Muhammad Akhter

Effect of Transplanting Dates on Cooking, Milling and Eating QualityParameters of Some Fine and Coarse Grain Rice Lines

In order to elucidate the effects of transplanting date on milling, cooking and eating quality traits of nine coarse grain and ten fine grain indica rice lines under four sowing date treatments were studied. Results suggest that very early transplanting is more damaging to milling and cooking of both, fine as well as coarse grain rice lines as compared to delayed transplanting. Likewise, much delayed transplanting is more destructive for milling and cooking characters in case of fine grain rice lines as compared to coarse grain type rice lines. In case of studied fine grain rice genotypes, head rice recovery was observed maximum when translated at 18th of June. Similarly, cooked grain length was improved significantly in case of fine rice lines with delay in transplanting. Results suggest fine grain rice varieties to be transplanted before onset of July in order to have least broken rice in milled rice. Delayed sowing date, milling quality, total and head rice recovery, cooked grain length and bursting percentages showed different trend with respect to the rice lines. KSK 133 and Basmati 515 showed maximum head rice recovery among coarse and fine grain rice lines respectively. Likewise, PK 8785-1-1 and PK 8671-24-4-1-20 showed maximum cooked grain length among coarse and fine grain rice lines respectively.

Molecular screening of rice ( Oryza sativa L.) germplasm for Xa4 , xa5 and Xa21 bacterial leaf blight (BLB) resistant genes using linked marker approach

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) has now become one of major rice diseases. During recent years, its occurrence has increased in Pakistan, particularly in ‘Kallar tract’ which is well-known for quality rice cultivation. Development of new resistant varieties by utilizing the available resistant gene-pool is most reliable breeding technique for the plant breeders. The present study was conducted to explore the genetic resources regarding presence and absence of BLB resistance genes Xa4 , xa5 and Xa21 through DNA marker technology. Effectiveness of Xa21 followed by xa5 and Xa7 genes has been reported to confer more resistance level for BLB in traditional rice belt of Pakistan. For this purpose, eighty (80) rice genotypes comprising of diverse origin including three isogenic lines viz., IRBB4 (carrying Xa4 ), IRBB5 (carrying xa5 ) and IRBB21 (carrying Xa21 ) as positive resistant gene checks and IR24 (carrying none of these) as negative gene check were genotyped. DNA fingerprinting results indicated the presence of Xa4 gene in 41 entries, while 14 lines were positive for xa5 gene. Only one local line was carrying Xa21 gene along with Xa4 . Thus, the present study will not only be helpful for rice breeders to develop new rice varieties carrying disease resistant genes, but will also provide the donors to incorporate / pyramid disease resistant genes in popular rice varieties like Super Basmati and Basmati 515 which are susceptible to BLB disease. Keywords: Molecular screening, rice germplasm, Xa4, xa5 and Xa21 genes, bacterial leaf blight