Functional marker-assisted selection for bacterial leaf blight resistance genes in rice (Oryza sativaL.)

Abstract

Evolving high yielding rice genotypes with durable resistance to bacterial leaf blight (BLB) is pertinent considering the extensive damage caused by the disease in most of the rice growing regions. Two high yielding BLB susceptible indica rice cultivars, ÔADT43Õ and ÔASD16Õ popular among farmers and consumers across South India have been introgressed with three BLB resistance genes xa5, xa13 and Xa21 from isoline IRBB60 using functional markers. The F 2 populations of 500 plants from ADT43 · IRBB60 and 806 plants from ASD16 · IRBB60 crosses were screened for the presence of all the three resistance genes. Thirty genotypes with three genes in homozygous and 55 genotypes with two genes in homozygous and one gene in heterozygous condition were identified. These pyramided genotypes with two or three resistance genes exhibited high levels of resistance against two predominant Xanthomonas oryzae isolates of South India. Among the 30 pyramided genotypes (xa5 + xa13 + Xa21), 12 were found to be significantly high yielding with desirable agronomic characteristics and the selection efficiency of the present markers was hundred percent.

Detection of bacterial blight resistance genes in basmati rice landraces

“…MAS is a pivotal tool for the pyramiding of such recessive genes in the presence of dominant genes such as Xa4 and Xa7. Successful pyramiding of these genes has delivered very promising results (Perumalsamy et al, 2010). Lack of both genes in commercial cultivars and their presence in the landraces tested in this study proved their erosion during the development of modern basmati rice cultivars.…”

“…Several BB-resistance genes have been identified and characterized in non-aromatic rice and incorporated and pyramided through MAS to develop resistant cultivars (Perumalsamy et al, 2010;Rajpurohit et al, 2010). However, their incorporation into the basmati background impairs the superfine grain quality and aroma of basmati rice.…”

“…Polymerase chain reaction (PCR)-based DNA markers for some of these genes have been identified: MP1 and MP2 for Xa4 (Ma et al, 1999), RM122 for xa5 (Chen et al, 1997), M5 for Xa7 (Porter et al, 2003), and RG136 for xa13 (Zhang et al, 1996). These markers have been employed to identify germplasm containing these genes (Blair and McCouch, 1997) and develop rice cultivars with single and multiple resistance genes (Perumalsamy et al, 2010;Rajpurohit et al, 2010). However, these studies have utilized non-aromatic sources as a donor parent in back-cross breeding approaches, which makes it extremely difficult to recover the prized basmati aroma and grain quality.…”

“…To date, approximately 34 genes (23 dominant and 11 recessive) conferring resistance against various strains of X. oryzae have been identified (Chen et al, 2011), largely in non-basmati rice. Major resistance genes, including Xa4, xa5, Xa7, xa13, and Xa21, have been incorporated into rice cultivars, in order to develop new resistant varieties (Perumalsamy et al, 2010). However, the cultivars containing a single major resistance gene proved susceptible due to pathogen mutation.…”

Identification of bacterial leaf blight resistance genes in wild rice of eastern India

“…To date, 34 genes (23 dominant and 11 reces sive) have been identified that confer resistance to various strains of Xoo (Chen et al, 2011). Major resistance genes, including Xa4, xa5, Xa7, xa13, and Xa21, have been incorporated into rice cultivars in order to develop new resis tant varieties (Perumalsamy et al, 2010). However, cultivars containing a single ma jor resistance gene proved susceptible due to pathogen mutation.…”