A study on the susceptibility of rice cultivars to Striga hermonthica and mapping of Striga tolerance quantitative trait loci in rice

Abstract

Summary• Striga is a parasitic weed attacking mainly maize, sorghum, millet and cowpea. Studying the interaction between rice and Striga is valuable since rice is a model monocot. In this paper, the susceptibility of different rice cultivars to S. hermonthica was tested and quantitative trait loci (QTL) for Striga tolerance mapped on the Bala × Azucena F 6 population.• Seven rice cultivars were grown with and without S. hermonthica for 14 wk. For the mapping experiment, 115 recombinant inbred lines (RILs), along with Azucena and Bala, were grown with and without Striga for 11 wk.• Rice cultivars tested had different susceptibilities to Striga, ranging from highly susceptible to completely resistant. Azucena and Bala differed in the speed of Striga emergence and the impact on host growth. A genomic region between positions 139 and 166 cM on chromosome 1 was identified containing strong QTL (LOD = 4.9-15.7) for all traits measured.• This indicates that genes for Striga tolerance exist in rice germplasm and the mapped QTL can be further studied to promote understanding of the nature of resistance/tolerance and breeding for Striga-resistant crop plants.

Natural variation of rice strigolactone biosynthesis is associated with the deletion of two MAX1 orthologs

“…The later establishment of infection in Azucena likely explains the higher tolerance to Striga, similar to what was observed in sorghum, where tolerant varieties generally exhibit later Striga emergence (40). Intriguingly, Striga postattachment resistance mapped to the same position on chromosome 1 as the QTL discussed in the present work (near marker C1370) in a cross between Nipponbare and Kasalath (21), with the Nipponbare allele conferring greater resistance (41). Nipponbare contains the same allele as Azucena, and we confirmed that Kasalath carries the same allele as Bala for the locus under study.…”

“…However, although decreased SL biosynthesis results in less Striga germination, it is unclear whether SL levels also affect Striga attachment. In earlier work, Striga tolerance mapped to the same region as qSLB1.1, with the Azucena allele increasing Striga tolerance (21), even though in the present study we showed there were more Striga emerging on Azucena in controlled environments (Fig. 1A).…”

“…all five SLs detected in rice exudates. This locus was also detected as a QTL for rice-Striga interaction in a previous study that used the same population (21). Here we show that the QTL is due to a rearrangement of a 51-to 59-kbp stretch between 28.9 and 29.0 Mbp of chromosome 1 in the Bala genome.…”

“…Given the different amounts of SLs found in the parental lines, we used the Bala × Azucena mapping population (21) to map Striga germination, the level of SLs in root exudates, shoot and root fresh weight (fwt), and tillering. The broad sense heritabilities of all traits were high (78-97%) with the exception of methoxy-5-deoxystrigol isomer 1 (44%).…”

Evaluation of ecologies and severity of Striga weed on rice in sub-Saharan Africa

“…Gurney et al (2006) Gurney et al (2006). However, in the study conducted by Kaewchumnong and price (2008) on rice cultivars tolerance to Striga showed that the QTL for all rice traits in the Striga infected were present between position 139 and 169 cM on chromosome 1. The QTL LOD scores ranged from 4.9 to 15.7 and they were significant at 3.2.…”