Effects of Phaseolus vulgaris QTL in controlling host-bacteria interactions under two levels of nitrogen fertilization

Abstract

ported that photoperiod influences the expression of CBB, with susceptible tropical genotypes showing a higher level of resistance when grown under sub-tropical conditions. So far, the effect of nitrogen on the phenotypic expression of resistance genes of Phaseolus to Xanthomonas has not been studied. This is an important area of research, since in tropical areas common beans are cultivated under a variety of geographic and technological conditions which affect the amount of nitrogen available to both host and pathogen.The traditional genetic analysis and breeding for an increased number of Rhizobium nodules (NN) and resistance to X. axonopodis pv. phaseoli is hampered by the fact that both traits are under oligogenic control. In such cases, molecular markers have been used successfully to identify individual oligogenes and to study their phenotypic effects (see Young, 1996 for references). Nodari et al. (1993b), for example, found at least four quantitative trait loci (QTL) in P. vulgaris which accounted for 50 and 75% of the phenotypic variation in NN and CBB resistance, respectively. One of these QTL was found to be associated with both traits, and was also reported to control resistance to the variant fuscans of X. axonopodis pv. phaseoli (Boscariol et al., 1998 AbstractMolecular markers were used to estimate the effect of mineral nitrogen on the phenotypic expression of quantitative trait loci (QTL) controlling the number of Rhizobium nodules (NN) and resistance to Xanthomonas axonopodis pv. phaseoli in the common bean. Recombinant inbred lines derived from a BAT-93 x Jalo EEP558 cross were grown in a greenhouse in the absence or presence (5 mM NH 4 NO 3 ) of nitrogen. Resistance to Xanthomonas was assessed as diseased leaf area (DLA) and the number of nodules was obtained by direct counting. Analyses of variance were used to detect significant associations between 85 marker loci from 12 linkage groups (LG) and quantitative traits. In the absence of nitrogen, 15 and 11 markers, distributed over 7 and 5 LG, showed a significant association with NN and DLA, respectively. The combined percentage of phenotypic variance explained by the marker-loci and QTL associations was 34% for NN and 42% for DLA. In the presence of nitrogen, there were only five significant associations for NN and eight for DLA, which explained 28 and 26% of the total phenotypic variance, respectively. The effects of some QTL were detected only at a certain level of nitrogen. The contribution of parental alleles at two NN QTL was dependent on the level of nitrogen. Four QTL were associated with both the number of Rhizobium nodules and resistance to Xanthomonas, suggesting a common genetic control of responses to bacterial infections in the common bean. Despite the dramatic environmental interactions noted with some QTL, in other cases the phenotypic effects were not affected by the amount of nitrogen. The stability of the latter QTL may be relevant when breeding cultivars adapted to variable soil fertility.

INCREASING NODULE SIZE1 Expression Is Required for Normal Rhizobial Symbiosis and Nodule Development

“…Quantitative trait locus (QTL) analysis is a powerful approach for understanding genetic variation and mechanisms of host participation in symbiotic interactions. QTLs related to BNF have been identified in several legumes, including pea (Bourion et al, 2010), Lotus japonicas (Tominaga et al, 2012), and common bean (Phaseolus vulgaris; Tsai et al, 1998;de Souza et al, 2000). At present, few QTLs controlling nodulation traits in soybean have been described.…”

Identificação de QTL associados à simbiose entre Bradyrhizobium japonicum, B. elkanii e soja

“…Isso indica que essas características fenotípicas são controladas por QTL estreitamente ligados ou pela ação de um único QTL com efeito pleiotrópico (Lebreton et al, 1995;Loudet et al, 2003). QTL com efeitos pleiotrópicos já foram observados em vários caracteres morfológicos e de desenvolvimento na soja e no feijoeiro (Keim et al, 1990;Mansur et al, 1993;Nodari et al, 1993;Souza et al, 2000;Nicolás et al, 2006). A maior dificuldade que se apresenta diante desse tipo de interações consiste em distinguir QTL fortemente ligados, que afetam várias características, de um único QTL com efeitos pleiotrópicos.…”

Breeding Annual Grain Legumes for Sustainable Agriculture: New Methods to Approach Complex Traits and Target New Cultivar Ideotypes

“…There have been a few QTL studies on genetic determinants for nodule traits, mainly for nodule number per plant, and to a lesser extent, for nodule biomass and nodule area (Nodari et al, 1993;Souza et al, 2000;Nicolás et al, 2006;Bourion et al, 2010). Bourion et al (2010) identified nine different genomic regions controlling nodule development and growth on pea (Figure 9).…”