Evaluation of groundnut (Arachis hypogaea L.) advanced breeding lines for resistance to cercospora leaf spots and rust diseases in Kano State, Nigeria

Cercospora leaf spots and rust diseases are among the biotic factors that cause yield reduction in groundnut. However, screening groundnut breeding lines that are tolerant to these diseases and having higher yield potentials would help farmers and breeders to make the right choice for cultivation or for further improvement. Therefore, this study was conducted to evaluate 18 groundnuts advanced breeding lines and 2 improved/local varieties against these diseases, during July-October 2016 rainy season in a field designated as endemic to Cercospora leaf spots and rust diseases, at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) Research Farm at Minjibir, Kano, Nigeria. Significant differences (p<0.01) were observed in all the traits studied (viz., days to 50% flowering, normalised difference vegetation index, pod yield (Kg/ha), fodder yield (Kg/ha), 100 seed weight (g), disease incidence (%) and disease severity) except chlorophyll content. The top nine (9) high yielding breeding lines (ICGV's-IS 13980, 07947, 07828, 09011, ICGX-IS's 11003, 11057, 13011, ICGV-SM 07539 and ICG 5891) were all resistant to early leaf spot, moderately resistant to late leaf spot and rust except ICGV's-IS 07828, 09011 and ICGX-IS 13011 which were susceptible to rust.Keywords: Cercospora, Rust, Groundnut, Resistance, Yiel

Genomic tools in groundnut breeding program: Status and perspectives

Groundnut, a nutrient-rich food legume, is cultivated world over. It is valued for its good quality cooking oil, energy and protein rich food, and nutrient-rich fodder. Globally, groundnut improvement programs have developed varieties to meet the preferences of farmers, traders, processors, and consumers. Enhanced yield, tolerance to biotic and abiotic stresses and quality parameters have been the target traits. Spurt in genetic information of groundnut was facilitated by development of molecular markers, genetic, and physical maps, generation of expressed sequence tags (EST), discovery of genes, and identification of quantitative trait loci (QTL) for some important biotic and abiotic stresses and quality traits. The first groundnut variety developed using marker assisted breeding (MAB) was registered in 2003. Since then, USA, China, Japan, and India have begun to use genomic tools in routine groundnut improvement programs. Introgression lines that combine foliar fungal disease resistance and early maturity were developed using MAB. Establishment of marker-trait associations (MTA) paved way to integrate genomic tools in groundnut breeding for accelerated genetic gain. Genomic Selection (GS) tools are employed to improve drought tolerance and pod yield, governed by several minor effect QTLs. Draft genome sequence and low cost genotyping tools such as genotyping by sequencing (GBS) are expected to accelerate use of genomic tools to enhance genetic gains for target traits in groundnut

Germplasm enhancement for increasing groundnut productivity and production in West and Central Africa

West and Central Africa (WCA) account for almost 70% of groundnut production in Africa playing and important role to farmers' livelihood and significantly contributes to the export sector of the countries in the region..

Genetic mapping of tolerance to iron deficiency chlorosis in peanut (Arachis hypogaea L.)

Iron deficiency chlorosis (IDC) under calcareous and alkaline soils is a significant abiotic stress affecting the growth and yield of peanut. In this study, the genomic regions governing IDC tolerance were mapped using a recombinant inbred line (RIL) population derived from TMV 2 (susceptible to IDC) and TMV 2-NLM (tolerant to IDC), which was phenotyped during the rainy seasons of 2019 and 2020 in the iron-deficient calcareous plots. The best linear unbiased prediction (BLUP) values for IDC tolerance traits like visual chlorotic rating (VCR), and SPAD chlorophyll meter reading (SCMR) were used for QTL analysis along with a genetic map carrying 700 GBS-derived SNP, AhTE and SSR markers. In total, 11 and 12 main-effect QTLs were identified for VCR and SCMR, respectively. Among them three QTLs were major with the phenotypic variance explained (PVE) of 10.3–34.4% for VCR, and two QTL were major for SCMR with PVE of 11.5–11.7%. A region (159.3–178.3 cM) on chromosome Ah13 carrying two QTLs (one each for VCR and SCMR) was consistent with the previous report. A SNP marker, Ah14_138037990 identified from single marker analysis for VCR was located in the intronic region of the gene Arahy.QA0C1, which is important for protein-binding. Overall, this study identified new QTLs and also validated QTL for IDC tolerance. These genomic resources could be useful for genomics-assisted breeding of peanut for IDC tolerance

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Mapping late leaf spot and rust resistance using an improved consensus map in peanut (Arachis hypogaea L.)

