Allelic relationships of anthracnose (Colletotrichum lindemuthianum) resistance in the common bean (Phaseolus vulgaris L.) cultivar Michelite and the proposal of a new anthracnose resistance gene, Co-11

Abstract

The genetic resistance of Phaseolus vulgaris L. cultivar Michelite to races 8 and 64 of Colletotrichum lindemuthianum, causal agent of bean anthracnose, was characterized. Crosses were made between Michelite and Mexico 222 cultivars and the F2 population was inoculated with race 64 in order to study the inheritance of resistance to anthracnose in Michelite. The segregation of F2 population fitted in a ratio of 3R:1S, showing the presence of a dominant gene in Michelite gene conditioning resistance to race 64. Allelism tests were conducted with F2 populations derived from crosses between Michelite and AB 136, AND 277, BAT 93, Cornell 49-242, G 2333, Kaboon, Mexico 222, Michigan Dark Red Kidney (MRDK), Ouro Negro, Perry Marrow, PI 207262, TO, TU, and Widusa. All the cultivars (except Mexico 222) were resistant to race 64. While F2 derived from the Michelite x Mexico 222 was inoculated with race 8. Additionally, allelism tests indicated that the gene present in Michelite is independent from Co-1, Co-2, Co-3, Co-4, Co-5, Co-6, Co-7, Co-9 and Co-10 genes. The monogenic inheritance observed in Michelite and the independence of this gene from those previously characterized allow the authors to propose that the anthracnose resistant gene in Michelite should be named Co-11

<b>Classification of <i>Colletotrichum lindemuthianum</i> races in differential cultivars of common bean

“…In Santa Catarina State, according to Gonçalves-Vidigal, Silva, Vidigal Filho, Gonela, and Kvitschal (2007), race 65 was the most frequent, identified in 11 of the 32 isolates evaluated. Those results agree with the results obtained in this study, in which races 65 and 81 were the most frequent among the 51 isolates classified (Table 3).…”

New Insights into the Anthracnose Resistance of Common Bean Landrace G 2333

“…Genetic resistance is the most cost effective means to control the disease. Eleven major anthracnose resistance genes (Co-1 -Co-11) have been characterized in common bean and are available for use in breeding programs [1,2]. Achieving durable anthracnose resistance poses a challenge to bean breeders.…”

“…Young et al [7] also demonstrated that SEL 1308 carried a single dominant gene that proved to be allelic to the Co-4 gene in the differential cultivar TO. This allele was named Co-4 2 as it conditioned resistance to a broader array of races than the original allele in TO. RAPD markers linked to the Co-4 2 allele confirmed the presence of Co-4 2 in G 2333 and afforded the opportunity to identify the third gene in G 2333.…”

“…Since race 515 defeats the Co-5 gene, a 2-gene segregation ratio would imply presence of Co-4 2 and Co-7 genes, where Co-7 is resistant to race 515. In the case of race 3 to which Co-4 2 and Co-5 genes condition resistance, the Co-7 gene must be susceptible to race 3.…”

“…Since race 515 defeats the Co-5 gene, a 2-gene segregation ratio would imply presence of Co-4 2 and Co-7 genes, where Co-7 is resistant to race 515. In the case of race 3 to which Co-4 2 and Co-5 genes condition resistance, the Co-7 gene must be susceptible to race 3. Alzate-Marin et al [9], in Brazil, reported another15:1 segregation ratio in a F 2 population from the cross Ruda/G 2333 inoculated with race 73, again suggesting that G 2333 possesses only two independent genes Co-4 2 and Co-5, based on the published work.…”