposons being significant in groundnut mutations, genotyping such mutants with transposon-specific markers might reveal marker-trait associations useful for groundnut improvement

Development of late leaf spot and rust tolerant genotypes from TMV 2 and JL 24 by marker assisted backcross breeding in groundnut

Foliar diseases like late leaf spot (LLS) and rust cause severe loss in the quantity and quality of the yield in groundnut. Development of foliar disease resistant genotypes, especially from the varieties that are already under commercial cultivation, but are susceptible to LLS and rust, is a promising approach in resistance breeding. The QTL and markers identified to be linked to LLS and rust resistance would hasten the selection scheme in the breeding program. TMV 2 and JL 24 released during 1940 and 1978, respectively for cultivation are still popular, except for their disease susceptibility. They were crossed to LLS and rust resistant genotypes like GPBD 4 (a released variety), ICGV 86699 (interspecific derivative), ICGV 99005 (interspecific derivative) and a second cycle derivative involving synthetic tetraploids. The F1s were selected based on the allele type at LLS and rust resistance-linked markers. Three cycles of backcrossing was attempted, and a few homozygous plants were identified from the BC3F2 from JL 24 x GPBD 4, JL 24 x ICGV 86699 and JL 24 x ICGV 99005. Selected BC3F3 families were highly resistant to LLS and rust, and they carried resistant allele at linked markers like IPAHM103 and GM2301. These lines were on par with the recurrent parent (JL 24) for test weight, SMK and yield. The background genome recovery in a selected family (JG_BC3FL18) of JL24 x GPBD 4 was up to 86.6% when checked with 30 polymorphic transposable element (TE) based markers. Currently, BC3F4 lines are being evaluated in larger plots for productivity and disease resistance

Genetic diversity analysis based on nutritional, oil quality and yield component traits in mini core collection of groundnut (Arachis hypogaea L.)

Groundnut (Arachis hypogaea L.) is an annual legume, grown primarily for high quality edible oil and easily digestible protein in its seeds. It is cultivated in 109 countries, in tropical, subtropical, and warm temperate regions of the world. In India during 2010-11 it was grown on 4.93 million ha with an estimated total production of 5.64 million tonnes (groundnuts in shell) and an average productivity of 1144 kg/ ha (FAO 2011)..

Genetic analysis for yield, nutritional and oil quality traits in RIL population of groundnut (Arachis hypogaea L.)

A total of 268 recombinant inbred lines (RILs) were evaluated for genetic variability for yield, nutritional and oil quality traits under two consecutive seasons at two locations. Analysis showed that variability exists in the population for the nutritional and oil quality as well as for yield component traits. Majority of the yield components and oil quality traits were governed by additive effects. The nutritional and oil quality traits were not affected by environmental factors and simple phenotypic selection ensures increased performance of the genotypes. Yield components showed moderate to high heritability but with great influence of environment

Phenotypic and molecular dissection of ICRISAT mini core collection of peanut (Arachis hypogaea L.) for high oleic acid

High oleic acid (O) and low linoleic acid (L) make peanut oil ideal for longer storage and better human health. Among the ICRISAT mini core collection accessions, oleic acid ranged from 33.60% to 73.54%. Accessions belonging to ssp. hypogaea had higher oleic acid (54.16%) compared with those of ssp. fastigiata (45.70%). An O : L ratio up to 6.93 was found among ssp. hypogaea. Additional varieties, mutants, germplasm lines and breeding lines had oleic acid within the range of mini core accessions. Mutations in ahFAD2A, which along with its homologous gene, ahFAD2B code for delta-12-desaturase, resulted in higher oleic acid and O : L ratio. ahFAD2A mutant allele was found in 49.5% of the accessions, and its frequency was higher in ssp. hypogaea (84.52%) than in ssp. fastigiata (19.39%). ahFAD2A mutation had a maximum contribution of 18.82, 12.98 and 10.52 towards the phenotypic variance of O, L and O : L ratio, respectively. Genotypes with high oleic acid levels could not reveal ‘A’ insertion mutation in ahFAD2B. Accessions with high oleic acid could be employed for improving peanut oil quality

Genetic variability and association studies for seed yield and longevity with component traits in soybean [Glycine max (l.) Merill.]

The nature and extent of genetic variability and correlation coefficient for productivity traits like seed yield and longevity of 225 soybean genotypes were evaluated. Significant variability (5%) was recorded among genotypes for agronomic and seed quality parameters. Number of pods per plant (23.76%), test weight (21.61%), seed yield per plant (28.07%), final germination (36.7%), seed coat permeability (30.09%), electrical conductivity (40.09%) and germination reduction (40.03%) showed high phenotypic and genotypic coefficient of variation, heritability and genetic advance. The association studies revealed that, number of branches and pods per plant and test weight (g) showed positive and significant correlation with seed yield (g). Phenotypic and genotypic correlation for seed longevity was negatively correlated and significant with test weight (g), seed coat permeability (%) and electrical conductivity (dSm-1). Superior genotypes like PK 7379, PI 284815, PI 204336, CO-1 and JS 79-307 were identified with high seed yield (3041.67-3708.33 kg/ ha) and good longevity

Foliar fungal disease-resistant introgression lines of groundnut (Arachis hypogaea L.) record higher pod and haulm yield in multilocation testing