Late leaf spot and rust are the major biotic stresses in peanut worldwide. An effort was made to map late leaf spot and rust resistance using the recombinant inbred line populations derived from TAG 24 x GPBD 4 and TG 26 x GPBD 4 in peanut. The new genetic maps were developed by mapping a large number of Arachis hypogaea transposable element (AhTE) markers in addition to the previously mapped SSR markers. A consensus map was generated based on these two independent maps, which was employed for detecting the genomic regions governing late leaf spot and rust resistance measured at three stages (70, 80 and 90 days after sowing) in 12 seasons. Details of the quantitative trait loci identified from this study will be discussed so as to use them in molecular breeding of peanut for improving late leaf spot and rust resistance

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

Advances in groundnut breeding for drought prone West and Central Africa

The West and Central Africa region accounts for more than 70% of the groundnut production in Africa. The crop is challenged by various biotic and abiotic production constraints with drought being the main abiotic constraint. ICRISAT has been working with national breeding programs to develop improved groundnut varieties. The approach used included identifying sources of resistance, developing populations, evaluating in target environments and releasing improved farmer preferred varieties for production. The Tropical Legumes project initiated in 2007 has been instrumental in strengthening the breeding program in the region. Nine drought resistant/tolerant accessions were identified from evaluation of the mini core collections, and these accessions have been utilized as parents in crossing programs. Since 2007, ICRISAT distributed more than 1000 advanced breeding lines to national programs. Farmer participatory variety selection was found very useful for fast track release and adoption of improved varieties. Twenty two varieties have been released/registered across the region as a result of project efforts (4 in Ghana, 5 in Mali, 4 in Niger, 3 in Nigeria and 6 in Senegal). These varieties are high yielding (yield advantage of >20%) with resistance or tolerance to drought and major diseases. Currently, efforts are underway to improve the efficiency of breeding programs and to enhance genetic gain. These include designing product pipelines based on traits of breeding interest; reducing generation advancement process of breeding populations by growing 2 to 3 generations per year; integrating modern genomic tools; digitizing data collection, analysis, management and sharing by using BMS; and enhancing the skills of breeders and technicians

Evaluation of multiple stress tolerant groundnut genotypes for productivity and nutritional quality in Nigeria

Groundnut plays a very important economic role for smallholder farmers in the semi-arid tropics as a major cash crop for many households; a nutritious and safe food thereby contributing to improved health of the rural population. It is rich in protein, oil and micronutrients such as iron and zinc. High iron and zinc contents are especially beneficial for women and children at risk of anemia and have proven to be genetically malleable. High oleic acid and low linoleic acid make groundnut oil ideal for storage and better human health. Evaluation of 541 advanced breeding lines along with local landraces and improved varieties for their reaction to drought, rosette and foliar diseases besides productivity parameters over two locations during 2014 main season resulted in identification of 45 promising lines with significantly superior pod yield (1304-2796 kg/ha) compared to check entries (189-1005 kg/ha). Further, these superior genotypes were evaluated for nutritional quality and in trials during 2014/15 dry season to confirm their superiority. Nutritional quality (oil, 0/L ratio, protein, Fe and Zn content) analyses lead to the identification of nutritionally dense genotypes. Genotypes ICGV IS 11060, Samnut 23, ICGV 00064, ICGV O 1276, ICGV IS 07827 and Kampala had high oil content (53-54%); while ICGV 07813 had high 0 /L ratio of 6.1 followed by ICGV IS 09992, ICGV SM 05593 and ICGV SM 06722 with 3.0 0/L ratio. Genotypes ICGV IS 07833, ICGV IS 3980, ICGV SM 08553 and ICG 589 I had high protein (30-32%), Zn (46-51 ppm) and Fe (23-34 ppm) content. These serve as ideal genetic resources to develop agronomically superior and nutritionally enhanced groundnut cultivars with multiple resistances to biotic and abiotic stresses

Development of NILs from heterogeneous inbred families for validating the rust resistance QTL in peanut (Arachis hypogaeaL.)

Heterogeneous inbred families segregating for rust resistance were identified from the two crosses involving susceptible (TAG 24 and TG 26) and resistant (GPBD 4) varieties of peanut. Rust-resistant (less than score 5) and rust-susceptible (more than score 5) plants were identified in each HIF and evaluated under rust epiphytotic conditions. The set of plants belonging to the same HIF, but differing significantly in rust resistance, not in other morphological and productivity traits, was regarded as near-isogenic lines (NILs). Largely, rust-resistant NILs had GPBD 4-type allele, and susceptible NILs carried either TAG 24 or TG 26-type allele at the three SSR loci (IPAHM103, GM1536 and GM2301) linked to a major genomic region governing rust resistance. Comparison of the remaining genomic regions between the NILs originating from each of the HIFs using transposon markers indicated a considerably high similarity of 86.4% and 83.1% in TAG 24 × GPPBD 4 and TG 26 × GPBD 4, respectively. These NILs are useful for fine mapping and expression analysis of rust resistance