Rice is the second most important cereal crop in  Malawi, after  maize.  It is  grown  in  three  ecologies  of  rain  fed lowland, irrigated lowland and rain fed upland with 80, 15 and 5% share, respectively.

The traditional rice cultivars in the rainfed ecosystem have many valuable genes possessing resistance to various biotic and abiotic stresses, unique grain quality and plant architecture.  Among these local strains, selections had been done and resulted in pure lines namely Faya 14 M 69 and Kilombero. Farmers prefer these landraces because they are aromatic, have large grains and are non-glutinous (Abade et al., 2016). However, these pure lines have shortcomings such as low yield potential, photoperiod sensitivity and prone to lodging. Rice productivity in Malawi is thus very low, with mean yields of only <2 t/ha (FAOSTAT, 2013).

The advancement in Biotechnology has allowed breeders to develop varieties in a much quicker way than anticipated. Different molecular markers such as Simple Sequence Repeat (SSR) are being used not as a replacement for but a valued supplement to conventional breeding in order to study valuable traits such as grain yield (Jeke, 2019). In a similar manner, several Doubled Haploid germplasms were produced through anther-culture in South Korea where plantlets are produced from the second filial generation (F2) or third generation (F3) by applying tissue-culture techniques using chemicals such as colchicines. In this study varieties that were selected and shared from elite doubled haploid germplasms of a collaborative project of KAFACI (RDA) and AGRA at Suwon in Korea and other lines from Senegal were used as plant materials. Anther-culture helps to reduce the breeding duration as the lines reach homozygosity within a shorter period than conventional breeding (Osman et al., 2020).

The objective of the present study was to evaluate grain yield of improved KAFACI rice varieties and assess their potential, and farmers’ preferences for growing under lowland conditions in Malawi.

Plant

Prior to conducting of the mother-baby trials, other trials were conducted in 2015 and 2016. This involved an on-station screening of 694 KAFACI rice germplasms collected from Korea and Senegal mainly for adaptability and performance in 2015. Thereafter 200 lines were selected and advanced into Observation Yield Trials (OYT) and Advanced Yield Trials (AYT) in 2016. In 2018 irrigated conditions, 100 KAFACI germplasms were also evaluated and seed increase conducted as a continuation process after a one season recess towards the Mother – Baby trials. The traits of focus as selection criteria were earliness to maturity, resistance to lodging, threshability, grain quality, resistance to abiotic and biotic stress conditions, grain quality and grain yield among others (Table 1).  

Experimental sites

The germplasms were evaluated at three (3) sites during the two seasons in a mother-baby trial approach. The description of the sites is presented in Table 2. The soils at the sites could be described as Vertisols comprising <45% clay and average pH 8.3 (Sistani et al., 1998).

Data collection and analysis

The recording of data was done on  productive tillers per square metre, plant height, days to attain 50% flowering, panicle length and grain yield (kg per ha) following the principles established by Jennings et al. (1979), at respective crop stages, using scoring procedures and scales prescribed in the Standard Evaluation System (SES) for rice (IRRI, 2013). Grain quality traits were determined for the genotypes, and results are presented in the form of DUS and VCU for the two varieties proposed for release. Data were analyzed statistically using GenStat software (VSN International, 2018). From the ‘Baby trials”, two traits were measured: days to maturity, as determined by the farmers, and grain yield measured from standard 5 m² plots. Genetics and Genotype × Environment (GGE) biplot analysis was adopted to evaluate the relative performance of genotypes for target environments based on principal component analysis and specifically the AMMI2 model that considers main effects and two axes (Kempton et al., 2012; Gomez and Gomez, 1984). The model for the GGE biplot (Yan, 2002), based on singular value decomposition of the first two principal components, was:

Yij – ì – aj = el îil cjl + e2 îi2 cj2 + εij,

where Yij is the measured mean of genotype i in environment j, ì is the grand mean, aj is the main effect of environment j, ì + aj  is the mean yield across all genotypes in environment j, e1 and e2 are the singular values for the first and second principal components, respectively, îi1 and îi2 are eigenvectors of genotype i for the first and second principal components, respectively, c1j and c2j are eigenvectors of environment j for the first and second principal components, respectively, aij is the residual associated with genotype i in environment j.

