Fertility,genome stability,and homozygosity in a diverse set of resynthesized rapeseed lines

Rapeseed(Brassica napus,AACC)was formed by hybridization between progenitor species Brassica rapa(AA)and Brassica oleracea(CC).As a result of a limited number of hybridization events between specific progenitor genotypes and strong breeding selection for oil quality traits,rapeseed has limited genetic diversity.The production of resynthesized B.napus lines via interspecific hybridization of the diploid progenitor species B.rapa and B.oleracea is one possible way to increase genetic variation in rapeseed.However,most resynthesized lines produced so far have been reported to be meiotically unstable and infertile,in contrast to established B.napus cultivars.This hinders both maintenance and use of this germplasm in breeding programs.We characterized a large set of 140 resynthesized lines produced by crosses between B.rapa and B.oleracea,as well as between B.rapa and wild C genome species(B.incana,B.hilarionis,B.montana,B.Bourgeaui,B.villosa and B.cretica)for purity(homozygosity),fertility,and genome stability.Self-pollinated seed set,seeds per ten pods as well as percentage pollen viability were used to estimate fertility.SNP genotyping was performed using the Illumina Infinium Brassica 60K array for 116 genotypes,with at least three individuals per line.Most of the material which had been advanced through multiple generations was no longer pure,with heterozygosity detected corresponding to unknown parental contributions via outcrossing.Fertility and genome stability were both genotypedependent.Most lines had high numbers of copy number variants(CNVs),indicative of meiotic instability,and high numbers of CNVs were significantly associated with reduced fertility.Eight putatively stable resynthesized B.napus lines were observed.Further investigation of these lines may reveal the mechanisms underlying this effect.Our results suggest that selection of stable resynthesized lines for breeding purposes is possible.

Status and strategies in breeding for rust resistance in wheat

Wheat along with rice and maize is fulfilling half of the calories demands of the world. Global Wheat production has increased tremendously since green revolution in 1960’s and helped in minimizing hunger and malnutrition. Developing countries, which consume 60% of the global wheat production, have shown a higher yield increase than the developed countries in the past [1]. It was driven by the hunger prevalence in these countries and was attributable to the introduction of high yielding and rusted resistant semi dwarf varieties developed under the collaborative efforts of International and National research systems during the last 50 years. Whereas, climate change and the emergence of new pests and diseases are threatening the food sustainability. The evolution of new races of disease pathogens like stem rust (Ug 99) is of serious concern. In order to feed the ever increasing population we have to increase wheat production at the rate 1.6% which can be achieved by developing high yielding varieties having a good tolerance level for biotic and abiotic stresses.

Molecurar Breeding for Resistant Varieties Against Asian Rice Gall Midge in China

Asian rice gall midge (GM) is a major rice pest in South China. Breeding resistance varieties has been a viable and ecologically acceptable approach for managing the pest. This paper reports that the progress of

Evaluation and Bulked Segregant Analysis of Major Yield QTL qtl12.1 Introgressed into Indigenous Elite Line for Low Water Availability under Water Stress

Near isogenic lines carrying large-effect QTL （qtl2.1）, which has a consistent influence on grain yield under upland drought stress conditions in a wide range of environments, were evaluated under water stress in the fields. The line which gave higher yield under drought was crossed with a local elite line, PMK3, and forwarded to F2：3 generation. Significant variation was found among the F2：3 lines for agronomic traits under water stress in the fields. Low to high broad sense heritability （H） for investigated traits was also found. Water stress indicators such as leaf rolling and leaf drying were negatively correlated with plant height, biomass and grain yield under stress. Bulked segregant analysis （BSA） was performed with the markers in the vicinity of qUl2.1, and RM27933 was found to be segregated perfectly well in individual components of drought resistant and drought susceptible bulks which were bulked based on yield under water stress among F2：3 lines. Hence, this simple and breeder friendly marker, RM27933, may be useful as a potentially valuable candidate marker for the transfer of the QTL qtl12.1 in the regional breeding program. Bioinformatic analysis of the DNA sequence of the qtl12.1 region was also done to identify and analyze positional candidate genes associated with this QTL and to ascertain the putative molecular basis of qUl2.1.

Breeding Strategies for Improving Rice Yield—A Review

An increase in productivity is always one of the main goals of any crop breeding program including rice. However, many goals can be identified for this crop varying in importance from region to region, country to country, and even within a given country. Increase in grain yield potential is the major goal of almost all rice breeders programs. The major impacts are related to the development of new strategies to increase the genetic grain yield potential of the varieties. Rice breeders have been very successful in improving the crop. Some milestones are the contribution to the green revolution with the semi-dwarf varieties, the new rice plant type and hybrid rice. The main breeding method used to improve rice is the pedigree, but development of hybrids and population improvement are added to the breeder’s portfolio. Breeders have been taking advantage of biotechnology tools to enhance their breeding capacity;however, many programs are still struggling on how to integrate them into the breeding programs and how to balance the allocation of resources between conventional and modern tools.

Genetic Variability and Elite Line Selection for High Essential Oil and Nepetalactone Content in Catmint (<i>Nepeta cataria</i>L.)

Nepeta cataria L., commonly known as catmint or catnip, belongs to the family “Lamiaceae” and is indigenous to Europe and Asia. The essential oil of this species is known for the richness and diversity of nepetalactones (NPL) which are used as mosquito/insect repellents in perfumery and cosmetic industries. Reports on Indian catmint germplasm are very meager and warrants exploration of its commercial potential as a natural, non-toxic source of insect repellents. With this objective, commercial open-pollinated seeds of catmint collected from its native, temperate habitat in Himalayas were introduced in the tropical plains. Subsequent to adaptation to a new zone we were able to isolate nineteen individual plants based on plant growth. Hydrodistillation of the fresh herb yielded essential oil in the range of 0.01% to 0.2%. Gas Chromatography (GC) and GC-Mass Spectrometry (GC-MS) analyses of the oil revealed the dominance of monoterpene hydrocarbon, namely, 4aα,7α,7aα NPL (1) isomer (84%). The other two isomers of nepetalactone, 4aα,7α,7aβ NPL (2) and 4aα,7β,7aα NPL (3) were also present, although in very less amounts (1.0% and 1.6%, respectively). Sesquiterpenes identified were α-humulene (traces), (E)-caryophyllene (0.6%) and caryophyllene oxide (1.7%). We compared the identified Indian catmint chemotype with the other oils from temperate, sub-tropical and tropical locations based on literature search. The Indian chemotype was found to be similar to the oils from Burundi, France, Turkey, UK and USA, mainly due to more accumulation of 4aα,7α,7aα NPL (1) isomer. These oils grouped together in Principal Component Analysis. Breeding lines are presently being developed to improve yield related traits in this plant. Multidisciplinary R&D efforts along with setting up industry related guidelines are required to successfully commercialize catmint cultivation. Several species of Nepeta genus have high nepetalactone content too and their potential as a commercial source of these isomers still needs to be explored.

Improving genomic tools for outcrossing crops

For decades,practical limitations and cost have created a bias in plant genetic studies toward species that tolerate self pollination.An important work by Chen et al.(2021)in this issue provides key tools to overcome this bias and paves the way toward more efficient genetics and breeding in outcrossing crops.