Validation of foreground microsatellite markers for introgression of shootfly (Atherigona soccata) resistant QTLs into elite sorghum varieties

Sorghum is an important cereal and fodder crop which plays pivotal role in human nutrition. Important challenge that threatens the long term production of sorghum is shootfly. Shootfly is the major limiting factor in sorghum as it effects both production and productivity. Leaf glossiness, trichomes on the leaf surface, Ovipositional non-preference and seedling vigor are the major component traits governing shootfly resistance in sorghum. The quantitative trait loci's (QTLs) responsible for these traits are present on chromosome number SBI 01, SBI 05, SBI 07 and SBI 10 respectively. So, to provide ready to use markers for foreground selection in marker assisted breeding for sorghum we have used 20 recurrent parents and 9 donor parents for shootfly resistance. These simple sequence repeat (SSR) markers are validated for introgressing the QTL's into elite postrainy sorghum cultivars. The results reveal, out of 58 SSR markers, 33 markers showed distinct polymorphism among the donor and recurrent parents. For each QTL minimum of five markers from the QTL flanking region were polymorphic for all the parents and are used for foreground selection for the presence of QTLs

Variations in structure and saccharification efficiency of biomass of different sorghum varieties subjected to aqueous ammonia and glycerol pretreatments

Sorghum biomass is a potential feedstock for lignocellulosic bioethanol production. The selection of suitable sorghum variety is essential to obtain high ethanol yield. In this paper we screened sorghum varieties belonging to sweet sorghum, post rainy sorghum, and hybrid sorghum. These varieties were screened based on their agronomic traits, amenability to pretreatment methods, and enzymatic digestibility. The sorghum biomass was pretreated using glycerol (60 %) at 190 ̊C for 60 min and aqueous ammonia (15 %) at 120 ̊C for 60 min. The digestibility of the pretreated biomass was determined using commercial cellulase (Cellic CTec2) at 10U/g loading, and the structural changes in the pretreated biomass were analyzed by spectroscopy and scanning electron microscopy. Sweet sorghum varieties showed significant variations in phenotypic traits such as fresh stalk yield, dry fodder yield, and juice yield. The cellulose digestibility among the sorghum varieties after the pretreatment also differed significantly. The cellulose digestibility levels of glycerol range from 64 % to 89 % and ammonia pretreated sorghum from 63 % to 81 %. The total sugar yields varied from 227 mg/g to 356 mg/g and 209 mg/g to 313 mg/g for sorghum pretreated with ammonia and glycerol, respectively. Although the delignification of sorghum varieties was higher (31%–65%) after ammonia pretreatment than glycerol pretreatment, the cellulose digestibility was higher for the glycerol pretreated biomass. These results indicated that effect of delignification on cellulose digestibility is trivial. This study explores factors affecting pretreatment and cellulose digestibility of sorghum varieties for maximum sugar yield in the cellulosic ethanol process

Comparison of shoot fly resistance qtls in sorghum introgression lines using snp genotyping

Shoot fly is a major pest in sorghum that causes significant annual yield loss. Use of pesticide to control this pest is an expensive and environmentally unsafe approach. Present study investigated the host plant resistance mechanism to develop shoot fly resistance (SFR) lines through transfer of shoot fly resistance QTLs (glossiness, trichome density, ovipositional non-preference) using SSR marker assisted backcrossing. Genomic regions for SFR showed four QTLs on SBI 01, SBI 07, SBI 05 and SBI 10 contributing up to 11.5%, 18.3%, 14% and 14.7% phenotypic variation. But QTLs on SBI 05 and SBI 10 for glossiness and trichome density are the major QTLs for which 10 SNPs have been designed. In earlier studies, three QTL regions associated with shoot fly resistance were successfully introgressed into elite cultivar SPV 1411 (Parbhani Moti) and a B line ICSB29004 using donors viz. J2658 (SBI01), J2614 (SBI10), and J2714 (SBI07) (which are derivatives of BTx 623). Phenotyping of introgression lines (ILs) led to the identification of resistant lines for each QTL region present on chromosome SBI-01, SBI-07 and SBI-10. Hence, in this study we have analysed the above developed ILs using single-nucleotide polymorphism (SNP) markers tightly linked to shoot fly resistant QTLs. The results showed that introgression lines with QTL present on chromosome SBI-10 were segregating for favorable alleles for leaf glossiness and for trichome density in homozygous condition. Other introgression lines with QTLs on chromosome SBI-01 and SBI-07 for component traits - oviposition non-preference, seedling vigor are segregated for glossiness trait also thus showing the transfer of non-targeted region, which in this case proved beneficial for SFR. This study showed that these SNPs can be used to analyze introgression lines and can be used as genomic markers for early generation selection of shoot fly resistance lines

