Sugarcane brown rust, caused by Puccinia melanocephala, is one of the main diseases of sugarcane in China. The identification and discovery of new resistance genes have important theoretical and practical significance for preventing outbreaks of brown rust and ensuring the sustainable production of sugarcane. To screen for polymorphic simple-sequence repeat (SSR) molecular markers for localization of brown rust resistance genes, we used two populations that are suitable for genetic linkage map construction and mapping of new resistance genes to construct resistant and susceptible genetic pools. We then screened 449 pairs of primers to identify polymorphic SSR markers in the parental lines and the resistant/susceptible genetic pools. The results showed that 25 pairs of primers directed amplification of polymorphic DNA fragments between the parents of the cross combination ‘Yuetang 03-393’ × ‘ROC 24’, and 16 pairs of primers amplified polymorphic fragments between the parents of the cross combination ‘Liucheng 03-1137’ × ‘Dezhe 93-88’. Four pairs of primers (SMC236CG, SCESSR0928, SCESSR0636 and SCESSR2551) amplified polymorphic DNA fragments between the parental lines and the resistant/susceptible genetic pools in ‘Yuetang 03-393’ × ‘ROC 24’. The results of this study will establish a solid foundation for the mapping of new brown rust resistance genes, genetic linkage map construction and the development of closely-associated molecular markers in sugarcane.

Cotton fibre yield and quality are markedly influenced by drought and high-temperature stress. We examined the traits of the leaf stomata in 39 cotton genotypes subjected to exogenous phytohormone abscisic acid (ABA) signalling, electrolyte leakage under 40°C thermal stress, and relative GhHsfA, GhbZIP and GhHSP70 expression levels under two treatments. Stomatal density and area ranged from 66 to 182/mm2 and 663 to 1305 μm2, respectively. Under exogenous ABA signalling, the changes in stomatal aperture (ΔSAp) were in the range of 2.5–31.2%; ΔSAp and relative GhHsfA, GhbZIP and GhHSP70 expression levels were significantly correlated, respectively. Electrolyte leakage increased unequally among cotton genotypes after heat stress. The changes in electrolyte leakage (ΔEL) and relative GhHsfA, GhbZIP and GhHSP70 expression levels were very strongly correlated, respectively. Their relative expression levels could be used as references for the rapid identification of stress-tolerant cotton strains. Cluster analysis of the 39 cotton genotypes indicated that Xinluzao36, Shiyang1, shinong98-7 and Zhongmiansuo293 are heat- and drought-resistant. We integrated both analysis of physiological parameters and molecular methods to identify cotton varieties with the drought and heat tolerance, in order to provide a reference for the selection of materials and methods for the research and production of cotton.

Iron walnut, Juglans sigillata Dode, restricted to southwestern China, has its centre of distribution in Yunnan Province which has a varied climate, geography and rich plant diversity. Yunnan contains abundant J. sigillata germplasm. In this study, a provincial-scale set of walnut germplasm resources (14 populations comprising 1122 individuals) was evaluated for genetic diversity based on 20 simple sequence repeat (SSR) loci. The number of SSR alleles per locus ranged from 7 to 27, with an average of 17.55. Mean allelic richness and mean private allelic richness ranged from 3.40 to 4.62 and 0.11 to 0.36, with average of 3.93 and 0.30, respectively. Expected heterozygosity (He) varied from 0.26 to 0.78, with an average of 0.57. Polymorphism information content ranged from 0.22 to 0.79, with an average of 0.57. Genetic differentiation (FST) was 0.05, indicating that only 5% of total genetic variability was inter-populational, a finding supported by an analysis of molecular variance and STRUCTURE analysis. Relatively high gene flow (Nm = 6.70) was observed between populations. A unweighted pair-group method with arithmetic analysis classified the 14 populations into two major groups. Mantel testing uncovered a significant correlation between geographic distance and genetic distance (r = 0.33, P = 0.04). Overall, the research revealed a moderately high level of genetic diversity in the germplasm and low genetic differentiation among populations, which showed great potential for further development and exploitation of this resource.

Cordia sinensis, locally known as ‘Goondi’ in India, is an underexploited multipurpose fruit species found in hot arid regions that is well adapted to drought, salt and hot conditions. The present study was undertaken to collect fruit samples from different locations in the Kachchh region of Gujarat, India, and to determine their field establishment for characterization, conservation and utilization. The maximum distribution of the species was observed in Bhuj (45%) and Mandvi (25%). Field boundaries (35%) and scrub forests (30%) had greater frequencies, whereas backyards had rarer frequencies (10%). The species most commonly occurred on levelled topography (60%) with a soil pH in the range of 8–8.5 (63%). Morphological data of three-year-old plants in the field gene bank showed a maximum coefficient of variation in the number of leaves per plant (66.6), followed by the number of branches per plant (45.62) and collar diameter (27.69). Wide variations were recorded in plant height (121.67–212 cm), spread (118–223 cm2) and the number of branches per plant (6–24.33). Specific accessions were identified for fodder (CBCG-12, CBCG-13 and CBCG-16), early flowering and fruiting (CBCG-12, CBCG-13 and CBCG-14), easier propagation by seeds (CBCG-12 and CBCG-13) and salt tolerance (CBCG-15 and CBCG-16). Preliminary findings and information provided about this species' utilization and other aspects might be useful for future research on its domestication, sole plantation and conservation aspects, improving the exploitation of this species by present and future generations.

