K. N. Ganapathy

Morphological and molecular diversity reveal wide variability among sorghum Maldandi landraces from India

Maldandi is a popular sorghum variety for post-rainy or rabi cultivation in southern and central states of India, which is predominantly used for food purpose. Over time many landraces have been collected from these states which have vernacular connection with Maldandi. Genetic diversity among 82 Maldandi landraces, collected from such geographical regions was evaluated using both morphological (quantitative and qualitative) and SSR markers. In general, both morphological and SSR diversity revealed wide variability among the accessions studied. Euclidean distances based on 17 quantitative traits classified the accessions into two major clusters with two out groups, while the 19 qualitative traits clustered the accessions in one major cluster with six out groups. Sixteen out of 20 (80%) SSR markers detected polymorphism among the accessions with average PIC value of 0.36. Un-weighted neighbor joining clustering grouped the accessions into three clusters with 46, 16 and 17 accessions, respectively throwing three outliers. Average similarity coefficients of 0.62 and 0.34 based on morphological (qualitative) and SSR data indicated presence of wide variability among the Maldandi landraces. The standard check, M 35–1 (a selection from the original Maldandi) could not be differentiated from EP 98, LG 2, LG 10, IS 4509 and IS 40791 based on qualitative data alone, while EP 54 and IS 33839 were indistinguishable from M 35–1 solely using SSR markers. Either of the dendrogram threw unique grouping patterns with some identity. Thirteen promising Maldandi accessions selected based on field performance as well as morphological and molecular diversity could be used in the rabi improvement programme. SSR markers combined with morphological traits may effectively be used for designing breeding strategy and management of biodiversity and conservation of Maldandi genetic resources.

History of post-rainy season sorghum research in India and strategies for breaking the yield plateau

Post-rainy (rabi) sorghum grows under residual soil moisture conditions and is important for food and fodder security especially during dry seasons in semi-arid regions of India. Unlike rainy sorghum being dominated with hybrids, post-rainy sorghum growing areas are cultivated with varieties especially landrace selections. Much of the area is covered by M 35-1, a landrace selection developed seven and half decades ago. Post-rainy sorghum research did not receive much emphasis until nineties and the varieties or hybrids bred and released could not match M 35-1 in yield or quality. Some progress has been made recently with the release of varieties for specific soil depths viz., shallow, medium and deep soils. Efforts made to develop hybrids with wider adaptability to varied production environments did not fetch much success. The hybrids lacked significant heterosis, grain quality and shoot fly resistance comparable to M 35-1. Also, low temperatures at anthesis caused poor seed settings in hybrids. Strategic research is required to develop new varieties and hybrids for post-rainy season to break the yield plateau.

Genetic association and frequency distribution in segregating generations derived from pigeonpea crosses

Correlation and presence of genetic interactions was studied using F2 and F3 generations in three pigeonpea crosses for yield and its component traits. Most of the characters studied were positively skewed and were being governed by several genes indicating quantitative inheritance. Variance, skewness and kurtosis have also indicated that homozygosity has increased over the generation in pigeonpea crosses. Cross BRG 1 x ICP 8863 was found better than other two crosses (TTB 7 x ICP 8863 and TTB 7 x ICPL 87119) in providing high yielding segregants displaying parental diversity. Seed yield and other associated characters such as plant height and number of pods per plant had complementary gene action with other genes governing these characters. Yield increase is possible by following rigid selection for yield and its component characters. A shift in correlation coefficients between the generations was recorded which is likely to be attributed to difference in gene complementation of linkage blocks and an indication of unstable nature of breeding population.

Sorghum for Health and Business

Sorghum is the fifth most important cereal crop cultivated globally on an area of about 40.51 million ha. Grain sorghum is vital food crop for millions especially for the people in the arid and semi-arid parts of Africa and Asia. In developed countries, the crop is majorly used as animal or poultry feed. With continuous increase in the human population and decreasing agricultural resources especially irrigation water, sorghum represents important crop for future as it can produce optimum yield under drought and other stress conditions. The major challenges facing sorghum research and development is to deliver technologies that will enable the agricultural sector to affect transformation of “subsistence farming” to sustainable and market oriented. This can be achieved through reassessment of crop research in terms of current and future demand, resolving specific production constraints by improving productivity, development of post-harvest processing and value-addition technologies, creation of demand, marketing strategies and policies that would result in additional farm income and employment without sacrificing overall goal of attaining sustainable food and nutritional security.

Identification of AFLP markers linked to Fusarium wilt disease in pigeonpea [Cajanus cajan (L.) Millsp.]

