Finger millet (Eleusine coracana (L.) Gaertn) is an important crop for food security because of its tolerance to drought, which is expected to be exacerbated by global climate changes. Nevertheless, it is often classified as an orphan/underutilized crop because of the paucity of scientific attention. Among several small millets, finger millet is considered as an excellent source of essential nutrient elements, such as iron and zinc; hence, it has potential as an alternate coarse cereal. However, high-quality genome sequence data of finger millet are currently not available. One of the major problems encountered in the genome assembly of this species was its polyploidy, which hampers genome assembly compared with a diploid genome. To overcome this problem, we sequenced its genome using diverse technologies with sufficient coverage and assembled it via a novel multiple hybrid assembly workflow that combines next-generation with single-molecule sequencing, followed by whole-genome optical mapping using the Bionano Irys® system. The total number of scaffolds was 1,897 with an N50 length >2.6 Mb and detection of 96% of the universal single-copy orthologs. The majority of the homeologs were assembled separately. This indicates that the proposed workflow is applicable to the assembly of other allotetraploid genomes.

A number of genetic maps for Fusarium wilt resistance in chickpea have been reported in earlier studies, however QTLs identified for Fusarium wilt resistance were unstable. Hence, the present study aims to map novel molecular markers and to identify QTLs for Fusarium wilt resistance in chickpea. An intraspecific linkage map of chickpea (Cicer arietinum L.) was constructed using F10-F11 recombinant inbred lines (RILs) derived from a cross between K850 and WR315 segregating for H2 locus. A set of 31 polymorphic simple sequence repeat (SSR) markers obtained by screening 300 SSRs and were used for genotyping. The linkage map had four linkage groups and coverage of 690 cM with a marker density of 5.72 cM. The RILs were screened for their wilt reaction across two seasons in wilt sick plot at International Crop Research Institute for Semi-Arid Tropics (ICRISAT), Hyderabad, India. Five major quantitative trait loci (QTLs) were detected in both seasons for late wilting (60 days after sowing). A stable QTL (GSSR 18-TC14801) for wilt resistance was identified in both the seasons, and the QTL explained a variance of 69.80 and 60.80% in 2007 and 2008 rabi respectively.

Structural genes of pollen are expressed in both sporophytic and gametophytic generations. This genetic overlap makes possible superior pollen genotype selection. Pollen selection is more effective than sporophytic selection since more pollen grains can be exposed to selection pressure at the haploid level. In this study, selection pressure was applied in the F1 generation at the pollen level for heat tolerance. The frequencies of heat‐tolerant plants were studied for seed yield in F2 and F3 generations and for seedling heat tolerance in F4 generations. The heat‐susceptible inbred line BTM4 was crossed to heat‐tolerant inbred line BTM6 of maize (Zea mays L.). In response to heat stress, we compared F2 plants produced by selfing of heat‐stressed pollen grains and without heat‐stressed pollen grains. The resulting F2 plants from heat‐stressed pollen grains showed significantly higher seed yield per plant (5.41 ± 0.31 g) than control F2 (2.90 ± 0.19 g) populations under stress. The selected and control F2 plants were also subjected to genotyping using simple sequence repeat (SSR) primers. We observed that the frequency of alleles from tolerant parents was higher in selected F2 populations, providing genetic evidence for positive effect of pollen selection. The heat tolerance of F4 generation progenies of the same cross suggested that the cyclic pollen selection for heat tolerance in F1, F2, and F3 generations has significantly improved the tolerance of progenies. The results from this study demonstrate that the feasibility of this approach seems to be promising for hastening the incorporation of desirable alleles in a short time.

Gametophytic selection can drastically reduce the number of selection cycles during crop improvement programs. The objective of the present investigation was to test whether the nature of inheritance of two unlinked disease-resistant loci, h(1) and h(2), against Fusarium wilt in chickpea (Cicer arietinum L.) under gametophytic (pollen) selection was similar to that already observed at sporophytic level. A homozygous dominant (H(1)H(1)H(2)H(2)) susceptible genotype JG-62 was crossed to a recessive (h(1)h(1)h(2)h(2)) resistant genotype WR-315 to produce 20 F(1) hybrid seeds. In the following generation, flower buds of 10 F(1) hybrid plants were subjected to toxin stress before anthesis and the remaining ten control F(1) plants' flowers were sprayed with water. Thirty-four selected BC(1) plants were generated by test crossing resistant WR-315 individuals with pollen from toxin-stressed F(1) individuals. Both control and treated F(1) plants were selfed to produce respective F(2) generations. Two DNA markers, CS-27(700bp) and A07C(430bp), linked to susceptible alleles H(1) and H(2), respectively, were used to study the inheritance patterns of h(1) and h(2) loci in the F(2) and BC(1) generations. One hundred and forty-four selected F(2), 129 control F(2), and 34 selected backcross individuals were tested for the presence or absence of DNA markers. Except for the control F(2), observed ratios of selected F(2) and BC(1) populations exhibited significant chi-square deviations from expected monogenic and digenic ratios. Our results suggest that gametophytic selection is as effective as that realized at the sporophytic level, and that the gametophytic selection can be an effective breeding tool for plant breeding programs.

Patil B.S., Ravikumar R.L., Bhat J.S., Soregaon C.D. (2014): Molecular mapping of QTLs for resistance to early and late Fusarium wilt in chickpea. Czech J. Genet. Plant Breed., 50: 171-176.A molecular map of chickpea was constructed using F 9 :F 10 recombinant inbred lines from an intraspecific cross between Fusarium wilt susceptible (JG 62) and resistant (WR 315) genotypes. A total of 23 markers with LOD scores of > 3.0 were mapped on the recombinant inbred lines (RILs). Twenty sequence tagged microsatellites (STMSs) and three amplified fragment length polymorphisms (AFLPs) covered 300.2 cM in five linkage groups at an average inter-marker distance of 13 cM. Early and late wilting due to Fusarium infection was recorded in RILs at 30 and 60 DAS, respectively. There was a significant variation among RILs for wilt resistance for both early and late wilting. QTLs associated with early (30 days after sowing (DAS)) and late (60 DAS) wilting are located on LG II. The flanking markers for these QTLs were the same as those of previous reports. Five STMS markers located on LG II of reference map (interspecific) were mapped on LG II of the present map (intraspecific) with minor changes in the order of markers indicating the conservation of these genomic regions across the Cicer species.