Introgression lines (ILs) of groundnut with enhanced resistance to rust and late leaf spot (LLS) recorded increased pod and haulm yield in multilocation testing. Marker-assisted backcrossing (MABC) approach was used to introgress a genomic region containing a major QTL that explains >80% of phenotypic variance (PV) for rust resistance and 67.98% PV for LLS resistance. ILs in the genetic background of TAG 24, ICGV 91114 and JL 24 were evaluated for two seasons to select 20 best ILs based on resistance, productivity parameters and maturity duration. Multilocation evaluation of the selected ILs was conducted in three locations including disease hot spots. Background genotype, environment and genotype × environment interactions are important for expression of resistance governed by the QTL region. Six best ILs namely ICGV 13192, ICGV 13193, ICGV 13200, ICGV 13206, ICGV 13228 and ICGV 13229 were selected with 39–79% higher mean pod yield and 25–89% higher mean haulm yield over their respective recurrent parents. Pod yield increase was contributed by increase in seed mass and number of pods per plant

Multiple biotic stress resistant and productive genotypes identified under Spanish bunch background in groundnut (Arachis hypogaea L.)

The cultivated groundnut is an important oil seed crop of the world. Several pest and diseases damage the crop and reduce groundnut yields considerably. Cultivation of resistant varieties is an ecologically sound and economically viable approach to reduce the loss due to these stresses, but their occurrence and intensity vary in space and time necessitating the use of multiple stress resistant genotypes. Several diverse groundnut germplasm were assessed for different biotic stresses under epiphytotic conditions. Most of the cultivated varieties were susceptible to different stresses. Interspecific deri vati ves constituted the best source of resistance to late leaf spot (LLS), rust and Sclerotium; while mutants were superior for late leaf spot, Spodoptera and bud necrosis. Pedigree of multiple stress resistant genotypes revealed contribution of wild species for resistance to many biotic stresses. Trait association studies indicated late matUling nature of resistant germplasm. Induced mutagenesis and extensive hybridization with interspecific derivatives were sought to break these undesirable associations. Several foliar disease resistant mutants and second cycle interspecific-derivatives were isolated in Spanish bunch background. Mutant (28-2) and second cycle interspecific derivative (GPBD-4) were resistant to foliar diseases with high yield potential even under foliar disease epidemic. 28-2 was also resistant to Spodoptera, thrips and Aspergillus infection besides having bold kernels. GPBD-4 was iron absorption efficient and had OIL ratio of 1.68. They also possessed desirable agronomic features, early maturity, high partitioning and better quality. Mutant 28-2 and GPBD-4 have been registered with National Bureau of Plant Genetic Resources (NBPGR), New Delhi with INGR numbers 98003(IC296686) and 0 I 031 (IC2968LO), respectively. These cultures had stable and superior performance over popular cultivars (JL-24 and TMV-2) across years. GPBD-4 has been accepted by farmers and traders; under active seed chain and cultivation in the farmers' fields in India. GPBD-4 has been widely employed for MABC at ICRISAT and UASD as the source of resistance to LLS and rust

Backcross breeding in groundnut (Arachis hypogaea L.)

Rust caused by Puccinia arachidis Speg. is the most serious disease of groundnut and causes substantial yield loss and reduces the fodder and seed quality. Recombinant inbred lines (F6) were generated by SSD method from cross GPBD-5 x GPBD-4 and the rust resistant plants were backcrossed to the recurrent parent (GPBD-5) to develop a backcross population (BC1F4). The objective ofthis experiment was to study the possibilities of linkage break-down between yield component traits and rust resistance in groundnut. Analysis of data revealed that there was a shift in correlation from negative (F6) to positive significant direction (BC1F4) between pod yield per plant with plant height and between plant height with number of primary branches. Similarly there was linkage break-down between negative significant to positive significant association of number of primary branches with number of pods per plant, kernel yield per plant and shelling percent at both genotypic and phenotypic levels. Altogether a desirable shift in association and the proof of broken repulsion phase linkage and release of concealed variability, which is useful in plant breeding, provides a lot of scope for selection. Unchanged negative association between pod yield per plant with reaction to rust and shelling percent in both phenotypic and genotypic level in both the populations, indicated the operation of strong linkage blocks and which requires an intensive selection to combine disease resistance with yield. Otherwise inter-mating of highly extreme segregants in the populations also would cause breakage of these stubborn linkages. Thus, for yield component traits, backcrossing of selected plants is more rewarding than the single cross and advance by single seed decent method of breeding in groundnut

Validation of markers linked to late leaf spot and rust resistance, and selection of superior genotypes among diverse recombinant inbred lines and backcross lines in peanut (Arachis hypogaea L.)

Recombinant inbred lines (RILs) from four populations involving cultivated varieties, and backcross lines from three populations involving cultivated varieties and synthetic tetraploids (developed from wild diploids) were employed for validating late leaf spot (LLS) and rust resistance-linked markers and identifying superior genotypes in peanut. GM2009, GM2301, GM2079, GM1536, GM1954 and IPAHM103 markers showed significant association with rust resistance. They were successfully validated in a new RIL (TG 19 × GPBD 4) and two backcross (DH 86 × ISATGR 278-18 and DH 86 × ISATGR 5) populations. GM1954, GM1009 and GM1573 markers showed significant association with LLS resistance. TAG 19 × GPBD 4 and ICGS 76 × ISATGR 278-18 populations showed strong co-segregation of LLS-linked markers with the phenotype. From these genetic resources, six superior genotypes were identified. RIL 78-1 was resistant to LLS and rust, and recorded 30 % more pod yield than GPBD 4 (control). It also had higher kernel yield and oil yield along with higher oleate and linoleate content over GPBD 4. These genetic and genomic resources could be useful in breeding for LLS and rust resistance in peanut