Drought and submergence have been the major constraint in rice production. The present study was conducted to develop high-yielding rice lines with tolerance to drought and submergence by introgressing Sub1 into a rice line with drought yield QTL (qDTY; QTL = quantitative trait loci) viz. qDTY3.1 and qDTY12.1 using marker-assisted breeding. We report here the effect of different combinations of Sub1 and qDTY on morpho-physiological, agronomical traits and yield under reproductive stage drought stress (RS) and non-stress (NS) conditions. Lines with outstanding performance in RS and NS trials were also evaluated in vegetative stage submergence stress (VS) trial to assess the tolerance level. The QTL class analysis revealed Sub1 + qDTY3.1 as the best QTL combination affecting the measured traits in RS trial followed by Sub1 + qDTY12.1. The effects of single Sub1, qDTY3.1 and qDTY12.1 were not as superior as when the QTLs are combined, suggesting the positive interaction of Sub1 and qDTY. Best performing lines selected from the RS and NS trials recorded yield advantage up to 4453.69 kg ha-1 and 6954 kg ha-1 over the parents, respectively. The lines were also found having great tolerance to submergence ranging from 80% to 100%, contributed by a lower percentage of shoot elongation and reduction of chlorophyll content after 14 days of VS. These lines could provide yield sustainability to farmers in regions impacted with drought and submergence while serving as important genetic materials for future breeding programs.
Pembiakbakaan padi tahan kemarau menjadi agenda utama ahli pembiak baka namun ia amatlah penting bagi memastikan
kultivar padi baru tahan kemarau yang bakal dihasilkan mampu memenuhi cita rasa pengguna daripada segi ciri
fisio-kimia serta kualiti beras dan nasi. Dalam kajian ini, sebanyak sepuluh genotip padi yang terdiri daripada lapan
titisan piramid padi tahan kemarau (PLs) dan dua induk, MR219 dan MRQ74 dinilai bagi ciri fisio-kimia dan kualitinya.
Kesemua genotip mempunyai kandungan amilosa (AC) yang sederhana iaitu dalam julat 20% hingga 25% kecuali PLMR219-G1 (AC rendah - 16%) dan induk MRQ74 (AC tinggi - 27%). Selain itu, kesemua genotip juga mempunyai suhu
pengelatinan (GT) yang sederhana, konsistensi gel (GC) yang lembut serta mempunyai bentuk beras yang tirus. Tiada
perbezaan yang signifikan diperoleh antara PLs dan induk untuk kesemua atribut dalam analisis hedonik kecuali bagi
ciri aroma dalam populasi MRQ74. Skor PL-MRQ74-G1 bagi ciri aroma dalam ujian sensori berbeza secara signifikan
dengan induk menunjukkan bahawa nasi yang dihasilkan PL ini tidak wangi. Analisis genotip turut mengesahkan gen
yang mengawal ciri aroma, alel badh2 tiada dalam PL-MRQ74-G1 disebabkan rekombinasi semasa silangan. Namun
demikian, alel badh2 hadir dalam PL-MRQ74-G2 yang menyokong hasil ujian hedonik dan PL ini tidak berbeza dengan
MRQ74 bagi atribut aroma. Secara amnya, PLs serupa dengan beras komersial yang merupakan induk mereka bagi ciri
fisio-kimia dan kualiti. PLs yang tahan kemarau ini boleh dikomersialkan kerana memenuhi cita rasa pengguna Malaysia
yang sukakan nasi yang lembut dan tirus selain tempoh memasak yang singkat.
Drought has been a major limiting factor for rice production. Drought yield QTLs (qDTYs; QTLs = quantitative trait loci) were pyramided into MRQ74 and MR219 to produce drought tolerant lines. In this study, new drought tolerant MRQ74 and MR219 pyramided lines (PLs) were evaluated under drought stress (RS) and non-stress (NS) conditions to evaluate the effects of different qDTYs combinations on morphological and agronomical traits. MRQ74 PLs having qDTY12.1 possessed the best root length (RL) under both RS and NS but the effect was only significant for MR219 PLs under RS. Some qDTYs combinations also found to have consistent effect on the same trait of both populations. PLs with only qDTY12.1 showed the highest grain yield (GY) under RS in both populations which means qDTY12.1 controlled RL and caused higher GY under drought condition. The interaction of major-effect qDTY12.1 with qDTY2.2 also shows significant effect on leaf rolling (LR) of both PL populations. These qDTYs proved to be beneficial in improving traits related to drought tolerance. Selected PLs with qDTY12.1 combinations also found to have better RL and root weight (RW) under RS. Improvement of morphological and agronomical traits led to higher GY of PLs. Therefore, qDTY12.1 either is present singly or in combination with other qDTYs was the best qDTY due to its consistent effect on morphological and agronomical traits and GY across populations under RS and NS.