Browsing by Author "Kimani, John M."

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    Evaluation of photoperiod and thermosensitive genic male sterile lines for hybrid rice seeds production in Kenya
    (2013) Kanya, James I.; Njiruh, Nthakanio P.; Kimani, John M.; Wajogu, Raphael K.; Kariuki, Simon
    Photo–thermo-sensitive genic male sterile (P(T)GMS) rice is a new hybrid rice technology that uses prolonged light length and high temperatures to induce sterility. This technology is being introduced in Kenya but such growth conditions are lacking in the tropics. To overcome this, we grew P(T)GMS under greenhouse conditions where day light length was prolonged to 14 hrs using solar illumination and day and night temperatures were maintained above 36Cº and 24ºC respectively. Sterility of P(T)GMS was determined by the level of abortive pollen and seed set rates. Hybrid seeds were produced by crossing three P(T)GMS lines (V1PGM, V2TGM and V3PGM) as female lines with Basmati 370 and Basmati 217 varieties as pollen donors. Under long and normal day lengths and high temperatures, pollen sterility ranged from 99-100% but no seeds were set in PGMS lines. However, TGMS recorded 3% and 2% seed set under similar conditions. Under natural conditions both PGMS and TGMS reverted to fertility. Agronomic evaluation showed outstanding (P<0.01) performance of hybrids over parents in flag leaf length (V2370; 35.8 cm), panicle exsertion (V2217; 8cm) and shorter flowering time (V3217; 85 days) under greenhouse conditions while flag leaf width (V1370; 1.48 cm) and tillering (100) performed better under natural conditions. Percentage seed set positively correlated with flag leaf related traits and flowering days but negatively correlated with panicle length, panicle exsertion and tillering. We conclude that the P(T)GMS lines are adaptable for hybrid rice seed production in Kenya but there is need to review the P(T)GMS lines’ background so as to minimize incompatibility in hybrids.Key words: Oryza sativa, Basmati, PGMS/TGMS, seed technology, pollen sterility.
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    Production of Hybrid Basmati Rice in Kenya: Progress and Challenges
    (2013) Njiruh, Nthakanio P.; Kanya, James I.; Kimani, John M.; Wajogu, Raphael
    Photoperiod sensitive genic male sterile (PGMS) and Thermosensitive genic male sterile (TGMS) rice varieties require a long day light length and high temperature respectively growth conditions for them to be completely male sterile. In hybrid rice seed technology complete male sterility is required in pollen recipient parent so as to avoid contamination of hybrid seeds by selfbred seeds. Natural weather conditions necessary to achieve this are difficulty to obtain in the tropics thus limiting the use of the PGMS/TGMS lines. In this research PGMS and TGMS rice plants were grown under a tropical daylight length that was prolonged to 14hour using solar light illumination gadget while minimum daytime temperature was raised to ≥36°C using greenhouse. This was done under non-automated ordinary greenhouse conditions. The objective was to induce complete male sterility in PGMS or TGMS and to produce hybrid seeds. Under greenhouse growth conditions it was possible to induce complete male sterility in PGMS and TGMS. When grown outside the greenhouse the PGMS and TGMS were male fertile which is required for their own self propagation. The male sterile plants were cross pollinated with elite basmati rice to obtained F1 seeds. This paves the way for hybrid rice production in Kenya. One other major challenge is that the characteristic aroma found in basmati is not felt in hybrid plants because it is under a recessive gene control.
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    Segregation disortion of anthocyanin morphological marker in F2 population of cross between basmati and environment genic male sterile rice lines
    (2013) Njiruh, Nthakanio P.; Kanya, James I.; Kimani, John M.; Wanjogu, Raphael K.; Kariuki, Simon N.
    Basmati rice (Oryza sativa L.) is preferred by many Kenyans yet its yield per hectare is low. This challenge led to initiation of Basmati hybrid rice project in Kenya with a goal of leaping yield benefits of heterosis. Since quality traits in Basmati are under recessive gene control, then the two parents in hybrid programme must possess the traits to avoid their masking at F1 by any other dominant gene. In the process of breeding for suitable parents, Basmati and Environmental genic male sterile lines V1-IR-73827-23-76-15-7S (V1), V2-IR-77271-42-5-4-36S (V2) V3-IR-75589-31-27-8-33S (V3) were crossed to produce F1. All the F1s plants had strong presence of anthocyanin on the base of their stems but segregated at F2 population. Thus, the objective of this study work was to evaluate and understand the mode of anthocyanin gene segregation at F2 population as a potential morphological marker. The F2 population was analyzed to test hypothesis that anthocyanin marker(s) is under simple Mendelian gene control. However, the results obtained indicated that F2 did not obey the Mendelian laws of gene segregation. This led to the conclusion that anthocyanin marker experience segregation distortion in F2 population.