Abstract
RD6 is one of the most favorable glutinous rice varieties consumed throughout the north and northeast of Thailand because of its aroma and softness. However, blast disease and salt stress cause decreases in both yield quantity and quality during cultivation. Here, gene pyramiding via marker-assisted backcrossing (MAB) using combined blast resistance QTLs (qBl 1, 2, 11, and 12) and Saltol QTL was employed in solving the problem. To pursue our goal, the RD6 introgression line (RGD07005-12-165-1), containing four blast-resistant QTLs, were crossed with the Pokkali salt tolerant variety. Blast resistance evaluation was thoroughly carried out in the fields, from BC2F2:3 to BC4F4, using the upland short-row and natural field infection methods. Additionally, salt tolerance was validated in both greenhouse and field conditions. We found that the RD6 “BC4F4 132-12-61” resulting from our breeding programme successfully resisted blast disease and tolerated salt stress, while it maintained the desirable agronomic traits of the original RD6 variety. This finding may provide a new improved rice variety to overcome blast disease and salt stress in Northeast Thailand.
Highlights
Rice (Oryza sativa L.) is consumed as a staple food in Asia, especially in the southeast region.In Thailand, the indica rice variety RD6 developed from KDML105 through gamma irradiation is one of the most favorable glutinous rice consumed throughout the northeast of Thailand [1,2]
The F1 population (RGD07005-12-165-1 × Pokkali) was backcrossed with RGD07005-12-165-1 using marker-assisted selection (MAS) through BC2 F2, in which the MAS contained genes of the glutinous type, aromatic, and gelatinization temperature (GT); and the BC2 F2:3 populations were evaluated for salt tolerance and blast resistance
Was crossed back to RD6 to produce the BC3 F1, in which the BC3 F1 was developed through the BC3 F4 population by MAS
Summary
Rice (Oryza sativa L.) is consumed as a staple food in Asia, especially in the southeast region.In Thailand, the indica rice variety RD6 developed from KDML105 through gamma irradiation is one of the most favorable glutinous rice consumed throughout the northeast of Thailand [1,2]. Its yield of 4.16 ton/ha fails to meet its potential, due to biotic and abiotic stress. Rice blast disease caused by the fungus Pyricularia grisea (Cooke) Sacc. Leads to crop losses up to 85% of total yield [3]. Disease symptoms occur in all stages of plant growth, beginning with blast discoloration and wilting of the foliage [4]. Neck blast can be found at the flowering stage, accelerating plant death [5]. Development of new rice varieties resistant to blast fungus is an alternative approach to diminish or control the invasion of this pathogen. The resistance quantitative trait loci (QTL) have been investigated to achieve parental varieties, which are further used for gene pyramiding in breeding programmes. More than 100 blast-resistant genes have been identified, of which
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