High temperature influences both grain yield and end-use quality of wheat. The objectives of this study were to evaluate the performance of selected wheat genotypes under heat stress and to examine the effects of high temperatures during grain filling on grain yield and end-use quality parameters. Fifteen bread wheat genotypes in 2000/2001 and 18 genotypes in 2002/2003 were evaluated under the optimum and latesowing conditions of the irrigated hot environment of the Gezira Research Farm, Wad Medani, Sudan. The genotypes comprised released varieties and elite lines from the Sudanese wheat improvement programme. Data collected included grain yield, grain weight and grain end-use quality including protein content, protein composition, SDS sedimentation values (SDSS) and gluten strength as determined by mixograph analyses. High temperatures significantly decreased grain yield by decreasing grain weight. Although genotypes exhibited variation in magnitude of response, results indicated that high temperature during grain filling increased both soluble and insoluble protein contents, SDSS, mixograph peak height (MPH) and the descending slope at 2 min past peak (MDS). In contrast, mixograph peak time (MPT) and the curve width at 2 min past peak (MCW) were significantly decreased. Flour protein correlated positively with SDSS, MPH and MDS and negatively with MCW. MPT correlated negatively with MDS and positively with MCW. Results indicate that high temperature increased both soluble and insoluble protein contents, SDSS and MPH, and hence the gluten strength, but decreased flour mixing time and tolerance and hence the dough elasticity. Variation observed among genotypes suggests that grain end-use quality could be improved under high temperature conditions utilizing the available variability; however, it might require evaluation under various growing conditions.

Grain texture is one of the most important characteristics that affect the end-use quality of wheat (Triticum aestivum L.). Mutations in the puroindoline-a and puroindoline-b genes are associated with hard grain texture. The expression patterns of the PINA and PINB proteins differ among Pin alleles. We studied the effect of Pin alleles on grain hardness, and milling flour properties using near isogenic lines grown at two different locations. The genotype was found to significantly affect quality parameters related to grain hardness. Grain hardness, flour particle size, damaged starch content were significantly low in Pinb-D1b as compared to Pinb-D1c, Pinb-D1p, Pina-D1b, and Pina-D1k. Grain hardness of Pina-D1k, lacking both PINA and PINB, were the highest, followed by Pina-D1b lacking PINA. Pina-D1k and Pina-D1b showed high damaged starch contents and CO 2 production. Damaged starch is associated with water absorption of flour and CO 2 production during dough fermentation, an important characteristic in bread-making. The alleles might be useful for improving bread-making quality. These results indicate that the grain texture of hard wheat is affected by the amount of PINs each allele.

No abstract

No abstract

No abstract