Two distinct classes of QTL determine rust resistance in sorghum

Background: Agriculture is facing enormous challenges to feed a growing population in the face of rapidly evolving pests and pathogens. The rusts, in particular, are a major pathogen of cereal crops with the potential to cause large reductions in yield. Improving stable disease resistance is an on-going major and challenging focus for many plant breeding programs, due to the rapidly evolving nature of the pathogen. Sorghum is a major summer cereal crop that is also a host for a rust pathogen which occurs in almost all sorghum growing areas of the world, causing direct and indirect yield losses in sorghum worldwide, however knowledge about its genetic control is still limited. In order to further investigate this issue, QTL and association mapping methods were implemented to study rust resistance in three bi-parental populations and an association mapping set of elite breeding lines in different environments. Results: In total, 64 significant or highly significant QTL and 21 suggestive rust resistance QTL were identified representing 55 unique genomic regions. Comparisons across populations within the current study and with rust QTL identified previously in both sorghum and maize revealed a high degree of correspondence in QTL location. Negative phenotypic correlations were observed between rust, maturity and height, indicating a trend for both early maturing and shorter genotypes to be more susceptible to rust. Conclusions: The significant amount of QTL co-location across traits, in addition to the consistency in the direction of QTL allele effects, has provided evidence to support pleiotropic QTL action across rust, height, maturity and stay-green, supporting the role of carbon stress in susceptibility to rust. Classical rust resistance QTL regions that did not co-locate with height, maturity or stay-green QTL were found to be significantly enriched for the defence-related NBS-encoding gene family, in contrast to the lack of defence-related gene enrichment in multi-trait effect rust resistance QTL. The distinction of disease resistance QTL hot-spots, enriched with defence-related gene families from QTL which impact on development and partitioning, provides plant breeders with knowledge which will allow for fast-tracking varieties with both durable pathogen resistance and appropriate adaptive traits

The effects of lowering the leaf water potential on the stomatal resistance and photosynthetic rate of some sorghum bicolor (L.) Moench genotypes

The overall objectives of the study were to determine (i) if genotype variation of stomatal sensitivity to water deficit exists in Sorghum bicolor (L.) Moench and (ii) the extent to which stomatal closure contributes to the reduction in photosynthetic rate in response to water deficit, in some selected sorghum genotypes. All the plants tested were in the vegetative phase of growth. They were grown and tested in a controlled environment chamber under conditions of high irradiance (equivalent to full sunlight), a 12 hour photoperiod, 30C air temperature, 27C dewpoint temperature, and 320 ppm CO?éé. Twenty-three genotypes were first screened for stomatal sensitivity to decreasing soil water potential, by growing a single plant of each genotype in a pot along with a single plant of a control genotype which was common to all pots. A genotype's sensitivity was then measured in relation to that of the control genotype grown in its pot. This test showed that considerable variation far stomatal sensitivity existed among the 23 genotypes. The relationship between leaf diffusive conductance and leaf water potential was obtained far Alpha and Shallu which were found to be sensitive in the screening test and for I.S.1598C and H35-1 which were found to be Insensitive. This test confirmed the results of the screening test. It showed that for each genotype the relationship between leaf diffusive conductance and leaf water potential was best fitted with a second order polynomial equation. ..

The effects of lowering the leaf water potential on the stomatal resistance and photosynthetic rate of some sorghum bicolor (L.) Moench genotypes

The overall objectives of the study were to determine (i) if genotype variation of stomatal sensitivity to water deficit exists in Sorghum bicolor (L.) Moench and (ii) the extent to which stomatal closure contributes to the reduction in photosynthetic rate in response to water deficit, in some selected sorghum genotypes. All the plants tested were in the vegetative phase of growth. They were grown and tested in a controlled environment chamber under conditions of high irradiance (equivalent to full sunlight), a 12 hour photoperiod, 30C air temperature, 27C dewpoint temperature, and 320 ppm CO?éé. Twenty-three genotypes were first screened for stomatal sensitivity to decreasing soil water potential, by growing a single plant of each genotype in a pot along with a single plant of a control genotype which was common to all pots. A genotype's sensitivity was then measured in relation to that of the control genotype grown in its pot. This test showed that considerable variation far stomatal sensitivity existed among the 23 genotypes. The relationship between leaf diffusive conductance and leaf water potential was obtained far Alpha and Shallu which were found to be sensitive in the screening test and for I.S.1598C and H35-1 which were found to be Insensitive. This test confirmed the results of the screening test. It showed that for each genotype the relationship between leaf diffusive conductance and leaf water potential was best fitted with a second order polynomial equation. ..

