Shamsiah Abdullah

Rice plays a crucial role in global food security, yet it is highly vulnerable to diseases, particularly bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo). Sustainable rice production, such as mutagenesis, can help in the development of new rice varieties with imrpoved agronomic performances. Consequently, this investigation was designed to develop potential rice mutant lines resistant to Xoo from the MR297 rice variety using gamma radiation. In the preliminary stage (radiosensitivity test), MR297 seeds achieved a 50% lethality rate (LD50) or the highest mutation frequency at 382.245Gy. The M1 generation was established using 10,000 irradiated seeds at a dose of 384.245 Gy. In the subsequent M2 and M3 generations, the derived lines demonstrated superior yield and agronomic traits compared with the parental cultivar MR297. Disease screening against the Xoo pathotype indicated that M2 and M3 plants exhibited resistance scores ranging from 1 to 3. Genotypic evaluation of 30 selected M3 individuals showed that all carried the recessive Xa5 allele, while seven plants possessed a gene combination of the dominant Xa21 and recessive Xa5. These seven lines were classified within Cluster II of the UPGMA dendrogram at a similarity coefficient of 0.78. Overall, the results highlight these lines as promising breeding resources for developing high-yielding rice varieties with durable resistance to BLB.

Genetic diversity has been pivotal in unleashing the roles of genes and traits in crop productivity and resistance ability against multiple stresses. In this study, the main objective was to investigate the genetic variation of six local aromatic rice varieties in Malaysia for twelve agronomic characters by using multivariate analysis, viz., genetic parameters, correlation analysis, path coefficient analysis and cluster analysis. The results illustrated that the phenotypic coefficient of variance (PCV) was higher than the genotypic coefficient of variance (GCV) for all characters, despite small differences in values among them. All the characters also revealed a high heritability index (h2 b) except for the length of the panicle. Five characters, namely plant height, number of tillers, number of panicles, weight of 1000 grains and number of unfilled grains per panicle, possessed both a high heritability index and genetic advance as percentage of mean (GA%). These five characters could be used as primary selection criteria for future rice hybridisation or improvisation of the sole aromatic variety. As for the correlation analysis, the number of filled grains per panicle and the length of the seed illustrated a strong correlation and a positive direct effect on the yield rate per plant. According to UPGMA cluster analysis, the varieties were clustered into three groups. Rice variety in Cluster III (MRQ 76 and MRQ 104) and II (MRQ74, MRQ88 and MRQ103) could be considered for further hybridisation to attain a wide spectrum of variation as well as the greatest performance in agronomic performance.

Aromatic rice is a premium rice variety due to multiple distinctive essential qualities viz., strong aroma, long grain, intermediate amylose content, and intermediate gelatinization temperature. The strong aroma is majorly contributed by 2-acetyl-1-pyrroline (2AP), a volatile organic compound that is 10-100% higher in aromatic rice. The long grain represents a large endosperm that contains more starch and nutrients. Intermediate amylose content in aromatic rice is preferred as the rice becomes moist and tender upon cooking. As for the gelatinization temperature (GT), aromatic rice has an intermediate GT which defines a shorter time in cooking. In the world, major aromatic rice cultivars include Basmati (India & Pakistan) and Khao Dawk Mali 105 (Thailand). The production of the aforementioned varieties as well as other minorities is declining due to multiple constraints. The demand-export clash, climate change, disease outbreaks, and other abiotic factors have proven challenging for all rice industrial players. Several breeding techniques are practiced in combatting those problems. In the past, conventional pure line breeding had proven to initiate the cultivation of Basmati-370 (India) and Khao Dawk Mali 105 (Thailand). However, hybrid breeding (combination of desirable traits) is a much more effective breeding method through the release of Pusa Basmati-1 (India), Lateefy (Pakistan), and MRQ104 (Malaysia). From the genetic perspective, quantitative traits locus (QTL) mapping is used to assist in the breeding of aromatic rice cultivars. QTL mapping successfully improved yield, agronomic traits, and stress resistance by providing a strong foundation for advanced in-depth breeding technologies including marker-assisted selection (MAS), mutagenesis, and CRISPR/Cas9 mediated genome editing.

