Biology subjects

Wissuwa, M.

Publications and source records attributed to Wissuwa, M..

4 recordsLinked to original sources

bioRxiv2025

New rice varieties with improved phosphorus-efficiency for low-input smallholder rice production in Africa

Smallholder farmers in Sub-Saharan Africa frequently produce rice in marginal environments where low soil fertility and other biotic and abiotic stresses limit productivity. Rice varieties developed by centralized breeding under favorable conditions on research stations have often not been adopted by farmers in such marginal environments. Our objective was to develop modern rice varieties adapted to such low-input conditions through combining pre-breeding research with subsequent selection and variety testing directly in the target environment: smallholder farmers fields in Madagascar with phosphorus (P) fixing soils. Two breeding populations were developed for this purpose, one based on marker-assisted introgression of the Pup1 locus into IR64, the second using a donor (DJ123) for internal P utilization efficiency and external P acquisition efficiency. Selection within these populations was conducted in fields managed according to local farmers practice without mineral fertilizer addition. Selected breeding lines underwent government-supervised variety release testing including farmer participatory evaluations in four Malagasy regions between 18-1350 masl altitude, and two lines were released as varieties FyVary32 and VyVary85. Both had between 0.47-0.8 t ha-1 higher grain yield than parent IR64 and local check X265. Yield advantages were stable across a range from 2.1-5.5 t ha-1 (national average: 2.8 t ha-1). Higher yields were accompanied by superior root development and P uptake and by more efficient internal P utilization in FyVary85. Results show that decentralized breeding in marginal environments can produce varieties not only superior in lowest-yielding environments but across a broader range, clearly surpassing national average yields.

plant biology↗

bioRxiv2025

Natural variation in IBF1 disrupts its interaction with CHS1 and affects metabolism of hulls in rice

Secondary metabolites in plants have various physiological functions, including antioxidant and antibacterial activities. Previous studies have suggested genes and associated molecular mechanisms involved in the production of diverse secondary metabolites. However, much less is known about the genetic bases underlying within-species diversity in metabolite accumulation patterns, particularly in less focused tissues such as rice hulls. In this study, we aimed to identify the causal variant that affects flavonoid accumulation in rice hulls. We identified an F-box containing protein IBF1 is causal for genotypic differences in hull color through positional cloning. The variety IR64, with straw-white hulls, harbors functional IBF1 proteins that interact with a chalcone synthase, CHS1. Conversely, frame-shift mutations of IBF1 in the variety DJ123, which has pigmented hull color, resulted in a lack of a Kelch domain essential for the IBF1-CHS1 interaction. As a result, the DJ123 variant of IBF1 (IBF1DJ123) no longer interacted with CHS1, which was further supported by deep learning-based protein structural modeling. Further metabolome and transcriptome analyses using IR64 and an IR64-based chromosomal segment substitution line (CSSL) carrying IBF1DJ123 revealed an increase in the content of multiple flavonoids (such as naringenin and luteolin), while suppressing the expression of CAD involved in lignin synthesis. Metabolites in the CSSL carrying IBF1DJ123 suppressed the growth and siderophore generation activity of Pantoea species, which can act as beneficial or pathogenic endophytes. This study highlights the impact of a single gene on diverse metabolite accumulation patterns and suggests that this change may provide defense against pathogens.

plant biology↗

bioRxiv2024

A DJ123 allele at the heading date quantitative trait locus qHd7.1 promotes early heading without yield penalties under natural short-day and low fertility conditions in Madagascar

QTL analysis of heading date (Hd) was performed using a recombinant inbred line population derived from a cross between rice cultivars IR64 and DJ123. Phenotypic data was obtained from sites in Japan and Madagascar differing in photoperiod and soil fertility. The Japan site had long-days (LD) and high fertility, while the Madagascar site had short-days (SD) and low fertility conditions. Under LD in Japan, we discovered two Hd QTL on chromosome 7, qHd7.1 and qHd7.2, whereas only one of these (qHd7.1) was detected under SD conditions in Madagascar. RILs carrying DJ123 alleles at both QTLs headed 9.5 days earlier in Japan (LD) compared to IR64 alleles, whereas the effect of DJ123 alleles at qHd7.1 under SD conditions of Madagascar was 4 days and a combined effect of qHd7.1 and qHd7.2 did not exist. In Madagascar, early heading did not carry a yield penalty, whereas it caused reduced grain yield in Japan. These results suggest that RILs harboring the DJ123 allele of qHd7.1 have high yield potential and good adaptation to low fertility conditions in Madagascar and that this can be achieved in a shortened cultivation period, improving resilience to effects of climate change for African rice farmers.

plant biology↗

bioRxiv2024

Comparative root transcriptome analysis suggests down-regulation of nitrogen assimilation in DJ123, a highly phosphorus-efficient rice genotype

Many cultivable lands across the globe are characteristically low for plant-available phosphorus (P). This necessitates application of P fertilisers, but this increases farming costs beyond the affordability of marginal farmers. Thus, developing cultivars with high P-use efficiency (PUE) is necessary in high-yielding modern rice varieties, which are typically inefficient in P usage. However, the molecular and physiological bases to increase PUE in crops remain elusive. Here, we studied root transcriptomes of two breeding parents contrasting in PUE via RNA-seq to elucidate key physiological and molecular mechanisms that underlies efficient use of P in rice. Examination of transcriptome data obtained from plants grown under P-sufficient and P-deficient hydroponic conditions in DJ123 (an upland rice genotype adapted to low P soils) and IR64 (a modern rice variety less efficient in P use) revealed that the genes encoding nitrogen assimilation-related enzymes such as glutamine synthetase [EC. 6.3.1.2], glutamate synthase [EC. 1.4.1.13], and asparagine synthetase [EC. 6.3.5.4] were down-regulated only in DJ123 roots while it was not significantly affected in IR64 under low P conditions. In addition, DJ123 roots had a lower total nitrogen (N) concentration than IR64 irrespective of P conditions. Taken together, we surmise that the low level of N concentration together with down-regulation of the N assimilation-related genes allow DJ123 to operate at a low level of N, thus leading to formation of root tissues with lower metabolic investment and a greater PUE.

plant biology↗