Abstract
Understanding of genetic diversity is important to explore existing gene in any crop breeding program. Most of the diversity preserved in the landraces which are well–known reservoirs of important traits for biotic and abiotic stresses. In the present study, the genetic diversity at twenty-four most significant blast resistance gene loci using twenty-eight gene specific markers were investigated in landraces originated from nine diverse rice ecologies of India. Based on phenotypic evaluation, landraces were classified into three distinct groups: highly resistant (21), moderately resistant (70) and susceptible (70). The landraces harbour a range of five to nineteen genes representing blast resistance allele with the frequency varied from 4.96% to 100%. The cluster analysis grouped entire 161 landraces into two major groups. Population structure along with other parameters was also analyzed to understand the evolution of blast resistance gene in rice. The population structure analysis and principal coordinate analysis classified the landraces into two sub–populations. Analysis of molecular variance showed maximum (93%) diversity within the population and least (7%) between populations. Five markers viz; K3957, Pikh, Pi2–i, RM212and RM302 were strongly associated with blast disease with the phenotypic variance of 1.4% to 7.6%. These resistant landraces will serve as a valuable genetic resource for future genomic studies, host–pathogen interaction, identification of novel R genes and rice improvement strategies.
Highlights
Rice (Oryza sativa L.) is the staple food for more than half of the world’s population [1] and depends on rice for more than 20% of their daily calorie intake [2]
Based on the blast disease scoring data for consecutive two seasons in the Uniform Blast Nursery (UBN), 161 landraces were categorized into three groups; twenty one (HR; 13.04%) were highly resistant, seventy (MR; 43.47%) exhibited moderate resistance and seventy (S; 43.47%) showed susceptible reaction (Table 2)
We investigated the genetic diversity of geographically diverse Indian landraces which are unique, unexplored and untapped germplasm for blast resistance genes that originated from nine major rice growing states of India with diverse ecology using major blast resistance genes
Summary
Rice (Oryza sativa L.) is the staple food for more than half of the world’s population [1] and depends on rice for more than 20% of their daily calorie intake [2]. By 2035, it is expected that an extra 116 million tonnes of rice will be required to feed the world’s increasing population [3]. This projected production has to be inevitably met with the expected water scarcity, less arable land, new emerging pathogens and pests and likely adverse effects of climate change [4]. The rice crop is affected by several diseases, of which blast disease caused by the fungus Magnaporthe oryzae is one of the most devastating disease causing enormous losses worldwide. The utilization of R (resistant) genes is the most economically viable and environmentally friendly choice for the control of this disease. Resistance is generally conferred by either major R genes that provide complete protection against few races of the pathogen or minor genes, which conferred partial protection [10]
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