Watermelon (Citrullus lanatus) is one of the most popular fruits in Cameroon and the world at large. However, the extreme sensitivity of watermelon to parasites and climatic vagaries makes its cultivation demanding of chemical inputs that can have negative impacts on human health and the environment. In Cameroon, there is a slow improvement of fruit yield in watermelon breeding due to the lack of natural heritable genetic variation, which is a prerequisite for genetic improvement of crops. Such variation can be created through either random or targeted processes on genotypes with appropriate doses of radiation. Genetic improvement by induced mutagenesis appears today alongside hybridization as an alternative method of creating new plant varieties. However, the success of this approach is determined by the application of an appropriate and ideal dose of mutagen. The objective of this study was to evaluate the radiosensitivity of the two most cultivated watermelon varieties in Cameroon to gamma radiation from 60Co in order to determine an optimal dose or lethal dose 50 (LD50) for the induction of the genetic variability necessary for genetic improvement. Seeds of the Kaolack and Crimson sweet watermelon varieties were irradiated with five doses of gamma radiation (100, 200, 300, 400 and 600 Gy) in the laboratory of the International Atomic Energy Agency in Seibersdorf, Austria. These seeds were cultivated in a greenhouse following an utterly randomized device with three repetitions, and parameters such as the germination rate, the survival rate and the shoot length of plants were evaluated. High rates of 90% and 75% germination were obtained, respectively, for the control treatments of Kaolack and Crimson sweet, while the lowest rates were 35% at 600 Gy for Kaolack and 30% at 400 Gy for Crimson sweet. The highest survival rate of plants (96.66%) was obtained with the control seeds of the Kaolack. This variety had the lowest survival rate (45.6%) at 600 Gy dose. Statistical analysis of data obtained helped to estimate the ideal LD50 doses based on growth reduction of seedlings’ heights after gamma-ray treatment. Using a linear regression model based on parameters like plant size, the LD50 doses for Kaolack and Crimson sweet were calculated at 225.40 Gy and 221.56 Gy, respectively, and predicted between 200 and 250 Gy. These results show that the two varieties evaluated were radiosensitive as clearly expressed in the parameters evaluated, where the values decreased with the increase in the irradiation dose. The LD50 doses from this study could be safely applied as reference doses for large-scale gamma irradiation of watermelon genotypes to create desirable agronomic traits in the mutation breeding efforts.

中文翻译：

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两种西瓜（Citrullus lanatus）对不同剂量伽马辐射的辐射敏感性

西瓜（Citrullus lanatus）是喀麦隆乃至全世界最受欢迎的水果之一。然而，西瓜对寄生虫和气候变幻莫测的极端敏感性使其种植需要化学投入，这会对人类健康和环境产生负面影响。在喀麦隆，由于缺乏自然遗传的遗传变异，西瓜育种的果实产量提高缓慢，这是作物遗传改良的先决条件。这种变异可以通过随机或有针对性的过程对具有适当辐射剂量的基因型产生。如今，通过诱导诱变进行的遗传改良与杂交一起出现，作为创造新植物品种的替代方法。然而，这种方法的成功取决于应用适当和理想剂量的诱变剂。本研究的目的是评估喀麦隆种植最广泛的两个西瓜品种对 60Co 伽马辐射的辐射敏感性，以确定诱导遗传改良所需的遗传变异的最佳剂量或致死剂量 50 (LD50)。在奥地利塞伯斯多夫的国际原子能机构实验室中，Kaolack 和 Crimson 甜西瓜品种的种子接受了五种剂量的伽马辐射（100、200、300、400 和 600 Gy）。这些种子按照完全随机的装置在温室中培养，重复 3 次，并对植物的发芽率、成活率和枝条长度等参数进行评估。Kaolack 和 Crimson Sweet 的对照处理分别获得了 90% 和 75% 的高发芽率，而 Kaolack 的最低发芽率为 35%，在 600 Gy 下为 35%，在 400 Gy 下为 30%，对于深红糖。用考拉克的对照种子获得了最高的植物成活率（96.66%）。该品种在 600 Gy 剂量下的存活率最低 (45.6%)。对获得的数据进行统计分析有助于根据伽马射线处理后幼苗高度的生长减少来估计理想的 LD50 剂量。使用基于植物大小等参数的线性回归模型，Kaolack 和 Crimson Sweet 的 LD50 剂量分别计算为 225.40 Gy 和 221.56 Gy，预测值介于 200 和 250 Gy 之间。这些结果表明，评估的两个品种对辐射敏感，如评估参数中明确表达的那样，其中值随着辐照剂量的增加而降低。这项研究的 LD50 剂量可以安全地用作西瓜基因型大规模伽马辐射的参考剂量，以在突变育种工作中创造理想的农艺性状。