Adaptation to aridity in lizards of the Egernia Whitei species-group

122 leaves : ill.Thesis (Ph.D.)--University of Adelaide, Dept. of Zoology, 197

Evaluating Australian bulls on indexes of other countries and international bulls on Australian indexes

This paper briefly describes a new facility, developed within 'BreedObject on the web', where Australian seedstock (eg. bulls, semen) are able to be ranked on overseas and Australian indexes as well as overseas seedstock ranked on Australian indexes. The development was at the request of Australian and overseas breeds, who agreed to share the availability of their indexes. Through the ability of ‘BreedObject on the web’ to calculate indexes on-line, and through its on-line access to breed databases, results for the indexes of different countries are able to be reproduced, on demand, for any selection of animals from the databases. The facility has the potential to assist the export of superior Australian seedstock, and to expand the gene pool for Australian breeders by increasing the effectiveness with which animals with desirable genetic merit are identified in overseas populations

Two distinct classes of QTL determine rust resistance in sorghum

Background: Agriculture is facing enormous challenges to feed a growing population in the face of rapidly evolving pests and pathogens. The rusts, in particular, are a major pathogen of cereal crops with the potential to cause large reductions in yield. Improving stable disease resistance is an on-going major and challenging focus for many plant breeding programs, due to the rapidly evolving nature of the pathogen. Sorghum is a major summer cereal crop that is also a host for a rust pathogen Puccinia purpurea, which occurs in almost all sorghum growing areas of the world, causing direct and indirect yield losses in sorghum worldwide, however knowledge about its genetic control is still limited. In order to further investigate this issue, QTL and association mapping methods were implemented to study rust resistance in three bi-parental populations and an association mapping set of elite breeding lines in different environments

Managing vertebrate pests: feral goats

https://researchlibrary.agric.wa.gov.au/books/1004/thumbnail.jp

Methods and consequences of including feed intake and efficiency in genetic selection for multiple-trait merit

Methods are presented for including feed intake and efficiency in genetic selection for multiple-trait merit when commercial production is from any combination of pasture or concentrates. Consequences for the production system and for individual animals are illustrated with a beef cattle example. Residual feed intake at pasture (RFI-p), residual feed intake in the feedlot (RFI-f), and cow condition score are additional traits of the breeding objective. Feed requirement change is costed in the economic values of other objective traits. Selection responses are examined when feed costs are ignored, partially or fully included in the breeding objective, and when net feed intake (NFI) EBVs are added to the index. When all feed cost was included and NFI EBVs were in the index, selection (with selection intensity, i = 1) increased production system $net return by 6.0$ per unit of product by 5.2%, $per unit of feed by 6.6$ net return, $per unit of product, and$ per unit of feed. At the individual trait level, when feed was fully included there were increases in weaning weight-direct (0.8 kg), feedlot entry weight (1.4 kg), dressing % (0.04%), carcass meat % (0.36%), carcase fat depth (0.12 mm), carcass marbling score (0.02 score), cow condition score (0.01 score), calving ease-direct (0.97%), calving ease-maternal (0.22%) and cow weaning rate (1.3%), and decreases in weaning weight-maternal (-0.9 kg), RFI-p (-0.09 kg DM/d), RFI-f (-0.11 kg DM/d), sale weight (-1.6 kg) and cow weight (-8.7 kg). Gains were evident over a range of feed price. Selection for $net return also increased$ net return per unit of feed, suggesting that $ net return per unit area would increase in grazing industries. Feed cost for trait change was the source of a major genotype x environment interaction affecting animal rankings. Where industry production environments vary, and feed cost for trait change varies with the environment, we recommend that industry indexes be derived for more than one level of feed cost. Cow condition score did not decline while biological and economic efficiency of the production system and individual animal were improving, suggesting that efficiency can be improved under multiple-trait selection without compromising breeding cow welfare