An experiment was conducted to identify markers linked to Fusarium wilt disease resistance, Parents namely TTB 7 and ICP 8863 were screened using 151 SSRs markers and 16 AFLP primer combinations. Parental screening revealed five SSR primers and 12 AFLP primer combinations polymorphic between parents. Bulk segregant analysis identified five AFLP primer combinations generating seven markers polymorphic between resistant and susceptible bulks while, none of the SSR markers were polymorphic. This indicates that, these markers are putatively linked to wilt disease. Screening of F2 segregating population of cross TTB 7 x ICP 8863 with these putatively linked markers revealed four markers (E-AAT/M-CTG850, ETCG/M-CTT650, E-TCG/M-CTA730 and E-TCG/M-CTT230) which segregated in 3:1 mendelian pattern. Simple linear regression performed on these four markers had identified two markers namely E-TCG/M-CTT650 and E-TCG/M-CTA730 linked to disease.

Genetic diversity in sorghum mini-core and elite rainy and post-rainy genotypes of India

Knowledge on genetic diversity is necessary to determine the relationships among the genotypes, which allow the selection of individual accessions for crop breeding programmes. The present study aimed at assessing the extent and pattern of genetic diversity within a set of 251 sorghum genotypes using SSR markers. A total of 393 alleles were detected from the 251 genotypes, with the number of alleles ranging from 2 (Xcup11) to 24 (Sb5-206) and an average of 10.07 alleles per primer pair. Pairwise Wright’s FST statistic and Nei’s genetic distance estimates revealed that the race and geographical origin were responsible for the pattern of diversity and structure in the genetic materials. In addition, the analysis also revealed high genetic differentiation between the rainy and post-rainy sorghum groups. Narrow diversity was observed among the different working groups in the rainy (restorers and varieties) and post-rainy (varieties and advanced breeding lines) sorghum groups. Neighbour-joining and STRUCTURE analysis also classified 44 elite lines broadly into two distinct groups (rainy and post-rainy). However, limited diversity within the rainy and post-rainy sorghum groups warranted an urgent need for the utilization of diverse germplasm accessions for broadening the genetic base of the Indian breeding programme. The diverse germplasm accessions identified from the mini-core accessions for utilization in breeding programmes are discussed.

Genetic appraisal of F2 generation of Dolichos bean for yield and yield attributing traits

In the present study F 2 generation was evaluated for yield and yield contributing traits to understand genetic variability and association among yield contributing traits in dolichos bean. High phenotypic and genotypic coefficient of variability (PCV and GCV) was observed for first flowering initiation and total seed weight per plant in both the crosses. The differences between PCV and GCV values were narrow for all the traits studied, which indicates the low level of environmental influence in the expression of these traits. High heritability and GAM was noticed for all the traits studied in both the crosses indicating that influence of additive gene effects in expression of these characters. Skewness and kurtosis indicate that seed weight per plant (SW/P) was governed by complementary gene interaction with fewer numbers of dominant genes. Hence, SW/P could be increased either by increasing 100SW or seeds per pod among the crosses studied.

Comparative Genomics of Cereal Crops: Status and Future Prospects

Cereals are members of grass family and play an important role in providing food security to billions of people across the globe since the beginning of agriculture. Cereal crops differ considerably from each other in terms of morphology, adaptation and genetic architecture. This has motivated researchers across the world to study their evolution, genetics and development. During the last few decades, phenomenal progress in genomics research has paved the way for comparative genomic studies across crop species, especially the cereals due to their economic importance. These studies together have revealed a good level of conservation across cereals both at macro and micro level. However, most of the comparative studies in cereals prior to genome sequencing projects have been performed at genetic map level. Large-scale genome sequencing projects during the beginning of the twenty-first century, especially in rice, sorghum, maize, barley, wheat and foxtail millet, led to better understanding of the conservations of genes/genomic regions at sequence level. This chapter reviews the status of cereal comparative genomics prior to genome sequencing and progress post-genome sequencing of major cereals. The genomic organization of major cereals has been discussed in detail. The chapter also describes the distinguishing features and the mechanism of evolution of cereal genomes. The advancement in genome sequencing technologies, especially the next-generation sequencing technologies and its effectiveness in performing genomic studies across crops, is also discussed. The various genomic tools, databases and resources for performing comparative genomic studies are reviewed here. The chapter presents the opportunities on how the knowledge gained from comparative genomics of cereals can be used for gene discovery programmes, functional genomics and subsequently genetic improvement of cereal crops.