Exploring Plant Genetic Variations with Morphometric and Molecular Markers

For centuries, crop improvement has served as the basis of food security of ever increasing human population. Though vast germplasm collections are available; their exploitation for crop improvement still depends upon efficient assessment of genetic diversity. Genetic variability is the key element in adaptation of plants to varying climates. While crops with narrow genetic diversity are vulnerable to stresses. The estimation of extent and pattern of genetic variability is a prerequisite for generating superior varieties. Genetic diversity analysis generates key information to dissect genetic variations in crop germplasm with the help of morphometrical, biochemical and molecular tools. Among these, DNA markers provide a reliable and detailed insight into the similarities and differences among crops. In this chapter, we discuss the applications of phenotypic and molecular markers to probe genetic divergence in crops and present case studies that describe the significance of these tools to characterize sorghum germplasm. Furthermore, we spotlight sorghum biodiversity exploration efforts worldwide and propose future directions.

CHARACTERIZATION OF BROOM SORGHUM ACCESSIONS USING MORPHO-AGRONOMIC DESCRIPTORS

The straw broom production is a traditional and very old activityamong small farmers in Brazil. Much of the straw broom production ismanufactured with native species, which in turn are in the process of beingextinct. The objective of this work was to evaluate the genetic diversity andto characterize one sample of broom sorghum germplasm constituted of 66accessions. The experiment was carried out in Viçosa, MG, in a randomizedblock design with two replicates, being each plot composed of one 5 m row,with 0.7 m spacing, where eight morpho-agronomic traits were evaluated.The studied accessions presented genetic variability for most of the traits.The accessions 2, 7 and 16 presented the lowest plant heights. Regardingstem diameter, accessions 7, 11, and 13 presented the highest values. Asto the number of days from emergence to flowering, the accessions 42, 65,and 66 were the earliest ones. Based on the evaluations carried out, it can beconcluded that accessions 2, 7, 11, 13, 42, 65, and 66 are the most promisingfor new studies and launches.

Elucidating Anthracnose Resistance Mechanisms in Sorghum—A Review

Sorghum (Sorghum bicolor) is the fifth most cultivated cereal crop in the world, traditionally providing food, feed, and fodder, but more recently also fermentable sugars for the production of renewable fuels and chemicals. The hemibiotrophic fungal pathogen Colletotrichum sublineola, the causal agent of anthracnose disease in sorghum, is prevalent in the warm and humid climates where much of the sorghum is cultivated and poses a serious threat to sorghum production. The use of anthracnose-resistant sorghum germplasm is the most environmentally and economically sustainable way to protect sorghum against this pathogen. Even though multiple anthracnose resistance loci have been mapped in diverse sorghum germplasm in recent years, the diversity in C. sublineola pathotypes at the local and regional levels means that these resistance genes are not equally effective in different areas of cultivation. This review summarizes the genetic and cytological data underlying sorghum’s defense response and describes recent developments that will enable a better understanding of the interactions between sorghum and C. sublineola at the molecular level. This includes releases of the sorghum genome and the draft genome of C. sublineola, the use of next-generation sequencing technologies to identify gene expression networks activated in response to infection, and improvements in methodologies to validate resistance genes, notably virus-induced and transgenic gene silencing approaches.