Low temperature, particularly during the reproductive stage in rice (Oryza sativa L.), leads to reduced fertility and yield and is a major constraint faced in temperate rice ecology. The floral trait anther dehiscence length has not been quantified in relation to low-temperature tolerance in rice. Two controlled-temperature glasshouse experiments evaluated 120 genotypes from BC1F6 recombinant inbred lines when exposed to low air temperature at the booting (young microspore) and flowering stages. Genotypic differences existed for spikelet sterility (SS) after low-temperature exposure at booting and flowering stages, and a significant positive correlation (R2=0.22**) was found between SS of individual genotypes at booting and flowering stages. Number of dehisced anthers had the highest correlation with SS, and accounted for 58% and 44% of variation in SS with exposure to low temperature at booting and flowering, respectively. Anther dehiscence length and number of dehisced anthers were highly correlated (r=0.90**). After low-temperature exposure at booting, pollen number in the anther as well as the pollen’s capacity to germinate effectively further differentiated low-temperature-tolerant and -susceptible genotypes. Positive relationships (r=0.56** and 0.46*) between SS in the glasshouse and in field experiments in 2015 and 2016 seasons, respectively, provided validation of the phenotypic glasshouse screening methods utilised for low-temperature tolerance in relation to target production environments. This repeatable phenotyping system in combination with improved understanding of underlying floral traits will lead to increased efficiency in breeding for low-temperature tolerance in rice.

Prioritas pembangunan pertanian untuk memenuhi kebutuhan pangan nasional semakin meningkat seiring peningkatan jumlah penduduk. Peningkatan produksi salah satunya dengan penggunaan pupuk anorganik, namun penggunaan yang terus menerus memicu terjadinya degradasi lahan dan air. Pupuk organik merupakan salah satu solusi untuk memperbaiki kondisi tersebut. Penelitian bertujuan untuk menganalisis respon pertumbuhan, hasil dan efisiensi pemakaian air padi Inpari 33 pada perlakuan pupuk anorganik dan organik. Penelitian dilaksanakan pada bulan Juli-Desember 2020 di IP2TP Sukamandi Balai Besar Penelitian Tanaman Padi Subang Jawa Barat. Rancangan percobaan yang digunakan split plot design dengan tiga ulangan. Petak utama adalah pupuk anorganik yang terdiri dari perlakuan tanpa NPK (kontrol), tanpa N, tanpa K, tanpa P dan NPK. Anak petak yaitu pupuk organik terdiri dari pupuk kandang sapi, kompos jerami dan tanpa organik. Hasil percobaan menunjukkan bahwa pupuk anorganik meningkatkan jumlah anakan 44-49%, nilai SPAD 11-12%, hasil 33-51%; dan efisiensi pemakaian air tertinggi 1.17 g gabah L-1 air pada perlakuan tanpa pupuk P. Pupuk organik tidak meningkatkan pertumbuhan, hasil dan efisiensi penggunaan air. Interaksi pupuk anorganik dan organik mempengaruhi jumlah anakan, jumlah malai per rumpun, berat 1,000 butir dan total evapotranspirasi. Penambahan pupuk kandang sapi sangat mempengaruhi jumlah anakan dan total evapotranspirasi pada perlakuan tanpa pupuk P. Kata kunci: evapotranspirasi, hara, kompos, NPK, pupuk kandang

Low temperatures at the young microspore stage (YMS) decreases spikelet fertility and is a major limiting factor to rice production in temperate Australia. Low temperature tolerance is a difficult trait to phenotype, hence there is a strong desire for the identification of quantitative trait loci (QTL) for their use in markerassisted selection (MAS). Association mapping was used in several breeding populations with a known source of low temperature tolerance, Norin PL8, to identify QTL for low temperature tolerance. A novel QTL for spikelet fertility was identified on chromosome 6, qYMCT6.1, in which the Australian variety, Kyeema, was the donor for increased fertility. Additional five genomics regions were identified that co-located with previously reported QTL, two of which have been previously cloned. Additionally, for the first time a QTL for spikelet fertility qYMCT10.1, has been shown to co-locate with the number of dehisced anthers qYMCTF10.1 which increases the shedding of pollen from the anthers. This study revealed one new QTL for low temperature tolerance at YMS in temperate japonica germplasm and identified an additional five previously reported. These QTL will be utilised for MAS in the Australian rice breeding program and may have merit for temperate breeding programs globally.