Understanding genetic control of biotic stress resistance in sorghum for applied breeding

Sorghum yield and production stabillity are constrained by various biotic stresses such as different insects and diseaes. The biotic stresses not only reduce the yield but results in poor grain quality thus hampering its marketability and utiilization leading to severe economic losses. Development of host plant resistance is one of the cheapest and sustainable methodss for managing the insect pests and diseases. Improvement in stress resistance will increase ecological fitness, reduce pesticide use, and facilitate creation of a sustainable production system with increased efficiency, profitability and to enhance grain quality/end use traits. An integrated synergistic system involving plant breeding and genomics research using advanced molecular tools could increase the efficiency and precision of crop improvement. This chapter deals with recent development with regard to sorghum adaptation to different production systems, major biotic stresses affecting sorghum production, understanding genetic control of biotic stress resistance, screening techniques developed, QTLs identified for various stresses and the program made in cultivar development using this knowledge

Heterosis and Combining ability studies for improving grain Fe and Zn concentration and agronomic traits in Sorghum [Sorghum bicolor (L.) Moench]

Objective: Sorghum is a staple food for more than 300 million people in more than 30 counties. It is a rich source of micronutrients. Biofortifying sorghum with enhanced grain Fe and Zn is a major breeding objective. The present study was aimed at formulating suitable breeding program by studying gene action, heterosis and combining ability for improving grain Fe and Zn concentration in sorghum. Materials & Methods: This study was conducted in Line × Tester mating design involving seven parents. Twelve hybrids were developed by mating three lines with four testers. The combining ability of the crosses indicated predominance of dominance variance than additive variance for the agronomic traits such as days to 50 % flowering, grain yield, grain Fe and Zn concentration except for plant height and 100 seeds weight. Main Findings: Higher magnitude of SCA than GCA variance for grain iron and zinc concentration indicated the importance of non-additive gene action in these nutritional traits improvement. Hybrids showed heterosis for agronomic traits and for grain Fe concentration and limited heterosis for grain Zn. Most of the traits showed significant positive heterosis over mid parent value indicating the predominance of dominant gene action except the trait -100 seeds weight. Significant positive midparent heterosis for grain iron (Fe) indicated that there would be an opportunity to exploit heterosis in improving for grain Iron. But for Zn concentration, there is limited possibility for exploitation of heterosis. This study suggested that simple selection will improve plant height and 100-seed weight in sorghum but heterosis breeding is more useful for improving grain yield. While both parents need to be improved for improving grain Zn concentration there is good scope for exploiting heterosis for improving grain Fe concentration in sorghum. Conclusion & Recommendations: We released first biofortified sorghum variety ‘Parbhani Shakti’ (45 ppm Fe and 32 ppm Zn) with higher yield (4 tha-1), higher protein (11.9%) and low phytates content (4.1 mg/100 g) and released in 2018. Biofortified sorghums complements the on-going approaches for combating dietary induced micronutrient malnutrition

Heterosis and combining ability for grain Fe and Zn concentration and agronomic traits in sorghum [Sorghum bicolor (L.) Moench]

Studies on genetics and trait relationships with grain yield and other agronomic traits are critical for improving the micronutrients content in the grain and it forms an effective strategy for breeding bio fortified sorghum. It greatly contributes to addressing micronutrient malnutrition in poor people who are dependent on sorghum as a staple food. Development of hybrids with high grain Fe and Zn and higher yield enables delivery of commercial products that address both food and nutrition while bringing profits to farmers. The present study was aimed at developing suitable breeding strategy and improving breeding products using gene action, heterosis and combining ability analysis for improving the grain Iron (Fe) and Zinc (Zn) concentration and grain yield in sorghum. This study was conducted in Line Tester mating design involving seven parents. A total of 12 new hybrids were developed by mating three lines with four testers. The combining ability of the crosses indicated predominance of dominance variance than additive variance for the agronomic traits such as days to 50% flowering, grain yield, grain Fe and Zn concentrations except for plant height and 100 seed weight. Higher magnitude of SCA than GCA variance for grain iron and zinc concentrations indicated the importance of non-additive gene action in the improvement of nutritional traits. Hybrids exhibited heterosis for agronomic traits and for grain Fe concentration and grain Zn. Most of the traits showed significant positive heterosis over mid parent value indicating the predominance of dominant gene action except the trait 100 seed weight. Significant positive mid-parent heterosis for grain iron indicated that there would be an opportunity to exploit heterosis in improving for grain Fe. But for Zn concentration, there is a limited possibility for exploitation of heterosis. This study suggested that simple selection will improve plant height and 100 seed weight in sorghum but heterosis breeding is more useful for improving grain yield. While both parents need to be improved for improving grain Zn concentration, there is good scope for exploiting heterosis for improving grain Fe concentration in sorghum

