Dna Marker Assisted Selection To Improve Drought Tolerance In Alfalfa Medicago Sativa L

Download or read book DNA Marker Assisted Selection to Improve Drought Tolerance in Alfalfa (Medicago Sativa L.) written by Ma Gina Maramara Babb and published by . This book was released on 2014 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: Alfalfa is a perennial forage legume grown extensively under both rainfed and irrigated conditions. It is the most important forage crop and the third most valuable crop in the United States of America. Alfalfa production is affected by abiotic stress factors such as drought that causes plant yield reduction. Because of this, plant breeding efforts are geared towards breeding for crop drought tolerance. Most traits governing drought tolerance are influenced buy multiple genes, referred to as quantitative trait loci (QTL), and environmental factors. The NMSU alfalfa genetics and breeding program previously conducted forage and root biomass QTL mapping experiments in two segregating alfalfa populations grown under drought-stressed field conditions. Ten shoot and root biomass QTLs were identified in that research and represented by 10 simple sequence repeat (SSR) DNA markers. These markers were selected for use in a marker assisted selection (MAS) experiment in alfalfa in the current study. MAS was imposed on the unselected control (C0) (base population) by selecting plants that possessed (+), or did not possess (-), specific combinations of DNA marker alleles associated with high shoot (HS), low shoot (LS), high root (HR), and low root (LR) biomass, all designated as Cycle 1. the Cycle 1 populations that possessed (+) the marker alleles and the C0 population were then crossed to the three cultivars Malone, Melton and Multileaf to develop 18 cultivar-MAS hybrids (referred to as Malone-MAS, Melton-MAS, and Multileaf-MAS). A total of 32 populations were evaluated for shoot biomass production under normal irrigation (NI) and limited irrigation (LI) field conditions during 2011 and 2012. The goal of this research study was to validate if these drought tolerance QTLs can be used to improve the performance of three elite cultivars for yield under NI and LI management. The impact of MAS on forage quality factors and leaf relative water content was also monitored. Results show that selection for high shoot biomass markers and high root biomass markers in the MAS-derived Cycle 1 populations improved forage yield by 23% and 20%, respectively in the LI study. IN addition, selection for the low shoot and low root biomass marker alleles in the same populations decreased forage yield by 3% and 15%, respectively, in the LI study. In the NI study, selection for HS3+ improved forage yield by 9% (not significant) while all other population yield differences were small. For the cultivar-MAS hybrids two superior Malone-MAS and Multileaf-MAS hybrids outperformed their respective parent cultivar by 6% and 19% in the LI study, and 6% and 7% in the NI study. While no Melton-MAS hybrids outperformed their drought tolerant Melton parent in the LI study, one of the hybrids yielded 7% more than Melton in the NI study. Forage quality results indicated that most of the MAS-derived Cycle 1 populations had significantly higher leaf to stem ratio (LSR) than the three cultivars and their cultivar-MAS hybrids under the LI and NI management. For the cultivar-MAS hybrids, results show that under the LI and NI studies, one and two Multileaf-MAS hybrids, respectively, had a significantly higher LSR than the Multileaf cultivar; five and six Malone-MAS hybrids, respectively, had a significantly higher LSR than the Malone cultivar; and four and six Melton-MAS hybrids, respectively, had a significantly higher LSR than the Melton cultivar. For leaf relative water content (RWC), no significant year by entry, or main entry effect on leaf RWC were detected among the 32 populations under LI and NI management. The rankings among the populations were inconsistent in both studies. The overall results presented in this study validated the past QTL experimental outcome that the marker effects were in the same direction as previously determined under well-watered and water-limited environments. This study also demonstrated that DNA MAS was effective at improving forage yield of three existing cultivars in both limited irrigation and normal irrigation management.