Evaluation of inbred lines derived from commercial hybrids and their utilization in developing high yielding field corn (Zea mays L.) hybrids

Genetic enhancement and identification of genetically broad-based inbred lines for the development of new hybrids is the pre-requisite for the heterosis breeding. Newly derived 118 inbred lines were evaluated for their morpho-physiological characters in order to identify best suitable male and female parental lines. Total 10 best inbred lines were selected after thorough evaluation of 16 stable inbred lines, identified from the pool of 118 inbred lines. These inbred lines were crossed in line × tester manner, considering three inbred lines as male andrest as female, based on the Specific Combining Ability and General Combining Ability. Hybrids thus obtained were evaluated in two diverse agroclimatic situations and best heterotic hybrids were selected based on their standard heterosis and rank obtained in Duncan's Multiple Range Test analysis. Single location ANOVA for inbred lines and combined ANOVA for hybrids showed that selected inbreds and hybrids were significantly differing from each other. Since, there exists a Genotype × Environment interaction among hybrids, PCA also taken into consideration for giving weight as classification variable for the hybrids. Further, multi-location evaluation of these hybrids is proposed to identify stable hybrids suitable for large scale commercialization

Genetic variability, combining ability and molecular diversity-based parental line selection for heterosis breeding in field corn (Zea mays L.)

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGBackground: The demand of maize crop is increasing day by day, hence to reduce the production and demand gap, there is a need to extract the high yielding parental lines to improve per se yield of the hybrids, which could help to enhance the productivity in maize crops. Methods and results: The present investigation was carried out to select the best medium maturing inbred lines, among a set of 118 inbred lines. Based on the Duncan multiple range test, out of 118 lines, 16 inbred lines were selected on the basis of its high yield per se and flowering time. The molecular diversity was carried out using SSR markers linked to heterotic QTL and up on diversity analysis it classified selected genotypes in to three distinct groups. Among the selected inbred lines, a wider genetic variability and molecular diversity were observed. A total of 39 test crosses were generated after classifying 16 inbred lines in to three testers and thirteen lines (based on per se grain yield and molecular diversity) and crossing them in line × tester manner. Conclusion: Combining ability analysis of these parental lines showed that female parents, PML 109, PML 110, PML 111, PML 114 and PML 116 showed additive effect for KRN and grain yield, whereas male parents, PML 46, and PML 93 showed epistatic effect for KRN and PML 102 showed epistatic effect for grain yield. The generated information in the present investigation may be exploited for heterosis breeding in filed corn. Key messages To tackle the balanced dietary requirement of Indian population; we focused to enhance the productivity of maize hybrids using genetically broad based, elite, diverse inbred lines. Combination of selection criterion, not only augment the productivity but also improves the quality of hybrid/s

Strategic selection of white maize inbred lines for tropical adaptation and their utilization in developing stable, medium to long duration maize hybrids

White maize plays an important role in human diet, especially in traditional crop growing regions of northern hill region, north-eastern states and central-western parts of India. Breeding efforts to enhance the genetic potential of white maize was not so prominent as compared to yellow maize in the country. As a result, genetic base of the material utilized in white maize breeding program in India is very narrow and majorly contains indigenous germplasm and few introductions. Hence, efforts were made to use 365 white maize inbred lines from CIMMYT, Mexico, for breeding program. These new inbred lines were grown at winter nursery center, Indian Institute of Maize Research, New Delhi for its tropical adaptation. After preliminary evaluation, a total 47 inbred lines were selected and evaluated in randomized complete block design with two replications at Regional Maize Research and Seed Production Centre, Begusarai, Bihar, during rabi 2014. Out of this top performing 12 inbred lines viz, CML 47, CML 95, CML 314, CML 319, CML 377, CML 488, CML 494, CML 504, CML 517, CML 522, CML 531 and CML 538 were selected and were crossed in diallel manner to obtain 66 medium to long duration experimental hybrids. Stability analysis using AMMI model was done to identify adaptive hybrids with high yielding potentiality. According to the ASVi value obtained, the hybrid G38 appeared to be stable followed by G50 and G44. On the other hand, the hybrid G25 appeared as location specific hybrid suitable for high input conditions

Influence of different temperature regimes on seed setting behavior and productivity traits in rabi sorghum