Doubling grain Fe and Zn concentration in sorghum to combat the micronutrient malnutrition in sorghum eating populations

Dietary induced micronutrient malnutrition (MNM) is one of the greatest global challenges of our times and India has largest number of malnourished people globally. Sorghum is among the major staples and a cheapest sources of micronutrients therefore, biofortification of sorghum is of high priority. From screening of more than 4000 accessions and breeding lines we identified promising donors for Fe and Zn and established the genetic control. Fe and Zn are quantitatively inherited. While grain Zn in predominantly under additive gene control, non-additive gene actions also has role in controlling grain Fe. To develop hybrids with high Fe and Zn both parents should have high Fe and Zn. We demonstrated the prediction of F1 hybrid performance based on mid-parental value for Fe and Zn. Both Fe and Zn are positively correlated (r=0.6 to 0.8) and simultaneous improvement for Fe and Zn is feasible. Using RIL population sorghum genetic map was constructed with 2,088 markers (1148 DArTs, 927 DArTSeqs and 13 SSRs) covering 1355.52 cM with an average marker interval of 0.6cM. Forty-seven QTLs (individual) and 7 QTLs (across) environments with small maineffect and 21 co-localized QTLs for Fe and Zn were identified

Identification of QTLs and candidate genes for high grain Fe and Zn concentration in sorghum [Sorghum bicolor (L.)Moench]

Sorghum is a major food crop in the semi-arid tropics of Africa and Asia. Enhancing the grain iron (Fe) and zinc (Zn) concentration in sorghum using genetic approaches would help alleviate micronutrient malnutrition in millions of poor people consuming sorghum as a staple food. To localize genomic regions associated with grain Fe and Zn, a sorghum F6 recombinant inbred line (RIL) population (342 lines derived from cross 296B PVK 801) was phenotyped in six environments, and genotyped with simple sequence repeat (SSR), DArT (Diversity Array Technology) and DArTSeq (Diversity Array Technology) markers. Highly significant genotype environment interactions were observed for both micronutrients. Grain Fe showed greater variation than Zn. A sorghum genetic map was constructed with 2088 markers (1148 DArTs, 927 DArTSeqs and 13 SSRs) covering 1355.52 cM with an average marker interval of 0.6 cM. Eleven QTLs (individual) and 3 QTLs (across) environments for Fe and Zn were identified. We identified putative candidate genes from the QTL interval of qfe7.1, qzn7.1, and qzn7.2 (across environments) located on SBI-07 involved in Fe and Zn metabolism. These were CYP71B34, and ZFP 8 (ZINC FINGER PROTEIN 8). After validation, the linked markers identified in this study can help in developing high grain Fe and Zn sorghum cultivars in sorghum improvement programs globally

Delivering bioavailable micronutrients through biofortifying sorghum and seed chain innovations

Micronutrient malnutrition, particularly among women and children, is one of greatest global challenges of our times and the national Governments and international organizations are following various approaches to combat it. Biofortification –increasing the micronutrient density in edible plant parts by genetic means, is one of the cost-effective and sustainable methods to address the micronutrient malnutrition. Sorghum is one of the major staples globally and it meets more than 50% micronutrient requirements of low-income group populations in predominantly sorghum eating areas. We developed biofortified sorghums with elevated levels of grain Fe and Zn combined with higher grain yield possessing farmer-preferred grain and stover traits. The first biofortified sorghum cultivar ‘Parbhani Shakti’ was released in India in 2018, which, besides high Fe and Zn, has higher protein content and lower phytates content. An innovative ‘Seed Consortium’ was built to take this variety to the farmers in shortest possible time to benefit the farmers and consumers. Multi-stakeholder partnership was the key in this endeavour and Indian NARS, farmers, public sector seed organisations, media and Government played a key role along with ICRISAT