Identifying New Sources of Resistance to Brown Stem Rot in Soybean

Brown stem rot (BSR), caused by the fungus Phialophora gregata f. sp. sojae (Allington & D.W. Chamberlain) W. Gams (syn. Cadophora gregata), causes yield losses up to 38%. Three dominant BSR-resistant genes have been identified: Rbs1, Rbs2, and Rbs3. Additional BSR resistance loci will complement breeding efforts by expanding the soybean [Glycine max (L.) Merr.] genetic base. The objective of this research was to determine if PI 594637, PI 594638B, PI 594650A, and PI 594858B contained novel BSR resistance genes. The accessions were crossed to three genotypes with known BSR resistance genes and populations were developed for allelism studies. A minimum of 60 F2:3 families tracing to individual F2 plants in each population were used, and six seeds from each F2:3 family were tested. Resistant and susceptible controls and parents were also included. The BSR symptoms were assessed under growth chamber conditions 5 wk after inoculation by measuring foliar and stem severities and recovery of P. gregata from stem sections. Allelism tests of F2:3 plants from crosses of PI 594638B, PI 594858B, and PI 594650A with the resistant sources fit a 15:1 ratio, indicating that the resistant gene possessed by each of the PIs was nonallelic to Rbs1, Rbs2, and Rbs3. The three PIs contain at least one novel BSR resistance gene and have the potential to serve as donors to elite germplasm, increasing stability of host resistance to P. gregata. Allelism tests of PI 594637 segregated in a 3:1 ratio and no significant difference was found between PI 594637 and the susceptible controls, indicating that PI 594637 is susceptible to BSR

Motion of influential players can support cooperation in Prisoner's Dilemma

We study a spatial Prisoner's dilemma game with two types (A and B) of players located on a square lattice. Players following either cooperator or defector strategies play Prisoner's Dilemma games with their 24 nearest neighbors. The players are allowed to adopt one of their neighbor's strategy with a probability dependent on the payoff difference and type of the given neighbor. Players A and B have different efficiency in the transfer of their own strategy therefore the strategy adoption probability is reduced by a multiplicative factor (w < 1) from the players of type B. We report that the motion of the influential payers (type A) can improve remarkably the maintenance of cooperation even for their low densities.Comment: 7 pages, 7 figure

Cooperation and its evolution in growing systems with cultural reproduction

We explore the evolution of cooperation in the framework of the evolutionary game theory using the prisoner's dilemma as metaphor of the problem. We present a minimal model taking into account the growing process of the systems and individuals with imitation capacity. We consider the topological structure and the evolution of strategies decoupled instead of a coevolutionary dynamic. We show conditions to build up a cooperative system with real topological structures for any natural selection intensity. When the system starts to grow, cooperation is unstable but becomes stable as soon as the system reaches a small core of cooperators whose size increase when the intensity of natural selection decreases. Thus, we reduce the emergence of cooperative systems with cultural reproduction to justify a small initial cooperative structure that we call cooperative seed. Otherwise, given that the system grows principally as cooperator whose cooperators inhabit the most linked parts of the system, the benefit-cost ratio required for cooperation evolve is drastically reduced compared to the found in static networks. In this way, we show that in systems whose individuals have imitation capacity the growing process is essential for the evolution of cooperation.Comment: 16 pages, 2 figures. arXiv admin note: substantial text overlap with arXiv:1111.247

Registration of DT99-16864 Soybean Germplasm Line with Moderate Resistance to Charcoal Rot [\u3cem\u3eMacrophomina phaseolina\u3c/em\u3e (Tassi) Goid.]

Charcoal rot, caused by Macrophomina phaseolina (Tassi) Goid., is a disease that is a worldwide problem in soybean [Glycine max (L.) Merr.] production for which no highly resistant cultivars are currently available. It has been estimated that charcoal rot was among the most important diseases for suppressing yield of soybean in the USA from 1996 to 2007. Soybean breeding line DT99-16864 (Reg. No. GP-404, PI 675996), with moderate resistance to charcoal rot disease, was developed and released by the USDA-ARS, Stoneville, MS. DT99-16864 originated from a single F5 plant derived from a cross of ‘S59-60’ × ‘Bolivar’. The breeding population was advanced from the F2 to the F5 generation using the single-seed descent method. Colony-forming units, root and stem severity scores, and other rating methods indicated that DT99-16864 had significantly lower levels of M. phaseolina infection than susceptible checks in trials in Stoneville, MS, and Jackson, TN. In the Uniform Soybean Tests–Southern States, DT99-16864 was not significantly different from the check cultivars ’5002T’ and ’5601T’ for yield. DT99-16864 belongs to maturity group V and is later in maturity than DT97-4290, a moderately resistant charcoal rot line that is adapted to the midsouthern United States. The well-documented moderate resistance of DT99-16864 to M. phaseolina infestation, and good yield potential, will make this line useful for research and breeding