Evaluation of Cold Tolerance in NERICAs Compared with Japanese Standard Rice Varieties at the Reproductive Stage

Abstract

New Rice for Africa (NERICA) is a general name for interspecific rice varieties derived from a cross between the high-yielding Asian rice (Oryza sativa L.) between locally adapted African rice (Oryza glaberrima Steud.). Eight NERICAs were evaluated for cold tolerance (CT) at the reproductive stage and compared with their O. sativa parents and three Japanese standard rice varieties over 3 years. Cold tolerance was evaluated based on the filled grain ratio (FGR) after cold water irrigation. The FGR was greatly reduced by cold water irrigation. NERICA 1, 2 and 7 had higher FGR (51.9-57.9 %), while NERICA 6, 15 and 16 had lower FGR (6.2-14.5 %). NERICA 1, 2 and 7 were less affected by cold stress, with a 31 % mean reduction in FGR, while NERICA 6, 15 and 16 were greatly affected, with their FGRs being reduced by more than 80 %. NERICA 3 and 4 were moderately affected by cold stress, with about 45 % reduction rate in FGR. FGR significantly influenced the grain weights of the varieties with strong positive correlations (r = 0.83-0.91; P < 0.001), and thus, similar trends in grain weights were observed. Grain weights were reduced by 61.7-96.4 % under cold stress. NERICA 1, 2 and 7 showed significantly better performance than NERICA 3 and 4, while NERICA 6, 15 and 16 performed poorly under cold water irrigation. The Japanese varieties Koshihikari (very tolerant) and Ozora (moderately tolerant) were more affected by cold water irrigation than NERICA 1, 2 and 7. On the basis of the mean reduction rate (%) in FGR under cold stress, the varieties were classified as follows: NERICA 1, 2 and 7 as tolerant; NERICA 3 and 4 as moderately tolerant; and NERICA 6, 15 and 16 as susceptible to cold stress. However, NERI-CA 7 grain yields were lower under cold stress due to both greatly reduced number of panicles per plant and number of spikelets per panicle. Therefore, NERICA 1 and 2 are suitable candidates for production in the highland regions of East Africa and should be promoted for production.

Effects of different water management practices on the dry matter production process and characteristics in NERICAs

“…Moreover, heavy panicle-type varieties with large sink size tend to have a higher proportion of pre-heading reserve assimilates in total carbohydrates in the panicles (Gendua et al, 2009;Kusutani et al, 1993;Miah et al, 1996;Saitoh et al, 1991;Song et al, 1990;Yamamoto, 1991). NERICA varieties are classified as panicle weight-type (Tsunematsu & Takagi, 2004) because of the higher number of spikelets per panicle and fewer panicles (Kikuta et al, 2017;Matsunami et al, 2009;Wainaina et al, 2015). Thus, morphological characteristics of the panicles might explain the higher proportion of pre-heading reserve assimilates in the total carbohydrate in the panicles of NERICAs (Table 3).…”

Drought-induced root plasticity of two upland NERICA varieties under conditions with contrasting soil depth characteristics

“…There are currently 18 varieties suited for upland growth conditions (NERICA 1 to NERICA 18) (Wainaina et al, 2015). The use of these improved rice varieties is expected to achieve remarkable yield improvements (Kijima et al, 2006) and therefore catalyze a rice green revolution in sub-Saharan Africa (Matsumoto et al, 2014).…”

Identification and validation of QTLs for cold tolerance at the booting stage and other agronomic traits in a rice cross of a Japanese tolerant variety, Hananomai, and a NERICA parent, WAB56-104

“…The relationship between spikelet fertility and panicle number should be an important consideration while progressing crop improvement for cold tolerance involving WAB56-104 and its descendants such as the NERICAs. We have previously observed such a relationship to contribute to relatively high grain weights per plant under cold stress in NERICA 3 and 4 due to production of few panicles with high number of spikelets per panicle coupled with relatively high filled grain ratio (Wainaina et al, 2015).…”

“…Low temperatures, especially during panicle development and the booting stage, decrease the spikelet fertility of rice (Gunawardena et al, 2003;Shimono et al, 2002), resulting in considerable grain yield losses. In our previous study, we reported the suitability of NERICA 1 and NERICA 2 for production in the cold-prone regions of East Africa (Wainaina et al, 2015). Furthermore, we found out that WAB56-104 (O. sativa parent of NERICA1 to NERICA11) has greater cold tolerance based on spikelet fertility than the NERICAs and serves as a good genetic resource for breeding and improvement of cold tolerance of rice cultivars (Wainaina et al, 2015).…”

“…In our previous study, we reported the suitability of NERICA 1 and NERICA 2 for production in the cold-prone regions of East Africa (Wainaina et al, 2015). Furthermore, we found out that WAB56-104 (O. sativa parent of NERICA1 to NERICA11) has greater cold tolerance based on spikelet fertility than the NERICAs and serves as a good genetic resource for breeding and improvement of cold tolerance of rice cultivars (Wainaina et al, 2015). WAB56-104 has also been reported to possess other beneficial traits such as salinity tolerance and striga weed pre-attachment resistance (Awala et al, 2010;Jamil et al, 2011).…”