During participatory variety selection (PVS) and sensory tests, visual assessment of grain quality and organoleptic assessment of cooked rice were recorded. The hierarchical clustering was also done using Genstat 18th edition (Euclidean distance) to assess the diversity existing among the test rice genotypes.

Grain weight is a key determinant of grain yield in rice. The weight of the grain reflects capacity of the rice leaves to carry out photosynthesis processes in order to provide assimilates for grain formation. In essence, rice  genotypes that contribute large 1000 grain weight may imply ability to give higher spikelet fertility due to large assimilate sink size per panicle during early maturity stages. In this study, genotypes with the highest 1000 grain   weight   were   SR33705-HB3381-91  followed   by SR35285-HB3469-6, Sahel 177 and SR33705-HB3381-88 which were at par. Also, nine (9) genotypes had been classified as medium (21-25 g) while four (4) genotypes as high (26-30 g). In this regard, SR33705-HB3381-91 has the largest grain filling ability followed by Sahel 177, SR33705-HB3381-88 and SR35285-HB3469-6, and all surpassed the check variety. These results are in great agreement with earlier reports by Efisue et al. (2014).  The number of spikelets per panicle is one of the basic traits in the development of high yielding crops. It is the contribution of several spikelets within a plant which result into yield thus varieties with a reasonable number of spikelets result into increased yield. In this regard, the high mean number of spikelets/panicle in Sahel 328 (151) may be a contributing trait of making it a high yielding line while keeping other traits constant. The length of the panicle is a very important parameter in yield of crops because it helps to determine the number of spikelets which can be carried by a rice crop. The likelihood is that a rice crop with a longer panicle will possess more spikelets than a crop with a shorter panicle. In the present study, when other traits are kept constant, Sahel 328 (27 cm) Mtupatupa (26 cm), Sahel 177 (25 cm), Sahel 134 (24 cm) and SR-HB-6 (24 cm) would likely give high yield than those with shorter panicles, for example, SR35300-HB3467-5.

One of the selection criteria in rice breeding is plant height and is a fundamental agronomic trait for crop yield (Mathan et al., 2016). The International Rice Research Institute proposed that the “new plant type” should ideally have plant height of 90 to 100 cm. Furthermore, Li et al. (2014) hypothesized that in order to attain high grain yield in rice, plant height range of 110 to 125 cm should be attained. This is exacerbated by the fact that tall plants are well exposed to sunlight for the processes of photosynthesis thus increased yield. In the present study, the range of plant height for the KAFACI rice varieties was 76 to 95 cm as measured across three environments over the two seasons. According to the Standard Evaluation System for Rice (IRRI, 2013), these varieties are categorized as semi-dwarf. This implies that between the two varieties under release, Sahel 328 belongs to a new plant height category (92 cm) while SR35285-HB3469-6 does not belong to a new plant type. Nonetheless, the semi-dwarf plants have an advantage of withstanding lodging to which tall plants are prone.

The flowering behaviour of the test genotypes could be described as early maturing and therefore desirable for the rice cropping system in Malawi.

Days to 50% flowering, also defined as days to pre-heading period (PHP), can estimate growth period of varieties. Longer PHP gives vigorous rice plants and improves grain yield.  Li et al. (2014) stated that average PHP of 97 days was ideal for high-yielding varieties. The PHP results in this study showed that the mean PHP for the test varieties was less than 90 days. This suggests that the test varieties are early maturing and are  all  ideal for terminal drought escape and improving grain yield.

The tillering ability of varieties is illustrated by number of panicles/m² and is a key component of grain yield (Xing and Zhang, 2010). Panicle number is the basis for increasing the source and sink, and often guarantees higher yields. Li et al. (2014) reported that mean panicle numbers of 308 m^-2 was ideal to increase grain yield. Across the three sites in 2018/2019 season, the best two varieties produced 396 panicles/m² for SR35285-HB3469-6 and 414 panicles/plant for Sahel 328 and these were above the check variety. The number of panicles per plant directly controls the yield of a particular variety, Joachim (2015) and the general yield trend scales up from low to high for few to many panicles per plant, respectively.

