Novel Sources of Pre-Harvest Sprouting Resistance for Japonica Rice Improvement.

Jae-Sung Lee,Ji-Ung Jeung,Kenneth L Mcnally,Ajay Kohli,Youngjun Mo,Woong-Jo Hyun,Dmytro Chebotarov,Valerien Pede,Tri Deri Setiyono,Rency Raquid

doi:10.3390/plants10081709

Abstract

Pre-harvest sprouting (PHS), induced by unexpected weather events, such as typhoons, at the late seed maturity stage, is becoming a serious threat to rice production, especially in the state of California, USA, Japan, and the Republic of Korea, where japonica varieties (mostly susceptible to PHS) are mainly cultivated. A projected economic loss by severe PHS in these three countries could range between 8–10 billion USD per year during the next 10 years. Here, we present promising rice germplasm with strong resistance to PHS that were selected from a diverse rice panel of accessions held in the International Rice Genebank (IRG) at the International Rice Research Institute (IRRI). To induce PHS, three panicle samples per accession were harvested at 20 and 30 days after flowering (DAF), respectively, and incubated at 100% relative humidity (RH), 30 °C in a growth chamber for 15 days. A genome-wide association (GWA) analysis using a 4.8 million single nucleotide polymorphisms (SNP) marker set was performed to identify loci and candidate genes conferring PHS resistance. Interestingly, two tropical japonica and four temperate japonica accessions showed outstanding PHS resistance as compared to tolerant indica accessions. Two major loci on chromosomes 1 and 4 were associated with PHS resistance. A priori candidate genes interactions with rice gene networks, which are based on the gene ontology (GO), co-expression, and other evidence, suggested that a key resistance mechanism is related to abscisic acid (ABA), gibberellic acid (GA), and auxin mediated signaling pathways.

Highlights

International Rice Research Institute (IRRI) station (Figure 1), it had not been defined for when Pre-harvest sprouting (PHS) stress level is highly likely station (Figure 1), it had not been defined for when PHS stress level is highly likely to to increase under Philippine weather conditions
PHS resistance was higher in the 20 days after flowering (DAF) group with a mean of
PHS resistance was higher in the 20 DAF group with a mean of 69.08% than

Summary

Introduction

Pre-harvest sprouting (PHS), the germination of seeds on mother plants before harvest, occurs in many cereal crops, such as wheat, barley, and rice, when seeds lose dormancy under warm and humid circumstances prior to harvest [1,2]. Seed dormancy is a critical trait for survival in nature because it suppresses germination until favorable environmental conditions occur for plant growth. The excessive loss of dormancy can cause serious PHS damage, decreasing crop yield and resulting in significant economic loss [4]. As compared to wheat or barley, PHS has been much less of a threat to rice production since the weather during rice harvest seasons is relatively dry and cool.

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Results