**1. Introduction**

Uganda is a tropical country that lies astride equator, but with modified climatic conditions due to large water bodies and high peaked mountains. The altitude varies from 614 to 5,111 metres above sea level (masl) with much of the rice production areas falling within an altitude ranging from 1,000 to 1,400 masl. The least and the highest recorded temperature within the rice production agro-ecology is 8°C and 38°C, respectively, whereas on the basis of the average for the entire country, lowest temperatures range between 10°C and 17°C and highest from 23°C-25°C. The annual rainfall intensity in Uganda varies from 600 mm to 2,500 mm with much of the country receiving between 900 mm and 1,800 mm of rainfall. Owing to the diversity in the climatic conditions, rice production ecologies in Uganda are

classified into three broad categories of rain-fed upland, irrigated and rain-fed lowland production areas. The total land area suitable for rain-fed upland rice production constitutes an estimated 70% of the arable land in Uganda and are mostly located within Upper Nile basin in the Northern region and Albert basin in Western Uganda [1]. The area is classified into four zones on the basis of availability of water for production and proximity to critical services for rice production, namely Upper Nile basin, Albert basin, Victoria basin and Kyoga basin. The upper Nile basin drains an area of 48,911 sq. km<sup>2</sup> comprising Albert Nile (21,234 sq. km<sup>2</sup> ) and Aswa catchment. The Albert basin covers 21,875 sq. km<sup>2</sup> with 4.5% of the area being permanent wetlands and 3.5% seasonal/ temporary wetlands while Victoria zone covers 30, 880 sq. km<sup>2</sup> and Kyoga zone covering 137,500 sq. km<sup>2</sup> . Overall, a total of 239,166 sq. km<sup>2</sup> catchment basin suitable for rice production is located in Uganda. Of the Uganda's 241,500 sq. km<sup>2</sup> catchment area, 15% is open water and 3% represent permanent wetland area while 9.4% comprise the seasonal wetland area. In essence, therefore, much of the Uganda's land surface is collectively suitable for rain-fed and irrigated rice production.

Rice was introduced to Uganda in the early 1900's, but the exact year remains contradicting as the different years of 1904 [2] and 1910 [3] were reported. In addition, other authors believed that rice was already introduced into the country by end of the 1870's, the time when the Arab community grew rice for their consumption [4]. However, it was believed that rice was first introduced in milled form for consumption by European administrators and Indian businessmen as well as Indian rail construction workers, the 'coolies' who built the railway line then referred to as the 'Iron Snake', from Mombasa to Uganda. Subsequently, small observation and minimal fields were latter established during the period from 1904 to 1940 by Swahili and Indian staff and Church Missionary Society (CMS) staff [2]. In the year 1921, rice was already recognized and reported as one of the food crops produced and promoted in the country [5]. Rice production was promoted further during the World War II in 1939–1945 to provide food to soldiers. Progressively, a successful irrigated rice trial was launched in central Uganda [2] and by 1940's, commercial production of rain-fed lowland rice in the country had increased [2, 6]. Later, during the 1950's, the Uganda government developed further interest in rice and potential for irrigated rice farming. Subsequently, two irrigation schemes of Kibimba and Doho were developed in the 1970's in Eastern Uganda and later on a third rice irrigation scheme was constructed at Olweny swamp in Northern Uganda.

Given the relatively many decades of rice cultivation of the introduced rice crop and with expanding acreage under production, a long-standing draw back to irrigated and lowland rice production of pests and diseases were reported [2, 3, 6–9]. In most cases, some of the then existing varieties were dropped due to susceptibility to insect pests and diseases [7]. With this background constraints threatening rice yield, the rice breeding program was inevitably established to identify and incorporate broad-spectrum and durable resistance (BSDR). The initial stage was to identify the genetic donors for the targeted traits for the improvement through characterization and conservation of germplasm collections. This was followed by development of segregating populations and selection of genotypes possessing the desirable traits and identify candidate rice genes contributing towards BSDR through co-localization with resistance to different stress genes. The new lines generated were then advanced through anther culture technique and modified Rapid Generation Advance (RGA) technique, for which the anther culture technique has proved useful in improvement of selection efficiency for yield and other traits of low heritability. In addition, the doubled haploid lines developed from the RGA have been associated more with additive genetic variance component compared to the conventional F2 and F3 generations as the dominance variance

### *Irrigated and Rain-Fed Lowland Rice Breeding in Uganda: A Review DOI: http://dx.doi.org/10.5772/intechopen.97157*

component is eliminated in double haploid technology, implying higher irritability of these economic traits in rice [10]. It was reported that in the case of F3 and F4, both additive and dominance gene effects contribute to phenotypic differences between individuals, which tends to mask the expression of the desired traits [11] whereas variation in doubled haploid progeny is only due to some environmental effects.

The elite breeding lines were then evaluated in replicated yield trials and multilocation testing to identify promising lines for onwards evaluations on-farm and testing in National Trials following the National Variety Release guidelines and subsequently the promising lines basing on the key preferred production and quality attributes are nominated to the National Variety Release Committee of Uganda for approval and release as new rice varieties.

Key attributes of preferred rice for production are highlighted below:

