the utility of lateral branching of the primary root for tolerance to phosphorus stress and drought in the common bean (phaseolus vulgaris L.)

Open Access
Author:
Camilo, Samuel Alves
Graduate Program:
Horticulture
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
October 11, 2013
Committee Members:
  • Jonathan Paul Lynch, Thesis Advisor
  • Kathleen Marie Brown, Thesis Advisor
  • Ricky M Bates, Thesis Advisor
Keywords:
  • common bean
  • root architecture
  • taproot lateral branching
  • drought
  • phosphorus common bean
  • taproot lateral
Abstract:
Common bean (Phaseolus vulgaris L.) is essential to the food security of millions people in developing nations. Inadequate precipitation and low soil fertility, especially low phosphorus availability, are the primary constraints in most rain-fed bean production regions. This study aimed to evaluate the utility of lateral branching of the primary root for tolerance of phosphorus stress and drought in the common bean (Phaseolus vulgaris L.). Recombinant inbred lines contrasting in taproot lateral branching were evaluated in pots with stratified water and phosphorus availability in a greenhouse with four treatments: 1) adequate water and phosphorus; 2) limited phosphorus and adequate water; 3) limited water and adequate phosphorus; and 4) combined drought and phosphorus stress. Another greenhouse study focused on drought stress in pots with stratified water availability in a greenhouse. In addition field studies were conducted in which drought stress was imposed by automated rainout shelters at Rock Springs; field experiment at URBC, Republic of South Africa and Sussundenga research station, Republic of Mozambique. Overall, drought and phosphorus treatments significantly reduced growth parameters (shoot biomass, leaf area and number of leaves). In the field study at Rock Springs drought stress caused a reduction of 50% in shoot biomass, 64% in leaf area, and 48% in number of leaves at flowering. Total taproot length in the bottom horizon of the stratified water greenhouse system (2013 greenhouse study ) was correlated with shoot biomass, although in these results as well as those from the field experiments (Rock Springs, URBC and Sussundenga), phenotype groups did not have significant effects on shoot biomass and most of the parameters measured. Results suggest the need for more research testing whether the differences in root length, branching, as well as the size of lateral branches (and their anatomical traits such as metaxylem vessels) has an influence in water uptake. How much water is taken up after imposition of drought would be related to the root length density and its size, since in our experiments we have observed that strong drought stress led to more fine roots production and allocation in the deeper horizons.