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Accueil du site → Master → Etats Unis → 2017 → Improving biomass productivity of alfalfa (Medicago sativa L.) under water limited environments : DNA marker assisted breeding and performance evaluation under variable irrigation strategies

New Mexico State University (2017)

Improving biomass productivity of alfalfa (Medicago sativa L.) under water limited environments : DNA marker assisted breeding and performance evaluation under variable irrigation strategies

Singh, Lovepreet

Titre : Improving biomass productivity of alfalfa (Medicago sativa L.) under water limited environments : DNA marker assisted breeding and performance evaluation under variable irrigation strategies

Auteur : Singh, Lovepreet

Université de soutenance : New Mexico State University

Grade : Master of Science (MS) Plant and Environmental Sciences 2017

Notes
Alfalfa (Medicago sativa L.) is the most important cultivated forage crop in the world. However, large proportions of alfalfa acreage in the western USA experience water deficit on a regular basis. Consequently, the current studies investigated the application of both molecular and conventional plant breeding approaches to improve alfalfa productivity under limited water conditions. The objectives of these studies were to : i) conduct marker assisted selection for favorable biomass QTL and to select against unfavorable biomass QTL that were segregating in three different elite alfalfa genetic backgrounds, ii) assess the impact of one cycle of phenotypic selection for drought resilience on frequencies of marker alleles linked to biomass QTLs, iii) determine the productivity of 24 elite alfalfa germplasms under fully irrigated, chronic (deficit irrigation throughout the season) and acute (mid-summer irrigation termination) water stress conditions, and iv) determine if elite alfalfa populations vary in their response to variable irrigation management regimes. DNA marker assisted selection (MAS) was imposed on five base populations previously developed via MAS and phenotypic selection for biomass productivity under water limited conditions. A total of 26 MAS populations were developed by selecting for and against various combinations of eight biomass QTL. These populations will be planted in the field in fall 2017 to evaluate forage yield productivity under deficit irrigation management. Additionally marker frequency shifts at six out of the eight biomass QTL were investigated among the five base populations in response to one cycle of phenotypic selection for drought resilience. A total of 26 tests were conducted and nine significant marker allele responses were detected. Among the nine significant responses, six were consistent with QTL directional effects while three were inconsistent. The inconsistent responses potentially highlight QTL by genetic background interaction and repulsion phase linkage between genetic factors associated with shoot biomass and fall plant regrowth height in alfalfa. Overall, the results demonstrated a neutral to positive impact of one cycle of phenotypic selection on the majority of target genome regions previously affiliated with biomass production under drought in alfalfa. Twenty-four alfalfa populations were evaluated in three separate field nurseries near Las Cruces, New Mexico in 2015 and 2016. Each nursery received different irrigation treatments including : control (CO), irrigation termination (IT), and deficit irrigation (DI) management. Significant differences were detected among the alfalfa populations for dry matter yield in all treatments during 2015. However, dry matter yield differences were not significant for CO and IT in 2016. The mean forage yields of populations over two years were 18.35, 10.76, and 10.86 Mg ha⁻¹ in the CO, IT, and DI treatments, respectively. Data analyses indicated that genotype by irrigation management interactions were significant in 2015 and nonsignificant for 2016 and across years. Analysis of response of individual populations based on the regression of population x Irrigation regime (IR) x year means on their respective IR x year means, enabled classification of populations into four categories. One commercial cultivar, Ameristand 803T, and three experimental lines NM14BMHS1, NM14MalHS3, and NM14BMHS3 were identified as superior germplasm for improving irrigated alfalfa poduction in the western United States.

https://nmsu.primo.exlibrisgroup.co....)&offset=0 Présentation (NMSU Library)

Page publiée le 12 octobre 2018, mise à jour le 24 décembre 2019