Low-light stress is known to have a significant impact on pumpkin yield in greenhouse conditions, it is crucial to understand the characteristics of low-light tolerance and identify resistant germplasm resources. In this study, four pumpkins (Cucurbita moschata) varieties were used, including three inbred lines (10–32, NY-1, and JB-1) and one hybrid line (NY-1×JB-1). Various low-light treatments (T0, no shade; T40, 40% shading; T80, 80% shading) were set, to explore their effects on morphology, photosynthetic characteristics, osmotic regulation substance content, and antioxidant enzyme activity in pumpkin seedling leaves. In the results, seedlings of inbred lines 10–32 and JB-1, as well as hybrid NY-1×JB-1, exhibited low-light resistance with shading rate increases. The maximum photochemical quantum yield of photosystem II (Fv/Fm) of all varieties decreased under low-light stress. Catalase (CAT) activity initially increased and then decreased, while superoxide dismutase (SOD) activity showed the opposite trend. Peroxidase (POD) activity gradually increased in 10–32, JB-1, and NY-1×JB-1, with JB-1 showing a significant increase at T80, and NY-1 displaying an initial decrease followed by an increase. Noteablely, the soluble proline (Pro) content decreased in 10–32, NY-1, and NY-1×JB-1. Significant differences in malondialdehyde (MDA) content were observed among the seedlings of four varieties. The MDA contents increased in 10–32 and JB-1 under T0 and T40, while showed no significant change in NY-1. The MDA content at T80 significantly decreased in NY-1, and first decreased and then significantly increased in NY-1×B-1. The soluble sugar content in 10–32 remained unchanged between T0 and T40, but significantly increased at T80. While in JB-1 and NY-1, it initially increased then decreased with increasing shading rate. The trend in NY-1×JB-1 was opposite to that of JB-1 and NY-1, with initially decreased followed by a significant increase. In conclusion, morphological characteristics associated with low-light tolerance can serve as reference indices for breeding low-light tolerance pumpkins. These parameters can be used as reference indices to assess pumpkin resistance to low-light stress.

Cabbage is a heat-stress-sensitive cool-season crop. When exposed to high temperatures, cabbage plants can experience reduced growth, wilting, leaf yellowing, and premature bolting (the formation of a flowering stem). The regulatory mechanism controlling heat stress is poorly understood in cabbage. To investigate this mechanism, physiological changes and transcriptional profiling for different heat treatment times were analyzed in this study. The results showed that superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD) activities were enhanced under heat stress. In particular, the increase in SOD and POD activities after 12 h of heat treatment was greater than that after 4 h of heat treatment. With increasing heat treatment duration, the leaf CAT activity and H₂O₂ content decreased after the initial increase. The electrolyte leakage and malondialdehyde (MDA) content dropped significantly, while the proline content increased. Alongside that, 7007 and 5537 upregulated genes were identified in the experimental group treated with heat stress for the 4 h and 12 h treatments, respectively. We found that 10,479 DEGs were shared in the heat stress treatment, of which 1241 were associated with the heat treatment time. By integrating the expression patterns and functional annotations of genes related to heat stress, we identified 15 hub genes that respond to heat stress in cabbage. Meanwhile, we had constructed a physiological to molecular model of cabbage response to long-term heat stress. These findings provide new insights for the comprehensive analysis of cabbage response to heat stress and genetic resources for breeding new varieties of cabbage with heat tolerance via genetic engineering.

The completion of more and more high-quality cabbage genome sequencing attempts provides an important reference genome sequence for resequencing a large proportion of B. oleracea populations. This has laid a foundation for the study of the population diversity of B. oleracea and the excavation of genes related to important agronomic traits. Here, we performed genome resequencing of 91 B. oleracea accessions from 14 countries. We produced a total of 983.84 Gb of high-quality sequencing data, and the average sequencing depth of the genomes was over 15.71 among the 91 accessions. A total of 3,432,341 high-quality SNPs were detected in these B. oleracea accessions. A phylogenetic tree indicated that the leaf ball shapes of “Gaobian” accessions and most “Jianqiu” accessions converge with “Bianqiu” accessions, while “Yuanqiu” accessions were individually assigned to a branch. The principal component analysis (PCA) result was consistent with the phylogenetic relationships. The LD distance of “Yuanqiu” was 38.69 Kb, while that of “Bianqiu” was 30.16 Kb. This result indicated that the linkage degree of the “Yuanqiu” population is greater than that of the “Bianqiu” population, which may indicate that the “Yuanqiu” population has received more positive selection. Our analysis showed that, for the 91 accessions, the best population structure number was four. A total of 560 genes were identified across the 203 selected sweep regions identified in the “Yuanqiu” accessions. Similarly, 682 genes were identified across the 304 selective sweep regions in the “Bianqiu” accessions. Finally, several functional terms were identified via enrichment analysis of the genes in the selective sweep regions. In conclusion, this study will provide rich resources for studies on gene function related to leaf ball development and the population diversity of B. olearcea.