The range of panicle number in this study for the test varieties was between 357 and 438 panicles/m², and this could be regarded as very ideal. 

The determination of physical dimension of rice varieties is of great importance because rice marketing is dependent on grain size and shape in addition to aroma. The grain length and width are fundamental attributes that determine rice shape. According to SES for rice (IRRI, 2013) on the brown rice length, the varieties were classified as medium (5.51 to 6.6 mm) for 3 varieties, long (6.6 to 7.5 mm) for 8 varieties and extra-long (more than 7.5 mm) for 3 varieties. Joachim (2015) reported that long grain rice is highly demanded by the rice consuming people and this also reflects well for consumers of rice in Malawi. In terms of grain length and width ratio, varieties of this study were categorized into two groups as medium (2.1 to 3.0) for 6 varieties and slender (over 3.0) for 7 varieties using the Standard Evaluation System for rice (IRRI, 2013) scale. Despite that the preference for rice grain traits differs with consumer groups, long and slender grains are generally preferred by Malawian consumers and farmers and are good valuable attributes that could be exploited to improve characteristics of the rice grain. The long and extra-long grains obtained in SR35285-HB3469-6 and Sahel 328, respectively, therefore can be used to meet the need of rice consumers in Malawi. The medium and slender shapes have also been used to describe the two varieties, namely, SR35285-HB3469-6 and Sahel 328, respectively.

Across the three sites in 2017/2018, the best two varieties were SR35285-HB3469-6 and Sahel 328, whose respect yields were 17 and 13% above the average yield of the check variety. The best two varieties in 2019 were also SR35285-HB3469-6 and Sahel 328, whose yields were 17 and 13% above the mean yield of the check variety, Mtupatupa.

GGE biplot analysis applies the functions of joint regression (Joachim, 2015) and additive main effects and multiplicative interaction (AMMI) (Gauch, 1992) to depict patterns of G×E interaction. The varieties SR35285-HB3469-6 and Sahel 328 gave high yields at  three  sites, suggesting above average adaptability. In a GGE Biplot, genotypes near to origin and with shortest vector illustrate both high mean and insensitive to the environmental interaction thus highly stable. Two main clusters have been identified in a hierarchical clustering pattern before other sub-clusters were identified among the studied rice varieties.

The two varieties, namely, SR35285-HB3469-6 and Sahel 328, showed grain yield superiority above the other 11 varieties (check variety inclusive) during both years of testing in all three locations. The plant height class for the test varieties was determined to be semi-dwarf, which is an idle character to minimize the risk of lodging which could result into the loss of grain. The two varieties also exhibited early maturity traits, and could be planted twice in a year. The variety Sahel 328 was high yielding and deemed to possess above average adaptability while SR35285-HB3469-6 also had high mean yields as well as high stability. Farmers preferred these two varieties because of acceptable grain qualities that included medium to  slender shape and length, average cooking time, absence of white belly and slight aroma good taste. The two varieties SR35285-HB3469-6 (a doubled haploid) and Sahel 328 were therefore released for lowland cultivation in Malawi mainly because results from this study had shown that they are high yielding, early maturing, have acceptable grain quality traits and very stable. The two varieties SR35285- HB3469-6 and Sahel 328 had been therefore released as Wachangu and Makafaci, respectively. The local name Wachangu translates to “earliness to maturity” while Makafaci is a borrowed acronym for Ma to mean Malawi and KAFACI to mean Korea-Africa Food and Agricultural Cooperation Initiative, thus Makafaci.

The authors have not declared any conflict of interests.

The test varieties in this study were collected through Korea Africa for Food and Cooperation Initiative (KAFACI) & AfricaRice Center (Senegal) programme. The study for the project was financially supported by Alliance for a Green Revolution in Africa (AGRA) & Rural Development Administration (RDA) of Korea. The Department of Agricultural Research Services (DARS) in Malawi provided technical know-how. Special thanks are extended to the staff of the Departments of Agricultural Research  Services  (DARS)  and  Agricultural  Extension Services (DAES), collaborating farmers at Mkondezi, Domasi and Nanzolo rice growing schemes for the tremendous support and active participation during Participatory Variety Selection (PVS).