Crown rot (CR), caused by various Fusarium species, is a chronic wheat disease in Australia. As part of our objective of improving the efficiency of breeding CR resistant wheat varieties, we have been searching for novel sources of resistance. This paper reports on the genetic control of one of these newly identified resistant genotypes, 'CSCR6'. A population derived from a cross between CSCR6 and an Australian variety 'Lang' was analyzed using two Fusarium isolates belonging to two different species, one Fusarium pseudograminearum and the other Fusarium graminearum. The two isolates detected QTL with the same chromosomal locations and comparable magnitudes, indicating that CR resistance is not species-specific. The resistant allele of one of the QTL was derived from 'CSCR6'. This QTL, designated as Qcrs.cpi-3B, was located on the long arm of chromosome 3B and explains up to 48.8% of the phenotypic variance based on interval mapping analysis. Another QTL, with resistant allele from the variety 'Lang', was located on chromosome 4B. This QTL explained up to 22.8% of the phenotypic variance. A strong interaction between Qcsr.cpi-3B and Qcsr.cpi-4B was detected, reducing the maximum effect of Qcrs.cpi-3B to 43.1%. The effects of Qcrs.cpi-3B were further validated in four additional populations and the presence of this single QTL reduced CR severity by up to 42.1%. The fact that significant effects of Qcrs.cpi-3B were detected across all trials with different genetic backgrounds and with the use of isolates belonging to two different Fusarium species make it an ideal target for breeding programs as well as for further characterization of the gene(s) involved in its resistance.

Production of pure lines is an important step in biological studies and breeding of many crop plants. The major types of pure lines for biological studies and breeding include doubled haploid (DH) lines, recombinant inbred lines (RILs), and near isogenic lines (NILs). DH lines can be produced through microspore and megaspore culture followed by chromosome doubling while RILs and NILs can be produced through introgressions or repeated selfing of hybrids. DH approach was developed as a quicker method than conventional method to produce pure lines. However, its drawbacks of genotype-dependency and only a single chance of recombination limited its wider application. A recently developed fast generation cycling system (FGCS) achieved similar times to those of DH for the production of selfed pure lines but is more versatile as it is much less genotype-dependent than DH technology and does not restrict recombination to a single event. The advantages and disadvantages of the technologies and their produced pure line populations for different purposes of biological research and breeding are discussed. The development of a concept of complete in vitro meiosis and mitosis system is also proposed. This could integrate with the recently developed technologies of single cell genomic sequencing and genome wide selection, leading to a complete laboratory based pre-breeding scheme.

Flow regimes are believed to be of major evolutionary significance in fish. The flow regimes inhabited by cyprinids vary extensively from still flow regimes to riptide flow regimes. To test (i) whether flow-driven swimming performance and relevant morphological differentiation are present among fish species and (ii) whether evolutionary shifts between high-flow and low-flow habitats in cyprinids are associated with evolutionary trade-offs in locomotor performance, we obtained data on both steady and unsteady swimming performance and external body shape for 19 species of cyprinids that typically occur in different flow regimes (still, intermediate and riptide). We also measured the routine energy expenditure (RMR) and maximum metabolic rate (MMR) and calculated the optimal swimming speed. Our results showed that fish species from riptide groups tend to have a higher critical swimming speed (U crit ), maximum linear velocity (V max ) and fineness ratio (FR) than fish from the other two groups. However, there was no correlation between the reconstructed changes in the steady and unsteady swimming performance of the 19 species. According to the phylogenetically independent contrast (PIC) method, the U crit was actively correlated with the MMR. These results indicated that selection will favour both higher steady and unsteady swimming performance and a more streamlined body shape in environments with high water velocities. The results suggested that steady swimming performance was more sensitive to the flow regime and that for this reason, changes in body shape resulted more from selective pressure on steady swimming performance than on unsteady swimming performance. No evolutionary trade-off was observed between steady and unsteady swimming performance, although U crit and MMR were found to have coevolved. However, a further analysis within each typically occurring habitat group suggested that the trade-off that may exist between steady and unsteady swimming performance may be concealed by the effect of habitat.

This study quantified and compared hypoxia tolerance and swim performance among cyprinid fish species from rapid-, slow-and intermediate-flow habitats (four species per habitat) in China. In addition, we explored the effects of short-term acclimation on swim performance, maximum metabolic rate (Ṁ O2,max ) and gill remodelling to detect habitat-associated patterns of plastic response to hypoxia. Indices of hypoxia tolerance included oxygen threshold for loss of equilibrium (LOE 50 ) and aquatic surface respiration (ASR 50 ), and critical oxygen tension for routine metabolic rate (P crit ). Critical swimming speed (U crit ) and Ṁ O2,max were measured under normoxic and hypoxic conditions after 48 h acclimation to normoxia and hypoxia, and gill remodelling was estimated after 48 h of hypoxia exposure. Both traditional ANCOVA and phylogenetically independent contrast (PDANOVA) analyses showed that fish species from rapidflow habitats exhibited lower LOE 50 compared with fish from intermediate-and slow-flow habitats. Habitat-specific differences in P crit and U crit were detected using PDANOVA but not traditional ANCOVA analyses, with fish species from rapid-flow habitats exhibiting lower P crit but higher U crit values compared with fish from intermediate-and slow-flow habitats. Fish species from rapid-flow habitats were also characterized by less plasticity in swim performance and gill morphology in response to hypoxia acclimation compared with species from slow-flow habitats, but a greater drop in swim performance in response to acute hypoxia exposure. The study detected a habitat-specific difference in hypoxia tolerance, swimming performance and its plasticity among fish from habitats with different flow conditions, possibly because of the long-term adaptation to the habitat caused by selection stress. The PDANOVA analyses were more powerful than traditional statistical analyses according to the habitat effects in both hypoxia tolerance and swimming performance in this study.

Fusarium crown rot (FCR) is a major disease of wheat and barley, and stem‐base browning has been routinely used to measure resistance. Compared with barley (Hordeum vulgare L.), bread wheat (Triticum aestivum L.) shows less severe FCR stem‐base browning symptoms (indicative of greater resistance or tolerance) but suffers higher yield loss (indicative of greater susceptibility), whereas durum wheat (T. durum Desf.) shows similar FCR severity but suffers much worse yield loss. To understand these differences, fungal biomass in bread and durum wheats and barley was estimated by real‐time quantitative PCR at different stages of FCR disease development. Similar to a previous report on bread wheat infection by Fusarium graminearum, FCR infection caused by Fusarium pseudograminearum also showed ‘three distinct phases’ in each of the three crop species analysed. During all stages of FCR disease development, barley varieties invariably displayed earlier and faster fungal accumulation compared with either bread or durum wheat. Although suffering much greater yield loss than barley, durum wheat appears to accumulate significantly lower levels of F. pseodugraminearum during infection. These results demonstrate that bread wheat varieties are more resistant to FCR infection and pathogen accumulation than barley varieties, and the less yield loss of the latter is likely due to its better tolerance to this disease. If also existing among different sources of resistance within a given species, these different features of disease resistance and tolerance could be exploited to minimize yield loss of new varieties.