Bread wheat (Triticum aestivum) is one of the most important food crops in the world. Its physiological and morphological traits are closely related to yield. Therefore, it is generally important to discover the genomic region associated with these traits. In this research, associations between 21 simple sequence repeat (SSR) markers and 10 inter-simple sequence repeat (ISSR) markers with some traits related to root structure at the embryonic and seedling stages and also some agromorphological traits at the whole plant stage were evaluated on a set of 102 wheat genotypes. A highly significant coefficient of variation among different genotypes was observed in all measured traits. A high level of polymorphism with SSR and ISSR markers was obtained. Genetic structure analysis revealed two distinct subpopulations. Significant correlations were found between genomic markers and evaluated traits. A total of nine markers, including four SSR markers in 1A, 3A, 5A and 2B chromosomal regions and five different ISSR markers were related to the studied traits. Several molecular markers were significantly associated with more than one phenotypic trait, suggesting the possible presence of pleiotropic or indirect effects. The phenotypic variation justified by these alleles ranged from 4 to 15%. Obtained genetic information can be targeted for further validation and genetic analysis in the relevant populations or other breeding sets.

Asian palmyrah palm (Borassus flabellifer L.) is a multipurpose, economically important tree widely distributed in the Indian subcontinent and Southeast Asia. The multifaceted uses (~800 uses) of the tree as food, wood and medicine make it a viable industrial crop. However, the dioecious nature of the tree coupled with long juvenile phase (12–20 years to initiate flowering), long stature and considerable variations in the productivity of male and female trees necessitates the application of new biotechnological tools for crop improvement. This review provides comprehensive information on the extent of genetic diversity of the crop, problems associated with palmyrah cultivation along with its multifaceted application and research gaps to be addressed for the effective utilization and conservation of palmyrah palm genetic resources.

Knowledge of the genetic diversity and relationships among maize inbred lines can facilitate germplasm management and plant breeding programmes. The study investigated the level of genetic diversity among S6 lines developed from a tropical-adapted shrunken-2 (sh-2) maize population and their relationship with normal endosperm tropical inbred lines of known heterotic groups. Ninety-one sh-2 maize inbred lines (UI1-UI91) developed in the University of Ibadan super-sweet Maize Breeding Programme were genotyped at 30 simple sequence repeat (SSR) loci, alongside five normal endosperm maize inbred lines viz. TZi3, TZi4, TZi10, TZi12 and TZi15, four of which belong to two heterotic groups. Twenty-three SSR markers were polymorphic and detected a total of 61 alleles, with a range of 2–7 and an average of 2.65 alleles per locus. The polymorphic information content ranged from 0.12 in bnlg1937 to 0.77 in phi126, with an average of 0.36. The gene diversity (He) averaged 0.43. Cluster analysis resulted in five groups consisting of 16, 36, 17, 23 and 3 inbred lines, with one sh-2 line ungrouped. TZi 12 and TZi 15, both of which are of the same heterotic group, clustered with TZi 3 of another heterotic group. Considerable genetic diversity exists among the 96 inbred lines. Only two of the five normal endosperm lines shared clusters with the sh-2 lines. The clustering of the normal endosperm inbred lines is not related to their established heterotic patterns. Inbred lines in two clusters offer the possibility of guiding the exploitation of heterosis among the sh-2 lines.

Genetic resources are of paramount importance for developing improved crop varieties, particularly for biotic and abiotic stress tolerance. Spot blotch (SB) is a destructive foliar disease of wheat prevalent in warm and humid regions of the world, especially in the eastern parts of South Asia. For the management of this disease, the most effective measure is the development of resistant cultivars. Thus, the present investigation was carried out to confirm SB resistance in 200 germplasm accessions based on phenotypic observations and molecular characterization. These elite breeding lines obtained from the International Centre for Maize and Wheat Improvement, Mexico, are developed deploying multiple parentages. These lines were screened for SB resistance in the field under artificially created epiphytotic conditions during 2014–15 and 2015–16 along with two susceptible checks (CIANO T79 and Sonalika) and two resistant checks (Chirya 3 and Francolin). Eighty-two out of 200 germplasm accessions were found resistant to SB and resistance in these lines was confirmed with a specific SSR marker Xgwm148. Three accessions, VORONA/CNO79, KAUZ*3//DOVE/BUC and JUP/BJY//URES/3/HD2206/HORK//BUC/BUL were observed possessing better resistance than the well-known SB-resistant genotype Chirya3. These newly identified resistant lines could be used by wheat breeders for developing SB-resistant wheat varieties.

Guinea grass (Megathyrsus maximus Jacq.) is an important forage species in vast rangelands/grasslands of India and several tropical countries owing to its high biomass yield, good nutritional quality and wide adaptation. Evaluation of the existing natural variation and selection of desirable genotypes is the most plausible breeding method for this apomictic and polyploid grass. Developing a core sub-set to narrow down the number of germplasm required for future genetic studies is also pertinent. The present study involved characterization of 152 diverse M. maximus germplasm representing collections from different agro-ecological zones of India as well as those procured from Africa and Brazil; and development of a core sub-set. Nineteen metric, seven non-metric and nine nutritive traits together established the presence of wide variability among the genotypes. Clustering of the genotypes resulted in eight distinct clusters. The largest cluster included genotypes from Ethiopia, north India, north-western India, south India and north-eastern hill region, thus represented the highest diversity. Eleven of the total 26 Ethiopian genotypes clustered together. Non-metric morphological traits effectively differentiated the genotypes, and were associated with nutritional quality also. Genotypes which flowered once in a year showed slightly better crude protein and digestibility. The clusters were further sub-clustered and representatives were selected to develop the core sub-set of 23 genotypes comprising 20 indigenous and three exotic accessions. Comparison of the range of diversity and mean value for traits as obtained in the core sub-set and that in the total germplasm indicated successful capturing of maximum diversity in the core sub-set.