Cucurbita maxima Duch is a widely cultivated and consumed vegetable with high economic and nutritional value. The complete mitochondrial (mt) genome of C. maxima was characterized by Illumina paired-end sequencing and is reported here. The size of the complete mt genome was 640,814 bp, and its GC content was 43.37%. Sequence analyses showed that the mt genome encoded 68 genes, consisting of 38 mRNA, 27 tRNA, and 3 rRNA genes. Phylogenetic analysis indicated that C. maxima was most closely related to Cucurbita pepo (NC-014050.1). This study provides useful genetic information for further studies on the genetic structure and evolutionary patterns of C. maxima for species identifications. The genome can be accessed on GenBank with the accession number (OL350846.1).

Hybrid incompatibility and F₁ hybrid dysgenesis in the interspecific hybridization between pumpkin (Cucurbita moschata Duch.) and winter squash (Cucurbita maxima Duch.) have been previously noted. For this reason, it is difficult to obtain F₂ generations due to F₁ sterility. However, back-crossing and add-crossing can be utilized to overcome these incompatibility barriers in interspecific hybridization. To date, few studies have focused on parental selection, the back-crossing process, and offspring characteristics related to interspecific hybridization. Hence, we explored the F₁ seed acquisition rate, plant characteristics, and F₂ generation fertility after interspecific back-crossing and add-crossing hybridization of C. moschata and C. maxima. Moreover, as a female parent, X-1 (C. moschata) yielded F₁ seeds when crossed with winter squash (C. maxima) 10-04-3, 10-37, or 10-05-2. BC₁F₁ seeds and plants could be obtained with winter squash (C. maxima) as the recurrent parent. Some healthy F₂ seeds and plants were obtained from the interspecific hybrids, including ZJ-13, ZJ-8, and ZJ-11. Further fruit nutrition quality analysis showed that the starch, polysaccharide, cellulose, and dry material contents of ZJ-7 and ZJ-8 were significantly higher than those of the parent pumpkin and winter squash lines. The bioflavonoid content of ZJ-8 was lower than that of its parents, and its soluble protein was at the median value. Meanwhile, the bioflavonoid content of ZJ-1 was lower than that of its parents, but its soluble protein was significantly higher. These results suggest that back-crossing and multi-crossing can overcome the barriers to interspecific crossing of C. moschata × C. maxima. Some interspecific hybrid fruits had nutritional contents much higher than those of their parent lines. Additionally, X-1 (C. maxima) was found to act as a bridge species in interspecific hybridization. Collectively, in this study, the barriers to interspecific hybridization of C. moschata × C. maxima were addressed through crossing methods and choice of parents, and the obtained results are expected to provide novel support for interspecific hybrid breeding between C. moschata and C. maxima.

The increasing demand for chilli has drawn the interest of chilli breeders to improve the production of this crop. Mutation breeding is applied in many crops improvement programs as it can rapidly create the variability of inherited traits in crops. This study evaluates the effects of irradiation doses of radioactive cobalt (60Co) γ rays on seed performances, morphological characteristics and yield of chilli (Capsicum annum L.) var. Kulai grown under laboratory and glasshouse conditions. The chilli seeds were treated with gamma radiation at 0, 20, 40, 60, 80, 100, 200, 300, 400, 500 and 600 Gy. The effect of gamma-rays was assessed towards germination, survival rate and several morphological characteristics. From the observation, seeds from all treatments were germinated (100%) in 10 days. However, the gamma radiation affects the survival rate, fruit length, fruit weight, plant height, and most of the results were lower upon exposure to higher doses particularly 100 Gy and above. Germination rate, plant height, plant survival rate and other morphological characteristics of the irradiated plant were observed to improve at lower doses (40, 60 and 80 Gy). Apparently, lower gamma-ray doses (<100 Gy) were more suitable to study the effect on seed germination as well as other morphological characters of Capsicum annuum L. especially Kulai variety. Mutagenic dose of 300 Gy was estimated as the LD50 for Kulai variety. The findings of this study provide useful information for mutation breeding in Capsicum annuum L. using gamma radiation for future breeding programmes in chilli.

A total of sixteen oil palm interspecific hybrid progenies were evaluated for their fatty acid composition, iodine value, carotene content, height and height increment at Malaysian Palm Oil Board (MPOB) Bagan Datuk, Malaysia. Based on the results, unsaturated fatty acids were higher with a range of 60% compared to current breeding materials. Iodine value showed a considerable amount of the oil palm interspecific hybrid which was around 65. Carotene among some individuals showed an outstanding value of 3424 ppm. Height and height increment showed lower value than current breeding materials with an average 0.17 m height increment per year. Heritability values showed that the genetic component gave higher influence towards height and height increment while the fatty acid composition and carotene content were largely influenced by the environment.