1a. Objectives (from AD-416):
(1) Identify and functionally characterize genes central to the adaptation of plant to water-deficit and thermal stresses. (2) Discover and/or develop germplasm enhanced for stress resistance traits. (3) Identify and characterize water-deficit and thermal stress-responding promoters for using the controlled expression of stress resistance genes and for testing of a user-friendly plant stress reporter system for crop management.
1b. Approach (from AD-416):
A multidisciplinary research approach will be utilized because of the complexity of the problems to be addressed. Genes will be identified via expression databases and mutational analyses. Physiological and molecular characterizations will be used to identify germplasm with enhanced stress tolerances. Transformational technologies will be used in the development of plant with enhanced stress tolerances and plant with stress responsive reporter genes.
3. Progress Report:
The goal of this project is to identify marker-genes responsible for resistance to root knot nematode and Fusarium wilt, both of which cause yield losses in cotton. Marker-genes are being mapped to selected cotton chromosomes. Specifically, we have interest in chromosomes 11 and 21. These two chromosomes were found to harbor resistance (R) or pathogen-induced R genes. For the first time in cotton, a putative NBS-LRR gene is being reported within clusters and in the vicinity of discovered root-knot nematode and Fusarium wilt resistance marker-genes on chromosome 11 and 21. Genome sequencing and physical alignment of genomic regions into chromosomal maps are steps that will improve the accuracy of detecting R genes and gene functions of important biological processes in crops. Sequence information obtained through these studies can be used to develop improved tools to discover additional resistance genes, and to speed efforts to incorporate resistance genes into germplasm and breeding lines. We have evaluated the response of 15 selected maize inbred lines to drought stress treatment under field conditions at two locations. Different classes of metabolites were extracted from leaf samples and analyzed analytically. Lines with distinctive drought tolerance characteristics were crossed in 2011 season. The responses of hybrids and inbred parental lines to drought stress were evaluated at 2 field locations in 2012. Yield stability of the hybrids and maternal effects on field stability under drought condition were evaluated at the end of season. Drought stress will be implemented at V14-staged. Changes of specific metabolite among F2 plants before and after stress will be analyzed in association with their field drought tolerance phenotypes. We examined the effect of drought stress on fiber cell development and changes in fiber gene activities under drought is detailed using cotton transgenic lines containing CesA1-GUS construct. The transgenic cotton lines were grown under 3 different irrigation treatments with 3 replicates per condition. Cotton flowers were tagged daily as they opened for about 5 weeks, and cotton bolls at set DPA were collected and fiber tissues harvested. GUS report gene activities in fiber tissues were quantitatively determined by fluorometric analysis. The pattern of CesA1 gene activity (GUS report gene activities) during secondary cell wall deposition phase of fiber development was quantitatively determined by fluorometric analysis. The fiber structural changes within fiber cells over time were analyzed. We collected cotton fiber from plants from 7 planting dates and 4 irrigation levels in 2011 and 2012. Fiber collection in 2011 was based on air temperature heat unit accumulation. Fiber collection in 2012 was based on canopy temperature heat unit accumulation. Fiber quality and yield were determined. Data analysis in conjunction with collaborators from CSIRO is underway, with publication anticipated in 2014.
1. Drought disrupts the normal pattern of cotton fiber development. Cotton fiber production can be severely inhibited by drought. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, have used cotton fiber gene activity analysis to identify a shift in cellulose production and a shortening in the time for fiber cell elongation and secondary cell wall deposition. Fibers of drought-stressed plants matured much faster than those of well-watered plants. Such changes are correlated with significant reductions in fiber quality components (fiber length, fiber elongation, fiber strength, and fiber uniformity). These findings provide new insights into candidate genes responsible for drought-induced changes in cotton fiber properties.
2. Corn heat sensitivity investigated. High temperatures routinely reduce corn yield throughout the U.S. Scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, have evaluated the responses of 15 selected maize inbred lines to drought stress. Lines with distinctive drought tolerance characteristics were identified. Hybrids and inbred parental lines were evaluated for changes in cellular metabolites. These findings identified corn lines exhibiting improved tolerance to high temperatures.
3. Winning the fight against Fusarium wilt in cotton. Fusarium wilt (FOV) is an important disease of cotton caused by a fungus that can survive for long periods in the soil. Race 4 of FOV represents the most serious disease threat to cotton in California. Analyses of Upland and Pima cottons by scientists within the Plant Stress and Germplasm Development Unit in Lubbock, Texas, and University collaborators identified major resistance genes to race 4 (Fov4) in Pima-S6, and race 1 (Fov1) in Pima-S7 and 3-79. Molecular markers associated with Fov4 and Fov1 resistance genes and with genetic interactions in the mechanism of resistance in Upland and Pima cottons resistant to race 4 Fusarium were determined. Identified markers should be useful for breeding Fusarium wilt resistance into elite cotton varieties by marker-assisted selection and resistant cotton for expanding the genetic base available to cotton breeders for development of Fusarium resistant varieties.
Rowland, D., Faircloth, W., Payton, P.R., Tissue, D., Ferrell, J., Sorensen, R.B., Butts, C.L. 2012. Primed acclimation of cultivated peanut (Arachis hypogaea L.) through the use of deficit irrigation timed to crop developmental periods. Agricultural Water Management. 113:85-95.