No abstract

Sugarcane (Saccharum spp.) has a large complex polyploid genome. Assay of molecular variation in the expressed component of its genome has relevance to the analysis of genetic diversity, variety identification and introgression of agronomically useful genes present in different members of the Saccharum complex. The present study was designed to evaluate single-strand conformational polymorphism (SSCP) as a potential tool to detect genetic variation in the expressed sequence tag (EST) derived microsatellites. Twenty primer pairs obtained from EST libraries and one designed from soluble acid invertase gene sequence were used to characterise 21 clones belonging to four different Saccharum species and 22 sugarcane varieties/genotypes. All the markers, including the two, which were reported monomorphic even at the interspecific level in an automated fragment analysis system in a previous study, could be successfully converted into polymorphic ones using SSCP analysis. A broad range of variation could be revealed by this technique. The Saccharum spp. clones could be grouped into distinct clusters, confirming the species relationships postulated earlier using morphological, biochemical and molecular methods. The polymorphic markers could also differentiate all the 22 sugarcane varieties from each other. This is a first report that demonstrates the usefulness of SSCP technique, in obtaining polymorphic microsatellite markers developed from EST sequences for various genetic and breeding applications, in this polyploid species.

The Indian sugar industry, a significant player in the national economy, has faced many challenges in the course of its journey. The threat posed by the growing pandemic novel corona virus (COVID-19), has been the most recent one and it is impacting sugar industry stakeholders and its integrated industries, not only in India, but all over the world. The entire value chain of the Indian sugar industry, viz., sugarcane, sugar, molasses, ethanol and their subsequent marketing and export, has been adversely affected from the spillover impacts. The major impacts of COVID-19 on Indian sugar industry are discussed.

SUMMARYSorghum [Sorghum bicolor (L.) Moench] grown in India is of two adaptive types: rainy and post-rainy. The post-rainy sorghum is predominantly consumed by humans. While releasing new cultivars through multi-location testing, major emphasis is given to the superiority of new cultivars over existing cultivars, with very little emphasis on the genotype × environment interaction (GEI). To understand the complexity of GEI in post-rainy sorghum testing location trials, the multi-location evaluation data of two post-rainy seasons (2009/10 and 2010/11) under the All India Coordinated Sorghum Improvement Project were analysed. In both years, location explained the highest proportion of total sum of squares followed by the GEI effect and main effect of genotype. Additive main effects and multiplicative interaction (AMMI), stability values (ASV) and genotype + genotype × environment interaction (GGE) instability values recorded high correlation resulting in identification of the best performing cultivars. However, the rank correlations were lower, though still significant. A mixture of crossover and non-crossover GEI was a common occurrence in both years. ‘Which-won-where’ analysis suggested the existence of four possible mega-environments (ME) among post-rainy testing locations, with a few non-informative locations within ME. Mega-environments are characterized by soil type, rainfall pattern and moisture conservation practices. The present study indicated the possibility of reducing the number of test locations by eliminating non-representative highly correlated locations and suggested the need to breed for location-specific genotypes rather than genotypes with wider adaptability.

Genetic dissection of economic traits in sugarcane requires sufficiently informative molecular markers that are currently lacking in this highly valued crop. Through comparative analysis of publicly available expressed-sequence data of sugarcane, sorghum and barley, and the whole rice genome-sequence survey, novel functional markers based on conserved-intron scanning primers (CISP) were developed and evaluated in different accessions across various taxonomic ranks of sugarcane. Polymorphism was moderate (55.2%), whereas 94.7% of the markers developed amplified fragments in selected genotypes. Mean polymorphism information content value was 0.582 (range 0.320–0.715), which was comparable to that with genic microsatellite markers (0.52) but lower than that with EST-SSR (0.73). Genetic-similarity coefficient ranged from 0.39 to 0.95, indicating variable levels of divergence depending on the taxonomic rank assessed. Cluster analysis revealed that the genotypes grouped in accordance with the taxonomical classification of sugarcane, with a relatively good support from a Mantel’s test (r = 0.847) and a moderate bootstrap value (65–89%). The CISP markers reported in the present study have potential utility for genetic-diversity analysis and application in sugarcane-breeding programs.