No abstract

Sorghum [Sorghum bicolor (L.) Moench] is a very important crop in the arid and semi-arid tropics of India and African subcontinent. In the process of release of new cultivars using multi-location data major emphasis is being given on the superiority of the new cultivars over the ruling cultivars, while very less importance is being given on the genotype 9 environment interaction (GEI). In the present study, performance of ten Indian hybrids over 12 locations across the rainy seasons of 2008 and 2009 was investigated using GGE biplot analysis. Location attributed higher proportion of the variation in the data (59.3-89.9%), while genotype contributed only 3.9-16.8% of total variation. Genotype 9 location interaction contributed 5.8-25.7% of total variation. We could identify superior hybrids for grain yield, fodder yield and for harvest index using biplot graphical approach effectively. Majority of the testing locations were highly correlated. 'Which-wonwhere' study partitioned the testing locations into three mega-environments: first with eight locations with SPH 1606/1609 as the winning genotypes; second megaenvironment encompassed three locations with SPH 1596 as the winning genotype, and last mega-environment represented by only one location with SPH 1603 as the winning genotype. This clearly indicates that though the testing is being conducted in many locations, similar conclusions can be drawn from one or two representatives of each mega-environment. We did not observe any correlation of these mega-environments to their geographical locations. Existence of extensive crossover GEI clearly suggests that efforts are necessary to identify location-specific genotypes over multi-year and -location data for release of hybrids and varieties rather focusing on overall performance of the entries.

Journal articleIFPRI3; ISIEPTDP

Polymorphism over approximately 26 kb of DNA sequence spanning 22 loci and one region distributed on chromosomes 1, 2, 3 and 4 was studied in 30 accessions of cultivated rice, Oryza sativa, and its wild relatives. Phylogenetic analysis using all the DNA sequences suggested that O. sativa ssp. indica and ssp. japonica were independently domesticated from a wild species O. rufipogon. O. sativa ssp. indica contained substantial genetic diversity (pi = 0.0024), whereas ssp. japonica exhibited extremely low nucleotide diversity (pi = 0.0001) suggesting the origin of the latter from a small number of founders. O. sativa ssp. japonica contained a larger number of derived and fixed non-synonymous substitutions as compared to ssp. indica. Nucleotide diversity and genealogical history substantially varied across the 22 loci. A locus, RLD15 on chromosome 2, showed a distinct genealogy with ssp. japonica sequences distantly separated from those of O. rufipogon and O. sativa ssp. indica. Linkage disequilibrium (LD) was analyzed in two different regions. LD in O. rufipogon decays within 5 kb, whereas it extends to approximately 50 kb in O. sativa ssp. indica.

Most traits of interest to medical, agricultural and animal scientists show continuous variation and complex mode of inheritance. DNA-based markers are being deployed to analyse such complex traits, that are known as quantitative trait loci (QTL). In conventional QTL analysis, F2, backcross populations, recombinant inbred lines, backcross inbred lines and double haploids from biparental crosses are commonly used. Introgression lines and near isogenic lines are also being used for QTL analysis. However, such populations have major limitations like predominantly relying on the recombination events taking place in the F1 generation and mapping of only the allelic pairs present in the two parents. The second generation mapping resources like association mapping, nested association mapping and multiparent intercross populations potentially address the major limitations of available mapping resources. The potential of multiparent intercross populations in gene mapping has been discussed here. In such populations both linkage and association analysis can be conductted without encountering the limitations of structured populations. In such populations, larger genetic variation in the germplasm is accessed and various allelic and cytoplasmic interactions are assessed. For all practical purposes, across crop species, use of eight founders and a fixed population of 1000 individuals are most appropriate. Limitations with multiparent intercross populations are that they require longer time and more resource to be generated and they are likely to show extensive segregation for developmental traits, limiting their use in the analysis of complex traits. However, multiparent intercross population resources are likely to bring a paradigm shift towards QTL analysis in plant species.

Sorghum [Sorghum bicolor (L.) Moench] is a drought‐resilient crop, grown extensively in semiarid tropics of the world. To understand the scenario of sorghum cultivation across the world, trends in area and yield gain and associated changes in yield stability were analyzed in the top 10 sorghum‐producing countries from 1970 to 2009. Asian countries and the United States recorded a large drop in harvested area. Grain yield levels increased substantially in all the countries except Sudan. Relative to yield level of 1970, sorghum productivity increased annually at 0.96% yr−1 across the top 10 countries analyzed. China (100.9 kg ha−1 yr−1) and Nigeria (48.6 kg ha−1 yr−1) experienced phenomenal yield gain before reaching a plateau. Overall yield gain was not associated with increased yield stability in a majority of countries except Ethiopia. In fact, in China and India (post‐rainy‐season sorghum), the yield variability increased over time. Genetic gain for grain yield over years in the Indian sorghum improvement program was prominent in rainy‐season hybrid trials (18.5 kg ha−1 yr−1), whereas both in post‐rainy‐season hybrid and varietal trials it was insignificant. Much progress in rainy‐season variety trials after 1985 was not observed. Across years in India, the gap between potential and farm yield declined 0.32% yr−1 among rainy‐season cultivars and 0.46% yr−1 among post‐rainy‐season cultivars. The analysis reveals that though substantial progress has been made towards yield gain, this was not represented by increased production because of extensive loss of the sorghum area to other remunerative crops.

No abstract

Callus induction and regeneration ability of five elite maize inbred lines, CM 111, CM 117, CM 124, CM 125 and CM 300 were investigated using 14-day-old immature embryos as explants. Genotype, medium, source of auxin and their concentrations influenced induction of callus. Explants grown on Murashige and Skoog (MS) medium supplemented with 2,4-dichlorophenoxyacetic acid at 1 mg l -1 showed the highest frequency of callusing. Among all the media tested, explants grown on N6 medium gave the highest frequency of organogenic callus. Moreover, N6 supplemented with Dicamba promoted higher callus response in terms of both frequency of induction as well as quality, compared to N6 medium with 2,4-D. N6 supplemented with 2 mg l -1 Dicamba induced the highest frequency of organogenic callus. Among the five genotypes tested, CM 124, CM 125, and CM 300 gave the best callus. Explants of both CM 124 and CM 300 incubated on MS medium supplemented with 1 mg l -1 benzyladenine and 0.5 mg l -1 indole acetic acid promoted the highest frequency of shoot induction. Though CM 124 induced higher percentage of shoot formation than CM 300, the mean number of developed shoots per explant was higher for CM 300. The highest frequency of root formation was observed when shoots were grown on MS medium supplemented with 2 mg l -1 naphathalene acetic acid. Percentage of regenerated plants ranged from 54 to 66.