The shortening of Aegilops speltoides segment did not facilitate recombination between stem rust resistance genes Sr36 and Sr39 . Robustness of marker rwgs28 for marker-assisted selection of Sr39 was demonstrated. Stem rust resistance genes Sr39 and Sr36 were transferred from Aegilops speltoides and Triticum timopheevii, respectively, to chromosome 2B of wheat. Genetic stocks RL6082 and RWG1 carrying Sr39 on a large and a shortened Ae. speltoides segments, respectively, and the Sr36-carrying Australian wheat cultivar Cook were used in this study. This investigation was planned to determine the genetic relationship between these genes. Stem rust tests on F populations derived from RL6082/Cook and RWG1/Cook crosses showed tight repulsion linkage between Sr39 and Sr36. The genomic in situ hybridization analysis of heterozygous F family from the RWG1/Cook population showed that the translocated segments do not overlap. Meiotic analysis on the F plant from RWG1/Cook showed two univalents at the metaphase and anaphase stages in a majority of the cells indicating absence of pairing. Since meiotic pairing has been reported to initiate at the telomere, pairing and recombination may be inhibited due to very little wheat chromatin in the distal end of the chromosome arm 2BS in RWG1. The Sr39-carrying large Ae. speltoides segment transmitted preferentially in the RL6082/Cook F population, whereas the Sr36-carrying T. timopheevii segment over-transmitted in the RWG1/Cook cross. Genotyping with the co-dominant Sr39- and Sr36-linked markers rwgs28 and stm773-2, respectively, matched the phenotypic classification of F families. The RWG1 allele amplified by rwgs28 was diagnostic for the shortened Ae. speltoides segment and alternate alleles were amplified in 29 Australian cultivars. Marker rwgs28 will be useful in marker-assisted pyramiding of Sr39 with other genes.
The objective of this study was to assess diversity for stem rust and stripe rust resistance in an international wheat screening nursery under greenhouse conditions using pathotypes with known avirulence/ virulence profiles. A set of 95 entries of an international wheat screening nursery collected from material generated by staff of the International Maize and Wheat Improvement Centre (CIMMYT) was tested against seven Australian Pgt and five Pst pathotypes through artificial inoculation under the greenhouse conditions using standard procedures. Ten all-stage stem rust resistance genes (Sr8a, Sr8b, Sr9b, Sr12, Sr17, Sr23, Sr24, Sr30, Sr31 and Sr38) and seven all-stage stripe rust resistance genes (Yr3, Yr4, Yr6, Yr9, Yr17, Yr27 and Yr34) were postulated either singly or in combinations based on seedling responses of test entries against pathotypes differing in virulence for commonly deployed genes. Sr30 and Sr38 were the most common stem rust resistance genes in this nursery. The Sr38-linked stripe rust resistance gene Yr17 was present in high proportion. The presence of rust resistance genes Sr24, Sr31/Yr9, Sr38/Yr17 and Yr4 were confirmed using the closely linked molecular markers. The adult plant resistance (APR) genes Sr2 and Lr34/Yr18/Sr57 were detected using linked molecular markers csSr2 and csLV34, respectively. Genotypes carrying combinations of stem rust and stripe rust resistance were identified for use as donor sources in breeding programs.
Field pea is a key source of household income, food and nutrition in Uganda mainly produced in the high land areas of country including south western and Mt. Elgon. The crop fetches a high stable price across markets compared to other grain pulses and yet it has remained outside the mainstream of the research process. The status of this commodity is largely unknown yet such information would support its research agenda to improve productivity and marketing. A study was conducted in the Mt. Elgon sub-zone to determine the status of field pea production, understand its constraints and map out its production cycle. This was done through a survey covering 5 districts namely; Bulambuli, Kapchorwa, Kween, Namisindwa and Mbale. In each district two major field pea growing sub counties were purposively selected, in each sub-county 25 respondents were randomly sampled from a list of field pea producers. A structured questionnaire was then administered; data collated, and analyzed using descriptive statistics and chi-square test. The results revealed that the crop is grown by all gender categories with 60% grown for home consumption and 40% for income. In the districts of Kween and Mbale it is mostly grown for income since the Kween farmers have relatively larger pieces of land whereas Mbale being a commercial hub of the region there is relatively higher price throughout the year which attracts farmers to sell. Field pea is grown alongside other crops which varied by district but was largely grown as sole crop, along boundaries and intercrops depending on availability of land. It is also important to note that it forms a very important part of the rotation system because it plays a significant role in soil fertility restoration as well as serving as a break crop suitable for rotation to minimize the negative impact of cereal based mono-cropping.
A study determined the effects of row direction and integrated weed management on the growth, productivity and economics of upland rice at Ikulwe Research Station using a completely randomized block design, replicated thrice with NAMCHE 5 upland rice in Uganda (2021b & 2022b). 12 treatments with 6 weeding regimes namely Pre- emergence Butanil (PREB) + 1hand hoeing (HH), 2HH, 3HH, PREB + Post emergence Butanil (POEB), weekly weeding (42 days) and control (EW & NS orientation) were adopted. Nitrogen (100 kg) Phosphorus (60 kg) and Potash (40 kg) were applied ha-1. Collected data on plant height, tillers, leaves, panicles; and grains were subjected to ANOVA (13th edition Genstat). Higher growth and yield parameters were in EW than NS direction. Leaves (27-28 leaves), height (65-70 cm), tillers (5-6 tillers and panicles (4-5 panicles) plant-1 were high under 2HH, PREB +1HH, PREB + POEB and 3HH (EW) compared to similar treatments in NS direction during 2021b and 2022b. Grain yield (2.34 t ha-1; HH), (2.26 t ha-1; PREB + 1 HH), (2.01 t ha-1; PREB + POEB), (1.89 t ha-1; 3HH) was significantly high in 2021b. During 2022b increased panicles (4-5 panicles), panicle length (21 cm), grains panicle-1 (110-117 grains) and grain yield (3.8 - 4.4 t ha-1) were recorded relative to 2021b. Weekly weeding (EW) developed high grains panicle-1 (102 grains) and grain yield (3.0 t ha-1) in 2022b relative to reduced tillers (4.5 tillers), filled panicles (3.6 panicles) and grain yield (1.9 t ha-1) in 2021b. Row directions had no effect on leaf width and grass biomass was numerically higher under EW than NS direction. Benefit Cost Ratios and Marginal Rate of Returns were optimum under 2HH and PREB + 1HH (EW). 2HH and PREB + 1HH (EW) may be recommended in Uganda having been the most economic technologies.
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