The experiment was conducted involving 35 rabi sorghum genotypes sown at six different dates of sowing (from Sept Istweek to October IVth week) during 2006-07 to assess the stability for pollen fertility (%), seed setting (%) and otherproductivity traits viz., plant height, days to 50% flowering, number of leaves, length of panicle, panicle weight, paniclediameter, number of primaries/panicle and 500-grain weight. The influence of dates of sowing on different phenotypiccharacters indicated that delayed sowing reduced the expression of all the traits. Flowering was early when genotypes weresown at 3rd date. The grain yield in general was high in the Ist date of sowing compared to the remaining dates. The seed set% (irrespective of sowing dates) was more than 65 as long as minimum temperature was more than 13 ºc where as, it wasdrastically reduced when minimum temperature was dropped down below 10 ºc. Pooled analysis of variance revealedsignificant difference among the genotypes and environments for all the characters indicating genotypes and environmentstested were diverse in nature. The G x E interaction was high and linear for most of the characters indicating significant andlinear response of genotypes to changing environment for these traits. On the basis of stability parameters it was revealedthat the two genotypes viz., DSH 4 and M 35-1 were stable for majority of the characters across the dates of sowing. As faras pollen fertility is concerned M31-2B, BJMS2B, 27B, 101B, BJMS204B, SPV570, BRJ62, RS29, AKR 150, BRJ 358,DSV5, DSV4, M35-1, DSH4, and CSH14 were stable in all the dates of sowing. The genotypes 1409B, 116B, M31-2B,101B, R354, C43, DSV5, DSV4, M35-1, DSH4 and BRJH 129 were stable in seed setting behavior across the dates ofsowing. With respect to grain yield/plant the two genotypes viz., 116B and M35-1 were most stable. In general, the B linesshowed less stability for many characters and the hybrids were found to be more stable across the dates of sowing for manycharacters indicating the scope for development of hybrids for rabi season. Among the hybrid parents R lines exhibitedstability for many characters across the dates of sowing while B lines were found to be not stable indicating the need for thedevelopment of stable B lines for rabi ecosystem. Among the 35 genotypes the lines viz., 296B, AKMS14B, C43, AKR150and B35 were not stable for any of the characters indicating their sensitivity to rabi environment as a whole

Effect of temperature on seed setting behaviour in rabi sorghum (Sorghum bicolor (L). Moench)

Pollen viability is an important parameter of yield as for as interaction of temperature with seed setting is concerned. Rabisorghum is one of the major cereal crops after rice, wheat and maize. In sorghum seed setting is affected when the floweringperiod coincides with minimum temperature. In this context comparison was made with pollen fertility percentage and seedsetting percentage vs minimum temperature at flowering. The study revealed that the range of pollen fertility percentage washigher than the range of seed setting percentage in all the dates of sowing and temperature regimes. Narrow range of seed set% was observed in BRJ-358, BRJH-129 and R-354.Varieties showed high seed set percentage (79.3) compare to hybrids, Rlines, B lines and stay green lines but mean pollen fertility was still higher than this i.e >90%. In other words, seed settingpercentage is more affected by temperature at all the six dates compare to pollen fertilit

Genomics-Enabled Next-Generation Breeding Approaches for Developing System-Specific Drought Tolerant Hybrids in Maize

Breeding science has immensely contributed to the global food security. Several varieties and hybrids in different food crops including maize have been released through conventional breeding. The ever growing population, decreasing agricultural land, lowering water table, changing climate, and other variables pose tremendous challenge to the researchers to improve the production and productivity of food crops. Drought is one of the major problems to sustain and improve the productivity of food crops including maize in tropical and subtropical production systems. With advent of novel genomics and breeding tools, the way of doing breeding has been tremendously changed in the last two decades. Drought tolerance is a combination of several component traits with a quantitative mode of inheritance. Rapid DNA and RNA sequencing tools and high-throughput SNP genotyping techniques, trait mapping, functional characterization, genomic selection, rapid generation advancement, and other tools are now available to understand the genetics of drought tolerance and to accelerate the breeding cycle. Informatics play complementary role by managing the big-data generated from the large-scale genomics and breeding experiments. Genome editing is the latest technique to alter specific genes to improve the trait expression. Integration of novel genomics, next-generation breeding, and informatics tools will accelerate the stress breeding process and increase the genetic gain under different production systems

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Not AvailableMaize is an important staple cereal crop grown for food, feed, and biofuel production owing to its multipurpose use, different types, and wider adaptability. To meet the increasing demand for animal and human consumption, maize production should be doubled, particularly in developing countries. Maize productivity in African and Asian countries including India is very low because it is mainly cultivated in arid and semi-arid regions as a rainfed crop. Maize production across the globe is mainly threatened by an increased incidence of severe droughts, waterlogging conditions during times of excess rainfalls, extreme temperatures (heat and cold), salinity, and nutrient stress. The effects of these stresses on maize are prevalent from seed germination to maturity and cause drastic yield losses. Drought is one of the major constrain in tropical maize growing areas and often it causes up to 100% yield loss if it occurs prior to and post reproduction phase. Recently waterlogging, becoming a major problem, and even one- or two-day continuous waterlogging may cause up to 30-40% yield losses. Further, frequent occurrences of extreme temperatures (heat and cold/chilling) affect plant growth and physiological process mainly photosynthesis, pollination, and grain filling. Salinity is reported to occur mainly in arid or semi-arid regions which are further aggravated by waterlogging and high temperature and impacts largely germination and seedling growth. Nitrogen (N) stress is also considered abiotic stress since maize growth and phenology is very sensitive to varying levels of N supply and thus influences yield attributing traits. In recent years most tropical countries experienced the simultaneous occurrence of different abiotic stresses and are more destructive to crop production than occurring separately. The combined strategies of crop improvement and production are the way forward for the development of abiotic stress tolerance. Crop production strategies include judicious use of water and other resources and the development of input-saving agronomic practices. While crop improvement involves pre-breeding, identification, and introgression of traits/genes/QTLs associated abiotic stress tolerance through marker-assisted and genomic selection. This approach demands understanding the complex mechanisms associated with abiotic stress tolerance. Further, the use of nutrients, soil amendments, bio-regulators, phytohormones, microbes also enhances abiotic tolerance level to some extent. Hence, adopting suitable and efficient strategies will help to mitigate and manage different abiotic stresses in maizeNot Availabl

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Not AvailableWhite maize plays an important role in human diet, especially in traditional crop growing regions of northern hill region, north-eastern states and central-western parts of India. Breeding efforts to enhance the genetic potential of white maize was not so prominent as compared to yellow maize in the country. As a result, genetic base of the material utilized in white maize breeding program in India is very narrow and majorly contains indigenous germplasm and few introductions. Hence, efforts were made to use 365 white maize inbred lines from CIMMYT, Mexico, for breeding program. These new inbred lines were grown at winter nursery center, Indian Institute of Maize Research, New Delhi for its tropical adaptation. After preliminary evaluation, a total 47 inbred lines were selected and evaluated in randomized complete block design with two replications at Regional Maize Research and Seed Production Centre, Begusarai, Bihar, during rabi 2014. Out of this top performing 12 inbred lines viz, CML 47, CML 95, CML 314, CML 319, CML 377, CML 488, CML 494, CML 504, CML 517, CML 522, CML 531 and CML 538 were selected and were crossed in diallel manner to obtain 66 medium to long duration experimental hybrids. Stability analysis using AMMI model was done to identify adaptive hybrids with high yielding potentiality. According to the ASVi value obtained, the hybrid G38 appeared to be stable followed by G50 and G44. On the other hand, the hybrid G25 appeared as location specifi hybrid suitable for high input conditions.Not Availabl

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Not AvailableContext. Establishment of true heterotic pattern in maize germplasm can increase the efficiency of hybrid breeding. Heterosis is dependent on the genetic diversity of parents and the extent of dominance at different loci. Estimation of genetic diversity through use of molecular markers is routine practice in maize breeding. Aims. The present study was designed to test whether simple sequence repeat (SSR) markers linked to yield-contributing traits are more reliable for heterotic grouping than random SSRs. Methods. Diallel crosses developed among 19 inbred lines were evaluated at multi-locations. The genotypes were also grouped using polymorphic random (50) and linked (47) SSRs. Key results. The crosses generated with lines belonging to different heterotic groups of linked SSR markers did not reveal any superiority over the crosses of the diallel set. By contrast, mean performance of inter-heterotic group crosses generated on the basis of random markers was superior to that of intra-heterotic crosses. Specific combining ability effects did not reveal any significant association with genetic distance of random or linked markers. Conclusions. The lack of improved efficiency of linked markers over random markers can be attributed to factors including the quantitative nature of the trait, genotype × environment interactions, genetic background of germplasm in which the markers are expressed, and multiple alleles. Implications. Markers linked to yield-contributing traits are no more reliable for heterotic grouping than random markersNot Availabl

Mean yield, IPCA1, IPCA2, ASVi and ASVi rank for genotypes over three locations.

Mean yield, IPCA1, IPCA2, ASVi and ASVi rank for genotypes over three locations.</p