Production of Hybrid Rice Using Environment Sensitive Genic Male Sterile (Egms) and Basmati Rice Lines
Kariuki, Simon Njau
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Rice is the third major food crop in Kenya and, its production is estimated at 129,000 tons which is below the annual national demand of 548,000 tons. Kenya rice yields per hectare are very low compared to major producers like China. Basmati (B) varieties, B370 and B217, are preferred by most rice consumers and are cultivated as a cash crop by 98.8% of Mwea rice farmers. This is because they have strong aroma. Due to the demand, basmati rice command high premium prices locally and internationally. Unfortunately, low yielding traits is a phenomenon shown by all basmati cultivars. To improve on yield, this study exploited hybrid rice technology using greenhouse structure to emasculate medium height, environmental sensitive genic male sterility (EGMS) lines for crossing with viable pollen from basmati lines for hybrid basmati rice production. EGMS lines namely, photoperiod sensitive genic male sterile (PGMS) and thermosensitive genic male sterility (TGMS) were crossed with local basmati varieties. Marker assisted selection (MAS) was used to identify F1 hybrids from various crosses. Results indicated that thermo emasculation at an average temperature of ≥34.5oC, using greenhouse (GH) structure, is possible for the temperate varieties PGMS which are emasculated by photo light (≥13hours) and also TGMS variety emasculated by temperature (≥33oC) but suffers significantly from temperature fluctuation. Microscopic observation of pollen viability of PGMS/TGMS lines at (p<0.01), confirmed this with 99-100% pollen sterility in GH cultivars. Control cultivars grown under natural environment had high pollen fertility of 62-78%. Results on produced hybrid plants, using PGMS/TGMS (female parent) and B217/B370 (pollen donors) indicated heterosis was achieved with desirable traits in seed setting, 1000 seed weight, height, panicle exertion and panicle length. Hybrids differed less significantly in maturity with Basmati (130 days) apart from TB217, TB370 and P2B370 which were early maturing (116 and 128 days). There was positive correlation (p<0.01) between seed weight and plant height and also maturity day. SSR markers used in identifying aroma gene (fgr), TGMS gene (tms) and PGMS gene (pms) and hybrids had large physical distance of between 3cM and 16cM with the targeted gene(s). The markers were therefore not specific and produced no clear polymorphism due to effect of close proximity genes present in the targeted loci. Application of marker assisted selection (MAS) using the SSRs visual scoring of amplified bands in agarose gel electrophoresis was not reliable in selecting rice at seedlings stage. Therefore, in visual scoring of amplified bands, SSR markers of ≤1cM are recommended in this work. More studies on mapping aroma (fgr), TGMS (tms) and PGMS (pms) surrounding genes will help develop tight linked SSRs.