Development and field performance of nitrogen use efficient rice lines for Africa

Abstract

SummaryNitrogen (N) fertilizers are a major input cost in rice production, and its excess application leads to major environmental pollution. Development of rice varieties with improved nitrogen use efficiency (NUE) is essential for sustainable agriculture. Here, we report the results of field evaluations of marker‐free transgenic NERICA4 (New Rice for Africa 4) rice lines overexpressing barley alanine amino transferase (HvAlaAT) under the control of a rice stress‐inducible promoter (pOsAnt1). Field evaluations over three growing seasons and two rice growing ecologies (lowland and upland) revealed that grain yield of pOsAnt1:HvAlaAT transgenic events was significantly higher than sibling nulls and wild‐type controls under different N application rates. Our field results clearly demonstrated that this genetic modification can significantly increase the dry biomass and grain yield compared to controls under limited N supply. Increased yield in transgenic events was correlated with increased tiller and panicle number in the field, and evidence of early establishment of a vigorous root system in hydroponic growth. Our results suggest that expression of the HvAlaAT gene can improve NUE in rice without causing undesirable growth phenotypes. The NUE technology described in this article has the potential to significantly reduce the need for N fertilizer and simultaneously improve food security, augment farm economics and mitigate greenhouse gas emissions from the rice ecosystem.

Expression of a cucumber alanine aminotransferase2 gene improves nitrogen use efficiency in transgenic rice

“…The seedlings were harvested at 21 days after seeding for evaluation of 6 traits: (1) root length, (2) shoot length, (3) root wet weight, (4) shoot wet weight, (5) root dry weight, and (6) shoot dry weight. The root dry weight was used as the criterion to select the lead events because previous studies show that expression of barley alanine aminotransferase leads to early establishment of a vigorous root system in transgenic rice [27, 28].…”

“…Evaluation was conducted in a greenhouse with applied nitrogen treatments following Selvaraj et al [27], i.e., N0 = 0 kg/ha, N1 = 90 kg/ha, N2 = 180 kg/ha, which was converted to the volume of soil in the pot. For N1 and N2, nitrogen was applied in three equal splits at 2 days after transfer (DAT), 10 DAT, and 30 DAT.…”

Genome-Wide Association Study and Identification of Candidate Genes for Nitrogen Use Efficiency in Barley (Hordeum vulgare L.)

“…Overexpression of OsNRT1.1 and OsNRT2.1 in rice increased NUE, grain yield, and plant growth ( Huang et al, 2017 ; Wang W. et al, 2018 ). In addition, an amino acid biosynthesis gene alanine aminotransferase incorporated from barley ( HvAlaAT ) into rice increased yields considerably under low-N treatment ( Shrawat et al, 2008 ; Selvaraj et al, 2017 ). Several transcription factors and protein kinases were reported to be involved in the plant N regulatory network ( Yang et al, 2014 ; Goel et al, 2018 ; Hsieh et al, 2018 ).…”

RDWN6XB, a major quantitative trait locus positively enhances root system architecture under nitrogen deficiency in rice

“…Nitrogen (N) pollution from fertilizers is the biggest environmental disaster affecting human health in multiple ways. Therefore, it is necessary to develop new rice lines/varieties with improved N use efficiency and high responses to N deficiency stress for rice breeding programs and sustainable rice production [13, 14]. Nitrogen deficiency conditions lead to a reduction in many agronomic traits and, as a result, growth rate, grain and biomass yield decrease [15].…”