TAXONOMY AND GERMPLASM RESOURCES

The genus Gossypium includes 4 different domesticated species: New World allopolyploids G. hirsutum and G. barbadense (2n=52); Old World diploids G. arboreum and G. herbaceum (2n = 26). The diversity is dwarfed by the entire genus, whose 49 species have a range encompassing most tropical and subtropical regions of the world. The wild species of cotton represent an ample genetic repository for potential exploitation by cotton breeders of the world. Primary, secondary, and tertiary germplasm pools provide a convenient way to classify germplasm in terms of its relative genetic accessibility and utility. Genetic accessibility of plant materials contained within the cotton germplasm collection is related to the classification of the genus. Germplasm pools are categorized by genome with the primary pool comprising the cultivated and wild tetraploid species; the secondary pool comprising the A, B, F and D genomes; and the tertiary pool comprising the C, E, G, and K genomes. Germplasm is useful in cotton improvement to the extent that it is available. Curatorial activities are focused on acquisition, maintenance, and distribution to preserve the broadest possible natural variability of Gossypium as a resource for efforts to modify and improve cotton cultivars. The collection maintains over 6,700 seed accessions of Gossypium species and represents genetic capital from 101 countries or jurisdictions. Transfer of desirable characters from exotic intraspecific and interspecific sources is documented and shows that introduction of desirable germplasm into agronomically acceptable cotton cultivars is an ongoing and dynamic enterprise. Sources of specific resistances have been found from a variety of germplasm sources and exploited by diverse cotton improvement programs.[1]


PANOMICS meets germplasm

Genotyping-by-sequencing has enabled approaches for genomic selection to improve yield, stress resistance and nutritional value. More and more resource studies are emerging providing 1000 and more genotypes and millions of SNPs for one species covering a hitherto inaccessible intraspecific genetic variation. The larger the databases are growing, the better statistical approaches for genomic selection will be available. However, there are clear limitations on the statistical but also on the biological part. Intraspecific genetic variation is able to explain a high proportion of the phenotypes, but a large part of phenotypic plasticity also stems from environmentally driven transcriptional, post-transcriptional, translational, post-translational, epigenetic and metabolic regulation. Moreover, regulation of the same gene can have different phenotypic outputs in different environments. Consequently, to explain and understand environment-dependent phenotypic plasticity based on the available genotype variation we have to integrate the analysis of further molecular levels reflecting the complete information flow from the gene to metabolism to phenotype. Interestingly, metabolomics platforms are already more cost-effective than NGS platforms and are decisive for the prediction of nutritional value or stress resistance. Here, we propose three fundamental pillars for future breeding strategies in the framework of Green Systems Biology: (i) combining genome selection with environment-dependent PANOMICS analysis and deep learning to improve prediction accuracy for marker-dependent trait performance; (ii) PANOMICS resolution at subtissue, cellular and subcellular level provides information about fundamental functions of selected markers; (iii) combining PANOMICS with genome editing and speed breeding tools to accelerate and enhance large-scale functional validation of trait-specific precision breeding.[2]


The Quest for Tolerant Germplasm

With arable land largely occupied with agricultural production, eyes are directed toward marginal lands where special problems confront agriculturists. Potential food scarcity is motivating scientists and farmers to seek new crops or new cultivars of old crops that can tolerate these problems. Many scientists and nonscientists are involved in the quest for tolerant germplasm. Tolerance to marginal habitats may open the last frontiers for agricultural development to feed and clothe the growing numbers of hungry people. Some obscure economic plants are particularly interesting because of tolerance to certain stresses, enabling them to flourish in marginal habitats. Among such obscure economic species, and their relatives, one might collect germplasm for stress resistance. Good ecological data are rarely associated with yield data on economic plants. Too often detailed ecological data relate to a long list of noneconomic species or extremely detailed data relate to a single commodity crop.[3]


Genetic Diversity Studies in Maize (Zea mays L.) Germplasm from India

In the present investigation D² values ranged from 36.84 to 369.02 and 40 genotype comprising 38 inbreds and 2 hybrids are grouped into seven and two clusters respectively. Among the clusters with inbred lines the cluster I with 16 inbreds emerged as dominating cluster followed by cluster III with 11 inbreds, cluster IV with 5 inbreds, cluster V with 3 inbreds and cluster II, VI, VIII were monogenotypic. The character grain yield per plant (46.15%) was the maximum contributor towards divergence followed by ear head height (37.69%), 100 grain weight (6.41%), and plant height (3.85%). On the basis of inter cluster distances, cluster means, per se performance observed in the present study the five genotypes viz Hyd 08R-2374-1, Hyd 08R-2614-2, GPM-320, GPM-35, and Hyd 08R-864-7 were found to be superior genotypes for further breeding programme.[4]


Evaluation of Rice Germplasm for Resistance against Pyricularia oryzae the Cause of Rice Leaf Blast

Rice blast caused by Pyricularia oryzae is one of the most important diseases in rice growing areas of the world. Fifty two rice genotypes including one susceptible check, Basmati C-622, were evaluated to find out new sources of resistance and assess their diversity based on the reactions against P. oryzae. The test genotypes were evaluated against leaf blast after three weeks of inoculation by following the standard evaluation system for rice introduced by the International Rice Research Institute, Philippines. Diversity of the 52 genotypes was also assessed based on blast symptoms. Moderately resistant reactions were observed with genotypes KSK-470, KSK-463, KSK-460, PK 8685-5-1-1-1, KSK-462, KSK-474, PK 3810-30-1, KSK-471 and KSK-472. The 52 genotypes were grouped in 4 clusters. The grouping of some genotypes in same cluster is based on their similar reaction against leaf blast. The results of this study can be useful for selecting suitable genotypes for the development of blast-resistant rice varieties through hybridization.[5]


Reference

[1] Percival, A.E., Wendel, J.F. and Stewart, J.M., 1999. Taxonomy and germplasm resources. Cotton: Origin, History, Technology, and Production. WC Smith and JT Cothren eds. John Wiley and Sons, Inc., New York, NY.

[2] Weckwerth, W., Ghatak, A., Bellaire, A., Chaturvedi, P. and Varshney, R.K., 2020. PANOMICS meets germplasm. Plant biotechnology journal, 18(7), pp.1507-1525.

[3] Duke, J.A., 1978. The quest for tolerant germplasm. Crop tolerance to suboptimal land conditions, 32, pp.1-61.

[4] Patil, S.M., Jakhar, D.S., Kumar, K. and Meena, S., 2017. Genetic diversity studies in maize (Zea mays L.) germplasm from India. International Journal of Plant & Soil Science, pp.1-6.

[5] Qudsia, H., Riaz, A. and Akhtar, M., 2017. Evaluation of rice germplasm for resistance against Pyricularia oryzae the cause of rice leaf blast. Asian Research Journal of Agriculture, pp.1-6.